Pre-Warning: This is a long description, but I am trying to give as much info as I can.

OK, so, my mom has a '97 Grand Prix that has sat in my driveway for a few months now (her and my step-dad reploaced it and want to sell it, a friend of mine is lined up to buy it so long as a couple items are fixed). The big thing it needed was to have the lower intake gaskets changed. Given the cold weather, last Friday, I drove the car to a friends large garage (where he has heat, keeps it around 50-70 degrees).

The car ran fine getting to the garage (about say 15-20 minutes from my home). When I got it there, I had learned my step-dad was topping off the cooling system with straight water (the over flow bottle was a solid block of ice). Luckily, I think the highest concentration of water was the over flow bottle.
I let the car sit over night and began working on it Saturday. Half the ice in the over flow bottle had melted. When I finally popped off the lower intake, it had a little coolant (but it smelled, looked, felt like good anti-freeze).
Put everything back together. Let it sit over night to let the sealant cure. Sunday, changed the oil and started it up. Engine runs great. Sounds great.
Here comes the problem. The car will report a "hot" temp per the temp guage. Fans do not come on (if I unplug the temp sensor they will, so I know the fans at least work). I get good heat from the blower inside the car. What I don't get is the cooling system is not building any pressure. I would expect that after running say 15-20 minutes, the upper radiator hose should start to feel "firm" (either from air pressure building up, which would need bled off with the bleeder valve on the t-stat housing or coolant building pressure up to the t-stat).
When feeling the radiator hoses, cap and radiator itself, it's about room temp (maybe a little warmer, but not much). I can touch the bolts to the intake and they are warm (not scolding hot), yet the temp guage wants to go to 260 (I think it's an air pocket).
The radiator is full of coolant. It has a new temp sensor (I broke the old one and I am confident this new one is working properly) and a new t-stat. After letting the car run say 20 minutes, I can pop the radiator cap and no steam, no pressure behind it. I put a radiator pressure tester on it and it holds pressure and no signs of a leak.

Some think because of the water the car may have an ice build up in it (not big enought to crack the block, but prevent proper coolant flow). I have my doubts, car sat inside from about 8pm Friday until 3pm Monday about 50-70 degree temp (enough that all the ice in the over flow bottle has melted and I have replaced with proper coolant).

I feel the high temp reading is due to the fact the car is not building up any pressure to open the t-stat, as a result, it's making it tough to bleed off all the air in the system. To the best of my knowledge, this condition did not exist prior to it being parked in my driveway a few months ago and did not exist Friday when I drove the car to the garage.

I have a feeling this will be something small or simple, but I'm running out of ideas. Anyone have any thoughts? Something I missed or something else I should check for?

Thanks everyone! If you made it to the end of this novel I wrote, I *REALL* appreciate it! Thanks again!

 

Have you changed the radiator cap??

 

I have not changed the cap. The thought crossed my mind, but since the car did not have this condition prior, I've been hesitant.

I supposed I could use the one from my Monte or our Impala just for testing.

The one other thing like makes me reluctant is the fact the radiator, hoses and cap don't even get warm. I would think the radiator would get warm and as it "should" build pressure, fluid would start leaking from the cap (so far, no sign of that).

 

True, I was just thinking something simple that hasn't been checked, especially since if the system isn't building up the 16 psi it should, the boiling point drops very close to the normal operating temperature and the coolant could be boiling away.

 

Maybe there's air in the system. In the past, when I've drained and refilled the coolant in my Monte or Lumina, the temp gauge has gone above "normal" temperatures due to air pockets in the system. When that happens, I let the engine cool off and then top off the radiator. While the car sits, air will bubble out into the overflow tank. All was fine once I purged the air out - which took a few of these heat up/cool down cycles. There should be a "bleeder" valve on top of the engine which will help get air out as well.

 

I am convinced air in the system is causing what I feel to be an incorrect high temp reading on the guage. The problem is that whatever is going on won't let me "bleed" the air out. The bleeder screw is at the top of the T-Stat housing. Since the cooling system never becomes "pressurized", there is nothing to bleed out (after the car had been running 15-20 minutes and still running, I open the screw and nothing comes out, no coolant, no steam, no air).

During this time, before opening the screw, I can squeeze the upper and lower radiator hoses with easy, they have no pressure and I'm willing to bet, the upper hose has little coolant (but the radiator is in fact full).

The engine gets warm/hot but the radiator and hose do not. I'm really beginning to wonder if there is something going on at the water pump (such as, is it possible for the impeller to NOT spin, make no noise and yet allow the pulley to spin properly).

This is a weird one.....

 

did you notice any signs of ice in the block when you tore it down to replace the gasket?

if there was enough ice in the area of the water pump, then it could have done some damage there. it probably wouldn't be a bad idea to pull off the water pump and check it over for damage.

 

I did not notice any other signs of ice or high concentration of water. Such as when I pulled the intake off the car, it was good coolant that spilled out and the radiator is good coolant (no signs of ice).

Not saying there wasn't ice elsewhere in the system. Last night, I double checked and the belt is on properly (I had this notion "is it possible to put the belt on wrong and get the pump moving in the wrong direction", well, I de-bunked that by re-confirning the belt is right).

One theory me and my friends thought of on Tuesday is much like you suggested, perhaps there was ice in the water pump area that when I started the car and drove it did some damage and the only reason the car's temp seemed to run normal was due to other ice build up and cold outside temps).

The damage we are thinking is perhaps something has caused the impeller to free spin or disconnect from the shaft. The theory I have is to drain as much coolant from the car as I can (I really don't want to waste good anti-freeze) and remove the lower radiator hose and loosen the bely. With that hose disconnected, take a wire and carefully insert it into the water pump and by hand try to spin/move the water pump pulley (see if I can feel the resistance of the wire OR of the pulley appears to spin freely). Basically so if the impeller is doing it's job, I don't have to replace a gasket.

My father thinks that perhaps the car still has ice in the system and to use a 60 watt light bulb near the engine with the hood closed and sitting for a while to try and "thaw" out a possible ice blockage.

NEW Finding (not sure what it means): Last night, letting the car run, I squeezed the the upper radiator hose leading to the T-Stat (again, no pressure). I found while squeezing the hose and revving the engine via the throttle body, the pressure in the hose changed slightly (while revving the hose had less pressure, stop revving it and you could feel it gain a little pressure). Again, I'm certain the T-Stat was closed at this time. Does this spawn thoughts with anyone? My current thoughts are a blockage somewhere (at a higher RPM, the pump can't move enough fluid or air to keep the pressure up).

Still looking for ideas.

 

I wanted to give an update about the Grand Prix problem. A friend of mine brought his Snap-On scanner over and we let the car run. We found that when the temp guage read 260 degrees, the computer read 163. He's going to try and bring home a GM Tech II from his work as he said that will let us see what data the body control module is then sending to the instrument cluster.

But, signs point to a failed instrument cluster!! With this temp issue with yesterday the car's fuel guage was WAY off (I knew it was near empty, took it to the gas station and it claimed to have a full tank, I put $15 in to just get it to half a tank and still it read full, later on the guage began showing a correct reading of half a tank).

So once we read the BCM, I think the car is in for a new cluster.... Should be an easy junk yard item.

 

some 3.8's were built in different assembly plants and some plants ahad a batch of waterpumps with plastic impellers pressed onto a steel shaft. if there was ice build up in that area the impeller likely broke or spins freely on the shaft now.

i only point a finger at this because when the bleeder screw is opened there should be turbulence in the cooling system from flow, and coolant will come out of the screw. other possibility is air lock's in the system, i've had to snap the throttle a couple times to about 3500 or even 4000 to get the air pocket out after is was running for a bit.