Boosted Car Coolant Issue

[Leonidas514]

Hey guys!

Finally got my car back together and running. I am waiting on a track day to take it out and start pitting some power into it.

I am having 1 issue.

I have an aftermarket expansion tank and when the car is running the upper radiator hose feels normal, however once I shut the car off it continues to build pressure. The hose will literally start to expand until it finds a weak spot to leak fluid. I replaced the radiator cap thinking it was defective but the upper hose never get soft after the car is off, even after the car is completely cool. If I start the car, the hose just gets harder and harder. If I leave the cap off, the hose NEVER gets hard. The car maintains between 185 and 195 when running so its not overheating. Yesterday about 4 hours after I shut the car off it started puking antifreeze out of my top hose at the clamp because so much pressure had built up. Any thoughts? It's pissing me off!!!! I am thinking if it was a head gasket it would build pressure in the system pretty quickly.

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[Zrussian13]

Hey guys!

Finally got my car back together and running. I am waiting on a track day to take it out and start pitting some power into it.

I am having 1 issue.

I have an aftermarket expansion tank and when the car is running the upper radiator hose feels normal, however once I shut the car off it continues to build pressure. The hose will literally start to expand until it finds a weak spot to leak fluid. I replaced the radiator cap thinking it was defective but the upper hose never get soft after the car is off, even after the car is completely cool. If I start the car, the hose just gets harder and harder. If I leave the cap off, the hose NEVER gets hard. The car maintains between 185 and 195 when running so its not overheating. Yesterday about 4 hours after I shut the car off it started puking antifreeze out of my top hose at the clamp because so much pressure had built up. Any thoughts? It's pissing me off!!!! I am thinking if it was a head gasket it would build pressure in the system pretty quickly.

Replace the top hose. If it still happens get rid of the aftermarket expansion tank.

 

[Angrey]

The expansion tank is supposed to have an overflow function to prevent this. The S550 also features a 1.5 Bar radiator cap (to prevent bursting anything more crucial in the system). It sounds like your expansion tank isn't functioning as it should.

 

[Leonidas514]

I'm wondering if the expansion tank isn't allowing fluid back into the engine after the car is off. I woke up this morning to a cold car and still tons of pressure built up.

 

[80FoxCoupe]

Heater hoses have been removed?

 

[Leonidas514]

Heater hoses have been removed?

Yes.

 

[fmc_smt]

Looking at your pictures , I would look at your vapor lines . The line from the radiator I would think should run back to the expansion tank . I wouldn't think they should be tee together at the upper radiator hose housing on the left head .

 

[Leonidas514]

Looking at your pictures , I would look at your vapor lines . The line from the radiator I would think should run back to the expansion tank . I wouldn't think they should be tee together at the upper radiator hose housing on the left head .

Yes . I had it running to the water outlet. Both run back to the expansion tank. Anyways... ordered another fitting, and I'm going to run it straight to the degas. I also had the passenger head running to the degas and I think that might have been bad idea.

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