Engine too cool issues with 2005 LLY

[n5lfh]

Nope, it's not another overheating complaint I have, but a drop in the normal engine temp range. I am the only owner, truck has 108K miles and normal engine temp has been 210 deg all it’s life…Texas hot or NY cold, unloaded or towing 10K lbs.
Several months (10K miles) ago I began to get the "Low Coolant Level" warning. I have gotten this message probably 10 times total. I didn't notice coolant blowing out, but would top off the coolant reservoir. Warning would stop, but coolant was going somewhere. About 7000 to 2000 miles ago, I began to get some blowout from the reservoir, but the engine temp was still a constant 210 deg. and we were in the high altitude of the Rockys. The truck hadn’t been over 8000 msl before then. Maybe the LLY didn’t like high altitude. Two weeks ago, after driving about 100 miles, I saw a pretty good size wet spot of coolant on the driveway. I also noticed the engine temp didn’t get above the 170 deg. mark on that trip. Dealer said the water pump was leaking and replaced it and the thermostats. All he could get were 180 deg. stats. Of course now I don’t get my normal 210 deg. engine range, but worse the temp gauge (and actual coolant temp) will change 30 deg. and is constantly on the moving between about 180 to 210 deg.
First, I can’t see why 210 deg thermostats aren’t avalaible, but mostly what is causing engine temp to be on the move constantly.
If you’ve got an idea, I’d like to hear it.
Greg

[Jake99Z71]

IIRC one thermostat is 180* and the other is 185*. Duramax has never had an option for higher temp thermostats. I would buy the correct one to replace the 180* that shouldn't be there.

[DmaxMaverick]

Having two of the same, lower temp stats in place would likely cause the condition you see. Not only will it allow full coolant flow at a lower temp, it would likely be abrupt opening and closing, compared to a staggered stat. Essentially, its progressive ability has been removed, causing the wild swings. The original stats (unless they are physically damaged or defunct), or OEM rated replacements should be installed.

[Mark Rinker]

It sounds likely from the coolant loss and temperature swings that you have developed a head gasket problem.

[JohnC]

It sounds likely from the coolant loss and temperature swings that you have developed a head gasket problem. ...which caused the water pump to leak...

Is the upper radiator hard as a rock? Is it still that way the next morning? If so, you may have a head gasket problem...

[n5lfh]

I've only put 30 miles on since the repair.
Water pump leak is fixed.
Radiator hose is soft when cool...someone said if the hose is hard...head gasket, but I'll try the pressure in the reservoir test.
Air in the system has been my thoughts too, but the tech at the dealer knew about the air bleed screw.
I had the oil changed right after the pump and stat repair...it looked good and you'd think the tech would say something if there was oil in the old coolant.
I truely believe the temp gauge is acurate (don't think I'm being too faked out). I don't see how the normal temp range had been so much higher for 4.5 years with 180/185 stats unless GM does not put those higher ones on the shelf.
Not much hot air from heater and heater core in/out lines were only warm to touch, so again I believe the gauge and actual temp is pretty close.
I ask about compression check and was told all cyl. were 100%...seems they can do that test thru the computer.
Really thank you for your thoughts.
Greg
2005 LLY CC SRW

[Mark Rinker]

Ahhhh...makes more sense, now. Give it time to work the air out of the system. Don't sweat the t-stats just yet. Search elsewhere on the Duramax forums to see what people have done to release trapped air.

If the upper radiator hose gets hard when engine is up to temp, and stays hard after engine cooled down - OR - you experience coolant loss out of overflow jug, well...then you likely have a head gasket problem.

If it were me, I'd drive the truck until fully warmed up, checking for excessive pressure on the radiator hose or overflow tanks, crack the cap on the overflow tank and let it idle for 30 minutes, close the cap and repeat for the next few days, or trips with the truck.

*** TEST UPPER RADIATOR HOSE FOR RELATIVE PRESSURE, BEFORE RELEASING PRESSURE AT OVERFLOW TANK. WEAR GLOVES AND EYE PROTECTION...OPEN SLOWLY...HOT HOT HOT ***

[JohnC]

I would not open it hot. The cap is on a tube that extends into the coolant. If there's pressure it'll push water, not air, out the cap.

[Mark Rinker]

Yeah its pretty hard to get it open without a fountain of hot coolant.

[n5lfh]

I have had pressure in the coolant reservoir and some antifreeze blow out in the last 10K miles, not under the testing proceedures described earlier, but didn't think much about it. Mainly, for the life of the LLY, I haven't had to open the reservoir cap and add anything. The level always seemed OK. Flushed the system at 60K miles.
It's at a dealer doing compression and getting their thoughts. This is not the dealer that replaced the waterpump/stats. Runs fine, no smoke or other odd experiences. The stats that were replaced were 180/185. Wonder if they are backwards?
I have seen some other 2005 LLY posts about the "A" head gaskets failing, but my GMPP ran out 6K miles ago. I was getting the low coolant warning before it ran out and stopped at a dealer in OK City, but didn't run it thru the shop. I'm still gonna call em.

We'll see....
Greg

[Kennedy]

If the dealer got the stats from GM (Isuzu) then they are correct temp as there are no options. I'd have to test to verify, but I believe they cannot be installed backwards or in the wrong holes or even if this was done it wouldn't hurt anything. A guy would have to have a major Duh moment to mix up the stats anyhow.

[n5lfh]

Hhmmm...wonder what happened to my latest posts. I mentioned replacing the coolant cap and other info...

[Mark Rinker]

Good luck with GM Customer Service. They are toeing a hard line with warranty exceptions/extensions.

Get your timeline and supporting documentation in place. You may want to consider printing this thread, with dates, to show how long you have been troubleshooting this problem.

Good luck - sincerely.

[whylly]

My worst nightmare became reality while towing my 30' camper through the mountains of Kentucky during extremely high temps this summer. Started using coolant and getting warning, but made it home to Idaho. Replaced the cap when I got home. Thought the problem might be solved when I could drive around without losing coolant. I saw the temp swings, pressures in the hoses, and warnings mentioned in this forum. Then I put the truck under load and dumped coolant all over my driveway!

So, I read lots of blogs and let it sink in before taking it to the dealer to confirm my fears. My warranty was up in April, gasket went in late June. Went to dealer and practically begged for mercy. The dealer/GM agreed to cover all but $2,000 of the repair after confirming I had no "enhancements" to the vehicle. I authorized the repair, knowing that the aluminum head(s) would have to be replaced and could not (safely) be milled.

I stopped in the other day and saw where the pass. side gasket blew and warped that head. My cost of materials would have been about $500 for gaskets and misc. parts plus about $1,500 for the one head! So I feel a little better not taking it on myself.

My problem now: should I trade the vehicle off? Mechanic says it will be like a new truck again...I plan to travel the Southwest next summer...

[Kennedy]

I seriously doubt that the "A" gasket is any more susceptible to this than any other. The block deck machining is zebra striped (I have pics) on these production engines and the fasteners marginal at best. When doing these we just default to teh C grade gasket as it cannot hurt you. We also skim cut the head surface to get reid of teh impressions left by the fire rings and use studs for much better clamping force.

Fix it right and it will last a long time...

[whylly]

Thanks for the reply Kennedy. I agonized over whether to take the truck elsewhere, but everyone in the Spokane/Coeur d'Alene area thought it was best to take it to the dealer. They all seemed to say that they weren't comfortable doing anything with the heads besides replacing them. I was unable to find anyone that had even done the head gaskets on an LLY. They were shocked to hear they had gone at 82,000 miles...

As far as the dealer is concerned, the mechanic seems knowledgeable, but he "isn't allowed" to use anything but GM parts, methods and specs. As I've read on this site, gaskets have been redesigned and should prove more reliable. But if the mechanics aren't experienced with the methods you are suggesting, maybe I'll see the same problem again. I will ask them about your advice, though. Doubt that he knows the diesels that well. He works on anything that comes through that dealership...

I love my truck...it's in great condition and has lots of add-ons. But, I'm not against "trading up" to the cooling system and 6-speed in the 06-07 Classic, and I'm even closer to considering the '11 with the improved fuel economy.