Coolant system problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

J/D/S · 09-26-2011, 03:29 PM

Why would the coolant system on my new Big Block keep pressurizing while running? Today when I went to check all the fluids I popped the radiator cap while the engine was running and it threw hot coolant all over the place. I checked the oil and it looks fine, so I kinda think that it's not a blown head gasket thats doing it.

Any ideas?

jdheff1982 · 09-26-2011, 03:37 PM

Um, in order for the water to cycle thru the engine, it needs to be pressurized via the water pump. Also, NEVER remove radiator cap while engine is hot. I saw a guy's face melt off at a drag strip from doing that. That's why there are warning labels on and around the rad. cap.

I would not be concerned unless your water temp is too high. Then I'd check to see if the thermostat is working. Or, there is a plug somewhere in the cooling system. But, if that were the case, you'd already blown something within the cooling system by now.

J/D/S · 09-26-2011, 04:36 PM

You can remove the cap while the engine is running, I've been doing that for years, you can't remove it while the engine is off and hot thats how you get a bath.

tucsonjwt · 09-26-2011, 05:31 PM

I use the type of radiator cap that lets you lift a lever and release pressure from the system - excess pressure is relieved into the coolant recovery tank, and later that coolant is sucked up back into the radiator. The coolant system is under pressure, but check you temperature as stated above to make sure everything is OK.

qksilver · 09-30-2011, 09:37 PM

The cooling system is pressurized to raise the boiling point of the coolant. Water boils at 212 degree's. Most of the 73-86 trucks run between 14 to 16 pound pressure caps.

If the engine is at running temp, releasing the pressure lever, boiling water can still blow past the the radiator cap instead of thru the over flow tube.

Steve

Hevy · 09-30-2011, 09:56 PM

Sounds like it's working properly to me.

motornut · 09-30-2011, 11:32 PM

Quote:

Originally Posted by J/D/S

You can remove the cap while the engine is running, I've been doing that for years, you can't remove it while the engine is off and hot thats how you get a bath.

i've never done it and having been told all these years not to open a hot rad,and note all the warnings around it, i wouldn't even suggest it to someone else

but it sounds fine

09-26-2011, 03:29 PM	#1
J/D/S Registered User Join Date: Jan 2008 Location: Fort Campbell KY Posts: 271	Coolant system problem Why would the coolant system on my new Big Block keep pressurizing while running? Today when I went to check all the fluids I popped the radiator cap while the engine was running and it threw hot coolant all over the place. I checked the oil and it looks fine, so I kinda think that it's not a blown head gasket thats doing it. Any ideas? __________________ John Bernard Books (The Shootist): "I won't be wronged, I won't be insulted, and I won't be laid a hand on. I don't do these things to other people and I expect the same from them."

09-26-2011, 03:37 PM	#2
jdheff1982 Registered User Join Date: Aug 2011 Location: Wichita, KS Posts: 318	Re: Coolant system problem Um, in order for the water to cycle thru the engine, it needs to be pressurized via the water pump. Also, NEVER remove radiator cap while engine is hot. I saw a guy's face melt off at a drag strip from doing that. That's why there are warning labels on and around the rad. cap. I would not be concerned unless your water temp is too high. Then I'd check to see if the thermostat is working. Or, there is a plug somewhere in the cooling system. But, if that were the case, you'd already blown something within the cooling system by now. __________________ Project and Truck Specs: http://67-72chevytrucks.com/vboard/s...d.php?t=483381

09-26-2011, 04:36 PM	#3
J/D/S Registered User Join Date: Jan 2008 Location: Fort Campbell KY Posts: 271	Re: Coolant system problem You can remove the cap while the engine is running, I've been doing that for years, you can't remove it while the engine is off and hot thats how you get a bath. __________________ John Bernard Books (The Shootist): "I won't be wronged, I won't be insulted, and I won't be laid a hand on. I don't do these things to other people and I expect the same from them."

09-26-2011, 05:31 PM	#4
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,188	Re: Coolant system problem I use the type of radiator cap that lets you lift a lever and release pressure from the system - excess pressure is relieved into the coolant recovery tank, and later that coolant is sucked up back into the radiator. The coolant system is under pressure, but check you temperature as stated above to make sure everything is OK.

09-30-2011, 09:37 PM	#5
qksilver Senior Member Join Date: Dec 2004 Location: Southern Pines NC Posts: 3,853	Re: Coolant system problem The cooling system is pressurized to raise the boiling point of the coolant. Water boils at 212 degree's. Most of the 73-86 trucks run between 14 to 16 pound pressure caps. If the engine is at running temp, releasing the pressure lever, boiling water can still blow past the the radiator cap instead of thru the over flow tube. Steve

09-30-2011, 09:56 PM	#6
Hevy Registered User Join Date: Aug 2011 Location: Phoenix, AZ Posts: 91	Re: Coolant system problem Sounds like it's working properly to me.



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