head lift or just need a swirl tank

[Zivic]

I have a 350z - open deck N/A car, converted to twin turbos, using APS twin turbo kit. I have a 9:1 compression motor, using HKS stopper style head gaskets and L19 head studs. 'The' combo to prevent head lift.... unfortunately I am seeing signs of head lift, but given the boost pressures I am running and the ultimate gasket/stud combo, me and my mechanic have our doubts.

The Z is notorious for getting trapped air pockets in the cooling system. I don't have much time to drive my car, so it can sit for 3-4 wks at a time. the issue I am seeing came on suddenly after the car sat for about 3 wks. essentially after some spirited driving, the coolant level in my overflow will have risen, and at times, will continue to rise after the car has shut off. air pockets in the system are the issue, but their origins is what I am concerned with.... if I don't bleed them out entirely a small pocket will snowball into bigger problems... or I did bleed them all out and the cooling system is being pressurized by some combo of headlift/shifting sleeves (stock sleeve motor)/failing headgasket....OR my thinking, getting localized hot spots in the system, causing airation in the system.

I am not getting a lot of coolant push, maybe 6-10 oz, but my overflow is fairly small, and once the pushing starts, again, it snowballs....

I have done loads of research on this platform, and my issue is not uncommon. that said, the use of a swirl tank on this application is. I think the hot spot of my coolant is coming off the turbos. I plan to try to plumb that into the swirl pot and then basically routing the remaining plumbing like standard swirl setups on most any other application. I have changed radiator caps, and today we plan to pull the stat and drill a small hole to help keep any air in the system moving vs getting stuck behind the stat.

My concern is, am I just masking a headlift/shifting sleeves/failing headgasket issue, or am I really resolving a localized hot spot issue? the sudden onset of the issue and not being able to bleed it out after 3 attempts is what is concerning me right now. I am trying to look at everything before we pull the motor and rip the heads off..... not easy, nor fun


just some more back ground
- the motor was done in 2007 and I have just over 11k miles on it. I have had smaller issues like this in the past, but all were resolved with additional bleeding of the system. I have gone through 3 bleeding sessions currently and my issue still remains.

 

[Bartman39]

If your concerned about a compression leak into the cooling system then a simple combustion leak test kit will settle that situation and you will have an area to focus on... If it reads negative then your back to the drawing board but would more than likely a flow issue or hot spot for some reason... Kits for combustion testing can be either test strips or a color changing liquid...

and today we plan to pull the stat and drill a small hole to help keep any air in the system moving vs getting stuck behind the stat.

This is quite common and is a practice I have done many times it helps to open the thermostat more rapid as well by allowing some coolant flow besides purging air pockets... Also 1/8" works for most apps...

 

[Zivic]

If your concerned about a compression leak into the cooling system then a simple combustion leak test kit will settle that situation and you will have an area to focus on... If it reads negative then your back to the drawing board but would more than likely a flow issue or hot spot for some reason... Kits for combustion testing can be either test strips or a color changing liquid...


The test has been negative in past. others have done the tests that have had head gasket issues and they haven't shown anything. It's a tough platform to diagnose. My mechanic is fairly savvy and says he has a few things we can test, so I am holding out hope we can figure it out this afternoon

This is quite common and is a practice I have done many times it helps to open the thermostat more rapid as well by allowing some coolant flow besides purging air pockets... Also 1/8" works for most apps...

good to hear. I am hoping that simple fix will do the trick.

thanks for the input

 

[phucheneh]

I would say either you have a really stubborn air pocket that you're not getting out, or there is an internal engine issue. The air is not just coming out of nowhere.

Combustion leak tester is easy (and cheap). I know NAPA sells (or at least used to sell...) the kits.

Honestly, I think you may just not be getting it bled well enough. When the coolant level rises and it starts puking everywhere...you gotta just keep going. It's like the car ate some bad fish, and it's just gotta throw it all up. :|

If you don't already have one of these, buy one:
http://www.amazon.com/Lisle-24610-Sp.../dp/B001A4EAV0

Turn the heater on, and keep the RPM's up. That's often enough. Kind of 'blipping' the throttle in addition to a constant elevated idle seems to help when the car wants to be stubborn. Usually, once the heater starts getting blazing hot, you've got most if not all the air out.

Raising the front of the car can also help, as the tilting creates a better 'high point' in the system for air to escape from.

However, if you have access to compressed air, you really need one of these:
http://www.amazon.com/UView-550000-A...words=air+lift

Those make Nissan/Infiniti V6 cooling systems their bitch.

 

[Zivic]

I would say either you have a really stubborn air pocket that you're not getting out, or there is an internal engine issue. The air is not just coming out of nowhere.

Combustion leak tester is easy (and cheap). I know NAPA sells (or at least used to sell...) the kits.

Honestly, I think you may just not be getting it bled well enough. When the coolant level rises and it starts puking everywhere...you gotta just keep going. It's like the car ate some bad fish, and it's just gotta throw it all up. :|

If you don't already have one of these, buy one:
http://www.amazon.com/Lisle-24610-Sp.../dp/B001A4EAV0

Turn the heater on, and keep the RPM's up. That's often enough. Kind of 'blipping' the throttle in addition to a constant elevated idle seems to help when the car wants to be stubborn. Usually, once the heater starts getting blazing hot, you've got most if not all the air out.

Raising the front of the car can also help, as the tilting creates a better 'high point' in the system for air to escape from.

However, if you have access to compressed air, you really need one of these:
http://www.amazon.com/UView-550000-A...words=air+lift

Those make Nissan/Infiniti V6 cooling systems their bitch.

I use the tower funnel and follow the APS procedure of heat cycling and reving. sometimes it is just stubborn, but this is to point I have concerns something else is going on.

the combustion tests come out fine for a lot of people even when issues are internal.

my coolant doesn't puke everywhere, it is more of a constant push. I will bring my gopro out today when my we work on it and get video of what I am seeing

 

[phucheneh]

Often times when a big air pocket comes out, it gradually pushes the coolant up and out of the radiator, until eventually 'burping' out the air and sucking back down. That's not what you're seeing?

Silly question, but do you know what your coolant temp is at? It's not boiling while you're trying to bleed (i.e. when not under pressure), is it?

 

[Zivic]

Often times when a big air pocket comes out, it gradually pushes the coolant up and out of the radiator, until eventually 'burping' out the air and sucking back down. That's not what you're seeing?

Silly question, but do you know what your coolant temp is at? It's not boiling while you're trying to bleed (i.e. when not under pressure), is it?

It will get to about 200 or so... when I know I have a big pocket after some pushing it will get to 215, but the air is keeping the stat from opening

 

[Zivic]

well after about 5 hrs of messing with the car... had to do some farm work here and there while I was heat cycling it, but it was the better part of 5 hrs. I really don't think I have internal issues.

I pulled the stat, had to disassemble the SOB as it comes as a complete housing, I cut off the toggle check valve, and drilled it out to 9/64, I then drilled two smaller holes on either side of it. reassembled it and reinstalled it. I then started bleeding the system, which took over two hrs. I did two heat cycles with just the tower funnel and two with the cap. I had the front end up on the hoist during the bleeding procedure.

We pulled the hood in prep to run a pressure tester on the system to see what kind of pressures the coolant system was seeing under boost. the tester wouldn't fit under the hood.

So after the stat modification, and 2 hrs of bleeding the system, I hit the road. I have a closed course 1-1/4 mile strip near my home. I proceeded to do pull after pull after pull. 3rd gear through 4th at full boost. I did this for over an hr, with a few idling sessions to check the coolant level in my overflow/expansion tank. after almost an 1 and a 1/2 hrs of this, I filled the overflow to about 3/4 full (from 1/4 full at start).... I am guessing maybe 16 oz of fluid. I did lose heat one time, but it came back quickly and I never saw my coolant temps spike like I did previously.

When I would come off an idle session, I would get a quick spike of about 10-15 degrees -> 195 to about 205. This is telling me that once I increase flow coming off a few minutes of idle, a hot spot is working its way through system. this is why I think I am getting some aeration from small hot spots in the system - mainly the coolant line coming off my turbos.

This is legitimaty the hardest I have driven my car in the 8+ yrs I have owned it, I had oil temps up to 242. in terms of coolant problems, I definitely didn't have the issues I saw over the past week or so. If it were a head gasket issue, I would have shown here today.

This is my HKS Camp2 readout. This is coming off the last pulls of the day.

At this point, I am going to order a swirl tank and plumb that in and go from there. I will try to drive the car as much as I can in the days leading up to it and see what kind of issues arise. I will post up as I go

with the hood on

 

[HarryLui]

Stock or aftermarket radiator?

I had to switch from a 16PSI radiator cap to a 18PSI camp to stop the bubble after changing to an aftermarket radiator. The filler neck was taller on the aftermarket part.

 

[Zivic]

Stock or aftermarket radiator?

I had to switch from a 16PSI radiator cap to a 18PSI camp to stop the bubble after changing to an aftermarket radiator. The filler neck was taller on the aftermarket part.

aftermarket koyo... I believe it's a 54mm. it is quite a bit bigger than oem.

I have gone through a few caps. I used to just run oem 300z turbo caps from nissan. I would change them out yearly. I did pickup a 1.3 (18#) koyo cap this past week and have been using that.

I spent a couple hrs last night researching cooling systems. What I really think I need is not technically a swirl pot, but a larger expansion tank, and it needs to be moved to the rear of the motor, near where the heater core line exists from the fire wall (basically where the oem purge is).

After my work yesterday I firmly believe this is an issue with a poorly designed cooling system. I think I am getting some localized boiling off the turbos. the air created has no where to escape. on a conventional system, this air would find it's way to the header tank on the radiator. In my case, my radiator sits lower than the motor, so this air stays trapped within the sytem. I am finding it stays either back on the back side of the motor near the heater core, or worst case scenario trapped by the thermstat. Drilling the stat I think I alleviated part of the problem, but I still need to address the fact my radiator is the low point in the system.

i am going to spec out a header/expansion tank this week

 

[skyking]

I could see how that could be a chronic problem with higher than stock temps/pressures/power.
One of my diesel friends had a drag truck that would blow out the rear freeze plug when he got off the throttle. His solution? put a fitting in there with a relief valve, plumbed into the blowoff tank. No way to fight the inevitable steam as coolant flow stops.

 

[JCH13]

I don't know if this EXACT cap would fit your car, but there are 22-24psi radiator caps out there:

http://www.flyinmiata.com/index.php?deptid=4532&parentid=0&stocknumber=09-46050

 

[Zivic]

I don't know if this EXACT cap would fit your car, but there are 22-24psi radiator caps out there:

http://www.flyinmiata.com/index.php?deptid=4532&parentid=0&stocknumber=09-46050

IMHO 18 is about the max I am willing to run. If I had a dedicated track car or some special application, I would give it a shot, but 20+ on a cooling system could open a can of worms - blowing hoses, water pump issues.

I think the majority of my issue is running twice the HP the car was designed around and on top of that, making that power using two turbos in a cramped space. the increased capacity with the larger radiator helps, but the overall design of the system is the main issue. basically no where for that air to go.

 

[JCH13]

Fair enough.

Have you considered heat-shielding or insulating the turbos? Or other sorts of heat management (hood vents, extra front intakes, etc) to prevent spot-boiling in the first place?

 

[Zivic]

Fair enough.

Have you considered heat-shielding or insulating the turbos? Or other sorts of heat management (hood vents, extra front intakes, etc) to prevent spot-boiling in the first place?

The turbos sit fairly back and low. The manifolds have heat shielding on them. the problem is the way the coolant runs. It comes out of the block on the LHS of the block, feeds the LHS turbo, then runs along the oil pan to the RHS turbo. It then returns back in where the highest point of system. Not much one can do in terms of shielding when the coolant is getting hit hard running through the turbos directly

 

[JCH13]

Wow... those are... REALLY convoluted cooling lines. You might consider wrapping the lines up with insulation, it might help a little.

If possible you might consider going to a coolant mix with more water in them, and possibly try an extra additive, like water wetter.

It sounds like the cooling system is right on the edge of being okay... you might need just a little more tweaking to get there.

 

[Zivic]

Wow... those are... REALLY convoluted cooling lines. You might consider wrapping the lines up with insulation, it might help a little.

If possible you might consider going to a coolant mix with more water in them, and possibly try an extra additive, like water wetter.

It sounds like the cooling system is right on the edge of being okay... you might need just a little more tweaking to get there.

drove the car up to the gym... pulled off some epic lifts but that is for another section of the forum.....


anyways, did some pulls on the way home. temps got to about 192-194. I pull into my driveway and my brother had my dad's truck, which he left at my house while he is out of town. anyways he parked it so I couldn't get the car in the garage. so I let my car idle as I went to grab the keys and move it. I checked the overflow as I went in. it held constant, no issues........
.
.
.
I move the truck, and proceed to pull my car into the garage. and all of a sudden I get a nice little spout coming out of the overflow. this is confirming that as the flow decreases at idle, the coolant is boiling somewhere in the system -> the turbos. as I increase the flow/bring up the revs a bit, it moves that boiled coolant through the system and the vapor can't find it's way out and I get increased pressure and it pushes coolant.

 

[JCH13]

Could install something like an oil cooler radiator between the turbos, that might get you the margin you need.

 

[skyking]

I'd re-plumb that so each turbo is independently fed, and returns at the best grade you can get to burp it out high.
That dropped line between them is the bastige, IMO. Get the turbos hot with pulls, back off throttle which reduces flow, and then the fluid gets double cooked.

 

[Zivic]

I'd re-plumb that so each turbo is independently fed, and returns at the best grade you can get to burp it out high.
That dropped line between them is the bastige, IMO. Get the turbos hot with pulls, back off throttle which reduces flow, and then the fluid gets double cooked.

that would be ideal, but seems like a lot of work.


My plan is to plumb a surge tank up near the stock bleader. Plumb in the turbo return to it, as well as the stock, overflow fitting off the radiator. fitting the radiator with a just a top cap. I will plumb the bottom port of the tank back to the radiator hose feeding the water pump.

so if whater get's boiled off the turbos, it goes directly into the surge (expansion) tank, without getting pushed back through the system

 

[Zivic]

pics of the two systems I have been able to find.

I plan to copy this one for the most part, but I want to find one with threaded ports.

This one here is from a shop in texas, that had a strong following for a while, then did not... but rumor has it, they fitted these tanks to their builds. this on is on a greddy tt kit, which doesn't have water cooled turbos

I am interested in this one. it has an integrated swirl tank. my only issue is, it would seem difficult to get the system bled. I don't understand once the coolant off the turbos enters the swirl pot and is deaerted how that air makes its way out?

 

[skyking]

yeah, I know a lot of work. Just one look at that engine compartment, YIKES!

 

[phucheneh]

I have no idea what the point of the 'swirl' is. Normally, when the reservoir is in the cooling system loop, the inlet is at the top, and the outlet is at the bottom. The air doesn't bleed out of the tank, it just collects at the top. As long as there is some coolant in there keeping the outlet covered, it works very well. I've never had to truly 'bleed' a stock cooling system that uses that type of reservoir. Worst case, you just run it with the cap off for awhile.

How do they recommend you tie that in? Does all the coolant flow through it, or is it just kind of a bypass route?

non-edit edit: Oh, I'm just realizing that there ARE outlets on the bottom. Two of them. So the swirliness is on the inlet, which makes a lot more sense. But it still seems like a gimmick...if the inlet just dumps out at the top of the tank, and the tank isn't full (system relies on an air pocket at the top), the air will come out without any kind of agitation. Why leads me to ask why there's a spot for an additional puke tank...again, if it's full (would have to be to go to spare overflow), it's not gonna work.

real edit: Well, I guess if you have a lot of air, and want to make sure you don't run low on coolant...said agitation will throw air bubbles out to collect at the top of a full or nearly full reservoir...and if that air comes under enough pressure to push the spring on the cap in, it will bleed out...rinse and repeat (okay don't rinse)...anyway, conslusion: do it. It can't hurt and it SHOULD help. Although I'm cheap and I'd probably just pull a reservoir off a Nissan truck at the junkyard (the V8's have used this type of system for awhile...no idea why the V6's don't)

Also of note: That tank needs to be at a high point, so you may have your work cut out for you as far as fitting it.

 

[JCH13]

The centripetal force in the swirl pushes any bubbles in the fluid to the center of the swirl pot and out of the fluid. It's a great way to de-aerate fluids.

 

[phucheneh]

So it's just a big hollow tube with some grooves in the sides to channel fluid, I guess? That seems like a fine idea, but is there a spot for the air to escape at the top? The cylinder looks sealed up there.

Personally, I wouldn't worry about getting the air out of the coolant once it's already in the tank- that's the easy part. The problems would come from the air finding some other high spot in the system and not getting pumped towards the tank.