1995 Grand AM Overheat

[Nomad767]

I am getting this car from my father in law after he takes the tranny. I will get the tranny he is taking out of his car and rebuild it(just slipping some). But the former owner of this car said it had overheating problems. I am not sure what all he replaced, but after much work, he decided to replace the head. After putting this head on the car, he said it ran fine for about 4-5 hours before it started overheating again. He then removed the head and gave up. Any thoughts on where i should start? This car is in beautiful shape. Interior is just a little dirty, and the front end only has a ding from what looks like his daughter catching a trailer hitch in the grill. I can see no damage to the radiator. I was wondering if he maybe didn't bleed the coolant system when he reinstalled everything, or maybe the heater core was drained and an air bubble came from there. I am hoping to get this thing running for driving back and forth to school. Gas mileage of my explorer is killing me. Then I will give it to my stepdaughter when she turns 18 in another year.

[93GAseV6]

the car may not even be overheating, my gauges say my car is running at 250* constantly but its my gauge and not the motor at all. my gauge cluster is fubared. my car is actually running at 185*

[Nomad767]

Well, I would like to think that it may only be the guage, but the milk jug of water in it makes me think he was losing coolant. When I get the chance to talk to the guy, I will ask if at was losing coolant. But like I said, the jug makes me think it was. I don't know if it was still losing coolant when he replaced the head, or he just saw the temp rising again. As I originally posted, I am just looking for suggestions to start with. My best hope is that the head gasket just failed. I see many posts about the head gaskets going out in here, and that the GM ones are not worth even looking at.

[93GAseV6]

i have a gallon of water sittining my car too but that was because my car was low on coolent when i bought it.

[Matt95GT]

Assuming it is actually overheating (vs inaccurate gauge)... suspect list:

1. Thermostat
2. Clogged radiator (internally or externally)
3. worn water pump

Check if the water pump (under exhaust manifold) is dripping from the weep hole. If it is, that is the biggest suspect, and needs immediate attention.

[Nomad767]

Which I hate to do because of money, is to put it back together and buy the best head gasket I can find for it to see if maybe the head gasket he put on went bad. The fact it ran for 4-5 hours before it overheated sounds like it was good for a while until something went bad again. The water pump looks like it has been replaced. I will put a new thermostat in, and I will bypass the heater core just to take it out of the equation. Any other thoughts to check on would be appreciated. I may replace the radiator too. The damage in the front doesnt look bad enought to hurt the radiator, but I may see if I can find one and try it out, or at least hook it up, run it and do a feel check on it. What is the best way to check the coolant temp sensor to ensure the computer is receiving the right temp for the fan?

[Matt95GT]

What is the best way to check the coolant temp sensor to ensure the computer is receiving the right temp for the fan?

Scan tool, in view live data mode...
http://www.youtube.com/watch?v=DqbOWD6jru4

OBD 1.5 on most of the 95's makes it difficult, as not all scan tools support it. I'm using an Actron CP9145 w/ CP9127 GM OBD1 cable.

[Nomad767]

Ok, new update. I removed the radiator to run water thru and flush it out some. When I did, the water ran through some, but I had alot of backpressure. I lightly knocked it against the ground (grass not concrete) and I had a lot of rust chunks and flakes coming out of it. The more I did it, the more came out, and the less backpressure I had on the end I had the water hose in. I continued to do it until I could barely get anything other than water out. So I am thinking this radiator was plugged. Now the question I have, is, I have never had a vehicle that had was filled from the tank next to the radiator, so what is the best way for me to flush this engine without the radiator in it to ensure that whatever I get out does not get in and plug the radiator again. Don't get me wrong, I am not somebody doing this for the first time, I am just looking for other thoughts and ideas that might help clean this up good enough to keep the radiator from plugging when I put it back in.

Edit:
My biggest reason for all these questions is that this is my first GM car to have to deal. The only ones I have really helped people with were older muscle cars, and I don't they compare in the way the are set up, so I am trying to get it done right and cheap (meaning the first time).

[Matt95GT]

There's no easy way to do a complete "in vehicle" flush, other than filling the coolant system with water + coolant flush additive and running for several minutes. When I "flushed" my system, I did this a few times (fill with water/flush, run, drain, fill with water/flush, etc) then drained and filled with the anti-freeze mix.

[Nomad767]

I have started to get this thing back together, but the person who had it before me took everything apart and I have no clue which bolts are which. Does anyone have a picture of the intake and exhaust mainfold bolts, or somewhere online they know that I can get a good look to figure out which bolts I need to use? I am trying to get this thing to a point that I can flush the coolant section of the engine and head before I connect the hoses, but I want to have things to a point that I won't get water in the engine. I also found some peice of aluminum in the engine head coolant section before I put it on. Must have been something left over from the casting. It almost looked like half a chain link that was twisted. This head was on the engine at one point, so I am glad I found it before it got somewhere it may mess things up.

[Nomad767]

Well, Got it back together and ran it, and now it is torn back down completely. Block is last thing I need to get out of the car. Rod bearing were so worn when I started it, they were hitting the exhaust valves in 2 cylinders. Found out that the car actually sat longer than I had originally heard. It has been sitting in the guys back yard for about 3 years. I really hope I can get this thing going again, but now it is a matter of money instead of time.