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2003 chevy trailblazer_lt
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9 Posts
Discussion Starter · #1 ·
I recently expietenced a cooling system failure on my way back to work on lunch break. My engine temp spiked and my engine alarms started going off. Luckily I was really close to my work. I was able to get it to the parking lot, opened up the hood and coolant was spraying/leaking everywhere. It appeared to be the water pump at that time. Had the vehicle towed back to my house so I could work on it, just to make sure I used a coolant pressure system check so I could see where the leak was. It was coming out pretty steadily around the basket of the water pump. I proceeded to change the water pump, but through deduction the water pump was in good shape and had been replaced last year, I went ahead and decided that maybe the thermostat got stuck it has been about 6 years since replacing it. I got everything replaced and put back together and started to refill the radiator when I noticed there still was a leak. It appears the leak is very large, about a whole gallon of water in less than a min. I checked the radiator hoses and the thermostat hose before install and from what I can see nothing in those hoses or parts are leaking. It appears to be leaking somewhere near the thermostat. But feeling around the thermostat it is not wet.

Has anyone had a coolant temperature gage sensor leak that bad? Is there an engine freeze plug around this area?

In case my profile doesn't have my vehicle info, I have a 2003 trailblazer 4.2L with 186k miles.
 

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2005 gmc envoy_slt_xl
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28 Posts
I just replaced my thermostat. When I was putting it back together, I pinched the gasket (o-ring) and had a similar leak as you describe, but I was able to feel/see where it was coming from. Interestingly, the o-ring that came with it was almost too small and kept popping out of the grove it was supposed to seat into. I went back to Autozone and they gave me a new one for free and it fit better.

As you say, the temperature sender is just above the thermostat. I'm not aware of much else in that area besides the hoses that connect to the thermostat.
 

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2003 chevy trailblazer_lt
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9 Posts
Discussion Starter · #3 ·
Thanks for the response. It is very possible it still is the thermostat leaking with the o-ring issue you were stating. Were you loosing that much water/coolant with the o-ring failure?

I am going to take off the alternator later today to see if I can tell better where the leak is coming from. I post later what I find in my investigation.
 

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2005 gmc envoy_slt_xl
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28 Posts
Yes, it was pouring out fast. I was in the same boat as well. I put everything back together (including the the alternator) before I started to refill the radiator. I won't do that again. Refill after putting in the thermostat.
 
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