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Engine Coolant Leak

Dynoconman

By Dynoconman
in Ask A GM Technician

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Dynoconman New Member

Dynoconman

Posted
Posted

Looking for help, advice, and support. My all paid for 2004 crew 5.3L sierra has an engine coolant leak, but there is no visual indications...I have had 3 compression tests, water pump inspected and heater core inspected. I have found that 2001-2006 castech made cylinder heads for GM and have been proven to be inferior and are known to crack and leak. You would think that this would be a recall,(pretty expensive one). I have also notice a knocking noise on colder mornings, but the knocking stops after the engine has been running for a few minutes. What would be the easiest and cheapest way to get this fixed. I love my truck and dont want to sell it, (especially that it is paid for).

 

Please anyone help.

ChevyTech77 Senior Enthusiast

ChevyTech77

Posted
Posted

The knocking noise is normal.

 

Have a combustion gas test done on the cooling system. Dollars to doughnuts it needs heads.

txab Senior Enthusiast

txab

Posted
Posted

Have you pulled the covers and verified the suspect Castech heads or the usual tell tale signs of coolant in the cover? The combustion gas test is important to have performed as stated.

rdnkcpa Enthusiast

rdnkcpa

Posted
Posted

The knocking at startup I would guess would be a stuck lifter. My Castech equipped truck did the same thing. You need to pull the valve covers and look for the Dexcool snot.

dukbludvl Enthusiast

dukbludvl

Posted
Posted

I have the same issue on my Yukon. I've had a slow coolant leak for almost 2 years now -- about 40K miles. I add about 2-4 cups of coolant to the reservoir every month. I have my oil tested regularly, and it has gone from about 0.25% coolant to about 0.5% coolant over that 2 year span for a 2,500-3,000 oil change interval. I've had it pressure tested and everything. They said they could tear down the engine and not find the leak because it's so small. And over the last 2 years, it hasn't caused any substantial noticeable damage to the engine. I'm now changing my oil every 2,000 miles or so just to be safe.

 

How much coolant are you losing?

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