We rarely take trips that involve driving uphill on steep grades, but how about the rest of you? Do you leave the tranny in overdrive?

Last weekend we took our '93 SSEi on a daytime trip to the mountains (Big Bear, Ca.). The outside temp was about 90 degrees F. At the base of the mountain, the temp gage read around 200 degrees F. The AC was off. We proceeded uphill and within 5 minutes the temp gage read about 1/8" from the red zone! I pulled over and let it idle (both fans were on) for several mintues so the the engine would cool off to 220 or less and then continued up the mountain. We had to do this 3 or 4 times over the span of the 15 miles or so up the mountain.

Our other car, '92 SSE */c, also got this close to the red zone within a few minutes on an uphill mountain climb a few years ago also, but on that trip it wasn't so hot outside and I turned on the AC and the temp gage dropped to 210 or so and stayed there.

What'* the deal? I didn't see any other cars pulled over letting their engines cool off...not even an old junker car! Should I just have kep driving while the gage was that close to the red zone?

I'm thinking you need a tranny cooler and a 180 T-stat. Is everything ok with the coolant system?

Nope, no coolant leak(*), and the reservoir level was ok.
I just put a 180 tstat and new coolant in this car about a month ago.

Now that this has happened to both of our supercharged Bonnevilles, either they both have the same problem or they both do this "normally".

Hmmm, I'll can it now and let the SC''d talk it up here.

I had the same problem with my bonneville when I was in AZ. Driving from Phoenix to Flagstaff it got up there around 240 but never hotter. I was running my AC because it was just to hot not to with kids in the back seat. I did turn the AC off for a little while but it didn't seem to help much so I left it on. I had did a complete service on the car before I went on the trip.

Flushed and replace coolant and changed to 180 degree thermostat.
Replaced spark plugs. NGK Iridium IX
Replaced all four tires.
Cleaned K&N air filter.
Changed Oil and flush.
Greased Front end.
Replaced Brake Pads.
Replaced Fuel Filter.
Replaced PVC Valve
Replaced Belt w/ a Gatorback.
Replaced O2 sensor.
Changed Transmission fluid and filter.

So it should have been in top notch. It only got hot enough for the check engine little to come on once and I pulled over but I never could figure it out. It runs 180 degrees around here and I am really hard on my car. The only thing I could think of was the transmission. I think it was working hard and heating up enough the heat was transferring to the engine and raising my temp. When we went down hill it would cool off really quick. I didn't have any kind of aftermarket transmission installed so I think it would have probably helped.

It'* definitely not normal behavior. I regularly take mine in to the mountains here in the summer and, while it does get warm after an extended 'spirited' trip up and thru the twisties, never ever near the red. I've never seen 3/4 even on the hottest, hardest driving days. I'd definitely suspect the tsat first - cheap and relatively easy replacement. How'* the fluid itself look? Resovoir?

I'd seperate the issues with the 2 cars because I'm not sure they are related unless you've been given the same (wrong) tstat for them by a common parts place or something, or unless you've run stop-leak or some other additive in both cars. I had my '97 Sebring motor seize up with 39k miles cuz someone put in WAY too much stop-leak - and that big pellettractor-trailer- type stuff to boot.

That being said, I'll venture a couple of gueses. I'd start with the fans. You mentioned the fans were on when you pulled over - do they run regardless whether the AC is on? I've seen other cars have a problem with the thermoswitch where the car would overheat unless the AC was on because the fans would not cut in otherwise. I wonder if your 92 has something like that going on, but I'm curious on the 93 if you left the AC off the whole time. Sounds like you did, so it'* probably not that unless your thermo switch is just not kicking in until it'* really too hot.

Second, has it ever gotten the least bit hot just in day-to-day hot driving conditions? Have you run it hard a little to see? Water pumps can fail even if there is no noise yet, but it'* rare. Check the drain on the pump to see if any fluid is leaking out, and see if there is any play in the pulley - this is probably not it, but good, easy things to check first.

Beyond these simple things, it could be a number of things. None good unless you just have a bad temp sensor or something around it is getting hot and creating a false reading. I believe, tho, the engine is actually getting hot - replace the tstat first and see where you are then would be my rec.

Hi Bill,
I live in the mountains and have no overheat problems with my 2k ssei.
I suspect you dont have enough antifreeze in your rad......cause antifreeze is also anti Boil. Try a rad flush and some new prestone, mix for 40 below.
The other thing may be altitude but this would seem very remote as you mentioned beeters passing you while waiting for you engine to cool (you would have noticed higher rpm'* and less power too). The magic number around here is 7000 feet for the snowmobiles then they have to stop and change out the Jets (carb) or on efi models flick a switch ( timming advance).
The last consideration is your tranny ok? A slipping tranny going uphill will build a lot of heat and transfer to the engine, any burnt smell in the interior while you were waiting?

Thanks for the suggestions so far, but let me clarify so we can overlook the obvious suggestions such as old coolant or defective tstat.

This car has a brand new 180 degree tstat and brand new coolant.
The coolant level is full.
There are no coolant additives.
Both fans turn on when the AC is on.
When the AC is off, both fans turn on when the engine is hot (over 220 or so).
The tranny is a GM SRTA unit that has less than 25,000 miles on it.
This engine doesn't drink any oil and runs great.
The water pump is less than a year old.

The temp stays around 200 degrees F even when it'* hot outside (low 90s is considered hot for So. Ca,) as long as the car is moving and isn't stuck in traffic. For example, coming down the mountain and then driving 80 more freeway miles last night, it was 90 degrees outside, and the temp gage was under 200 the whole time (2 hours).

The temp behavior in both cars is basically the same.
Whether the AC is on or not in uphill driving doesn't seem to make a difference. I usually turn the AC on in city driving if the temp reaches 220 or so and traffic will still be slow for a while, and that keeps the temp down to 200 or so, but this doesn't help when driving uphill.

Any other ideas?
Again, because this has happened on both of our supercharged Bonnies, I suspect the cause to be the same on both cars - the '92 is also stock and also has a rebuilt SRTA tranny in it, and probably has a 195 degree tstat in it. Its coolant level is full and there are no coolant additives.

Could the charger itself add any extra heat to the engine? I'm just brainstorming

Yes, from what I've read posted by other non-supercharged Bonnie owners, their cars don't run as hot.