Engine/Transmission (1994 - 1998) Pressure in the radiator!!!!!

[edgeman]

I own a 1997 Cummins and I am having troubles figuring this problem out. When I run my dodge the radiator becomes pressurized and I can't figure out what the problem is. There isn't any antifreeze in the oil and there isn't any leaking out on to the engine block. So that tells me it isn't the Headgasket. So what could it be? I know the thermostat is shot for the simple fact that the cab temprature fluctuates between hot and cold when I am running. Can anybody help me!?

 

[JoshPeters]

well 2 things...

depending on your T-stat... that is normal for the temp to swing the needle like a windsheld wiper.



The radiator cap is designed to hold 15psi. For every PSI your cooling system can hold your boiling temperature goes up.



If you have a stone cold truck, (overnight) pop the hood. Check your hose. Should be easy to squeeze. Start the engine. The hose should not get "hard" till the engine is up to operating temperature. If it gets hard within a minute or 2 you've got a headgasket blown from cylinder to cooling passage. It may not consume coolant because the gasket can withstand the 15psi that the cooling system is putting on it, but it can't withstand the 500psi+ of compression.

 

[JFaughn]

How much pressure is the the 1st thing , normal pressure , depending on altitude is 4- 12 lbs , so taking the cap off a warmed up or running eng is going to blow out some .
No oil & water mix does not mean that you do not have a head gasket problem , also some thermostats can make the gauge fluctuate .
A test for H. G. is to use a chemical tester to look for combustion gases in the radiator but it needs to be for diesels , different chem for gasers .

 

[edgeman]

Well here is the thing almost all of the antifreeze is in the overflow bottle. What would that mean. The radiator cap is old probably original. So it could be bad but as far as the temp goes the inside of the cab should not feel like the a/c is on when the heat is full bore!

 

[JoshPeters]

Well it sounds like you have low coolant. The cap is probably bad. The cap does 2 things... When you exceed the 15psi limit, it purges the excess coolant into the overflow. When the engine cools down there is maybe 1-2'' hg that pulls the coolant back into the radiator. If the cap isn't functioning, it's not allowing the small ammount of vacuum to pull the coolant back into the radiator.

 

[edgeman]

thanks that is what I was thinking! thanks alot!

 

[Partyat33]

Excess fluid in the overflow bottle can be a bad head gasket.

 

[edgeman]

yeah but we already came to the conclusion that it isn't. There isn't any antifreeze in the oil and there isn't any leaking out on to the engine block. so I don't know the cap is most likely what it is.

 

[JFaughn]

You never know what is isn't until you find what it is , thats called assuming , assuming can be an expensive way to fix things = putting in parts till its fixed instead of testing to see whats wrong .
You can have a bad HG with out mixing oil & water .
The rad cap is cheap so that would be less than finding a place that can pressure test a cap , but most often you can look at the seals of the cap & see if there are cracks = leaks .

 

[JoeBioDiesel]

Hi EDGEMAN,

A couple of guys have already posted that not having oil in the coolant, or an external leak does not mean the head gasket is OK. Not even close.

Your head gasket can fail with the only symptom being extra pressure in the radiator. Please take their advice seriously. There are a couple of really good suggestions on how to start diagnosing your problem... if there is one.

Good luck,

Joe

 

[edgeman]

I think that I found the problem last night. I took the radiator cap off and it looks like the seal is bad and the valve inside the cap is bad also. So that is where I am going to start. Thanks for your suggestions guys!

 

[CumminsPower98]

I hope it is just your cap that is bad but if not I will try to help you understand how the head gasket can give this exact same symptom. What happens is the gasket develops a compression leak from one of the cylinders to the water jacket and pressurizes the cooling system. This pressure (combustion gases) has to go some place so it pushes coolant out into the overflow bottle. Because of the HG leak, it is unable to pull this fluid back in when it cools down. Instead it sucks air from the cylinder thats leaking and leaves the overflow bottle completely full. This can happen without a drop of cross contamination or any visible external leakage.