'86 Jimmy O'heats


Old 12-07-04, 07:10 PM
Boeing Mech.
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'86 Jimmy O'heats

My full size Jimmy V8 305 runs fine at idle but when travelling around 45 mph, it starts to run hot and will overheat if you let it. When this happens, the heater also starts blowing cold. If you rev the engine, the temp. starts coming down and the heater blows hot again. I have replaced the thermostat twice.
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Old 12-08-04, 02:01 PM
Join Date: Apr 2002
Location: Pittsburgh,Pa
Posts: 2,417
Sounds like you have air in the cooling system and will need to run it with the cap off and burp the air out.Have you had a leak in the past or have one now?
Old 12-08-04, 08:59 PM
Boeing Mech.
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I have not had the truck for very long. It did blow a heater hose early on. I suppose it could have gotten air in it then. I will try to purge the air out. Thanks!
Old 12-09-04, 02:17 AM
Desi501's Avatar
Join Date: Oct 2003
Location: Boynton Beach Florida
Posts: 2,207
If somebody tried to fix that heater core by putting sealer in it, you may have some restriction in there also.
Old 12-09-04, 04:04 AM
Join Date: Dec 2001
Posts: 2,538
If the heater works good until the vehicle starts overheating it is probably just getting low on coolant from blowing some out the overflow.
suggest checking radiater for restriction, and fan clutch.

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