A Severe Overheating Problem -1995 Jimmy (I did a search – no help) - Anyone

[DelCoch]

My son has a live scanner, but he lives an hour from me. It will be a couple weeks before I will have a chance to run it on my Jimmy.

However, the electric cooling fan has its own heat sensor, which I installed inside the left radiator hose at the radiator. The elec fan is set to come on at 220 and go off at about 195, which is what the stock heat gauge reads when the electric fan goes on & off. Thus, I believe the heat gauge to be accurate. Plus, when the outside temp is 70, the heat gauge runs at 195 like it should. As I said before, it only overheats when the outside temp is 85 degrees or above. Yes, I still have the OEM fan shroud on.

Prior to adding the electric fan the heat gauge easily pegged out in the red in town and ran about 230 on the highway, when not running the air-conditioner. Adding the electric fan improved things, temp reads 230 on highway with air running and will go into the red in the city, but it no longer pegs out all the way. Since it improved the situation, I don’t think the electric fan is blocking air flow. (it’s mounted on the inside of the radiator) And, popping the hood onto the safety latch to allow more air into the engine compartment, when driving down the highway, has no effect on cooling.

Also, I don’t have fog lights or anything in the grill to obstruct the airflow.

I guess the only thing left is to try a fast flush and a back flush with the garden hose. Although I haven’t done anything to cause it to change, I probably should check the timing. It may have changed on its own and be a little advanced, but I doubt that. Or, I could ask the radiator shop to build me a bigger radiator. Other than that, I flat give up.

Does anyone know if a radiator for a 1998-2003 is any larger than my single core and maybe bolt into my 95?

DelC

[drdd]

have you checked your rad-to-overflow rubber tube?

I know mine was completely blocked with crud causing all sorts of weird problems temperature spiking problems. I completely took it off and had to ream it out with a coat hanger. I also reinstalled with some better quality hose-clamps.

good luck

[2000CAYukon]

How is the engine running? I have a 90 GMC K1500 that has been running warmer than I wanted it to. Not as warm as yours but warmer than normal. I have also been fighting a rough idle when warm. Recently, I replaced the pickup coil trying to find my rough idle. Right away, I noticed that the low end roughness was gone. I was also surprized that it started to run at the normal temp again.

I suspect that my rough idle/miss (I could see the miss with a timing light) was causing extra fuel to be dumped (since the plug was not firing) and the computer leaned out the fuel to compensate. Running leaner (I think) caused it to run hotter.

Something to look at when get it hooked upto a scanner.

//2000CAYukon

[DelCoch]

Originally Posted by drdd

have you checked your rad-to-overflow rubber tube?

Yep, overflow tube is ok. The thing is, I never had any gunk in the radiator, ever. The coolant looked clean when I started messing with it. Guess I should have left it alone.

DelC

[DelCoch]

Originally Posted by 2000CAYukon

How is the engine running?

Engine runs fine - never misses a beat, idle is fine. Gas milage is where it has always been, 20 mpg on hwy.

[CharlotteHawk]

Perhaps I missed it but have you checked your radiator for cool spots? And as for runniing a pressure washer through your radiator, this will not tell you if there is a partial plug inside. Water will find a way out unless the radiator is COMPLETLY plugged. When the radiator is warmed up you should be able to tell by touch if it is uniformly warm, if there are areas that are noticeably cooler than I would lean towards a partial block which will cause overheating at higher speeds.

[DelCoch]

Originally Posted by CharlotteHawk

Perhaps I missed it but have you checked your radiator for cool spots? And as for runniing a pressure washer through your radiator, this will not tell you if there is a partial plug inside. Water will find a way out unless the radiator is COMPLETLY plugged. . .

Maybe I didn't explain it very good, but the radiator guy took the tanks off the radiator and ran the pressure washer through the tubes of the core, and said it appeared to be fine.

I haven't checked it for cool spots, as there isn't room to get your hand between the radiator and the air conditioner core, and I have the electric fan on the other side. I guess I need an infra-red / laser type thermometer.

DelC

[JimmySLS]

You said your antifreeze still looked green?Have you always had the green antifreeze?I was just asking this because if you ever had dex cool in the engine prior to the green and if the engine wasn't flushed good enough that maybe your problem..

[DelCoch]

Originally Posted by JimmySLS

You said your antifreeze still looked green?Have you always had the green antifreeze?..

Yep, it has always had green in it from day one - I'm the original owner.

DelC

[bgr8ful]

I have been looking for days on the web, trying to locate someone else who is haveing the same overheating issues with a 4.3L GMC Jimmy. DelCoch's issues are identical to mine. My Jimmy runs entirely too well for this to be an unrepairable case. There has GOT to be a resolution. Please keep posting ideas. Would like to discuss via phone with Delcoch if possible before I lose my mind!

bgr8ful

[DelCoch]

bgr8ful,

I sent you a PM.

[bgr8ful]

Dont see one. I thought I sent you one yesterday as well. Guess you didn't get that either. Email me at bgr8ful@sc.rr.com. Thx

[blazes9395]

I had a problem like this on my old astro 4.3. I flushed the antifreeze and after that I had a warmer running engine. It turned out to be my intake gaskets were leaking internally, the flush loosened up some scale build-up and caused a leak, but it was being burned off while driving. This leak was big enough to make it run hot, but not really big enough to see it come out the exhaust pipe(as white smoke). I replaced the intake gaskets, throughly cleaned the intake - problem was solved. It took awhile to figure out through, because i had no leak. Also like rilth said, ever try a good back flush of the heater core? You can by-pass that by disconnecting the lines and connect them to each other. Also did you ever get the system pressure tested? Did the rad itself get pressure tested at the rad shop?

[DelCoch]

Originally Posted by blazes9395

I had a problem like this on my old astro 4.3. . . . turned out to be my intake gaskets were leaking internally, the flush loosened up some scale build-up and caused a leak . . ever try a good back flush of the heater core? . . . Also did you ever get the system pressure tested? Did the rad itself get pressure tested at the rad shop?

Internal leak is a good thought, as I do have a lot of condensation coming out of the exhaust when I first start it up. At least, I thought it was condensation, but now you got me wondering. The second muffler rusted out about a year after I started having the overheating problem. However, I never lose a noticeable amount of coolant.

I can't see where a plugged heater core could be a cause, as the coolant doesn't even attempt to flow through the heater core when the heater is turned off. Plus, when I turn the heater on it helps cool the coolant as it passes through the heater core. Also, if the heater core was blocked the heater wouldn't blow hot air.

Nope, no pressure test on anything, but I have a radiator pressure tester, so I will do a pressure test in a day or so. I do know the radiator has pressure when you go to take the radiator cap off when the engine is at operating temp, but maybe it don't have enough.

An internal leak into the intake is about the only thing that makes any sense, as I have replaced or checked everything else. But, I would think a coolant leak into the intake would make it run cooler, not hotter. Wouldn't the coolant leaking into the intake help cool the engine?

I must say I'm not a novice at mechanic work, as I worked as one for several years in my younger days, but I'm out of touch with current trends.

[blazes9395]

Originally Posted by DelCoch

An internal leak into the intake is about the only thing that makes any sense, as I have replaced or checked everything else. But, I would think a coolant leak into the intake would make it run cooler, not hotter. Wouldn't the coolant leaking into the intake help cool the engine?
.

If you have a leak, or an opening in the system, it will not run cooler, but warmer because it would not reach its operating pressure, and therefore be ineffecient.