So I started my jeep up this morning to defrost. 10 minutes later went to check on it and there was cold air blowing inside the jeep. So I decided to scrap my windows and drive and about ten minutes in the heat kicked on. To add some background I did have to change the upper radiator hose the day before because it split and dumped fluid everywhere. I used my air compressor to blow the loose fluid out from around the engine. Does anyone know what might be wrong ???

 

Low on coolant and/or bad thermostat would be my guess.

 

You need to include year, model and engine to get the best help. You also want to make sure you post in the correct forum, because not everyone reads the electronics board.

Off the top, it might be a clogged heater core. Try taking the heater hoses loose from the firewall and running water from a hose through the fittings the wrong direction to backflush the heater core and watch the nasty garbage flow out. Then alternate between the two fittings until it runs clean in both directions. If it's a stubborn clog, you might need a chemical or detergent flush to get it flowing again. You can search the board for thread after thread after thread discussing this.

If you have an older Jeep with a heater control valve, it also could cause a problem. I seem to recall that a stuck blend door can also cause lukewarm heat. But it's probably crud in the heater core.

 

It's a 1998 xj with 265000. So I woke up today and there was a puddle of coolant under the front of the car. Please help.

 

Open the hood and figure out where the coolant is coming from then report back.

 

When my heat was blowing cold, it ended up being a cracked head and block. No obvious coolant leak. Mines a 00 though so yours might not be cracked.

 

I'd second the low coolant. On cold starts coolant starts flowing from engine to heater core regardless of the thermostat. I can't remember what year the switch was made, but a '98 doesn't even have a bypass valve in front of the firewall so the only thing stopping heated coolant from getting to his heater core would be the water pump impeller spinning in air (unless the water-coolant ratio was too low and there's a frozen plug). How cold did it get overnight?


George, when you replaced your upper radiator hose there's a good chance it created an air bubble in the system, not fully submerging your water pump impeller and getting full flow to your heater core. Probably no harm done- it kicked on when you started driving because your engine's RPM were high enough to cycle the coolant despite the bubble. Top it off and double-check all of your hose clamps. The pressure differences generated when your engine warms up when driving and cooling off overnight (vacuum) should also be relieved by your radiator cap. Since air compresses/expands and liquid generally does not, that air bubble may not have been purged yet. Fill your system when it's coldest and flex the upper radiator hose to help it burp.

 

Iam no mechanic but I hear a loud noise by the fan on the passenger side of the radiator. Can it leak from there?

 

George... you have to open the hood and take a look.

 

After the puddle comment, I suspect you other folks are right about the low coolant.