Wierd Heater Problem - no heat until I move

Ok everybody, let me know if this has every happened to you. In the fall/winter I go out every morning to start the vehicle to let it get all warm and deforsted. This is the first fall with the new XJ and so I went out to start the jeep. Well I started it, put the slider to defrost and to heat and went back inside....came out 10 minutes later to go to work and it was still cold inside....AS SOON AS I START TO MOVE the heat came on.?!?!?! What would cause this to happen?

Not sure but here's my best guess. Your heat controls are vacumn activated, a small leak somewhere may mean that they won't function until the engine makes a bit more vacumn than just sitting idling. I have a similar problem in my car in that it will actually only make decent heat with the engine under load, seems like it doesn't have enough vacumn to hold the temp control all the way to the hot side without some engine load. You can let it sit and idle as long as you want and you won't get any heat, give it a little gas and you get great heat. Driving down the road at a steady speed (no load) it gradually gets cooler and cooler until you step on it a bit and then it's hot again. In your case I'd start by looking for vac leaks and possibly look at the heater box mechanism, perhaps it's getting a bit stiff and it just takes a little extra vac to get it to move.

yeah, its wierd, I can just move the jeep back and forth a foot and then leave it and the heat will start and continue like normal.

First off, vacuum is highest at an idle, so that is not the problem. It sounds like you are low on fluid or the heater core is plugged and the higher pressure caused by a faster spinning waterpump helps.

old_man said:

It sounds like you are low on fluid

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My first thought...

A coolant system flush might help this then?? I'm sure I could use it anyway. I know I have a leak somewhere in the coolant system because I can smell the antifreeze, but I haven’t seen a big drop in fluid level. I guess I need to check this out...this makes some kinda sense now. Thanks all! :cheers:

Is the coolant smell the strongest inside the vehicle? Check the passenger side floor board to see if it is wet. If you can, pressure test the cooling system. Any leaks should become apparent once pressure is on the system. Sometimes you can even hear the pressure escaping. You will have to look for fresh wet spots and listen for a hissing sound. A Mechanic stethoscope might be handy or a piece of hose.

chris

I have a simular problem with mine too.

I'd check for a vacuum leak as recommended, but I have watched the temp guage. It doesn't really move at all until I am cruising down the road.

Because its an auto I'm under the assumption that my radator just cools too well when I don't have a lot of tranny fluid running through the stock tranny cooler in the rad.

XJ Buzzard said:

Is the coolant smell the strongest inside the vehicle? Check the passenger side floor board to see if it is wet.

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The smell is on the outside (thats another issue I'll need to tackle later on), theres no smell or wetness on the inside at all and the heater is working just fine....once the vehicle moves... and I mean you just need to move it a little....this morning I went out, started it, went back inside, came out 10 minutes later and the engine was warm but the inside of the jeep was cold and blowing cold air. I move the jeep in reverse for 2 feet, then forward to feet and then the heat comes. Went back inside and came out 5 minutes later to a defrosted and heated XJ. =)

Next time wait 15 minutes.

Id start with a completle cooling system flush. My XJ was having heating problems when i first picked it up...would only blow mildly warm air till you got up to speed then it would blow hot. I flushed the system out with some cleaner i got at Autozone and refilled it with 50/50 antifreeze/water and its been fine ever since.

If I could enter the my own question here. I'm driving down the road, it's cold so I turn the heater on. It's all nice and toasty and fine untill a few minutes later it's justy luke warm if not, cold air coming through the vents. Shut it off (the heater) and wait a little while and presto, turn it back on you;ve got heat for a few more minutes...???