I felt like my engine had been running hot, but the temp gauge never went over 185 degrees. I watched it for a few days. It never went over 185. I replaced the coolant temperature sensor and coolant. Now I can watch the gauge climb to 210 degrees and stay there (225 or 230 at idle in traffic). So it seems to be staying mostly at 210, but who knows how long the sensor was bad. So I'm wondering, if the coolant temperature went way too high, and I didn't know it, what could the high temp have damaged, and how could I check for it?

 

from overheating? the only damage i can see would be a blown head gasket. one simple way of checking for it is having milky coolant or milky oil or if your car is smoking white or blue from the tail pipe(s). white smoke would indicate there's coolant getting into your combustion chamber and blue smoke means there could be oil getting into your combustion chamber from a blown head gasket or bad piston and oil rings. if you would like to spend your money u can get it tested by taking it to a shop and they put this chemical in your radiator that will change color if its getting any combustion gasses. hope this helps.

 

If you think it might have overheated, you might want to do a oil change on it to make sure the oil has not broken down. I would think that if it did indeed overheat, you would have known it because the temp of the coolant don't care what the guage reading is showing on the dash and you would have seen steam, smelled coolant or something.

 

I do not see smoke or milky oil. Could an overheat cause a warped intake manifold? I do have a coolant leak again. I replaced the plastic elbow behind the belt tensioner pulley about six months ago with no leaks until last week. I replaced the elbow again Saturday (it didn't look that bad when I took it out), but still seeing coolant loss (shows up on top of the engine). Makes me think intake manifold gasket (?).
What do you think?

 

No worries. If the coolant temp went dangerously high the cooling system would have boiled over.
Sounds like the 3.8s are like the 3.4s and run very hot in traffic. On a 3.4 the PCM doesn't even turn on the electric fan until cooloant temp reaches 225F! Yes, 225F. So without a radiator cap installed the coolant will boil over before the fan comes on. DAMHIK
On the highway the car runs at a steady "normal" temp of around 190F but in traffic it's high, low, high, low, etc. Seems crazy to me but it is normal.

 

Intake gasket is a very common issue on these motors. It is the one thing that seems to need replacing no matter how well you take care of it.

 

^^^ agree with the guys the normal operating range is 190 to 230. that said did you bleed the air out of the cooling system after changing the coolant and sensor? it may be that its not all out yet. you can change to a 180degree thermostat and have the ecu tuned for it to have it run a little cooler if your concerned.

 

Thanks y'all.
I think it is cooling normally right now. Just curious what to watch for if the temp got too high while the sensor was bad.
I did see the Helm factory manual mentioned that EBDII doesn't require a trouble code for bad Engine Coolant Temperature sensor (seems like they would want it to report bad sensor even if not required) -and- said if ECT sensor is bad it could affect fuel mixture, giving an inappropriate mix for the actual conditions based on the wrong information the sensor gave the PCM.
Hope that's helpful to someone.
As for the current coolant loss it sounds like it could be the lower intake manifold gasket. Not looking forward to that one.
Thanks again for your help.

 

My 3.8L both engines and my wife's LS1 all run at 210 all day long and get a little more in traffic but not to be alarmed by. I have had mine up to the red marks before I fixed the leak and it is still running fine today. Just dont run for an extended period with the gauges in the red. My friend has a 95 with a 3.4L and his likes to run just below the 210 mark and my friend's SLP modified Z runs normally with a 180º thermo so his stays below the 210 mark as well.

Massey

 

I really doubt your car overheated, if it had you would have known about it. Your gauge was just lying to you, and it's operating normally now just like it was before. Btw, the sending unit for the temp gauge has no control over how hot the engine gets.