Coolant System Mysteriously Pressurizing

[danc30]

Why would my coolant system get pressure in it while just sitting in the garage?

Car hasn't been started in more than 2 weeks. All of a sudden coolant started slowly dripping out of the overflow tank/tube.

I took off the radiator cap and there was a lot of air/coolant under pressure. Refilled and replaced cap, started dripping again and again, there was quite a bit of pressure in the system when I took the cap off again. I am assuming tthe system is getting up to 16lbs and letting the coolant to get past the pressure cap. My overflow and surge tank are lower than some of my other hoses and about centered in height with my engine. Meziere said it should be OK. It was for the first 2000 miles also.

I currently have in the system:
90% distilled water
10% anti-freeze
1 bottle water wetter\
1/4 ounce of tracerline UV dye. (helped me find a leak)

The Tracerline says it can be left in the system without harm. Funny thing is, this pressure thing started shortly after putting the dye in.

Could it be something other that the dye?

Any and all help is appreciated.
Dan

[danc30]

Here are some pictures:

[Silverback51]

The only thing I can think of is a chemical reaction causing the pressure buildup.

[patrickt]

I have never heard of a cooling system developing pressure from not being driven -- sounds like some sort of reaction to me as well. Flush and fill the system and see if it goes away.

[strictlypersonl]

Where do you live? I'd hate to think the pressure was from ice expanding...

[danc30]

Thanks all. I will drain and flush and refill. Hopefully it goes away.

I live in sunny FLA, so no worry about freezing.

Dan

[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!

[Doug I]

It's a little out of the box ...... but

Check a rodent hasn't chewed through some wiring causing you to now have a hot wire completing a circuit somewhere. If the block is part of the circuit you could be getting a reaction with the coolant. First thing I'd do is remove the battery and see if you still get pressure developing.

[Clois Harlan]

Get some of the aluminium head and block sealer and put it in your radiator. You probably have a small gasket leak that is allowing pressure to get into your cooling system. My coolin system did just as yours and I replaced head gaskets twice and had my heads resurfaced. Then I told an engine builder that hangs around here of my problem and he suggested I put in a small bottle of radiator/head/block sealer. Looks like metal flake silver paint by "Solder Seal". NO problems since then.

Clois

[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. You don't have any other things under the hood that are under pressure, do you? Anything like an AccuSump, Fuel Injection, a bottle of NOS, something else that's under pressure?

[vettestr]

Dan,
You mention system had 16 pounds pressure but because the cap was rated at 16LBS and leaking, right. I think you just have a bad cap or maybe a POS between the sealing surfaces.

16 PSI is a lot of pressure and more than would allow cap removal without some effort and a big mess. If you just removed the cap on the top hose and watched it would fluid keep coming out? I think there is just a leak on your lower cap to tank.

If overflow tank cap is lower than rest of system it will seek its own level of course but what if you throw a jack under car to lift front end till the cap is the high point and watch without a cap in place or can you swap with the other cap?

[Ronbo]

The dye may be reacting with the water-wetter. You could try the same mix in a mason jar and let it sit for a few days then see if any pressure develops. (throw a chunk of aluminum and iron in there as well) The dye was probably never tested with the water-wetter for issues in the first place.

What was the initial problem that you put the dye in for? (this may have been disguising the head gasket leak if there is one)

Also have you re-tourqed your heads recently? (do this first)

[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.

[Morris]

Put a zinc anode in the water system and all will be OK....

Morris