YJ Heat sucks

DansYJ

New Member
Joined
Nov 9, 2005
Location
Wilson,NC
when I first got my 1991 YJ you could fry eggs on the floorboard it would get so hot.

Couple of years later, today, it sucks. It is luke warm by the time i get to where im going.

I think it is my thermostat. We had some snow here in wilson a few weeks ago. I drove about 10 miles into town and back home. The snow was still on my hood and hadn't melted off yet, so i'm assuming my engine just isn't getting hot enough.

I'm going to change the thermostat this weekend. I'm also thinking about dropping the heater core and flushing it. any other ideas i should check as well? (4.0L YJ)
 
It's the thermostat, no question.
 
take both heater core hoses off and stick a water hose to one end. that should help get some :poop: out of there. however its not bad changing the heater core in a yj
 
had an issue with my CJ once. Went to a radiator shop. He hooked up a water hose and turned it on, draining it into a bucket. Not much came out. He went and got his home made apparatus, he put it on the end of the water hose, and connected it to the heater core, He then hooked up his air hose to it. turned the water on and then hit it with some air. A few short bursts of air and all kinda crud came out. Heater worked like new again
 
changed the thermostat this weekend. slightly better but not much. still luke warm.

Going to mess with this heater core. I've seen the two hoses going into the firewall, i'm going to disconnect both and try to blow it out with the water hose first. I almost just want to replace it, but i guess a good blow out would be just as good.
 
I know exactly how you feel man, I changed out my thermostat and water pump last winter thinking that was the problem and did the "hose flush" too but I still have zero heat also. I built a contraption to hook the air line to it but haven't used it, I will try it maybe today and see it that helps. A new core is only $40 but it just looks like a pain with A/C in the way.
 
wanted to update.

Got home and touched both hoses going into the heater core. They are both warm. I'm assuming if thats the case then hot coolant is actually traveling through the core. Doubting, i pulled them off and flushed it out anyway. Not much improvement on the heat side.

I guess i'm left with beating around the damper under the dash, only thing left.

I also had a steady drip of coolant coming from somewhere yesterday. Come to find out i had a steady drip coming from wheep hole under the water pump. Go figure. Going to replace that this weekend.
 
keep us posted. i'm having same issue. ive flushed my heater core and that didn't help me either.
 
Warm won't get it, needs to be hot. Might also look and see if it is opening up the passage going into the core. There should be a valve that is vacuum actuated to allow flow. if it ain't opening, then it will only get "warm"
 
My first Jeep was a YJ. When it was really cold outside my heater could never keep up. I remember jimmying open something so I could get air recirculated instead of always from the cowl.
 
bump, wanted to update again.

I put the new water pump on and i will say it feels slightly warmer now. I'm beginning to think the comments about the valve opening are true. Will mess around with that. I think all my dash vents are open/closed accordingly with the heating diagram i found.
 
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