Coolant pressure

[Butkie3248]

Sooo about a month ago I had my intake manifold replaced and I've been scratching my head about this and the place that the repair and I'm hoping people here could help some shine on this subject.. So my coolant system always has pressure, I get to work and I work 9 hour days and I twist the reservoir tank cap and there is so much pressure and the coolant just rises up and there have been times where it just almost or does overflow out of the tank. I have the 5.4l also I did change the cap to the tank and still does it. I'm really scratching my head about this. Any idea's?

 

[Don Hall]

Pressure could be developing from a faulty head gasket.. A ruptured gasket will allow exhaust gases to escape into the cooling system.

If this is happening, coolant will eventually be forced out of the system. Pressure will negate a return flow of coolant to the radiator during engine cool-down.

Check the coolant level in the radiator reservoir.

 

[Butkie3248]

It fluctuates

 

[Don Hall]

What fluctuates? You post that your cooling system ALWAYS has
pressure. There should not be any pressure with a COLD system.

 

[Butkie3248]

Like I said after it sits 8 to 9 hrs the system still has pressure

 

[Don Hall]

Like I said: you most likely have a ruptured head gasket, allowing exhaust gases to enter the cooling system which causes pressure to remain when the system is cold. There is a simple test for exhaust gases in the cooling system. Visit your local parts store for a test kit.

 

[Butkie3248]

On day the coolant will be on the bottom of the two lines another day it will be above the 2 lines another day it will be in between the two lines on the reservoir

 

[Hamfisted]

Do you smell exhaust gases in your reservoir ? Do you see any black sooty deposits in the reservoir or floating in the coolant? Is your oil still relatively clean, no sign of milky ?
You can also do a chemical test of the coolant, via the reservoir, for the presence of exhaust gases. Normal reservoir pressure should be 3-4 psi . When I had a bad head gasket I actually installed a 0-15 psi gauge in the small return line between the radiator and the reservoir to monitor system pressure, and as an added safety device so I knew how much pressure to expect if I took the cap off. I replaced the head gaskets with Fel Pro MLS Permatorque gaskets and all is good now, but I left the gauge in place just as a safety measure, and since it doesn't bother anything. That's how I know for sure, normal pressure is 3-4 psi . It will retain 3 psi for a long time. Even overnight.


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[BlackCoffee]

I would vote for a bad head gasket as well. Although, the coolant cap should allow the pressure to bleed off when the coolant cools down. How far do you drive to work and do you get an overheat lights at all? If coolant is flowing back into the cylinder because the head gasket is leaking, you will see white smoke on start up as it burns out, indications on the plug, and maybe even a misfire indication on check engine. Coolant level should stay the same. If you don't see coolant under the truck, the only place it is going is out the tail pipe.

You may be at the stage where gasket leak is small enough that it seals when the engine heats ups an expands. If this is the case, it would give you problems in the morning after the engine cools down and less during the day while it stays hot. My first head gasket leak went months and only showed up in the morning until it finally got the point where I was blowing coolant out the tail pipe and started to get misfires. The right side (PAX) head gaskets seem to go first, left side is a little better.

 

[Don Hall]

............the coolant cap should allow the pressure to bleed off when the coolant cools down.

The poster doesn't include the engine type, but I think both engines have the same cap. If so, the cap is rated at about 16# pressure. That means the cap will only allow pressure to escape until it reaches 16#. A pressurized system of 16# will not allow a siphon to occur, and the overflow bottle will keep filling with each run cycle, and the radiator will not refill with each cool-down cycle.

A test kit for exhaust gases in the coolant will help determine if a head gasket needs replacing.