Coolant cap untwisting itself, why?

turbotalon1g · 10-25-2009

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

notsostockgalant · 10-25-2009

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

munchgsx · 10-25-2009

Did you get the new HG installed?

turbotalon1g · 10-25-2009

No new hg. New cap 2nd new cap

95talonracer · 10-25-2009

Sounds like a bad HG.

Kevin 1G Drummer · 10-25-2009

Quote:

Originally Posted by 95talonracer

Sounds like a bad HG.

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

Pushit2.0 · 10-25-2009

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

95talonracer · 10-26-2009

Quote:

Originally Posted by Pushit2.0

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

But was yours pushing coolant as well?

Pushit2.0 · 10-26-2009

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

95talonracer · 10-26-2009

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

4g63tcrazy · 10-26-2009

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

desolate · 10-26-2009

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.

Pushit2.0 · 10-26-2009

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

turbotalon1g · 10-26-2009

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

deadeye · 10-26-2009

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.

turbotalon1g · 10-29-2009

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?

turbotalon1g · 10-29-2009

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.

blackrosenova400 · 10-29-2009

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.

Quote:

Originally Posted by turbotalon1g

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.

FattyBoomBatty · 10-30-2009

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.