YACT: Losing coolant... confused

[flood]

I had a coolant leak about a year ago in my bmw 735i. A faulty water pump was the culprit.
My coolant system has been fine ever since, but recently I've had to refill the resivoir twice. I took it to a shop to do a pressure test on the cooling system and they found no leak.
I had the head gasket done a year ago... any ideas?

 

[Eli]

Hmmm..

If it's not leaking anywhere visably..

Check your oil.. make sure it's normal..

With the car running, check your exhaust for white smoke..

I'd suspect the headgasket.

 

[flood]

no visible leaks and oil looks ok. resivor cap looks ok... makes a hissing sound when i unscrew it sometimes, so i know its sealing ok.

 

[LordMorpheus]

Aborting not an option. Suddenly, everything changed: "Tinplate Red Three, you are losing coolant." My radio blared over our squadron frequency. Cuzner had slid over into a tight formation, jammed his wing inside my tail and wing and was frantically pointing at the "overboard" vent on the front of my engine where ethylene glycol coolant periodically spurted out. Tiny splatters showed on my canopy. It was plain now: a pressure-suction relief valve or an actuator failure was ruining my warrior's dream, and I'd have to change things quickly. Almost immediately, the stern command, "Tinplate Red Three, this is Jigger. Abort!" came in loud and clear. Everyone recognized the voice of Col. Murphy, our Group leader for this mission, as he broke the radio silence. I did not want to say, "Abort where? I am at the point of no return," so I did not answer. My mind was busy with other things, like saving my fanny.

Now THATS loosing coolant (P-47 pilot who had an engine die over his target (read: too freaking far from base.)

interesting thing is he dove straight down and strafed the hell out of a German train and some AA batteries (and got hammered by flak) only to find (to his dismay) that a flak shell had stuck his cockpit closed so he couldn't bail . . and crashlanded in a field of stumps instead.

 

[Thegonagle]

Maybe your mechanic installed a sub-standard part. Where did you have the water pump replaced?

 

[LunarRay]

Check the hose that goes to the lower radiator. check it right near the clamp at the top.. My granddaughter's BMW did this exact thing and when I took off the hose I noticed a defect in the hose that opened only when the system was hot enough for coolent to be pressurized enough to go between the hose and the fitting... then leak and "burn" off...

 

[stonecold3169]

How long does it take to empty out? When you run it hot do you ever hear a slight hissing from the back of your block?

What can happen is that your intake gasket goes, like Eli was hinting at, but it rots on the OTHER side, so instead of going into your oil, it goes on the ground, which is much better. Usually starts small, and then starts to expand. Usually starts small enough that you heat it up during the day and it expands enough that it won't leak, it cools down at night and starts to leak. Over time, if this is whats happening, it will spread, and cause major engine problems when you start getting gasket bits in your engine. I'd get it checked out asap

 

Many possible culprits that include but are not limited to the following ;

(1)Head gasket / Cracked head

(2)Pinhole in radiator

(3)Pinhole in hose(s)

(4)Pinhole in heatercore

(5)Leaking overflow tank / hose

(6)Coolant leaking into automatic tranny through tranny cooler in radiator

(7)Leaking intake manifold gasket / throttle body gasket

(8)Cracked block

(9)Alcoholic next door nieghbor sucking on your petcock

 

[Eli]

Originally posted by: Roger

(9)Alcoholic next door nieghbor sucking on your petcock

OMG!

Bwhahahaahahah!!!

It's a good thing I didn't have anything in my mouth when I read that, or someone would be buying me a new monitor.

 

[etech]

Originally posted by: LordMorpheus

Aborting not an option. Suddenly, everything changed: "Tinplate Red Three, you are losing coolant." My radio blared over our squadron frequency. Cuzner had slid over into a tight formation, jammed his wing inside my tail and wing and was frantically pointing at the "overboard" vent on the front of my engine where ethylene glycol coolant periodically spurted out. Tiny splatters showed on my canopy. It was plain now: a pressure-suction relief valve or an actuator failure was ruining my warrior's dream, and I'd have to change things quickly. Almost immediately, the stern command, "Tinplate Red Three, this is Jigger. Abort!" came in loud and clear. Everyone recognized the voice of Col. Murphy, our Group leader for this mission, as he broke the radio silence. I did not want to say, "Abort where? I am at the point of no return," so I did not answer. My mind was busy with other things, like saving my fanny.

Now THATS loosing coolant (P-47 pilot who had an engine die over his target (read: too freaking far from base.)

interesting thing is he dove straight down and strafed the hell out of a German train and some AA batteries (and got hammered by flak) only to find (to his dismay) that a flak shell had stuck his cockpit closed so he couldn't bail . . and crashlanded in a field of stumps instead.

P-47s used an air cooled engine. Perhaps you are thinking of a P-51?

Check the hose from the radiator to the overflow tank. Flush the hose out and make sure it isn't clogged. Sometimes the debris from the radiator will clog the hose. When the coolant expands it forces it out at the clamp or a pinhole leak instead of going into the overflow tank. It's hard to find because it can be in the airflow and not leave much residue.
When the coolant cools back down it will pull a suction on the overflow tank and empty it.
Rare, but it happened on my Jeep.

 

[flood]

Thank for the replies... Lots of stuff I'll have to check out.

Some things that might help?....
Car starts normally most of the time. No white smoke while running - havent noticed any when starting, but havent really paid attention.
I have to refill the resivor once a week or so (~8 hours of freeway driving, ~2 hours of city driving).

I had the water pump replaced at a reputable shop with an OEM unit.
Radiator was replaced one year ago along with hoses.

Roger - How can i test for each of those possibilities? Would I have to take each unit out and do a pressure test on the individual components, or is there an easier way?

 

[Ladies Man]

check the hose going to the overflow

i had the exact same problem you're describing... turns out i had a pin hole there... and no one ever replaces that hose.

 

[Thegonagle]

Originally posted by: flood

I had the water pump replaced at a reputable shop with an OEM unit.

Good. I just wanted to make sure it wasn't some Pep-Boys rebuild special, because one of those could be leaking again by now.

 

Roger - How can i test for each of those possibilities? Would I have to take each unit out and do a pressure test on the individual components, or is there an easier way?

Leak detetion kit, and/or you an purhase a ooling system pressure tester, pump it up to 18 P.S.I and leave it overnight, if the pressure does not drop, you have a leak in the catch tank or catch tank hose or the system leaks during the expansion and contraction stages of operation.