This is topic random cooling/running temp. question??? in forum Tech Talk at Northern California Ford Owners  .


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Posted by shade-tree (Member # 298) on :
 
On my Tahoe like two weeks ago the H20 pump went out so I basically replaced everything, pump, radiator, all the hoses (even an oil cooler line and heater hoses).

So--- after the install the temp seems ok, but it would run from about 180 to damn near 240.... and it would rocket back to 160, and then gradually up to 180, where it would start the cycle all over again.

Really annoying.

anyways, so I bought a 180 thermo, and noticed the thermo had no bypass holes in it so I drilled a 1/8" hole in the thermostat. I also replaced the bypass hose (the one I was using was just heater hose and it was kinda kinked 'cause it wasn't happy making a quick 135 degree turn). So... cut to the chase.

Running at WOT in the heat, up a hill, I can't get it to go higher than 160 degrees. Idle parked with the A/C on is 150, freeway cruise is around 150-155 max.

WTF? That's too cold right? Was it the 1/8" hole I drilled?

Should I just put a stock 195 thermo in there?
 
Posted by BOUNTY HUNTER VERT (Member # 2754) on :
 
put in a 180 with no 1/8 in holes in it that should fix the problem [Whoo Whooooo!]
 
Posted by TriplePLAY (Member # 948) on :
 
shade-tree, remember when i took my car to your house last year? i have the same problem with my 96- the temp is just unstable, specially on hot days! everything has been replaced-except the 2heater hoses at the firewall. i might have to try the 180 t-stat and replace those hoses. thanks for the idea. i hate this hit and miss diagnostics!! specially when no one else, even dealers have a clue what cause is.
i'd go back to stock t-stat. try that and see if it works. let us know...good luck
 
Posted by Black94 5.0 (Member # 655) on :
 
I drill 1/8" holes in all my T-stats to help bled off the air that gets traped behind the t-stat...I've never had a problem...

Its possible that the first time that you installed the water pump, you didnt bled the coolant system properly...
 
Posted by shade-tree (Member # 298) on :
 
it was definitely bled properly--- I wasn't losing any coolant and put well over a 100 miles on it when it was topped up and doing the 160-180 degrees becomes 240 and back to 160 again routine (maybe 5-10 mintues a cycle on the freeway--- never a problem at idle).

Anyways weird. I guess I'll fill the 1/8" hole tonight and see if that increases the temp a little. Running around at 150 degrees all the time can't be healthy.
 
Posted by st5150 (Member # 51) on :
 
Verify your guage with a real thermometer before doing anything.
 
Posted by FasterDamnit (Member # 442) on :
 
My temp sending unit crapped out on my LX- temp would vary a lot, then settle down to the low end. I replaced it and it now reports correctly.
 
Posted by shade-tree (Member # 298) on :
 
I don't have thermocouples or anything... do you think taking the temp with a regular thermometer at the radiator cap is good enough? If I unplug the ECT sensor I'll cause a leak I believe when running (maybe not). What do you think?
 
Posted by st5150 (Member # 51) on :
 
I've got one of these "wireless" theremometers, but have no time to deliver:


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