On a 1996 Pontiac Grand Am I have changed radiator thermostat and it still overheats

Asked by Jul 02, 2016 at 02:07 PM about the 1996 Pontiac Grand Am 4 Dr SE Sedan

Question type: Maintenance & Repair

In November I change the thermostat and then it overheated in last month it overheated
so bad then off to the hose I change that both upper and lower hose and it still
overheated so I took it to a mechanic and he replace the whole radiator assembly it still
overheats when I turn on the air condition it goes down when I turn on my heater now it's
skyrockets to the red line which is really weird is it possible that I need to replace the
thermostat since that seems to be where all the problems initially started back when I got
replaced and if it overheated and I had to get a complete radiator assembly in it and it still
overheats is it possible that when it did overheat that new one was defective or bad

6 Answers

70,255

First thing is to make sure all the air is out of the cooling system. Your mechanic should have used a tool to pull the cooling system down into a vacuum before refilling it when the radiator was replaced. The fact that the temp goes down when air conditioning is selected tells me that the cooling fans are working. But to be absolutely sure, unplug the coolant temp sensor (with the engine off and cold). Now start the engine. The check engine or service engine soon light will come on because the sensor is unplugged. Ignore it. Now check that the cooling fans are both on. They should be. If they're not you'll have to find out why they're not coming on. If they do come on, shut off the engine and plug the coolant temp sensor back in. Make sure your 195°F thermostat is installed correctly as well. Pointy end up. If all this checks out, flush the cooling system using a chemical cleaner such as Prestone Fast Flush. Follow the instructions on the bottle. If that's not solving the problem replace the water pump. The impeller (fan looking thing on the inside that pumps the coolant) may be rotted away. Here's the water pump I took out of my '00 Grand Prix with the 3.8L V6 three months ago. It had an overheating problem as well. I actually did the flush, changed the radiator, and water pump all together. Runs right between 195°F & 205°F now (normal). As you can see the impeller was rusted away so the coolant was hardly flowing at all! HTH. -Jim

70,255

Here's the new water pump. You can see the difference! HTH. -Jim

10

Jim, I only have one fan and yes it does come on so I'm guessing my best bet would be the only 2 things left the thermostat AGAIN and the water pump thank you so much I'll let you know how it turns out.

1 of 1 people found this helpful.
70,255

You're welcome. Glad to help. Yes, please keep us posted. -Jim

5,195

Jim - When I have a problem, I hope someone will help me as well as you helped Rhonda here. Your advice was spot on, understandable, and thorough. She should be going again soon. Nice job!

I have a 2005 pontiac grand am gt and I put a thermostat in it and it still over heats what could be the problem

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