2003 Yukon Where Is My Coolant Going?!?!?

[PJS3]

If I were not already bald, I'd be pulling my hair out at this point.

2003 Yukon SLT 2WD
295K miles

I have been dealing with a coolant leak / disappearing coolant since winter 2016. I found that the heater hose connector was leaking coolant there. It is notorious for happening after a while. I swapped both the black and the white one out. All seemed to be well. The replacement failed in fabulous fashion (ie. the leak was even worse this time!) in about 3 or 4 months. I've replaced it again. Seems to be going strong. No leaking.

However, my coolant was still disappearing slowly but surely! I have seen no leaks or puddles. Could not figure it out.

I did not smell any coolant in the exhaust. This past week I did begin to smell coolant from the engine bay.
My mind went straight to "it must be the water pump.". Afterall, it's the original, and it just seemed to make sense. So I swapped out the water pump last week right before going on a 450+ mile trip. I get to my destination and I get a "Low Coolant Level" error on the dash. I checked the connections to the new water pump for leaks. Nothing. I checked the reservoir tank for leaks. Nothing. I did not tear the panels and covers off yet to get back into the engine to take a close look at the gaskets for the water pump yet, but from what I can see they seems to be fine. I torqued the mounting bolts for the pump to 22Ft-lbs. Smh.... I'm at a loss here.

Has anybody experienced this that can offer some insight as to what is going wrong here?

 

[PJS3]

Here's the heater hose connecters I replaced.
Here's the old original water pump.
Heres' the new. I did not replace the thermostat as I had purchased the wrong one. The one I need is the thermostat and the whole housing there. Yes, I know I gotta go back in, but it was a last minute discovery that I did not have the option to rectify immediately. I don't see any leaks from there though.

 

[shreksbrother]

That would be frustrating. That's a lot of miles on an original water pump! Have you had your oil tested by a place like Blackstone? Just to ensure you don't have a weak head gasket? For that matter, have you looked in your coolant tank and at your oil to make sure there's no visible mixing?

Info on Blackstone:

https://www.blackstone-labs.com/free-test-kits.php

 

[PJS3]

Nah, never had the oil tested. I will look into that. But no, the oil is still just a black as usual when I change it. Been running Mobil 1 full syn 5W30 since I've had the vehicle. I got it with 54K on the clock back in 2006. She's been good to us.

 

[sefiro]

Pressure test the coolant system (parts house rental tool). You can also get a liquid to mix with coolant to see if exhaust gasses are in the coolant (HG issue). Be sure to run the vehicle for a while and them sample the coolant)

Sent from my XT1053 using Tapatalk

 

[PJS3]

In my search on the topic, I think my problem could be that I did not burp the system. Like I said... the coolant is literally "disappearing" ... no puddles, no visible path of discharge anywhere.... no smell from the exhaust. I will attempt to burp it properly this evening to see if that makes a difference.

 

[M1Gunner]

One of two things is the culprit. Either you have the heads that with this amount of age develop hairline fractures and the coolant loss is there OR like you said, you did not bleed the cooling system properly. (This is more than likely the case since you did not complain of coolant lose before the initial leaks)

snag a funnel with adapters from a local auto store and attach it to the res. and properly bleed the system.

 

[chevync]

Check your heads, see if you have 706. If so Google castech heads. These heads are known to spring a leak around the oil jets. I had a bad set on my old Tahoe.

 

[mbp1979]

I had the same issues ur having and It was a hairline crack in the passenger side head in the very front. Look under ur oil fill cap what's it look like?

 

[PJS3]

Thanks for all the great replies! Yesterday I went home and properly burped the system based on information I got from another thread.

This morning my wife too the Kon out and came back. Now, based on how it was acting over the weekend the coolant fill level in the reservoir/tank should have dropped below the cold fill mark as though on it's way to giving me another "LOW COOLANT LEVEL" error again. However, it was still at just 1/2" over the fill mark. So that's promising. We'll keep monitoring it over the rest of the week, but this is already an improvement.

God knows I hope the whole hairline cracks and such are NOT my issue...

Now on to the next development.... Smh. My hi beams and my hazard lights have stopped working suddenly. smh...

Here's the method I used to burp it the system by the way. Review and comment please.


"12 To refill the system, install the thermostat and reconnect any radiator hoses.

13 Place the heater temperature control in the maximum heat position.

14 Be sure to use the proper coolant listed in this Chapter's Specifications. Slowly fill the surge tank with the recommended mixture of antifreeze and water to the FILL COLD mark.

15 With the surge tank cap off, start the engine and let it idle for about a minute.

16 Install the cap on the surge tank, but don't tighten it down (pressure must be able to escape). Raise the engine speed to approximately 3000 rpm in 30-second cycles until the engine reaches normal operating temperature and the thermostat opens.

17 Turn the engine off and remove the surge tank cap. If there is any hissing noise coming-from the tank, wait until it stops then remove the cap.

18 Start the engine and let it idle for one minute. Add coolant to the tank until the level is 1/2-inch above the FILL COLD mark, repeat Step 16, then turn the engine off.

19 Add coolant as necessary to bring the level to 1/2-inch above the FILL COLD mark on the tank. Install the surge tank cap securely.

20 Check the cooling system for leaks."