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98TJ Heat Issue

I'm looking for any ideas on this one, as it doesn't make much sense to me:'

I drove to get lunch, and sitting in the drive-thru line, turned on the heat. It was probably around 10 degrees Fahrenheit with the wind- chill. The engine was about 3/4 warmed up, at which point, I should (and have in the past) feel some nice heat. . But, all I got was cold air. Very cold air. Heater controls all looked good, so I left it on, and sat there, until the needle was vertical, and still, cold air.

So I turned the engine off, until I got my order, and fired it back up, and immediately had heat.

At the time, I turned the engine off, as I suspected a stuck thermostat, but later realized that the heater-core is always on the same loop as the engine as far as the coolant goes, so that couldn't be it. Any ideas? This is the first time this has happened, so I'll post more if it happens more.

Any ideas?

Reply to
Dave
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Always.... :)

Vac leak, possibly a cracked hardline or something that took a bit of heat from the engine to soften up and be able to seal. I'd check the hard lines running from the intake rail for splits or loose soft connections.

Although, IIRC the blend door is a stepper motor. In that case low vac would have just kept the output stuck to one setting.

If it's electrical or a stuck blend door (Guess if it got water in there it could freeze the rubber seals and make the door stick) Heat would then free it.

I'm out of ideas. :/

-- DougW

Reply to
DougW

Might have just gotten some water in it, frozen enough to stick the door, later the ice melted and problem solved.

Reply to
J. Clarke

Hi Dave, Check the coolant level at the radiator, cold. Many times an air pock may fill the theater core. Those dried deposits should be back flushed out, every two years alone with the coolant regular change. God Bless America, Bill O|||||||O mailto: snipped-for-privacy@billhughes.com

Reply to
L.W. (Bill) Hughes III

If your thermostat is stuck open the engine won't make any heat. Happened last winter in my `69 4L XJ.

Reply to
Lee Ayrton

Riiight :) The regular coolant change :) That would be a good idea.

On the way home from work, it seemed to heat up normally, but I noticed a couple strange things that don't seem familiar.. when the engine warmed up, the heat was warm, but not hot . . but when I was moving, or even when I revved the engine, the heat would get hot. At the same time, I also noticed that when at idle, when the heat was not as hot, my oil pressure guage would creep up to about 40, and then when I revved the engine and the heat got hotter, the oil-pressure dropped back down to about 25 or so..

Multiple problems showing up here?

The frozen blend door is quite possible, as the entire jeep was encased in 1/4" of ice on Saturday night, and then an entire day of rain followed.. I will check the coolant, and keep an eye on the situation, and report any other strangities that show up.

Thanks for the help guys!

Reply to
Dave

Sounds like low coolant.

Carl

Reply to
Carl S

Fatfingered. `96 XJ

Reply to
Lee Ayrton

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