Tinker951

Ok, my problem is this: I had a local shop do a flush and fill coolant service. They used the Green stuff in case it matters. Found no leaks in any hoses as I requested they look double hard. Drive it back home and the next morning, the resevoir is empty. I add a quart back into it to fill it up. I dont drive it and when I return, the resevoir is still where I left it. Drive it again, bring it back and I see the overflow hose is pouring coolant, about a pint I would say was left on the ground. It eventually stops but then the resevoir is empty again when I check in the morning after cool down.

I've done a ton of reading on this site and people have had problems like this where blockages were occuring somewhere in the system, and I may have that.

My questions are, does coolant expand when it gets hot in the motor? Does the pressure cap hold the pressure to a certain point, then do something to allow coolant to bleed to the overflow tube? If it expands upon warm up, is it safe to run the car hard when the resevoir is empty at cold? How about long distance, easy runs? Should a new cap be the first thing I do? Do I need a special one, or can a quick trip to the autoparts store for an over-the-counter cap do the trick?

thanks as always

fbgh2o

Yes

Does the car run hot?

I would have the car looked at by someone who know what they are doing, does not sound like it was bled properly and there may be a blockage somewhere. Really they should not have used the green coolant.

Luis de Prat

Are you sure they filled the system completely? The 944 cooling system takes around 2 gallons of liquid and it's common for pockets of air to form keeping the circuit from filling easily. You must also bleed the system completely, which usually takes persistence.

Use the phosphate-free pink "Autobahn" stuff from VW-Audi dealers or the Porsche coolant in a 50/50 mix with distilled water. Rennlist lore has it that the "pink stuff" contains an additive that extends waterpump life.

knfeparty

The green stuff will eat up the aluminum if you leave it in for too long. I would consider too long on the order of at least a year or two though. You can definitely get all sorts of air pockets- and air of course expands and contracts a lot with temperature (high coefficient of thermal expansion) and therefore any trapped air in the system will cause the coolant level to fluctuate dramatically.

944 cooling systems are uniquely hard to deal with. Definitely get some pro help...if the search was working better I believe you could find some good DIY articles on here but for now check

www.clarks-garage.com

and look at the garage shop manual for instructions. Just be patient and follow everything.

Tinker951

It has in the past, but it does not now. I have, though, been filling the resevoir before every drive just in case.

cruise98

If you are filling the reservoir frequently, you have a leak, or else the head gasket is blown and is forcing coolant out the overflow tube under boost. You need to investigate further. You can rent a coolant pressure tester from Autozone, but you will probably need to do a leak down test to check the head gasket, unless it is totally gone.

You can use the standard old coolant if you change it frequently. To really totally flush it, you have to drain the block, radiator, turbo loop and the heater core. It is such a PITA you do not want to do it very often.

Look for a phosphate and silicate free coolant and mix with distilled water. Zerex extreme, Prestone Extended life, Honda blue, Toyota red, Dex cool, VW etc. Pick something that is readily available.

Jay W

Either air in the system as has already been mentioned or a bad cap that is not able to hold the system pressure.

944Ross

It's confusing too that the words "Minimum level" and "Maximum level" are at the top of arrows that point down much lower on the reservoir. I was overfilling because the arrows were covered with dirt.

The proper spec coolant is GO-5. Prestone makes it and it is sold at NAPA. It is silica and phosphate-free.

krystar

i actually just looked at my two bottles of coolant. the one i got at pepboys is yellow bottle proline 50/50. has ammonium phosphate. the other one ..i think i got at wallyworld. blue bottle supertech generic is just ethyl glycol and diethyl glycol.

Tinker951

cool, thanks guys. i drove it this morning and hit above 0 psi boost 1 time on the drive, about 15 miles city driving on a hot day. parked it at the house, and could see the coolant was elevated, but not overflowing. left it there and now i will go back home to see where it is now that its cooled down. this is great info. I'm hoping for an air pocket.

If that friggin HG is blown again im gonna junk the car.

choinga

if the HG was gone you'd see white smoke for sure...and probably a lot of it.

87 944 C

did they check the block for leaks, or just the hoses?

also pressure check the cap

Tinker951

The shop that did the flush/fill for me just checked the hoses then ran around the block a couple of times to see if it went down any, which it didnt. I didnt ask them to do anything major because I didnt know anything major might be happening at the time.

how do i pressure check the cap?

how can i tell if the water pump is working?

this past weekend, I did a 500 mile round trip run and it lost only a little bit of coolant, around a pint. it did overheat during a 150mph+ race with a rx-7 3rd gen with what had to be a very nice turbo in it. btw, i put a car length on the thing until I mis-shifted into 5th. poor guy had his windshield wiper literally blow off the glass and bend around to his window. But I digress....

I can't tell if the damn thing is running hot until the red light in the temp gauge comes on or coolant vapor gets burned and a big white cloud comes out the back. The gauge just bounces around and sits in a random place. for a while it thought it was upside down since it when cold itd be near the hot side, then after driving it'd work its way down, but that doesn't seem to always be the case. also, i attempt to get a feel of how hot things are by turning on the heat and feeling the air.

i saw on clark's garage i think a way of pressure filling the coolant system. I know a guy that's rebuilt a 944 before here in town and i will take it to him to see if he can find a blockage if all else fails.

genikz

I would just replace the cap. They're super cheap and can save you thousands in engine repair by hopefully preventing all your coolant from pissing out at the wrong system pressure.

If you go to autozone you can rent a coolant system pressure tester. You can screw the pressure tester to the coolant resivour, loosen the coolant bleeder and then pressurize the system. This will force air out of the system thru the highest point on the system. It doesn't get 100% of the air out, but it gets you pretty damn close. I've used that tool 2 or 3 times now during my repairs and I've only have to "burp" the system a few times, instead of a few dozen times.

You can also test if the water pump is working by removing the coolant bleeder screw. When you crank the motor, and the water pump starts turning, it'll push coolant in a nice stream from that bleeder screw hole.

WizPorsche944

I run the pink VW pentosin stuff.