2003 Tahoe coolant system leak or head gasket leak?

[SnowDrifter]

Use a combustion gas tester on the cooling system. Only costs about $50.

Yep

And the other, noninvasive test I'd do, before do much as taking a bolt off: Is to grab an oil sample and send it off for analysis.


Gas check looks for, I believe CO2, which triggers a color change. You can blow fresh air through it until the color changes back to re-use it later, for what it's worth.

Also, regarding coolant schmoo: if, IF it's a combustion chamber link, one of the other things to look for is rapid pressurization of the system w/ key on and/or fluctuating cooling system pressure corresponding to manifold vacuum i.e. quickly revving it

<cheeky>

also: dude screw all that fix in a bottle stuff. If you need it to run short term or flip it (what are morals), sure. If you plan on keeping the rig - just do it right. No bottle fix is permanent. And *every* bottle fix comes with drawbacks. Sure, it'll seal the leak. But it'll also plug the heater core, rad, and thermostat (jiggle pin at a minimum). It'll also cause abrasive wear on your water pump seals. Or maybe it leaks in the oil. Mmmmmmmm abrasives in a hydraulic sytem

Besides... Assuming it does 'fix' it, that then affects your ability to perform future diagnoses.

</cheeky>

Oh, and fun fact I discovered with reading and testing: Ya know what happens when the heater core plugs on these rigs? They'll overheat. But they'll do so in a highly localized manner that won't necessarily reflect on the temp gauge. You'll see some increased temps if you have a digital readout, but even then, it'll only look on the high side of normal. Nothing that will give you any red flags until you turn the key off and listen closely.. Then you'll hear coolant boiling.

So yeah.... I'd evaluate very carefully before you start trying quick fixes.

Diagnose first. Then evaluate course of options.

 

[tomloans]

Any comments? I think this picture is the beginning of sorrows. LOL Please confirm for me. This looks like sludge and I change my oil every 3k miles come rain or shine.

 

[tomloans]

Would you guys change both Cylinder heads or just the one that is cracked? Would you get remanufactured or new?

 

[tomloans]

His was really bad as it had been going on for a long time. He had only owned the truck for maybe a year, if even that. I wouldn't be surprised if that was why the previous owner got rid of it. Under the cover and all inside the engine was thick and black gunk. You would've noticed that had yours been that bad. If yours is cracked, it could be somewhat recent and you can easily save it.

At the time, we couldn't find any known good heads. We figured our safest bet would be to track down non-Castech 706s but we found none. We ended up putting some low-mileage 799s from a 2010 5.3 on it. He lost a little compression with them. But, they were cheap and it's just his camp truck. I couldn't steer you towards any particular source for a rebuilt head. In my mind, they're all a risk. So, find someone reputable that is very much aware of such a failure and warranties their product. IIRC, a member here bought a head (or set of heads) from a rebuilder and one was cracked. The Castech failure mostly happens around the head bolt holes and doesn't show unless the head is installed/torqued down.

Huge thank you!

 

[tomloans]

Throw some alumaseal powder in it and see what happens. I would think a cracked head would show signs on a spark plug inspection?

Thanks I have sludge in the oil so something is going on for sure!

 

[tomloans]

Yep

And the other, noninvasive test I'd do, before do much as taking a bolt off: Is to grab an oil sample and send it off for analysis.


Gas check looks for, I believe CO2, which triggers a color change. You can blow fresh air through it until the color changes back to re-use it later, for what it's worth.

Also, regarding coolant schmoo: if, IF it's a combustion chamber link, one of the other things to look for is rapid pressurization of the system w/ key on and/or fluctuating cooling system pressure corresponding to manifold vacuum i.e. quickly revving it

<cheeky>

also: dude screw all that fix in a bottle stuff. If you need it to run short term or flip it (what are morals), sure. If you plan on keeping the rig - just do it right. No bottle fix is permanent. And *every* bottle fix comes with drawbacks. Sure, it'll seal the leak. But it'll also plug the heater core, rad, and thermostat (jiggle pin at a minimum). It'll also cause abrasive wear on your water pump seals. Or maybe it leaks in the oil. Mmmmmmmm abrasives in a hydraulic sytem

Besides... Assuming it does 'fix' it, that then affects your ability to perform future diagnoses.

</cheeky>

Oh, and fun fact I discovered with reading and testing: Ya know what happens when the heater core plugs on these rigs? They'll overheat. But they'll do so in a highly localized manner that won't necessarily reflect on the temp gauge. You'll see some increased temps if you have a digital readout, but even then, it'll only look on the high side of normal. Nothing that will give you any red flags until you turn the key off and listen closely.. Then you'll hear coolant boiling.

So yeah.... I'd evaluate very carefully before you start trying quick fixes.

Diagnose first. Then evaluate course of options.

I don't like quick fixes so this really resonates with me. Thank you!

 

[iamdub]

Any comments? I think this picture is the beginning of sorrows. LOL Please confirm for me. This looks like sludge and I change my oil every 3k miles come rain or shine.

View attachment 362558

I see hints of milkshake. But, during cooler weather, and especially if you do short trips, it could just be condensation that hasn't burned off yet. So that's not definitive. I feel I'm being a bit too optimistic, but we gotta remain open-minded, right?

 

[iamdub]

Thanks I have sludge in the oil so something is going on for sure!

Snowdrifter and Bill made valid points. I was focusing on diagnosing a Castech failure versus a head gasket failure. Cracking around the bolt hole(s) exposes a water jacket to the oil under the rocker covers and not combustion pressures/gases to the water jackets. Being thrifty, I'd take a closer look under the cover since that costs nothing. I agree with having an oil analysis and I have one done with every oil change. But, that takes about two weeks for the results and things could suddenly get worse in that time- making the damage more severe.

 

[Fless]

The combustion gas test that @Bill 1960 suggested would be immediate and informative, without turning a wrench.

 

[iamdub]

Would you guys change both Cylinder heads or just the one that is cracked? Would you get remanufactured or new?

I'd change both for the peace of mind. Remanufactured would be fine if the cores are fully checked, specifically for those cracks. The usual cracks, like between water jackets and combustion chambers are often much more obvious. New or refurb'ed, you gotta get whatever's available. If you happen to find some 243 or 799 for cheap, you can have 'em shaved about .025" to restore the compression ratio. You'll have the same CR but better flowing heads. Or, have 'em go .030" and run 91 octane for more power across the board if you're so inclined. Factory MLS gaskets and Summit TTY head bolts are all you need.