Engine Overheating Problem

[jayc]

We are taking our grandsons on a short vacation. The day before yesterday, we were traveling through the Texas hill country near Kerrville TX when the low coolant light came on. The temperature gauge didn't show hot on the dash, so as soon as possible I pulled over to check things out. I found no leaks but could detect a faint odor of coolant in the front of the truck. I added some water and the light went out. We continued on but I noticed that the engine temp went up on the next hill, especially when the transmission dowwnshifted to maintain speed. On the down side of the hill, the temp returned to normal. It did this a few more times before it settled down and ran at normal temperature.

We pulled into our overnight stop and after letting everything cool off, I checked further. Everything seemed normal, so we continued on our trip. The truck performed perfectly yesterday with no overheating at all. We stopped for lunch and left the dog in the truck with the motor running and no overheating.

The only thing I can think of is that there may have been some trash that may have somehow gotten into the cooling system and plugged things up. I checked the fan for play and it seems to be okay, the fan belt is new and seems to be at the right tension and not slipping and I don't see anything leaking.

My truck is a 2002 GMC with the Duramax diesel engine. It is high mileage (212,000 miles) but runs strong and holds good oil pressure. This is the only cooling system problem that I've had. As far as I know, nothing in the cooling system has been replaced. I know that another radiator flush is necessary but can't think of what else to look at.

 

[Rrloren]

When I had a similar problem with my old truck it turned out to be a head gasket. The mechanic checked for foam or water in the oil but found none. Mine would run normal until stressed with a hard pull or in heavy traffic. Without the trailer it would not overheat.

 

[jmgratz]

I had a problem in a previous vehicle and it turned out the radiator was stopped up (externally) with bugs. A good radiator cleaning and I was good to go.

 

[JohnDar]

Since it was your low coolant light that came on, it could be a minor leak from a hose or connection that has finally gotten to the realm of the sensor's low reading. Especially since you said you could detect the smell of coolant. Adding water to the coolant diluted it and changed it's heat dissipation temperature a bit until it mixed. (Was the overflow reservoir empty/low?) Check around your radiator for any small pinholes from hitting airborne stuff on the road, like buzzard-sized bees.

 

[Jellystone]

Jay, just a thought, your oil cooler may be partially stopping up with debris and this could be letting radiator fluid come out of the overflow. Loseing the coolant could be putting the fluid level below the sensor. Bryant

 

[newbie]

I have an 08 Duramax and got the low coolant light once the day after hard, hot mountain pull. Everything under the hood looked fine. I did some reading over at Diesel Place and learned that some guys over there had the same problem ...the fix...they filled the reservoir about a half inch higher than the full mark and the problem went away. I did the same thing and haven't gotten the message again. It's worth a try. Hope it's not your head gasket, that would really suck.

Good luck,
John

 

[wdk450]

A simple test that most shops can do is to pressuize the coolant system with a tester and see if it holds pressure (to check for leaks).

 

[jayc]

Well, the update is good news. I completed our trip to Carlsbad NM without any further problems. The temps never budged off normal, so we came on in. When I got here, I took the truck in for an oil change and radiator flush and found the radiator was a little low in coolant, which was corrected after the flush. We also pressure tested as well as doing a vacuum test and found no problems. I think that somehow the truck got hot and boiled some of the coolant out. It wasn't caught at the time, but this apparently was what caused my problem.

I want to thank everyone for all the suggestions and help that was furnished.

 

[hoefler]

It is normal for a cooling system to loose a little coolant due to evaporation. Since your temperatures never went above normal, I would say you never had a cooling problem, just a little low on coolant.

 

[JohnDar]

Cool, I like easy fixes like that. Don't ask me about going to the dealer to get a $2 fuse replaced for $40 because I didn't think to look in the "other" fuse box.

 

[jayc]

I am certainly happy now that everything is working well. We've been to Roswell and driven the hills around Carlsbad and the temp gauge hasn't budged.

Like John said, if I had taken the truck to a dealer, he would have kept it two days and charged me $400 to do the same work.

 

[jmgratz]

Cost me $800 to get the radiator cleaned (outside of it) at the Ford dealer in Laramie, WY. Now I put a window screen in front of the radiator to keep the bugs out of the radiator. When it gets bugs in it I just replace it. Sure is cheaper.

 

[jayc]

Well, I thought I had the problem fixed. I drove around the Carlsbad NM area for a couple of days and drove approximately 200 miles without a problem. This morning, I checked the level in the overflow tank and it was correct. We pulled the trailer for about 3 hours, covering a lot of miles before the low coolant light came back on. I stopped and bought a gallon of coolant and added it and came on to Las Vegas NM on our way to Colorado Springs.

I only noticed one time when the temperature gauge rose to 235 degrees or so when we were going up a long hill. Normal is 203 or so. It never made it into the red on the gauge and as soon as we started down the hill the gauge returned to normal. I don't see fluid leaking but it has a faint hot smell of coolant. Being late on Saturday afternoon, no mechanics are available. We are supposed to go into Colorado Springs tomorrow, so I'll probably go on and keep an eagle eye on the gauge.

 

[Invizatu]

Sounds like a very small leak that is happening under load. It is probably so small that it is evaporating and then stops when you slow down. They are difficult to find until they give out. Could be a hose clamp or a pin hole in a hose or a gasket at the thermostat or seal around the water pump or a radiator cap seal etc. etc. Usually find by looking for dried up residue near leak. Or worse case scenario a very minor (at this time) internal leak. Been there and done that, hate it. Good Luck and keep us posted.

 

[Tom of Ypsi]

Jay,

Should have bought Ricky's truck when you had the chance that was a good deal. Good luck on your travels and be safe and have fun

 

[jayc]

You know Tom, I thought about it but it IS a Ford, and that probably would have made me ill. And to think I was born and raised a Ford child. My dad was a Ford dealer. Give me a deal on another GMC or even a Chevy and I'm happy. I may even be persuaded to look at the new Dodges.

 

[jmgratz]

Hopefully you don't have a freeze plug leaking. Could also be the heater core.

 

[JohnDar]

If it is a small leak, it is very possible that the liquid does not make it to the ground. Look all around (as much as you can, anyways) for crusty deposits at any gasket seams, hose connections and freeze plugs. Check the outlet on the overflow reservoir, too, for any evidence of stuff flowing out.

Was your cooling system pressure tested?

 

[lwmcguir]

Your fan clutch might be getting weak and on occasion letting the temp rise a bit more than normal even though you might not see it on the temperature gage. On a Ford (the only truck to tow with) you can sure hear the fan come in however that don't happen often so it gets your attention.

 

[jayc]

I'll continue to check for any deposits but I'm really beginning to think the problem is with the low coolant sensor. The LC light came on this morning after I checked the coolant level before we left this morning and found it above the mark by about an inch. The temp gauge worked and showed the temps rising to 235 degrees, not into the hot zone, when it downshifted when climbing Raton Pass, a 6% grade. when coming down the other side, the temp fell substantially below normal operating temperature. Lots of air flowing through the radiator with little accelerator pressure. The truck does not overheat AT ALL! I believe it is in the idiot light for low coolant.

If the problem is in fact with the light, I'm thinking that any parts needed will have to come from a dealer because they are not likely to be available aftermarket, so I'm taking it to a dealer to have it checked.