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2007 chevy trailblazer_ss_1ss
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Discussion Starter #1 (Edited)
Truck is over heating. I noticed a leak coming from the bottom of my water pump and replaced both the pump as well as the thermostat and refilled cooling system with the pre-mixed 50/50 Dexcool mix. Both pump and thermostat were purchased from AutoZone and are supposed to be new OEM replacements. The truck is still over heating. Now, I've noticed that when I keep the truck's RPM's low (below 2500 RPM as much as possible at this point) and/or not go above 65 mph the truck doesn't over heat, as well as on idle and normal street driving. When I take it up to 80 and hold it there for a little while, the temperature gauge will stay at 210 all the way up to the point that I begin to slow back down to say 65. That's when the gauge will begin to climb a few marks past 210 and the fan engages. After a few minutes the gauge falls back to 210 and the fan disengages.
Today, 3/17/2015, I took it to a shop to see if they could find what the problem was and they weren't able to find anything wrong and recommended a lower temp thermostat like a 160 instead of the OEM 187. I've been thinking about having the radiator back flushed before I try replacing the thermostat AGAIN. Please don't scream at me for this, but it's my daily driver and has 134,000 miles on it and it's NEVER over heated on me up until this point and I'm the original owner. I honestly don't abuse the truck i.e. do burn-outs, donuts, racing or anything like that. Every once in a while I do haul a single axle trailer with 2 atvs and camping gear, none of which ever exceeded 3,000lbs and its never over-heated on me.
I personally think the radiator has a clog or multiple clogs in it preventing the coolant from cooling as efficiently as it should if it weren't clogged. Which, to me, would explain why the temperature gauge stays at 210 at lower RPM's and speed, and takes a few minutes to cool back down from higher RPM's and speed and why I want to have the radiator back flushed before replacing the thermostat AGAIN.
Any and all information/help given would be greatly appreciated.

Scott
 

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2004 gmc envoy_slt
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2,270 Posts
First of all, do not change to a lower temp stat, that will screw up the computer and will try to dump more fuel in the mixture and cause the catalytic converter to clog. BTW, the OEM stat is a 195 deg.

You may have air in the cooling system. Run the engine up to operating temperature with the radiator cap off and look for air bubbles.
 
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