head lift or just need a swirl tank

[Zivic]

the radium piece seems like it should have a bleed off on the top part of the swirl tank. once the coolant is deaerated, where is the air supposed to go when it is sealed? Does it condense back into a liquid in the swirl tank? I haven't found much info on how to install that piece, but it does talk about an initial bleed by unscrewing the feed line to the swirl tank. If that's the case, that isn't optimal for my situation. I need more info on that one. I liked that one because it would be an easy install, if it fits in my space. all the other tanks I am finding either are made for regular heater hose, or don't have enough ports, and I hate cutting up a $100+ tank to add one.

I want to run the return off the turbos directly into the expansion tank, or in the radum piece directly to the swirl - typically, one runs the return off the head to it. from what I read, most systems, feed the return off the head through the heater core, then through the main radiator. In most cases, the feed off the head is the hottest.... but in my case, I think the feed off the turbos is the hottest. running it directly to the expansion tank gives me the most likelihood of trapping the air in the tank vs sending it back through the system.

in terms of install, l would install it like the following pic: I have a 6" H x 8" W x 3.5" D area to work with. this is basically right above the stock bleeder screw. In the pic, the surge tank is right next to the FPR

something obviously came to a head, because when nissan introduced the HR motor in 2007, they redid the coolant system, adding a fill port to the upper radiator hose, and a surge tank on top of the radiator.... much like the R35 GTR

 

[JCH13]

Hrm. Adding a fitting to a tank is pretty easy, especially if you know of a welding shop.

You might try a setup like MR2 guys use to bleed their radiator. The radiator is lower than any other fill point on the car, but air bubbles get trapped there. So you stick a hose on the bleeder fitting and suddenly it becomes the highest point on the cooling system. This is how Mod Squad bleeds the cooling systems on the team's three race cars.

If you added barbed petcocks wherever you were worried about air getting trapped you could stick on a hose and bleed air out from multiple points at once.

 

[Zivic]

Hrm. Adding a fitting to a tank is pretty easy, especially if you know of a welding shop.

You might try a setup like MR2 guys use to bleed their radiator. The radiator is lower than any other fill point on the car, but air bubbles get trapped there. So you stick a hose on the bleeder fitting and suddenly it becomes the highest point on the cooling system. This is how Mod Squad bleeds the cooling systems on the team's three race cars.

If you added barbed petcocks wherever you were worried about air getting trapped you could stick on a hose and bleed air out from multiple points at once.

I have thought of putting in the petcock. I have a stock bleeders screw that I have opened when I have air in the system, but the problem is, when I have air in the system, it get's pushed around and isn't always ending up at the bleed point. I need to trap that air right way not allowing it to get circulated back into the system

 

[JCH13]

I have thought of putting in the petcock. I have a stock bleeders screw that I have opened when I have air in the system, but the problem is, when I have air in the system, it get's pushed around and isn't always ending up at the bleed point. I need to trap that air right way not allowing it to get circulated back into the system

Taking a step back and reconsidering the big picture:

If you're spot-boiling coolant (which is sounds like you might be) bleeding isn't the real solution, preventing the spot-boiling is. If you prevent spot-boiling your coolant than you won't need the swirl pot or extra reservoir. When you boil coolant you're making a coolant vapor, not air, when the vapor cools down again it will turn back into coolant.

There are several options for preventing spot-boiling:

-Running a higher pressure radiator cap, a proven solution but will stress your cooling system connections a bit more and might require upgrading hose clamps throughout the system
-Use a lower concentration of anti-freeze to improve the cooling capacity of the coolant, might be an issue if the car is exposed to extremely low temperatures. You might be okay with a 30/70 mix vs a normal 50/50.
-Use a coolant additive, like water wetter, that has been shown to drop coolant temperatures by a measurable amount. This might buy the margin you need.

Since you noted that this happens at idle you might also benefit from more powerful radiator fans and/or a fan shroud to improve stationary cooling.

If you are unable to properly bleed your car in the first place, which is an entirely different problem, the swirl pot MIGHT help. Though I would try the hose trick before adding the swirl pot.

 

[Zivic]

Taking a step back and reconsidering the big picture:

If you're spot-boiling coolant (which is sounds like you might be) bleeding isn't the real solution, preventing the spot-boiling is. If you prevent spot-boiling your coolant than you won't need the swirl pot or extra reservoir. When you boil coolant you're making a coolant vapor, not air, when the vapor cools down again it will turn back into coolant.

it should... problem is, when i get the boiling, it displaces the coolant

There are several options for preventing spot-boiling:

-Running a higher pressure radiator cap, a proven solution but will stress your cooling system connections a bit more and might require upgrading hose clamps throughout the system

I have already moved to an 18 # cap, up 6 # from stock (stock is 12). I really don't want to go higher

-Use a lower concentration of anti-freeze to improve the cooling capacity of the coolant, might be an issue if the car is exposed to extremely low temperatures. You might be okay with a 30/70 mix vs a normal 50/50.
but at the same time, I am lowering the boiling point... potentially making the problem worse. a switch to evans is another possiblity

-Use a coolant additive, like water wetter, that has been shown to drop coolant temperatures by a measurable amount. This might buy the margin you need.
I have ran it, it helps overall temps, but not really resolving the issue

Since you noted that this happens at idle you might also benefit from more powerful radiator fans and/or a fan shroud to improve stationary cooling.

there is an aftermarket shroud setup, but the way my car sits, I can't run it do to IC plumbing and larger radiator.

If you are unable to properly bleed your car in the first place, which is an entirely different problem, the swirl pot MIGHT help. Though I would try the hose trick before adding the swirl pot.

I know there are other potential solutions, but I think, beyond running separate feeds/returns to each turbo, which still could have potential for boiling, I think the swirl pot is the ticket. yes, localized boiling is a problem, but I think bigger picture, is that the system can't properly handle it. again, big picture I think it is more of a problem of a poorly designed cooling system, where the radiator is lower than the rest of the system.

I guess you need to look at like an elise ... or basically any car with with a front mounted radiator, but lacking the expansion tank... would one suggest they run a stronger cap or changing their coolant vs actually just fitting a proper expansion tank.

Not only will the system self bleed if I get localized boiling, it will take away the headache of bleeding the system from the start.

edit. I am trying to mock up a tank to fit my space. after hrs searching the web, I don't see a universal tank fitting my needs. I want about 2 qts of capacity, but I am working with very little space. I want to get my car over to my mechanic to make sure I am fitting it in the best area.

 

[JCH13]

I'm a little confused, are you saying you have no overflow tank?

Could you possibly fit in a slim profile set of fans with a shroud? There are after-market fans that flow very well in a very small profile. Just trying to complete the picture, you know your car better than I.

You are correct that running more water will reduce the boiling temperature of the coolant, but that is only half of the picture. The specific heat of the coolant increases as more water is added. This means that it takes more heat to raise the temperature of the coolant. Running more water ultimately improves the heat rejection of a cooling system, despite the lower boiling point.

I don't want to push you to do something you're not comfortable with, but I really think trying a less-expensive fix such as running more water with an additive is worth a shot. If it doesn't work, then go try to do a custom solution with swirl tank or extra reservoir.

FWIW the MR2s my race team drives all have front mounted radiators with rear-mounted expansion tanks. Aside from a crack inside of a cylinder wall causing coolant loss we've never really had a cooling issue that wasn't damage-induced. These are cars doing 14-25 hour races under extremely heavy load nearly all the time. FWIW we run straight water with a bottle of water wetter.

Edit: here is the FSAE cooling system I designed when I was in college. The overflow bottle (blue) was connected to the radiator cap. The cooling system functioned flawlessly in every event, including the 44-lap endurance. This car ran straight water with no additives. The cooling fan (fully shrouded puller) is not pictured.

 

[Zivic]

I'm a little confused, are you saying you have no overflow tank?

Could you possibly fit in a slim profile set of fans with a shroud? There are after-market fans that flow very well in a very small profile. Just trying to complete the picture, you know your car better than I.

You are correct that running more water will reduce the boiling temperature of the coolant, but that is only half of the picture. The specific heat of the coolant increases as more water is added. This means that it takes more heat to raise the temperature of the coolant. Running more water ultimately improves the heat rejection of a cooling system, despite the lower boiling point.

I don't want to push you to do something you're not comfortable with, but I really think trying a less-expensive fix such as running more water with an additive is worth a shot. If it doesn't work, then go try to do a custom solution with swirl tank or extra reservoir.

FWIW the MR2s my race team drives all have front mounted radiators with rear-mounted expansion tanks. Aside from a crack inside of a cylinder wall causing coolant loss we've never really had a cooling issue that wasn't damage-induced. These are cars doing 14-25 hour races under extremely heavy load nearly all the time. FWIW we run straight water with a bottle of water wetter.

Edit: here is the FSAE cooling system I designed when I was in college. The overflow bottle (blue) was connected to the radiator cap. The cooling system functioned flawlessly in every event, including the 44-lap endurance. This car ran straight water with no additives. The cooling fan (fully shrouded puller) is not pictured.

you need to think of my Z's system like the MR2s minus having the rear mounted expansion tank... instead, nissan used the radiator as the fill point, and put a bleeder screw at the high point of the system. if they had put an expansion tank at the bleader point, I doubt I would be having any issues

 

[JCH13]

you need to think of my Z's system like the MR2s minus having the rear mounted expansion tank... instead, nissan used the radiator as the fill point, and put a bleeder screw at the high point of the system. if they had put an expansion tank at the bleader point, I doubt I would be having any issues

Do you have any expansion tank at all?

Like I said, the MR2 has a bleeder screw at the radiator that needs to be opened when the system is bled, and the hose trick works perfectly for it. Heck, the radiator bleed screw is a LOW point in the system and it still works.

 

[phucheneh]

I've always heard expansion tank in reference to an 'extra' coolant reservoir (as in overflow tank/catch can)...which is never a fill point. I'm assuming you're talking about the pressurized reservoir type of system? One of us just has our terminology wrong (could be me).

I don't know why every manufacturer doesn't use the latter system (reservoir in the loop/used as fill point) on all their engines. Seems...more logical.

I missed the bit about coolant boiling, I guess...I agree with whoever said that's your problem; not bleeding the system. You're chasing the effect and not the cause.

What kind of coolant temps do you typically see? Do you have an aftermarket (as in aluminum/'performance') radiator?

edit: oh, you said way earlier in thread; I forget CTRL-F is handy...the next question would be what kind of fan setup do you have?

 

[Zivic]

Do you have any expansion tank at all?

Like I said, the MR2 has a bleeder screw at the radiator that needs to be opened when the system is bled, and the hose trick works perfectly for it. Heck, the radiator bleed screw is a LOW point in the system and it still works.

I don't have an expansion tank at all... I have a non pressurized overflow/catch. basically a catch can for the coolant so it doesn't spill on the ground.

on the MR2 the bleed screw on the radiator just makes bleeding the system easier. You could not have it, and just heat cycle the system a couple times and push the air out. with what I am planning on my system I can use the radiator fill like you use the that bleed screw. On our system, some people use the bleed screw on the back coolant line coming off the heater core as a fill point. if nissan would have just put an expansion tank where that bleed screw was, my problem would have self cured. worst case scenario I would have to increase it's capacity.

I've always heard expansion tank in reference to an 'extra' coolant reservoir (as in overflow tank/catch can)...which is never a fill point. I'm assuming you're talking about the pressurized reservoir type of system? One of us just has our terminology wrong (could be me).

I don't know why every manufacturer doesn't use the latter system (reservoir in the loop/used as fill point) on all their engines. Seems...more logical.

I missed the bit about coolant boiling, I guess...I agree with whoever said that's your problem; not bleeding the system. You're chasing the effect and not the cause.

What kind of coolant temps do you typically see? Do you have an aftermarket (as in aluminum/'performance') radiator?

edit: oh, you said way earlier in thread; I forget CTRL-F is handy...the next question would be what kind of fan setup do you have?

for the most part surge/swirl/expansion/header tank can all basically be used interchangeably... all are pressurized components of the cooling system. In a proper setup where the radiator/fill is the high point of the system the top tank on the radiator acts as this expansion tank. In my system, my radiator is not the highest point thus, I have no expansion tank. I simply have an overflow tank. problem is, coolant will not flow to a higher pressure environment.... so once the coolant leaves the pressurized system, it won't be sucked back in unless a vacuum is formed within the cooling system....


I am running stock fans and shroud.

after a lot of internet searching this tank seems to fit my space/needs.

Howe expansion tank from summit

 

[JCH13]

A vacuum is formed in the cooling system when the system cools down or cools off completely, that is when coolant is drawn back into it. This is how I've seen every cooling system function on every car I've built, worked on, or raced.

 

[Zivic]

A vacuum is formed in the cooling system when the system cools down or cools off completely, that is when coolant is drawn back into it. This is how I've seen every cooling system function on every car I've built, worked on, or raced.

yes, the vacuum is suppose to draw back in the coolant, but this doesn't work in my system for a few reasons.... 1.) the overflow is too small so the coolant pushes outside of it. 2.) even when the system pushes coolant, the system stays pressured for a long time, even after shut down. a lot of time, the pushing occurs after shut down.... meaning, I am driving it again, before it has a chance to suck back in, and the coolant pushing leads to more coolant pushing as things get hotter and we have air pockets in the system.

 

[phucheneh]

Again, though...why are you not concerned with coolant boiling? That needs to be addressed. Your air pockets are coming from the coolant boiling and spilling over, then sucking back down as stated...then, the low coolant level eventually forms an air pocket. Or, the boiling may be forming an air pocket, with the coolant not condensing back to fill that area.

If you've got a nice big radiator with a high pressure cap (and proper coolant mix), I would have to say you need to go for airflow.

What does the fan usually do? Is it constantly running on high due to the temps? Any idea what kind of cfm the stock fans pull?

Also, what's in front of the radiator? A/C condenser still there? I'm assuming the intercooler is the Big-Ass(tm) model?

 

[michal1980]

Again, though...why are you not concerned with coolant boiling? That needs to be addressed. Your air pockets are coming from the coolant boiling and spilling over, then sucking back down as stated...then, the low coolant level eventually forms an air pocket. Or, the boiling may be forming an air pocket, with the coolant not condensing back to fill that area.

If you've got a nice big radiator with a high pressure cap (and proper coolant mix), I would have to say you need to go for airflow.

What does the fan usually do? Is it constantly running on high due to the temps? Any idea what kind of cfm the stock fans pull?

Also, what's in front of the radiator? A/C condenser still there? I'm assuming the intercooler is the Big-Ass(tm) model?

bingo. fix the boiling issue since thats the root cause of your problem. No boiling, no bubbles to worry about.

Does the 370z have an electric water pump? If not, maybe swap the pump out for an electric one, with an external controller, so that the flow rate doesn't drop when you idle.

 

[Zivic]

Again, though...why are you not concerned with coolant boiling? That needs to be addressed. Your air pockets are coming from the coolant boiling and spilling over, then sucking back down as stated...then, the low coolant level eventually forms an air pocket. Or, the boiling may be forming an air pocket, with the coolant not condensing back to fill that area.

If you've got a nice big radiator with a high pressure cap (and proper coolant mix), I would have to say you need to go for airflow.

What does the fan usually do? Is it constantly running on high due to the temps? Any idea what kind of cfm the stock fans pull?

Also, what's in front of the radiator? A/C condenser still there? I'm assuming the intercooler is the Big-Ass(tm) model?

I am concerned about the boiling.. but short of pulling the motor and rerouting the coolant system in parallel not much I can do about it. With a proper coolant system, any localized boiling or cavitation will self bleed. even if I rerouted the coolant lines to/from the turbos, the expansion tank is still something I would want.

adding an electric pump is a possibility, but adding one would not be an easy addition.... and again, I would still want a proper expansion tank.

the fans come on at 200 degrees. they usually run till I see temps drop to <190. problem is, even when I get boiling, I don't get extreme temps. I might see temps jump to 204-208 degrees for a few seconds and the hot spot works through the system. high temps are really not the problem.

I have the kit supplied aps intercooler, stock ac condensor, and then koyo 54mm radiator out front.

 

[michal1980]

I am concerned about the boiling.. but short of pulling the motor and rerouting the coolant system in parallel not much I can do about it. With a proper coolant system, any localized boiling or cavitation will self bleed. even if I rerouted the coolant lines to/from the turbos, the expansion tank is still something I would want.

adding an electric pump is a possibility, but adding one would not be an easy addition.... and again, I would still want a proper expansion tank.

the fans come on at 200 degrees. they usually run till I see temps drop to <190. problem is, even when I get boiling, I don't get extreme temps. I might see temps jump to 204-208 degrees for a few seconds and the hot spot works through the system. high temps are really not the problem.

I have the kit supplied aps intercooler, stock ac condensor, and then koyo 54mm radiator out front.

Doing the right thing sometimes/most times isn't easy.

 

[Zivic]

Doing the right thing sometimes/most times isn't easy.

I know how much work pulling the motor is... no f^cking way am I going to do it. My mechanic isn't all that excited to do it. And he would be getting payed to do it. then you are basically talking about rerouting everything. I am pulling the hard coolant lines, drillinging tapping, finding fittings, looking for proper routing that will fit when we put it back together...

just not going to happen. besides, even with rerouting there is no guarantee we fix any issue related to localized hot spots. heck, we could make the issue worse elsewhere in the system. Maybe after we redo things, the flow coming off the head slows and now I have issues there.....

and all the while I still would be installing a proper expansion tank

 

[JCH13]

You've got target lock on making a 'proper expansion tank' when it's not obvious to anyone else that it will solve your problem effectively (spot boiling it seems) and when you already have a typical expansion tank setup that works on every other car I've seen.

To make sure all the bases are covered: have you tested the coolant to make sure the cylinders or head gasket aren't leaking?

 

[Zivic]

You've got target lock on making a 'proper expansion tank' when it's not obvious to anyone else that it will solve your problem effectively (spot boiling it seems) and when you already have a typical expansion tank setup that works on every other car I've seen.

To make sure all the bases are covered: have you tested the coolant to make sure the cylinders or head gasket aren't leaking?

I have a block tester and have used it... it tested fine.

not every car has a radiator sitting low like the Z does. I have found a guy running one for the last two years that had similar issues to mine before he installed it.

My target lock is based on;
1.) a cooling system that doesn't have the radiator top tank as the high point
2.) a system that does not have an expansion tank - my system has an overflow.
3.) this is the easiest potential solution at this point. obviously if this doesn't resolve the problem I will have to explore other options

http://www.pirate4x4.com/tech/billavista/Cooling/#CoolingSystemComponents

The overflow tank is not to be confused with a surge tank or coolant recirculation tank - though they do appear similar.

The overflow tank serves no function in the normal operation of the coolant system. It only comes into play if there is an overpressurization and the rad cap opens, and then it only serves as a safe, environmentally responsible collection point for expelled coolant.

If the system pressure reaches the cap’s pressure rating, the cap’s spring is compressed, forcing the valve open and allowing coolant to escape through the overflow tube to the overflow tank. After such an event, as the system cools it contracts, creating vacuum that opens the other spring- loaded valve, in the rad cap, allowing coolant in the overflow tank to be sucked back into the radiator.

The overflow bottle can be distinguished from the surge tank / recirculation tank in that:

-It is not pressurized
-It has no pressure cap. It may have a non-sealing cap to allow inspection, or no cap at all.
-It has only one line running to it - from the fitting located directly above the rad cap seal seat.
-It will often have a drain cock or valve installed in the bottom for manual draining (which wouldn't be present on a surge tank).

Surge Tank

The surge tank is a completely different animal from the overflow tank. It is an integral part of the cooling system through which coolant continually flows.

The surge tank also goes by many other names, adding to the common confusion between it and the overflow tank. You may see it referred to as a recirculating expansion tank, pressure tank, recirculation tank, coolant expansion fill tank, de-aeration tank, and others.

A surge tank serves two purposes. First it allows for "remote mounting" of the rad cap in situations where the top of the radiator is not the highest point in the system. Secondly, it serves as a de-aeration chamber, allowing for continual and effective removal of any vapour (air or vaporized coolant / steam) in the system.

it is also important to note that the surge tank does not take the place of the overflow tank - it is used in addition to the overflow tank. This can be seen in both the examples above where you can clearly see the fitting in the filler neck (the overflow tube) that connects to the overflow tank - exactly the same way it does when the filler neck / rad cap are mounted directly to the radiator.

 

[Zivic]

from an engine builder on the Z forums:

Well read through the whole thread, we built the motor and I tuned the car for the base map.


We have fitted a bleed system to a couple of TT 350z and this cures the problem of the water being boiled in the turbo,s after shut down, we have been tuning Skylines for 20 years and these cars have the same troubles.

Once you fit a proper self bleed system the car has a swirl pot higher than the entire cooling system of the car, this allow us to bleed water from the radiator and turbo return pipe into the swirl pot then returns this water back into the bottom hose , this bleeds the air from the cooling system all the time. So even after you shut down and the water boils in the cooling system the air is bleed to the highest point the swirl pot as soon as you fire the motor back up.

The APS overflow tank is FAR to small in my opinion , the water will expand on warm up it should push this water into the overflow tank once the car is turned off when it cools down it "should" suck the water fromt he overflow tank back into the radiator as the water "shrinks" agains as it cools down. I think the car definite needs a larger overflow tank.


Tim just get the car back to us , it isn't a HG problem it would just blow the water out of the car under load quickly if it was.


Mark

 

[Zivic]

to go even further, people have issues N/A when pushing the car hard:

I thought I was the only one having this problem. I'm on an N/A engine but weather here's hot. When I go out and play at the track, this same thing happens. At one Time Attack competition, I had to quit because most of the coolant was sprayed out during the practice and the engine started heating up. Everytime i drive the car really hard, I see coolant all the way up on my reserve tank. We need a proper solution for this. .. frikkin air bubbles!

 

[Zivic]

then another feller posted up about his build:

I do not have my car running yet, but my setup is very similar to yours. APS twins on de. I have the APS tall boy intake and altered atmosphere fuel rails. I mounted a carbing swirl pot to the intake manifold back passengers side. Very high. Kind of above the fuel rail. I have the pathfinder cooling mod and shaved the front crossover hose. moved the stock coolant temp sensor to the metal pipe above manifold and put a 6an fitting in the pathfinder pipe to feed the coolant to the turbos. Then I took the 6an that was the feed for the aps kit ( originally was the bleed). and connected it to a top port on the pot, and the outlet from the radiator cap to the other top port. Then the bottom port to the lower radiator hose. Run a blank cap on radiator and a regular style cap on the pot. Then overflow from the pot to the aps overflow tank. This should allow the system to bleed the air automatically. Alot of thought and experience has went into this system and should work great. So people complain about the shaved front crossover and I don't know if you have done that but the reason it is there is to allow coolant to pass around the thermostat to alow it to open up. If there is no coolant flow in the system the water will never get hot at the thermostat. With the crossover gone the heater core and the turbo cooling will allow enough flow to keep water circulating.

he modified his system to increase flow... easy to do when doing the build, not so easy after everything is installed. Even with modifying for flow, he chooses to run an expansion tank

 

[michal1980]

from an engine builder on the Z forums:

that engine builder needs to be slapped.

in one post he says he fixed the boiling problem, and goes on to say that the turbos still boil.


The goal should be to not have boiling in the system.


You however are fixated on your swril tank solution.


So heres a hint, if you dont like the answers, dont ask the questions. You want a swril tank, go ahead install it.

 

[Zivic]

that engine builder needs to be slapped.

in one post he says he fixed the boiling problem, and goes on to say that the turbos still boil.


he has made the system handle any potential boiling without it being a constant problem

The goal should be to not have boiling in the system.


You however are fixated on your swril tank solution.


So heres a hint, if you dont like the answers, dont ask the questions. You want a swril tank, go ahead install it.

Yes the goal should be to not have boiling in the system, but we have cases the car has the issue in stock form... what do you suggest for those people? Why does nissan have an elevated expansion tank on the GTR... and then why did they increase the capacity of this expansion tank on spec V setups by 50%? why didn't they just redesign the setup to not need one?

You are welcome to come pull my motor, completely reroute the cooling system, including plugging and welding ports, retapping new feeds, refitting new coolant lines to each turbo and reinstalling everything.

^^^ and that doesn't guarantee the boiling would be resolved. even with increased flow, individual feeds and returns from the turbos, there is still potential for localized hotspots, so an expansion tank is still needed. even further, rerouting and/or increased doesn't resolve any cavitation issues if they are the underlying problem.

the car is missing a key component in a cooling system. Sure, the car can get by in stock form with the system as is sits, but it still isn't ideal. heck, I could drive the car with turbos in a manner for it to be a non issue. It doesn't change the fact that the system is designed poorly. Adding in the expansion tank is rectifying a flaw in the base system.

I welcome the input, but why don't I just try putting a tube in the tire vs trying to reinvent the wheel? if it doesn't resolve the problem, I can move on to more extreme measures, but the addition of the expansion tank has no negatives that I can see. If anything I would add it simply to make the initial bleed of the coolant system exponentially easier.

As much as you all think I am fixated on the expansion tank, you seem to be against it.... why is adding one a bad thing?

 

[phucheneh]

Adding the tank isn't a bad thing, but it's not a heat exchanger. You need...more heat exchange. Either via bigger radiator or more airflow.

The NA Z/G cars with 3.5/3.7 engines don't have this problem. They're just hard to bleed.

Unfortunately, your problem is probably too much in the fundamentals of your turbo kit to change. e.g. don't use water cooled turbos. Or perhaps your turbos aren't really in their area of max efficiency (or too much exhaust backpressure). Having them underneath your exhaust manifolds probably isn't helping, either. There are a lot of things that may contributing to your cooling system being a bit overwhelmed- he's just saying that lacking a more efficient system of air removal isn't one of them.

Shit, I just took another look at the pics near the top...one turbo is being fed off the water outlet of the other? I think I would change that first.

edit: I would also feed them with bigger water lines/fittings. Stuff like that banjo bolt I see are probably excellent restrictors, which means the water is probably boiling before it even leaves the first turbo...