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One thing you will find with these cars is that they will run a lot hotter in slow traffic situations with the A/C off. That is normal and intentional. The fans aren't programmed to come on until approx 226 to 228 degrees if the A/C is not on. If the A/C is on, they run all the time.

Cruising on the highway, it should stay around 200 degrees..

My son drove it yesterday and we drove highway speeds in SD (65mph) and he had to turn the heat on to keep it cool.

that is not normal at least in my non-mechanical background.

The thermostat was replaced new with the new engine about a month ago along with the water pump.

I'm wondering what my next step is here.... new radiator? new temp control? new fans?

I can only tell you that last fall I took the car (before all of the engine troubles) to have the coolant flushed as it was all gummed up inside... Almost looked like cottage cheese at the top side. Not sure if the prior owner or someone mixed dexcool with regular antifreeze or what....

When I looked at the coolant the other day it was not like that but it did appear to be dirty looking but then again I don't think the garage put the true dexcool back into it... I think there is some new alternative to the dexcool and it certianly was not the green stuff.

my other car that has a v6, its not a pontiac but that vehicle never runs over 210... probably not a fair comparsion but I don't think it should get that hot but perhaps I'm totally wrong.....

Mixing coolants won't hurt anything at all. It just won't be a 5 year coolant any longer. As I stated before, these temps at low speeds would be completely normal but if you are seeing 220 or higher at highway speeds, then you have a problem. The sludge you spoke of concerns me. Dexcool will turn into a sludge if left in the system too long or if run with a leak that introduces air into the coolant. You will also make a total mess if you run straight water instead of coolant.

It sounds like your going to need another radiator and some serious flushing to the system when it's changed. Use some flush chemicals to loosen things up first and then flush it thoroughly. Remove the thermostat during flushing and then put it back in. You won't be able to save the radiator so plan on replacing that.

Ok, I ordered a replacement radiator.

In regards to flushing, do you purpose any specific type of solution that will loosen things up?

What is the benefit of removing the thermostat? Also, is there any danger in having it removed during this flush process?

I've heard that you can get air into the cooling system if not flushed right, is this true? If so, how can I avoid from having this happen?

Lastly, what is the best coolant to put back into the system. I know it had dexcool and then whent the motor was swapped out the garage put something else in that is not green and it is not dexcool either...

Just purchase a name brand flushing additive. Removing the thermostat first will allow the coolant to move around more and faster so it flushes better. Don't worry about the air until your refilling it with coolant. We use a vacuum fill to remove all air.

well, for those folks like me who do not have the vacuum filler... how does one refill and insure there is no air trapped in the sysem?

Look for a bleeder first. If it doesn't have one, then fill it, close the system, drive it around the block and run it until the fans come on. Shut it off and let it cool all the way down. Top it off and run it again until the fan cycles twice. Check the level one more time when cooled all the way and you should be good.

so what sort of coolant should I buy?

I should have the radiator on Saturday. Barring any troubles I hope to have it installed the same day.

However, not sure if I should put dexcool in it or go with something else.

it had dexcool and then when the motor was swapped out the garage doing the work put something else in that is not dexcool and its not the green stuff either.

any suggestions.

It's really not that important. Dexcool is a 5 year coolant and the green stuff is a 2 year coolant. The yellow stuff is a substitute for Dexcool with all the same properties as Dexcool but if green coolant contaminates either of the 5 years coolants, they just become 2 year coolants, regardless of the color. If your were to use Dexcool, you would have to thoroughly flush all the other coolants out first for it to do any good.

Well, I got the new radiator but did not get a chance to install it.

However, my son who drives this car, indicated that on his way back to college driving normal highway speeds without the air conditioning on says the car runs at about 250 degrees.

is that not a little too warm? We were only having mild 70's temp in our area too.

My other vehicles run around 210

Of course that's too hot but why are you driving it when you haven't installed the radiator yet? Your going to end up with a blown head gasket. That engine is very prone to that and that temp can easily do that. 230 is acceptable. 250 is not.

didnt have time.

I was not aware it would do that.

I will advise him to continue to run the heat/air to keep the temp down.

next time he is home I'll swap out the radiator.

How does one test if the fans are coming on at the right temp? I know the fans come on when the air is on and they do come on when it's not on but not until the car is around that 250 range.

Turning the heat on isn't going to save your engine. All that does is add a couple quarts more coolant into the mix but it only a momentary relief.

Don't worry about the fans right now. They have no effect at highway speeds.

I'm going to work on the car later today....

Just so I'm clear ... you suggest that I pull the thermostat and hook everything back up but add a flush addiative.

Let it run and then go ahead and empty everything and replace the radiator with the new one.

I can use the normal dexcool as a replacement and just run it a few cycles to insure the system is full.

That said... what should I be seeing for temps?

should I put a new thermostat in it too or can I use the existing.. it was new just a few months ago when the engine was replaced.

Also... on that temp guage where should I see it normally run? if it's working right should it ever go over the 4th tick mark closest to 260 ?

If the car has been real hot since the thermostat was installed, then replace it again. sounds like you understand everything. Normal temps would be 195 to 205 at cruising speed and as high as about 230 in traffic with the A/C off.

Yes, all that stuff has to be flushed out.
Remove the thermostat and put the empty housing back on. Use some strong flushing chemical and run the car for at least 30 minutes @ 2000RPM if it will do that without overheating. If not, you may have to repeat the process again.

When your finished flushing, remove the lower hose and upper hose and run the garden hose into the upper until it flows clear at the bottom with the engine off.. Then put your T-stat back in and replace the radiator. Don't install the new rad until you get all that junk out.

Gotcha!

Thanks for all of your help

I'll report the outcome...

I forgot to ask one thing....

since I am replacing the radiator.... should I replace the radiator cap too?

Not sure if that is needed or not or what sort of problem come from a bad radiator cap if there is any...

I try to change them when I can, especially when they get all gummed up. They are calibrated to a specific pressure for release and they have to remain accurate.

What a rig. I wonder how they spliced the wiring for that pass thru connector. Probably twisted the wires together and then taped them.

Been a while since I done one, but they sell the pass though connector and the pig tail harnesses. They would corrode from people spilling crap on the carpet or from water leaks.

The problem probably lies in that jerry rig they did.

I have the same problem, he installed the new pump one years ago and it worked fine, but now indicates good and suddently down to empty.

So is there a way to use that to get it working or is there a way to reset the gauges?

No, you have to find the faulty component and replace it. You really need a scan tool and some resisters to test it.

your going to have to try to be more descriptive in your symptoms.

as described it could be something as simple as a faulty sending unit up to a costly slipping transmission

Marry Christmas

Hope it fits. LOL

Dan