Where is my coolant going?

[rapidoxidationman]

I've had to add Dexcool on a distressingly regular basis, like once every week or so. It isn't showing up in the oil, the exhaust doesn't smell like antifreeze, and the system doesn't seem overpressurized, so I'm thinking the head gaskets are good. I MIGHT be seeing a drip by the expansion tank, maybe one of the tubes in or out, but I can't be sure cuz the roads are kinda wet and snowy around here.

Is there a "common" point of leakage in the LLY cooling system?

On the upside, if I wait long enough to fix it I won't have to worry about flushing the system when I hit 150K miles...

[DmaxMaverick]

Tough one....

Have a look behind the fan pulley. There's a small tube/hose connection (turbo coolant return) that can deteriorate and leak. If you see any scale or build-up on it, or under it, that's a place to start. It's hot enough in that area, that a small leak will vapor off before dripping where you can see it.

Other than that, you'll have to trace the system looking for any signs of a leak. You can pull glow plugs and look for signs of coolant. It will usually leave a pink residue on the tip, if there's coolant present. Compare all the plugs. If one is different (with the residue/color), you may have found the suspect cylinder. The EGR cooler is another possibility, but it's less common, and harder to diagnose.

[Mark Rinker]

Exactly how much are you adding to refill each time?

If you are pressurizing the overflow and losing it there, the top radiator hose will be hard and even ballooned after the truck is shut down. At idle with a flashlight, you'll see bubbles entering the overflow jug where the return line attaches.

No drips or orange (Dexcool) puddle under the truck, ever? I doubt its the waterpump or rubber hose...

[Kennedy]

I've heard claims that the EGR coolers can leak, but have not experienced this myself. Usually when there is an EGR cloler leak claim it's a pressurized system from a head gasket and I think they are looking for an easy way out that doesn't pan out.

[JohnC]

Usually when there is an EGR cloler leak claim it's a pressurized system from a head gasket and I think they are looking for an easy way out that doesn't pan out.

When I had the head gaskets done on mine they did the EGR cooler at the same time. Seemed unusual they'd both fail at the same time... :confused:

[NutNbutGMC]

Nothing here but sharing the pain...

http://www.thedieselpageforums.com/tdpforum/showthread.php?t=36734


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[rapidoxidationman]

Thanks for the link!
The first time I added fluid I suspected there was just some air in the system and it needed to be bled - I could hear gurgling when I squeezed the upper radiator hose. The second time I added fluid I talked myself into believing the same thing. The third time I began to have my doubts. The fourth time I didn't believe it anymore.

I have, on occasion, smelled the sweet smell of coolant after shutdown. I'm going to take a close look at the hoses going into the overflow reservoir this week or Saturday.

[NutNbutGMC]

Thanks for the link!
The first time I added fluid I suspected there was just some air in the system and it needed to be bled - I could hear gurgling when I squeezed the upper radiator hose. The second time I added fluid I talked myself into believing the same thing. The third time I began to have my doubts. The fourth time I didn't believe it anymore.

I have, on occasion, smelled the sweet smell of coolant after shutdown. I'm going to take a close look at the hoses going into the overflow reservoir this week or Saturday.I have looked everywhere, tightened hoses, had pressure tests (none failed), put cardboard under the engine, talked to people, flushed ice down the toilet, stuck a spoon on my tongue, and have worn my pajamas inside out. I still have not found the issue and keep adding fluid at intervals. Now shopping for another Suburban. They are hard to come by in a used market.

Good luck and post any results if you find the problem, please.

.

[DADGLW]

had the same problem with mine also.........put in a can of sealer and its been good for 6 8 months.....just a thought..........

[Kennedy]

I hate to say it but those "Cadillac Tabs" do work well.

[Heartbeat Hauler]

On my 01 I had this issue. Long story short, I had a leaking bypass hose which on my truck is hidden. I think it goes from the rad. to the turbo, not sure. Then eventually the water pump was leaking from teh weep hole. It was so little it didn't even leave a tell tale spot on the floor. Hoses and water pump replaced, no problems. Good luck.

[DmaxMaverick]

I hate to say it but those "Cadillac Tabs" do work well.
Ditto. Start with that. If it's a bigger problem, at least this won't hurt anything.

[rapidoxidationman]

I've been looking under the hood daily since my original post and am pretty convinced the leak is from one of the hoses going to the overflow reservoir - there's a wet spot below one of the clamps and I can see where the snow is melted away in the driveway. Had to add another quart of 50/50 dex/distilled water this morning. Looks like it'll be an easy fix once I move the air intake hose out of the way, but I'll post up what actually happens.

That said, if it turns into a bear, what are these "cadillac tabs" of which you speak? Googling the term yielded this quote from acdelcotechconnect:

SEALING TABLETS:
Cooling System Sealing Tablets (Seal Tabs) should not be used as a regular maintenance item
after servicing an engine cooling system. Discoloration of coolant can occur if too many seal
tabs have been inserted into the cooling system. This can occur if seal tabs are repeatedly used
over the service life of a vehicle. Where appropriate, seal tabs may be used if diagnostics fail to
repair a small leak in the cooling system. When a condition appears in which seal tabs may be
beneficial, a specific bulletin may be released describing their proper usage. After performing
specific procedures outlining seal tab usage, install an appropriate identification label to indicate
that the seal tabs have been installed. The recommended number of seal tabs depends on the
capacity of the cooling system. Use between 1 and 1-1/2 grams of seal tabs per liter of cooling
system capacity.

Are these tabs available from a GM parts desk? NAPA? Obviously I'd rather not have the impurity in my cooling system, but if the hose doesn't turn out to be the problem and these are as easy to use as it seems... might be worth looking into.

[DmaxMaverick]

"Cadillac Tabs (Tablets)" are a GM dealer only item. Ask for them by that name/description, they should know what you mean, and have them (I don't recall the actual branded label name). The description you posted doesn't apply to them. They are used as a maintenance item after cooling system repair/service (and in new Cadillacs, hence the name). They won't discolor the coolant, build up, or have any adverse affects on the system. They are NOT "Solder Seal", or like any of the traditional sealers. They are biodegradable and non-toxic (according to the label), if that means anything to you.

[Kennedy]

Last ones I got were in a blister pack on cardboard.

Ideally you would put inside system where there is high flow, but in the Dmax all you can really do without invasive procedure is put in the surge tank. I would make sure to fill above the midway point so the tablet is immersed.

[rapidoxidationman]

The leak kept getting worse, to the point where I was adding at least a gallon per week. Finally got off my butt and pulled the airbox and air intake hose out of the way so I could get a close look at the large hose (coming from the lower radiator hose) that connects to the overflow tank, the point where I'd seen drips from. The clamp was no longer round - it was more of an oval shape so did not clamp tightly on the bottom of that hose. Replaced it with a screw down clamp and it seems to have fixed it. I'll be keeping an eye on the coolant level for the next several days as the air bleeds out of the system, but I'm thinking it is conquered with no hard work involved. Yay!