Temperature Spiking in Car

Ok so my car kept overheating and I saw I had a small leak from the gasket on the water pump. I replaced the water pump and gasket but then it would zoom straight to overheating. I then assumed it was a stuck thermostat and replaced the OEM with a fail-safe thermostat. After topping off fluid and leaving the radiator cap off until I saw fluid running through it took it for a drive. The temp began to climb to overheating but dropped just as it was getting to the red and then began to fluctuate. Finally heat came through the car climate system and all was good until I had to come to a stop. It seems that whenever I have to stop at a light the temperature rises to overheating. I am out of ideas and would welcome any suggestions. Thanks.

After the thermostat the weird behavior was probably from air in the system. Its usually a good idea to get the radiator cap to be the highest point in the system if it isn’t already & run the car for a while.

At this point it sounds like the air may be gone, but that your cooling fan probably isn’t working.

With the car cold make sure the radiator is full of fluid, if it is one of those goofy GM cars with no radiator cap unbolt it remote tank and lift up to fill the rad.

Now drive or idle the car until the temp goes up and see if your radiator fan(s) is running. If it is not thats your problem . It can be a fan, relay, wiring or on some cars now a module or computer.

I’m with old timer, I think you have a fan issue. You can also turn the AC on, as this will force the fans on (assuming your AC works )

Regardless of which engine your Impala came with, 3.4L or 3.8L, you have to open the bleeder valve when refilling the coolant. One of these is incredibly helpful in getting rid of air in the system, as well: http://www.autozone.com/autozone/accessories/Lisle-Spill-free-funnel?itemIdentifier=291421 If you did not open the bleeder, you left loads of air in the system and that is why your temperature keeps spiking. If you are very unlucky, there may be further damage caused by these repeated overheating episodes, but let’s hope not.

Just curious: Wouldn’t running the car (at idle) with the radiator cap off, keeping the coolant topped off at the temp raised, until the upper radiator hose becomes hot indicating the thermostat is open be an effective way to bleed the air from the cooling system?

That method may work on the 3.8L, but for some reason, the 3.4L is really bad about retaining air and the only way to get it to behave is to bleed it through the bleeder. When you don’t, the temp gauge will be all over the place and frequently spike. Years ago, when I worked on one of those V6’s (may have been a 3.1L, same difference) for the first time, I did not bleed it through the bleeder, but used more conventional methods, and this is exactly what happened. That is why I bring this up as being a very good possibility.

One the 3.4 there is a good bit of the system higher than the radiator cap. I have found the bleeders are best used just as things you leave open while you fill until coolant comes out of them. I’ve found using them to bleed after filling with the car running to be quite tedious and not foolproof. The last time I did mine I just parked & ran it it on a fairly steep bank where I knew the cap was the highest point. That took care of it. Of course, the following drive I had to make through particularly hilly terrain probably didn’t hurt either.

Ok thanks for the info. I went home today and first checked the fans. After about 10 minutes of idle they did not come on so I engaged the A/C in order to force them on nothing. I then assumed that there was something wrong with the fans. With not having the equipment to diagnose the relays and such I took it to my local repair shop for them to do it for a small fee. As it turns out the fans do not come on with the A/C until the compressor is fully charged which takes a few minutes and my fans finally came on under idle after reaching a temp of 220 degrees. This took almost 45 minutes. I had them check the integrity of the head gasket which is still fine.So problem was an air-pocket in the coolant line. Bled out the air from the passenger side bleeder 1st then the driver side bleeder. Everything is working 100%.

In hindsight I should have bled out air line first and then checked the fans. Learned a valuable lesson for the future. Thanks again for the help.

Nice work. Be aware that we all, every one of us, always know what we “should have checked first” after we finish fixing the problem. It’s a fact that the last thing you check will always be the one the fixes the problem. I suppose it might be because it IS the one that fixes the problem. Were it not, it would not be the last thing you check.