'95 3100 Overheating problem

[Compufreek]

Last year (Nov) I did my intake manifold gasket and head gaskets. When I did that I switched to Dex Cool. Since that was done everything was going good then I started noticing my car running warm sometimes but recently it got close to overheating. Well I had to go in to replace a couple colapsed lifters (from the IM gasket going the first time) I did the lifters as well as a water pump and new thermostat (stant) last weekend but it was still heating up. Well I figure everything is new so it must be a bubble. I got a flush and fill kit as well as ran some super flush through it. While I was doing the super flush for the 10 min the car heated to the right temp and ran fine. Well I flushed it out with clean water again and added the dex cool. Once I did this and was running it to get the coolant mixed well it started heating up again. I don't know what is left to check, anybody have any ideas?

[ikessky]

Why did you switch to Dex-Cool? Most of the guys that I've talked to that were originally using Dex-Cool have switched to the good 'ole green stuff after doing their gaskets.

[Compufreek]

Did want to have to worry about doing a flush and fill once a year, LOL. I am trying to make the car basically maintence free for the next year or two. I have been considering going back though because that is the only thing that is left that is not the same as before or mechanically new.

[geoffinbc]

What ratio are you running? Sounds like you need more water. Make it 50/50 (water to coolant) or maybe even 70/30 (water to coolant)

[Compufreek]

If anything it is kinda week I put in maybe a gallon of coolant and and the rest water. It is wierd becasue it is not overheating anymore but it is getting really hot and sometimes the heat goes cold. That seems to have stopped but the car is registering 220-240 but the hoses are not overly hot.

[ikessky]

If the heat is going cold, perhaps you have a bad t-stat....... Make sure that it is not just a bad temp sender also as that will drive you crazy chasing other parts and what not.

[Compufreek]

Yeah but it was running at temp correctly with the flush and water in it. That is why I am lost, LOL. I saw the thing work. Has anyone heard of this maybe being caused by dex cool?

[Juglenaut]

It is the the regular water most people add, when replacing the coolant. This causes the coolant to be more corrosive and/or caustic.

I always run straight coolant or premixed.

[Anonymous]

Did you bleed the system when you filled it, may have air in there.

[Compufreek]

The small bolt just above the water pump has been sheared off but the right near the thermostat housing I did bleed and staight coolant came out for a good amount of time.

[Cliff8928]

My coolant is 1/2 dex-cool, 1/2 distilled water. Just like reccomended..


Cliff Scott
89 BerettaGT
89 Volvo740

[Compufreek]

Well then I am good. I was just out in a crappy ass rain storm testing some theories. The car was cold so I monitored it as it warmed up. The gauge was reading that the car was warming up fast but all the hoses had preasure in them and were only slightly warm. same with the head. As it got to 220-240 area on the gauge I was still able to touch the motor and the hoses even the metal return line that runs across the front of the motor. They where just warm not crazy hot like I would assume they would be. I am starting to think the sensor is gone. How hard is it to get at, according to the Haynes manual I have it is near the ICM but where?

[ikessky]

I forget which is which, but there is a sensor in the rear head and then there is one by the t-stat housing. I thought that the one by the t-stat was used for the guage and the one in the head was used for the computer.

[Compufreek]

Why would there be two and should I change them both? Is there a way to tell what the computer is seeing for temp?

[ikessky]

I'm not a GM engineer, so I have no clue why they put 2 on it. When they switched to OBD-II they went to 1 (3) wire sensor. I would imagine that if you are not having drivablity problems (just seeing the gauge go too high), then it is the one in the t-stat housing.