Coolant cap untwisting itself, why?
 

Why is my car trying to kill itself?

Boost is way down to 25psi. after doing a 2nd - 4th pull on the street with boost at 27psi that time, now turned down to 25psi.

The coolant cap was twisted about 45 deg. and it pushed coolant into the overflow bottle.

I just don't understand why the cap would unscrew itself.

Aaron

Re: Coolant cap untwisting itself, why?
 

maybe the rubber gasket under the cap is wore out. or the spring is uber weak just thought of that

Re: Coolant cap untwisting itself, why?
 

Did you get the new HG installed?

Re: Coolant cap untwisting itself, why?
 

No new hg. New cap 2nd new cap

Re: Coolant cap untwisting itself, why?
 

Sounds like a bad HG.

Re: Coolant cap untwisting itself, why?
 

+1. Sounds like the system is getting over-pressurized. Between that, and the vibration of the engine, it's forcing the cap to untwist.

Re: Coolant cap untwisting itself, why?
 

My car would do this, and only after 1 run on the dyno. So I used a zip tie to hold the cap from twisting, this fixed my problem. I say it was from engine vibration, and this is why I had to safety wire my oil filter.

~John

Re: Coolant cap untwisting itself, why?
 

But was yours pushing coolant as well?

Re: Coolant cap untwisting itself, why?
 

No, not even with the stock cap. But I was not out driving it and would tighten the cap after 1 run. I switched to a 23psi cap and it still did it, so then I used a zip tie. For the 20miles I put on the engine no coolant pushing problems.

~John

Re: Coolant cap untwisting itself, why?
 

If his starts to move the cooland into the overflow then I am guessing there is pressure there from a bad HG.

Re: Coolant cap untwisting itself, why?
 

If the cap twists off a little it will make it easier for the coolant to push into the overflow. Bad HG or not..

Re: Coolant cap untwisting itself, why?
 

Try one of the square coolant caps that comes with a red lever to release pressure. Knew a guy who was seeing the same problems but the square cap did the trick.

Re: Coolant cap untwisting itself, why?
 

The cooling system is designed to be under pressure to raise the boiling point of the water in the cooling system. If the cap is loosening, this will in turn lower the pressure at which the cap will allow coolant into the over flow tank. I would try to secure the cap and see if you still push coolant. If I recall your car would hit MBT before the knock sensor would show anything threw LINK.

~John

Re: Coolant cap untwisting itself, why?
 

Thx guys I will it out and see. I just the car drivable till I get home in may

Re: Coolant cap untwisting itself, why?
 

1+ the locking lever vent rad cap. Oreillys carries them and they work great. It will not come unscrewed without the lever being flipped up.

That being said I do concur with the others on here that its probably worth doing a cooling system pressure test just to be sure there isn't a underlying problem.

Re: Coolant cap untwisting itself, why?
 

Ok, just got back from the field. suckfest no shower for 4 days.

Um, did a coolant system test, lower hose slightly dripped, fixed leak. Test drive at 25psi, same thing pushes coolant.

I have limited time (I leave here next week and maybe have saturday to work on the car) and limited experience doing HG jobs, also limited tools. Anywho, u guys think it would be worth throwing in a new set of ARPs and a stock HG?

Re: Coolant cap untwisting itself, why?
 

Me=dumbass, what i meant by that last question is, could i do a hg without getting the head milled/block decked?
I don't have the time since I have to leave in a week and i can basically only do it on saturday, or will it be a complete waste of time to just slap a new HG and studs in there?

I'm thinking its worth a try.

Re: Coolant cap untwisting itself, why?
 

Get a straight edge and a feeler gauge to check the head and block when you pull the head. Id say nothing over .002 and you would probably be fine with a composite gasket.

Re: Coolant cap untwisting itself, why?
 

Reminds me of my engine, except the cap wouldn't twist off, it just lifted the head and put horsepower into the coolant. Sprayed everywhere.