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Old 01-07-2018, 09:20 PM   #20
OBS454
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Join Date: Aug 2014
Location: Dallas, Texas
Posts: 54
Re: 71 350 running hot coolant backup up problem

Quote:
Originally Posted by Gregski View Post
Where are you getting this information from? When I do a search for an OE replacement thermostat for a 1971 truck on AutoZone I get 195 degrees, I do the same for my 1974 and get the same result, I do it again for the latest 1986 square body and still get 195 as the direct replacement.
The 195 degree thermostats came about when ECM engines came out. The most common thermostat in V8 engines up till the early 80s was the 180 degree thermostat. I was also in auto repair starting in 1981 so I changed a lot of them. It's possible the 195 you have in there is not working properly. Get a quality 180 and install that. Check your engine timing - retarded can cause overheating to some degree. Move your hand around different areas of the radiator to check for cool spots - a partially clogged radiator core is possible. Feel the upper and lower hoses for temperature differences. If you grasp the upper hose after the thermostat has opened (use a rag or something to prevent burning) you can actually feel the water passing through as it scrubs against the inside of the hose. Check to see if the fan is pulling air - is it the correct rotation? Water pumps that are intended for serpentine systems (like my 1990) have pump impellers that are designed to work in a counter-clockwise rotation (and so is the radiator fan). Perhaps the wrong pump was installed.
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