Mysterious Engine Coolant Leak – 2000 GMC Yukon

[Davidson J Mott]

Hello fellow members. I am seeking information to my problem. My engine is the 5.7L Vortec to add into information. 204,000 miles

I am currently trying to hunt down a coolant leak that’s been going on for a little while. It only happens when the engine is running. Here’s what I’ve did and rules out so far. Also, there isn’t any coolant dripping to the ground, so I am thinking it evaporates before it gets to the ground
-Replace Intake Manifold Gasket
-Replaced upper radiator hose
-Ruled out head gasket
-Ruled out cracked head/block

When I fill up my radiator and expansion tank, it will usually go back to it’s previous level before topping off. When engine is warming up, it will often go to around 210 – 230 degrees before the thermostat opens. Some of the possible other causes I haven’t fully looked into are. I did notice that my heater hose at the intake where it has the quick connect fitting had a good amount of play and the plastic tabs are non existent.

-Bad radiator cap
-Leaky water pump
-some other leaking hose

What could also be some common area’s to look up.

Topic

[Richard Kirshy]

[quote=”skullabyss” post=185745]Hello fellow members. I am seeking information to my problem. My engine is the 5.7L Vortec to add into information. 204,000 miles

I am currently trying to hunt down a coolant leak that’s been going on for a little while. It only happens when the engine is running. Here’s what I’ve did and rules out so far. Also, there isn’t any coolant dripping to the ground, so I am thinking it evaporates before it gets to the ground
-Replace Intake Manifold Gasket
-Replaced upper radiator hose
-Ruled out head gasket
-Ruled out cracked head/block

When I fill up my radiator and expansion tank, it will usually go back to it’s previous level before topping off. When engine is warming up, it will often go to around 210 – 230 degrees before the thermostat opens. Some of the possible other causes I haven’t fully looked into are. I did notice that my heater hose at the intake where it has the quick connect fitting had a good amount of play and the plastic tabs are non existent.

-Bad radiator cap
-Leaky water pump
-some other leaking hose

What could also be some common area’s to look up.[/quote]
You do not mention how much coolant your losing.
Have you pressure tested the cooling system?
You state you see no signs of leaks or puddles and it only occurs when the engine is running.
That would lead me to suspect your:
1 Burning off coolant
Which, depending on the amount lost, can be checked by inspecting your spark plugs.
If any are extremely clean that is a tell tale sign.

2 If you have a transmission cooler in your radiator you may have a breach and the coolant is making its way into your transmission.

3 Your getting coolant into the crack case.

You state:
You replaced the intake manifold gasket, are you 1000% sure you did it properly?
-Ruled out head gasket
-Ruled out cracked head/block
How did you rule these out exactly?

I did notice that my heater hose at the intake where it has the quick connect fitting had a good amount of play and the plastic tabs are non existent.
But you say there is no sign of a leak

–Bad radiator cap….. possible, but would expect other issues.
–Leaky water pump ….would leave signs of a leak
–some other leaking hose … again you say there are no signs of leaks or puddles, so I do not believe so.

Just a thought do you happen to have coolant passage or hose(s) running to either the throttle body or intake manifold?
Might be sucking coolant into the engine and still have no signs of any external leak(s)

Again, inspect the condition of your spark plugs.

[Davidson J Mott]

How I ruled out the head gaskets and cracks is I wasn’t experiencing any other symptoms that would exhibit, like poor engine performance. My spark plugs look normal. Upon more careful inspection when I had my engine running, I did start seeing small drops of coolant coming from the front of the engine, abouts where the water pump is located. Reason I don’t see any puddles under my truck is because the coolant gets captured by some plastic pieces on the bottom.

[Richard Kirshy]

If that be the case…
First remove the debris shield(s)
I suggest you add some fluorescent coolant dye and pin point the source of the leak.
Be that, a gasket, a hose or water pump.

[Author]

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