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overheating 2002 5.3l

rmpmrace

New Member
Joined
Nov 20, 2015
Messages
5
Lurker and not a poster, but have gleaned a ton of great information here! Thanks. Now my problem, did a search of overheat issues and couldn't really find an answer to my problem. Truck sat for a week, and was not overheating when it was parked. Now it overheats within a few a few miles, cools back down at idle. The heat in the cab is great and doesn't  fluctuate at all. If it was low coolant would I still have heat ? the weather hear has been in the single digits, don't  know if that is a factor or not. Any help or thoughts ?  :help:
 
This may be a long-shot, but is your coolant to water ratio off?  Years ago I had a situation with my S10 Blazer where I had a slight leak and added too much water relative to the amount of anti-freeze.  We hit a very cold snap and the truck would overheat.  After sitting for a few minutes to let the temperature come down it I would fire it up and it would then be fine.  The only thing I was able to surmise is that the system had frozen created a blockage that prevented the system from flowing and that the blockage ultimately thawed when it was sitting thus allowing the system to flow properly.  This happened two days in a row.  I added more coolant to address the issue and it never happened again.
 
Made the mistake of removing the reservoir cap with it hot ( I know , very stupid!!). Lost a lot of the coolant , refilled it and problem still exists.
 
Sounds like a classic case of the thermostat stuck closed. That is where I would start since it is cheap and easy to change.
 
rmpmrace said:
If it was a stuck  t-stat, wouldn't it overheat at idle as well ?
Heat input from engine is not as much and I presume it is very cold outside and you are using the heater... so maybe you can remove the heat the engine makes at idle with heater and mother nature being cold outside.
 
rmpmrace said:
If it was a stuck  t-stat, wouldn't it overheat at idle as well ?

It may be open enough to cool at idle, but not open enough to cool at high speed - not enough coolant flow at higher soeed.
 
Ok, I finally got a chance to work on the truck. I replaced the t-stat and refilled with all new anti-freeze. everything seems good to go. I don't know if it was low coolant, or maybe slight freeze up . Or the t-stat. but its working now . Thanks for all the help.
 
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