Please help out a desperate BMW tech, 99 Grand AM

[asylummotorsports]

The T-stat could be all gummed up with stop leak, or just stuck and defective.

That stuff is hell on cooling systems if you use too much, which most people do in trying to fix a leak that is too big than what the product is designed for.

[90turbo1]

yeah I am leading towards a t-stat swap today. also would llike to have radiator cleaned.

one thing I have noticed if I prop the drain hose (the one right next to the cap on bottle) up over the strut and watch it. there is steam that comes out of it first almost like clock work and then the coolant will start flowing out of it. so to me it seems as if the motor is getting overly hot in some area like behind t-stat that isnt opening. but then again the temp guage on dash (not sure how reliable it is) never shows that it gets hot the highest I have seen it was about 1/8 inch over the 200 mark.

[walterdude]

I'd say you may have a problem with the rad.. Some passages could be plugged so the coolant follows the path of least resistance, instead of through ALL of the passages, out the over-flow..
Surprised no-one has mentioned but, Dexcool is BAD!! Well,, mostly when it's old.. Old Dexcool can plug radiators and heating cores and is a REAL pain to get rid of.. Most around here use green stuff.. I use Texaco HD, what a diesel would use, unfortunately the John Deere dealer now sells a premix that is more "Earth Friendly".. There is plenty of threads about this.. Stop-Leak sure can cause problems when used incorrectly... Like plugging the passages in a radiator!!

Myself, I had a radiator shop take the rad from my 93 Z34 apart (for my own peace of mind during an engine/tranny swap), cleaned and they found a crack in one of the tanks.. It wasn't leaking or overheating,, just the system is designed to run at 15psi (You said the hoses seemed soft) and a crack could prevent that.. I was glad to spend that $60!!
I'm sure you'll figure it out... As an X BMW mechanic, mostly bikes, I know they like their service people to be well trained... Spent plenty of time in NJ doing service classes.
Hopefully this helps,,,
Tom...

[walterdude]

This thing posted TWICE!!
SORRY!!
Tom..

[95Grand-Am]

If its not building pressure there has to be a leak. It could be the tank or the cap you put on it was the wrong design. Thats where i would start, but the thermostat might need changing also, Along with another flush.

[90turbo1]

there is no leak. when I vacumed the system using my vac-u fill system (matco) the sytem went to 26 inches of vacuum. and when closing off the valve it held going back to no more than 25 inch of vacuum. so no leak.

where is the temp sensor for the fans? is it in radiator or is it the temp sensor under the throttle?

a few things could cause no pressure in system, if there is no flow through radiator and some sort of blockage some where else the pressure wouldnt build. rember I have only let this thing run for an hour max. as I do not trust the engine because of what its doing.

we are going to replace the radiator/ t-stat and flush it again tomorrow.
i will keep you posted after that.


and cap is correct, its a brand new gm replacement unit from dealer. looks exactly same as old one that tested bad.

[no_doz]

have you installed a new thermostat since youve done all of these flushes?

[90turbo1]

nope like said I will be trying that tomorrow

[robertisaar]

this should help... only one temp sensor on the 96-up 3x00s.