1995 3100 overheating at idle

The car is overheating when either stuck in traffic, or simply idling (Worse when in gear). Prior to now, I would always keep the A/C on either Bi/lvl or Defrost and that keeps the fan on constantly and the car ran just fine. But, as of the last few days the car now overheats quite a bit at idle/low rpms. I tried hard wiring the fan into a toggle switch because my 134 must now be low and is no longer kicking my fan on (Or the compressor). This does not help any. When the car is overheating, I quickly hit the gas (to about 3k-4k RPM) and the temp quickly drops to the normal range, then steadily returns to overheating.

The car does use coolant, but I believe it is an external, cold water leak as I did pressure test the system when it was hot, and it remained steady. I only use about a quart of coolant a month, if that.

The car has 306k miles on it now and has given me very little trouble. The car burns 0 oil. I only use it as a commuter, but I feel it's days of reliabilty may be coming to an end.

Is it possible the stat is sticking slightly, and the surge of the motor is "Knocking" it to open? Or is this phenom a known symptom.

Could be lime and scale restricting flow somewhere and the water pump can't build up enough pressure at idle to overcome it fast enough. Especially at 300K. Radiators are notorius for clogging and restricing flow when they get old. Have you had the system flushed in recent years? Could be something as simple as air in the system too. If your recovery tank is empty, the system will draw air when it cools down. Might want to pull the cap while it's running and watch for circulation at idle. You'll at least purge air out doing that. Doesn't hurt to replace the stat. They are cheap.

While I wont rule out the possibility of any buildup in the system. The overflow tank has never been empty, therefore I can't imagine it's getting air bound. I might want to re-state this, cause even to me it doesn't make sense. It overheats at idle, and more when it is in gear... but all you have to do is literally "Whack" the gas pedal, not sustain a high RPM, just simply "Shock" the system...

I'll probably try a new stat next week and rebleed the system. We'll see how that turns out, otherwise... it may be destined for a salvage yard. But since I've owned it since day 1.. I can't complain too much...



Oh, one other thing, how would I see circulation in the overflow tank... as there is no physical cap on the radiator. (If I recall correctly, fluid moves slightly.. not in any particular direction but a general "movement" to it) Also, system has never been flushed, but I did replace the radiator fluid every 3 years.

While I wont rule out the possibility of any buildup in the system. The overflow tank has never been empty, therefore I can't imagine it's getting air bound. I might want to re-state this, cause even to me it doesn't make sense. It overheats at idle, and more when it is in gear... but all you have to do is literally "Whack" the gas pedal, not sustain a high RPM, just simply "Shock" the system...

I'll probably try a new stat next week and rebleed the system. We'll see how that turns out, otherwise... it may be destined for a salvage yard. But since I've owned it since day 1.. I can't complain too much...



Oh, one other thing, how would I see circulation in the overflow tank... as there is no physical cap on the radiator. (If I recall correctly, fluid moves slightly.. not in any particular direction but a general "movement" to it) Also, system has never been flushed, but I did replace the radiator fluid every 3 years.

I assumed you have a radiator cap for checking circulation. No, I wouldn't rule out restriction somewhere in the system. Is your water pump belt driven? If so, the second you hit the gas, you increase the water pump speed, increase coolant velocity, overcome restriction, and remove heat instantly. At least that has been the case with cooling problems of your nature for me. Coolant velocity is controlled by flow restriction and pump speed.

You may want to try removing hoses from the radiator and peak in the nozzles to see if you can see scale and lime built up in there.

Kill two birds with one stone.
the easyest and least expensive first move on the majority of the overheating problems is the thermostat replacement.
At that time you can check for whatever inside but I bet it is clean . You changed the coolant every 3 yrs. I cant see a build up happening there.
blead the system and see what it does.
Have you checked the tention of the belts?

Unit has a serpentine Belt with an automatic tensioner so I assume to tension is ok. This weekend I'll probably change out that thermostat and take a gander at the insides. It's far easier to just drive another vehicle then actually fix the old broken one... lol. I'll keep you informed, and appreciate any input. Thanks

Unit has a serpentine Belt with an automatic tensioner so I assume to tension is ok. This weekend I'll probably change out that thermostat and take a gander at the insides. It's far easier to just drive another vehicle then actually fix the old broken one... lol. I'll keep you informed, and appreciate any input. ThanksCheck the signature. ask someone who has owned a Beretta for sixteen years, 274,000 miles and has 17 in his "spare parts yard"...

you are proby leaking around the intake 3.1 are bad for that for a fast fix unplug the temp sen that will put the fans in safe mode and they will run the whole time the car is running the cut off when you turn it off so no problem with battery life