samx227

been having this issue since i rebuilt my motor. drive for a good 15-20 mins and the temp guage tends to creep all the way up the guage and then shoot straight back down to just under the halfway mark and be fine. and then do it again in another 20 25 mins and so on.. replaced thermostat, checked and rewired coolant temp sensor wire, new radiator hoses, bled the cooling system numerous times, im stuck. anybody have any other ideas?? no leaks at this time

samx227

Sorry 85 22re and replaced with oem parts

thefishguy77

iTrader: (1)

Check and clean your grounds. There is a link in this thread. We should all do this on a 30year old truck. It will fix a lot of seemingly random issues.

https://www.yotatech.com/forums/f116...points-135977/

Also here is a link to 4crawler. Great fixes on old yotas with troubleshooting.

http://www.4crawler.com/4x4/CheapTricks/index.shtml#Top

samx227

Awesome links thanks. I have also just went through all my grounds. Might be jumping the gun but I think maybe a block test is in store. I'd hate to find out that I have an issue like this after 2000 miles.

samx227

After some further diag I found my fan clutch not working. So gonna throw one of those in and hopefully fixes the getting hot issue.

RAD4Runner

Good that you figured it out. What symptoms do you see that indicates clutch no working? Not engaging even when hot?
I already replaced mine with OEM (Aisin). However, it would benefit the community if we could share what lead us to conclusion that fan clutch is broken.
I wonder if we have same symptoms. In my case, to test:

1. After a long drive (long enough to get engine to operating temp), I park the truck with engine still on
2. I wait about 5 minutes. This makes sure that fan clutch mechanism is only sensing actual heat from radiator, not cooled by air at high speed. In this condition, Fan Clutch should have maximum engagement.
3. I stop the engine and count how many seconds before fan stops.
   -My brand-new OEM fan stops turning within 2-3 seconds of shutting the engine off. Fan follows speed of pulley more closely, meaning more engagement with new OEM fan clutch
   -My 28-YO fan kept on running about 6 seconds after I shut off the engine. fan lags more behind pulley speed, meaning less engagement with old fan clutch.
   

I wonder if you see same behavior.
TIA,
RAD

samx227

I actually had a tech help me diag it at work. He said because there was no resistance against spinning the fan with engine at running temp (engine off) that the clutch was bad. He recommended I get a new one.

samx227

It does keep spinning for a while maybe 10-12 maybe even 15 seconds after I turn the engine off.

RAD4Runner

Cool.
THANKS YOU for confirming!
Makes sense. So yours was in worse shape than my original.
Number of seconds spinning seems to be a more exact measurement/way to compare than "resistance" which is "by feel" and very subjective.
It would be nice now to see how soon it stops after engine stops. Good baseline for future troubleshooting and to share info with others. I'll aslo post video of mine as soon as I get the chance.
Best regards,
RAD