Question about 1999 Pontiac Montana

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1999 Pontiac Montana Overheating

Normal 0 Normal 0 Normal 0 Hi Experts,

The temperature gauge on my 1999 Montana with 103k miles became erratic a couple of months ago (fluctuating from normal to red line) to the point where I had to do something.

In an attempt to diagnose the problem, I noted that the upper radiator hose was cool to the touch when the temp gauge was approaching the top limit of the range, indicating a faulty thermostat. After it was replaced, the gauge continued to fluctuate for the next couple of weeks. I monitored the antifreeze level and constantly removed air from the system. A pressure test was performed and no problems noted. The radiator cap was also changed. The temp gauge finally stabilized and remained solid in the normal range for several weeks. Then the gauge without warning began to fluctuate again.

Given that the temp gauge would rise when the vehicle was slowing and fall during acceleration, it was suspected that the water pump was the problem and was subsequently replaced. Unfortunately, this did not resolve the problem.

After limping home today with the gauge fluctuating between normal and red line, I tried to determine if there was a circulation problem as in a blocked radiator. The top radiator hose was hot to the touch but it seemed like the radiator itself was not hot.

I 'm thinking perhaps the radiator may be blocked but wanted your opinion. The lower intake gaskets were replaced at 60k miles and the cooling system flushed by the dealer. Although anything is possible, it seems hard to understand why the radiator would be blocked.

Any help would be gratefully appreciated.

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Sounds like you could have faulty gauges to meby check them out.... and yes its posible that its pluged

Posted on Dec 06, 2008

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  • 285 Answers

SOURCE: antifreeze ts boiling back into reservoir.

it sounds like a possible head gasket problem,you can get the fluctuation from combustion gases getting pumped into your cooling system and creating gas pockets,i would suggest taking it to a shop and have them do a block test to look for combustion in the cooling system to confirm the problem,that way you will know for sure,if it comes up negative they can also perform a flow test to make sure there is no restriction in the cooling system such as a plugged radiator or a bad thermostat,hope this sheds a little light on it

Posted on Sep 12, 2009

Testimonial: "I bet you've hit on the problem ! Car has been "using " antifreeze for a couple years now, with no leaking anywhere. Lost through the head gasket ?"

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Hello, randtshook40 and thank you for asking your question on Fixya!

Here is a simple process that will walk you through a few steps that will pinpoint the overheating problem on your
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How to diagnose your overheating
1999 Pontiac Montana

Get more great money saving tips and tricks about your vehicle from: twitter.com/acoates23234

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