I can say that I bought my fd and had it for a year of fun before any major issues have come up, but finally one has. I am losing coolant from the overflow every time that I shut off the car. Enough to set off the buzzer upon restart. I have been trouble shooting this for a couple of weeks, and here is what is going on:

-Car always starts, doesn't have any white smoke, and doesn't have a rough idle. Can't smell coolant but I do mix toluene which smells sweet like race gas
-Both the Thermostat housing and aftermarket AST caps have been replaced, and are in the correct positions.
-When I pressure test of the coolant system I might loose .5-1.0psi pver a period of 8 hours (I don't have the correct adapter so test was done on the AST).
-Champagne bubble test gives me a bunch of small bubbles (like carbonation) at idle (87C). If I blib the throttle, I will get 1-2 large bubbles immediatly.
-When I shut the car off and let it cool down the thermostat housing will be pressurized when I go back to check the level (When I open it there is a huge whoosh of air). When I refill I unhook the throttlebody hose.

I'm 90% shure that it's rebuild time, just asking for feedback to see if I have missed anything obvious. Any suggestions??

Thanks in advance

 

psi test your coolant system with 20 psi and let sit for an hour. this will let u find a leak while the engine is cold. if you find water coming out of the cast sections it is rebuild time, but I had a leak on top of my engine and would not ever hit the ground it would sit on top of the engine and evaporate and i never saw it.also you may have to bleed an air bubble or two. this can be a pain.

 

20 psi? isn't that a little high. From what I have read (here), people recomend no more than 16 psi. Though I am getting to the point that I will try anything.

 

+1

although it's a test, i've also been recommended to test a bit higher, but around 17-18psi. not 20.

 

20 psi is fine, in fact I believe thats what the FSM recommends. Any external leaks should become apparent within a hour. But small leaks in the combustion o ring have a bad habit of leaking only one way, and may not leak any coolant into the combustion chamber when you pressure test. A much more definitive test is to have a shop that does smog testing test for hydrocarbons coming from the filler neck.

 

Well I decided to pressure test the coolant system again, only this time I took it to 18psi. So I did it initially, and it lost pressure to 13psi in a few hours. I wasn't watching it though. So I tried it again, and 10 minutes into the test I heard a very faint hiss coming from the vicinity ofthe rats nest/upper intake mainfold (just behind the alternator). I had poor lighting, and it was late, so I didn't pursue it. Tonight I will get my work lights out and see if I can find the issue. I will keep my fingers crossed.