Coolant System Mysteriously Pressurizing

[RICK LAKE]

danc30 Dan Call Keith on this. Is the motor all aluminum or iron block/ aluminum heads?? How many miles are on it?? The only idea I have is a head gasket is bleeded down pressure from a cylinder after a heat cycle and some of the pressure is ending up in the coolant system. How much coolant are you leaken? Collect it in a overfill tank and check it how much. I'm thinking about heat cycles of expansion are a possible cause of this. I had this a long time ago and it was a head gasket not sealing. Is the car out in the sun all the time, with or without a car cover on it? This will also cause your problem if the cover can't breathe. Everything will get real hot and give you the same issue. Rick L. Ps I just saw your pictures and you have metal shields under the hood, this will cause the same thing after the car has been out for a run. Put a temp gauge under the hood and check the temps a couple of times after the car has cooled off and you put it away. That metal does reflect heat back at the motor and build up pressure from the car just sitting. The cap will hold pressure to the rating of the cap. ONLY vacuum will suck the coolant back into the system and stop when pressure is equal on both sides. You may have no problem at all. Is the car overheating or running real hot? Does the temp of the coolant go up in the 210-220f and hold there? Rick

[Jim Doak]

I agree with Rick Lake, sounds like a leaky head gasket. My first engine's cooling system would stay pressurized for days after being shut down. It would also puke coolant immediately after shutdown when warm. A leaking head gasket was pressurizing the cooling system with combustion gases.

Changed the head gaskets and fixed that problem.

[WarrenG]

It must be a microclimate of "global warming" in your garage!

[Silverback51]

Originally Posted by RICK LAKE

danc30 Dan Call Keith on this. Is the motor all aluminum or iron block/ aluminum heads?? How many miles are on it?? The only idea I have is a head gasket is bleeded down pressure from a cylinder after a heat cycle and some of the pressure is ending up in the coolant system. How much coolant are you leaken? Collect it in a overfill tank and check it how much. I'm thinking about heat cycles of expansion are a possible cause of this. I had this a long time ago and it was a head gasket not sealing. Is the car out in the sun all the time, with or without a car cover on it? This will also cause your problem if the cover can't breathe. Everything will get real hot and give you the same issue. Rick L. Ps I just saw your pictures and you have metal shields under the hood, this will cause the same thing after the car has been out for a run. Put a temp gauge under the hood and check the temps a couple of times after the car has cooled off and you put it away. That metal does reflect heat back at the motor and build up pressure from the car just sitting. The cap will hold pressure to the rating of the cap. ONLY vacuum will suck the coolant back into the system and stop when pressure is equal on both sides. You may have no problem at all. Is the car overheating or running real hot? Does the temp of the coolant go up in the 210-220f and hold there? Rick

After the car has sat for over 2 weeks?

[danc30]

Pulled the plugs tonight and put the cap back on. We'll see tomorrow if it pressurizes.

Dye was used to find a leak at the waterpump bypass hose to the manifold. Successfull.

Motor has sat in a garage with temps varying from 55 to 75, no cover.

Battery disconnect has been disconnected for 2 weeks.

Heads were re-torqued at 1,000 miles and I currently have 2,100.

Cast block, aluminum heads/ manifold.

I do get a fairly big mess when I released the cap after the pressure has built up.

Cap and surface it seals against are good, 2 different stant caps everything the same.

Nothing else under pressure in the car.

If the pressure does not come back, I will do a compression test on the cylinders, but I am betting it is still there.

Can anyone help with my plug readings?

I pulled my plugs tonight to diagnose the mysterious pressurizing coolant system.

Any input on how to correct what I am seeing with the plugs I just pulled.
Pics just loaded in my gallery are a lot higher res than I can attach to the thread.

#4 is a shiny brown and was wet with fuel. # 7 doesn't look right to me, all the rest look like they are doing well.

I'd post pics here but they can only be 39kb.

Any input is greatly appreciated.

Dan

[danc30]

Glad to report that the system re-pressurized.

I'm very glad it did. It means that there is some type of chemical reaction between the UV dye from Tracerline and either the Water-wetter, anti-freeze, or something else.

I will drain, flush and refill without the dye.

Thanks again to all of you that assisted in this diagnosis.
Kudos go out to patrickt and Ronbo

Originally Posted by patrickt

I think I would just loosen my plugs and let the pressure out of the cylinders and pull a cable off of the battery, and then when the engine has cooled off put the cap back on it and see if it continues to build pressure while it's just sitting there in the garage. If it does then it has to be a chemical reaction.

Originally Posted by Ronbo

The dye may be reacting with the water-wetter. The dye was probably never tested with the water-wetter for issues in the first place.

I'm really glad I don't have a blown head gasket.

Rule of thumb- Start with the simplest possible reason for an issue and go from there.

Dan

[patrickt]

Originally Posted by danc30

Rule of thumb- Start with the simplest possible reason for an issue and go from there.

Dan

Ain't that the truth.

[RICK LAKE]

danc30 Dan What color is the coolant? Green, Orange, Wierd Purple? I do know from GM that there are 2 different dyes for the coolants, Green and Orange. I run 50/50 orange and 1 bottle of wetter with dye and didn't have the problem you had. Gald you found it and have the fix for it. Rick L.