Resolved cooling issue-UPDATE post 8-better but not perfect

[kenny78]

The temp on my 82 k20 has been creeping past 195. It would climb to about 210 and climb from there if I turned the ac on. Idle, highway didn't matter. I replaced the tstat with a 195 ac delco(which is an Israeli made motorad)-no change. The water pump is an oreillys(Murray?) that is only a few months old and before the cooling problem started. That was a fun day on the highway-I'll change them preventatively from now on.

I had read on the internet and ruled out that a fan clutch issue would not cause overheating at highway speeds. WELL I can tell you that it was the fan clutch. I just wanted to post this so others might find it through searching

 

[1987 GMC Jimmy]

Did you test the fan clutch for resistance before you replaced to see if it was slipping too much? If so, what did you find?

 

[4WDKC]

Did you test the fan clutch for resistance before you replaced to see if it was slipping too much? If so, what did you find?

I have a similar issue, looks like I will br switching to electric fan sooner than I planned.

 

[kenny78]

I did and when engine was cold it would maybe turn 1/2 turn or less. Hot was around the same. Luckily I have a few spare squares to rob parts from before purchasing parts

 

[Cuba]

Great bit of info! Thanks for sharing. Making a mental note.

 

[donnieray]

Congrats on your success.

 

[Oldrider]

Glad you found the issue. T'stat, water pump, and radiator . Not much left.

 

[kenny78]

After several highway cruises the temp will rise a little above 195. Not much, but with ac it can rise to 205. This is with a mechanical gauge in the manifold by the stat.

I would almost put this in the margin of error but must rely on this truck daily and am fairly positive it wasn't doing this before. The fluid should be around 50/50 and looks fairly fresh. Coolant overflow system is intact and I am fairly certain is working properly. I don't think I can infrared the radiator because of the ac condenser.

I will update if or when I figure anything out.

 

[kenny78]

All right, at 55mph or so the temp stays around 195. This truck has a 4l80e so Rams are around 2k. By 70 it is around 208. If I drop it into d the temp will immediately go down. I believe that the truck is running lean at light throttle cruise. I am already assembling the pieces for an EGR which I think the carb is tuned for.

Or it's an rpm related flow/blockage problem, which I doubt but will investigate further if the EGR doesn't solve this.

I'm thinking it has always done this but I never noticed before. It spent the last 4 years or so as a on property firewood truck. Before that it was our primary road vehicle. Lots of forgotten things since then.

 

[4WDKC]

All right, at 55mph or so the temp stays around 195. This truck has a 4l80e so Rams are around 2k. By 70 it is around 208. If I drop it into d the temp will immediately go down. I believe that the truck is running lean at light throttle cruise. I am already assembling the pieces for an EGR which I think the carb is tuned for.

Or it's an rpm related flow/blockage problem, which I doubt but will investigate further if the EGR doesn't solve this.

I'm thinking it has always done this but I never noticed before. It spent the last 4 years or so as a on property firewood truck. Before that it was our primary road vehicle. Lots of forgotten things since then.

if temp goes down when you raise rpm I would check the pulley size for wp, if its bigger than stock the pump may not be turning the right speed fir flow.

 

[4WDKC]

Found my issue with my truck, PO had put an 18"x18" piece of cardboard between the radiator and the condenser. It was put in so it couldn't be seen without removing the fan shroud, truck might be too cool now with the 180* tstat.

 

[1987 GMC Jimmy]

Oh, wow. I wonder if that's there to help it warm up for the heater during the winter.

 

[Honky Kong jr]

Found my issue with my truck, PO had put an 18"x18" piece of cardboard between the radiator and the condenser. It was put in so it couldn't be seen without removing the fan shroud, truck might be too cool now with the 180* tstat.

Meh, that just means you can run it a bit harder and have a coolant temp cushion.

 

[Cuba]

I think the 180F T-stat is the sweet spot on most GMs. 160F too low... 195F Too high for my liking, at least in the summer.

180F is good all year round.

 

[Honky Kong jr]

I think the 180F T-stat is the sweet spot on most GMs. 160F too low... 195F Too high for my liking, at least in the summer.

180F is good all year round.

I have a 160 in my truck but then it's gonna get wooped on......a lot lol