Another coolant leak thread

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mattt

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Thank you for the peanut gallery comments. I was surprised with some of your calls in your posts and offerings here as well. So like you said your deal, your call. If you have something to add in regards to the issue I'm dealing with, I appreciate your post.
 

OR VietVet

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Well, I do like salted peanuts, so here goes. With the coolant hose tees, I am assuming you have rear heat. Check there for seepage when pressure tested.

With the pressure test results you stated, I fear the head gaskets too. There are a few chemical kits you can get at a parts store and do the instructed chemical sniff tests for exhaust gases in the coolant. The 6.0 engine is not supposed to be involved in the Castech cracked heads problems. Look at the "boss" at the front of the passenger side head and see if it says "317". That should not be in the "possible cracked head" category but could still have head gasket problems.
 

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Okay, I did the pressure test with the rental tool and the system holds 15psi with no visible leaks. Then I started the Tahoe and let it run with the 15psi still holding. As it ran longer, I noticed something that might be dreadful. The pressure increased the longer it ran. Is that the concern that I think it is, engine compression pressurizing the cooling system?

I keep forgetting to pull the passenger floorboard mat and check for wetness, I'll check it today. If the heater core is leaking is that where the coolant shows itself? Does it not go out the evaporator drain in the firewall?
The radiator cap should be releiving the system pressure if the head gasket is leaking and increasing the pressure in the system. Maybe you can monitor the level in the surge tank and look for bubbles.

Edit. The cap is no longer located on the radiator. The cap is now located on the surge tank and should be refered to as the "surge tank cap." The pressure relieving and vaccum breaker functions are located in the cap of the surge tank.
 
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The radiator cap should be releiving the system pressure if the head gasket is leaking and increasing the pressure in the system. Maybe you can monitor the level in the surge tank and look for bubbles.

These radiators generally do not have caps.
 

Donal

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These radiators generally do not have caps.
Yes, I should have been more clear in my post. The pressure regulating valve, vaccum breaking valve and fill function cap have been relocated to the surge tank. I will edit the earlier post to clarify. Thanks for catching the error.
 

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Bone dry.
Check the surge tank over flow/overpressure drain line. Look beneath the surge tank cap and see a small hose that goes down and along the front bottom of the surge tank. If the over pressure is venting, the hose should be damp or wet with coolant. That may be the source of the smell you detect occasionally.
 
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mattt

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Checked the surge tank overflow tube. Clean and dry underneath the surge tank and around the tube.

Is there anyone that has had a leaking heater core? How did you discover that it was leaking? Did it leak from anywhere?
 

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