I followed the service manual to the letter when replacing the water pump and the removal and install went very well. My question is how to tell if all the air is out of the cooling system? On my 95 there was a bleeder valve on the t-stat housing but how do you do this on my 98? I refilled the coolant while leaving the upper radiator hose off until coolant came out of the upper radiator hose then put the hose on and tightened it. The rest i did as the service manual said. I replaced the t-stat as well but now my engine temp is much higher than before. Previously i would be at 194* while crusing down the highway with the air on and now it's at 212*. What would cause this? Could the previous owner used a 180* t-stat?

 

212 sounds normal to me in sunny and warm summer weather.

 

Well before it would run 194-195* in 85 degree weather. After the change it's running 212-214 at night in 80 degree weather. Any ideas?

 

Maybe it was a cooler t stat. If you have the old t stat, check to see what degrees in celsius is stamped on it. But at least it's not overheating.

 

I am running the stock thermostat and in hot weather running at speed (not in traffic or driving slow) my temps are in the 192-196 area. Something appears to be amiss. If you have a set of ramps, drive the front up onto the ramps and once the motor cools pull the cap and check the fill again. I have changed mine a few times (cam, heads, etc.) and the only difference I can think of is the front of my car is usually higher because it is on blocks and I never had a problem. I also have an 02 and have been told the earlier cars were more difficult to purge of air, not sure why but hopefully someone can step in with the answer.

 

With a COLD engine be sure the coolant reservoir is at the FULL mark. If there is air in the system, after a run that heats the cooling system to about 200 degrees (and for long enough to have opened the thermostat) two things should happen:

1) The expansion of the air in the coolant should cause at least SOME of the air to bubble out into the reservoir

2) As the system cools after you shut off the engine, coolant from the reservoir should be pulled back into the radiator system, replacing the air that was bubbled out.

Possibly you had a lot of air in the engine block and it will take several heat/cool cycles to replace the air with coolant from the reservoir ... so ... KEEP CHECKING THE RESERVOIR .... if the level is dropping after a heat/cool cycle that is a clear indication that air is still being displaced.

If you're pretty sure all the air is out of the system, and you're still running at about 212 on the highway (which seems high regardless of the thermostat opening temperature) ...

1) Check that you put at least SOME antifreeze (50/50 is recommended by GM ... you can ... if your car is not exposed to freezing temperatures ... go with a 70 percent water 30 percent antifreeze mix) in the system .... an all water coolant doesn't remove heat from the engine as effectively as a water/antifreeze mix does.

2) Check the radiator area from under the car to see if you recently picked up some debris (such as a plastic bag or sheet of newspaper) in the intake area just behind/above the front air dam.

3) Check the serpentine belt and water pump pulley to make sure there is no slippage of the belt across the pump pulley. The belt tensioner and belt should be checked.

HTH

 

Good point

 

Thanks guys for the suggestions. I went over the fill proceedures again this morning while checking those items suggested in the above post and all seem good. However, the car still runs around 208-212 cruisng down the highway with the air on. I guess I'll drive it for a couple of days while carefully watching the temp and checking the overflow resivoir.

 

I had a similar issue that actually got bad enough that the hose blew off. I found air in a fitting on the top of the block. I'll try to explain. as you stand at pass side under the hood, just on the other side of the wheel well, there is an aluminum tube with I belive a 10mm fitting (banjo fitting I think). I loosened that and let some antifreeze bubble out. after that it was fine.

 

Why did you take the upper radiator hose off while filling?
I have drained and refilled my system with all the hoses connected and never had a problem.
Are you sure you got the correct antifreeze/water mixture and that the coolant recovery tank cap is holding the correct pressure on the system? It might be worth replacing the cap if you have not done so in awhile.

 

I think that probably the thermostat is just a little different. It's not overheating. Don't sweat it.....

 

Ditto...Also, the old thermostat could have been stuck open slightly.

 

212 isn't even close to overheating, so don't worry.

 

All seems to be good. I wasn't too concerned at the slightly higher temp but was just curious if 212 is a normal temp. Before the car ran at or near 194 before the water pump took a dump. Thanks for all the advice.

 

That's right, 212 is not overheating and you can probably leave it alone, but it is higher than "normal" on your car prior to replacing the old one. My car (2000 MN6) runs at about 196 cruising on the highway (65-80 mph speeds) with a stock thermostat in up to 100 degree weather, as well. I think that's fairly normal unless you're driving up a mountain pass or something. Maybe I'm picky, but I'd probably be thinking about swapping the thermostat again if it were my car and I was confident that the air was purged from the system.

 

I agree about swapping out for another new 192 degree thermostat........running 20 degrees over normal, isn't where I'd want it to be.

 

Having a 192 degree thermostat does not mean that your car will run at 192 degrees. It simply means that is when the thermostat starts to open. I have a 160 degree stat in mine and it runs 176-178 degrees.

 

Sure - I didn't see where anyone said different. If you have a 160, it will basically always be open unless it's freezing cold outside and you will run at whatever the radiator and fans can keep the temp at. In your case, that's 176 degrees.

Your post sort of implies that "JJ 86"s cooling setup can't keep the temps below 212. Well that's just not very likely unless he's got a very heavily modified engine, air in the system, or part of the radiator blocked off, or the thermostat is slow to open or restricted.

 

I was just making a general statement. Many people believe that the stated temperature on the thermostat is the temperature that the car will run. I'm saying that 212 is normal for a 192 degree stat. If his car ran 194 degrees before the swap, he probably had a 172 degree stat in it, which would make 194 about normal.

And a 160 thermostat will open and close, unless it's about 140 degrees outside. You don't think that 70-80 degree air going across a radiator can cool the radiator fluid to a temperature below 160 degrees? If what you are saying is true, and a 160 degree thermostat just stays open all the time, why put a thermostat in at all?

 

I respectfully disagree. I base this on my personal experiences with many cars and a number of thermostat replacements. For instance: My 1970 Olds Cutlass has a 180 and runs at 182ish, moving at about 45-50 mph in the summer. My 2000 Corvette has a stock thermostat and runs at 194-196 on the highway in the summer.

Sure, it will close if you can get your coolant temps (inside the engine, not the radiator) below 160... not otherwise. If this was happening, you wouldn't be claiming that your car runs 176-178 degrees. It would run slightly over 160 - by a couple of degrees. Unless you have a very efficient cooling system with a huge volume of coolant (think about a jet boat pulling water from a lake), this is tough to accomplish.

Good question - you should install a thermostat to get the engine temp up to standard operating temperature quickly. This is especially important in the winter months for the heater to operate correctly. I suspect that if you completely removed your 160 thermostat from an otherwise stock cooling system for the rest of the summer, you would only see a tiny drop in engine coolant temps (if any) and that would probably be mostly due to the increased volume of water that was flowing because you've removed some of the restriction in the cooling system. Try it and let us know...