strange coolant leak - The 1947 - Present Chevrolet & GMC Truck Message Board Network

exdrocca · 04-05-2009, 10:31 PM

I've recently noticed a coolant leak from my passenger side valve cover. It's a subtle drip from the valve cover that puddles up along the intake manifold towards the front of the engine. I don't know how long this has been going on but i was down about a half gallon of coolant. I did check the oil, and it's clean and normal as can be. How else could there be an external leak in that area that's not getting into the oil? This is for a 350

Thank you

westofb · 04-05-2009, 10:50 PM

No way it is coming from the valve cover...there is no water there. I would suspect it is coming from the intake manifold or the thermostat housing. Possibly a pin hole in upper radiator hose...lose hose clamp...heater hose....I believe that is all the possibles...good luck finding it!

**jaros44sr** · 04-05-2009, 10:52 PM

Or the intake mounting bolts weren't sealed with a good sealant

rico7769 · 04-05-2009, 11:34 PM

I had a similar issue with an intake plug at the rear of the manifold. I am running an aftermarket perf manifold and it came with plugs installed already. Check to see if the bolts are loose too as the other reply said. Water will always find the lowest point through gravity...like the valleys on the valve covers/manifold juntion. Running the motor, try a blacklight, the coolant should give a reflective quality to be able to see its origin.

OhioDan · 04-06-2009, 06:46 AM

Had a similar problem with one of those fancy chrome o-ring thermostat housings. Finally replaced it with a steel housing, and the leak stopped.

exdrocca · 04-06-2009, 07:01 AM

The thing is after noticing there was a leak, I cleaned the whole area. I then started it up and waited until I saw a leak. It really looks as if it's dripping down from the valve cover gasket on to the edge of the intake manifold. There is a little valley inbetween where it puddles up at. Could a cracked head cause something like this? It is my daily driver.

cparman · 04-06-2009, 07:01 AM

I agre with jaro. Might take the intake bolts out one at a time and put some thread sealant on them.

cdowns · 04-06-2009, 07:12 AM

r u sure the leak isnt from he heater hose connection to the heater core and just dripping down the hose onto the valve coveer

exdrocca · 04-06-2009, 08:13 AM

ok so I checked again and it now looks just to be the intake gasket. I think the fan was blowing the coolant back up under the valve cover a little bit since it was coming from the front side of the intake. Thanks for the quick replies!

04-05-2009, 10:31 PM	#1
exdrocca Registered User Join Date: Feb 2005 Location: Warrington, PA Posts: 75	strange coolant leak I've recently noticed a coolant leak from my passenger side valve cover. It's a subtle drip from the valve cover that puddles up along the intake manifold towards the front of the engine. I don't know how long this has been going on but i was down about a half gallon of coolant. I did check the oil, and it's clean and normal as can be. How else could there be an external leak in that area that's not getting into the oil? This is for a 350 Thank you

04-05-2009, 10:50 PM	#2
westofb I really hate wet sanding! Join Date: Dec 2008 Location: Brookfield, MO Posts: 601	Re: strange coolant leak No way it is coming from the valve cover...there is no water there. I would suspect it is coming from the intake manifold or the thermostat housing. Possibly a pin hole in upper radiator hose...lose hose clamp...heater hose....I believe that is all the possibles...good luck finding it!

04-05-2009, 10:52 PM	#3
jaros44sr Senior Member Join Date: May 2006 Location: Philadelphia, Pa. 19454 Posts: 9,704	Re: strange coolant leak Or the intake mounting bolts weren't sealed with a good sealant __________________ Semper Fi...Uncle Sam, you da man All parts offered to help are free, unless otherwise noted Dont try this stuff in my build thread, unless you have 55 years of mechanical OTJ training SAFETY FIRST AS usual, off topic They say your mind goes second, can't remember the first Jim

04-05-2009, 11:34 PM	#4
rico7769 Hybrid67 Join Date: Jan 2009 Location: Martinez, GA Posts: 195	Re: strange coolant leak I had a similar issue with an intake plug at the rear of the manifold. I am running an aftermarket perf manifold and it came with plugs installed already. Check to see if the bolts are loose too as the other reply said. Water will always find the lowest point through gravity...like the valleys on the valve covers/manifold juntion. Running the motor, try a blacklight, the coolant should give a reflective quality to be able to see its origin.

04-06-2009, 06:46 AM	#5
OhioDan Registered User Join Date: Apr 2002 Location: New Carlisle, Ohio,USA Posts: 1,404	Re: strange coolant leak Had a similar problem with one of those fancy chrome o-ring thermostat housings. Finally replaced it with a steel housing, and the leak stopped. __________________ LIFE AIN'T EASY WHEN YER FAT AND GREASY! GMC= Got More Class! 1970 GMC LWB, Fleetside, 350/4spd, Flowmaster "40's", 2002 GMC 16" Rallies, cowl hood,and added a bunch of options that weren't there when I started.

04-06-2009, 07:01 AM	#6
exdrocca Registered User Join Date: Feb 2005 Location: Warrington, PA Posts: 75	Re: strange coolant leak The thing is after noticing there was a leak, I cleaned the whole area. I then started it up and waited until I saw a leak. It really looks as if it's dripping down from the valve cover gasket on to the edge of the intake manifold. There is a little valley inbetween where it puddles up at. Could a cracked head cause something like this? It is my daily driver.

04-06-2009, 07:01 AM	#7
cparman sharp as a marble Join Date: Jan 2007 Location: atlantic beach,florida Posts: 1,082	Re: strange coolant leak I agre with jaro. Might take the intake bolts out one at a time and put some thread sealant on them.

04-06-2009, 07:12 AM	#8
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: strange coolant leak r u sure the leak isnt from he heater hose connection to the heater core and just dripping down the hose onto the valve coveer __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

04-06-2009, 08:13 AM	#9
exdrocca Registered User Join Date: Feb 2005 Location: Warrington, PA Posts: 75	Re: strange coolant leak ok so I checked again and it now looks just to be the intake gasket. I think the fan was blowing the coolant back up under the valve cover a little bit since it was coming from the front side of the intake. Thanks for the quick replies!



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