97 TJ not blowing much heat

Robb

Member
Joined
Jun 30, 2016
Messages
76
Location
CO
My daughter has a 97 TJ, 4.0 auto. She hasn't had much heat out of the heater all winter. Last weekend I replaced cap, rotor, plugs and put in an OEM thermostat and sadly that seems to have made no difference. It was a 196 degree thermostat, had the jiggle valve, and no real difference.
What's my next step, heater core flush?
We're in CO and a good heater is nice to have.
 
If her jeep is running at the proper temperature, your heater core is most likely coated with deposits and not conducting heat or the flow is greatly restricted. It is 22 years old, replacing it would not hurt. A good coolant system flush should not hurt, but mechanic in a can is rarely as good as component replacement IMHO. I just replaced my AC evaporator and I did the heater core at the same time even though I am unlikely to ever turn the heat on.
 
My daughter has a 97 TJ, 4.0 auto. She hasn't had much heat out of the heater all winter. Last weekend I replaced cap, rotor, plugs and put in an OEM thermostat and sadly that seems to have made no difference. It was a 196 degree thermostat, had the jiggle valve, and no real difference.
What's my next step, heater core flush?
We're in CO and a good heater is nice to have.
There are a couple write ups on doing a reverse flush on the heater core. I can't remember who started it. But basically you flush water or cleaner backwards.
@ac_ did this.

When i did mine i just hooked up my garden hose to the output and blew out the crud through the input.

Extreme change in temperature.
 
**NOTE** @Boinked posted his message a few short minutes before mine. And it so happens to be the same suggestion 🤙
——
Heater core flush. Running water through the heater core w a garden hose is a cheaper solution that may very well work.

My reasoning: A few years ago I changed my radiator, water pump, thermostat and replaced the coolant. After that, the heater was only getting up to warm temps. And it was in the dead of winter. Well, after flushing the heater core with water, I got my heat back. And it was unbearably hot! AND it cost me nothing. [emoji847]


Sent from my iPhone using Tapatalk
 
There are a couple write ups on doing a reverse flush on the heater core. I can't remember who started it. But basically you flush water or cleaner backwards.
@ac_ did this.

When i did mine i just hooked up my garden hose to the output and blew out the crud through the input.

Extreme change in temperature.
Honestly I back flushed the heater core front flushed it, and back flushed it again. It seemed like water was flowing really good through it. I also replaced all of my freeze plugs, and replaced my water pump and tstat, and all of my hoses. I virtually replaced everything except my radiator, and my heat is not that impressive. It is better than it was, but by no means will sauna me out of the Jeep. I am not really impressed with the heat or there is something that I am not thinking about is wrong, Like maybe a vent door, not sure. My AC cranks, and I live in AZ so heat isn't really an issue for me.

Maybe it is normal that the heat isn't awesome, I sure see a lot of threads on it. I also read a lot of people that live in snowy climates that drive TJ's, so I don't know what to think.

If I was too worried about it, I would crawl under the dash and check all of my vent doors, and I still may but not till after summer.
 
I just went through a coolant system flush on my 97 also.

It took one multiple hour garden hose flush back flush and no less than 10 further flush sessions to get it to flow clean.

Stay diligent and just keep buying distilled water for the final flushes. (I think I went through 15 gallons of distilled water adding it and running the Jeep for an hour then draining and pushing water back through it).

I also pulled the fan motor from the engine firewall and saw that the lower 1/3 of the heater core Fins were pretty well impacted with crud so I sprayed them out with the low pressure nozzle of the pressure washer being careful not to damage them.

It’s got plenty of heat nice and fast now.
 
  • Like
Reactions: ac_
Which line is "in" to the heater core and which is "out?"

Knowing that we will reverse these for the flush.

And, I've heard that a vinegar soak helps breaking up the crud. Anyone know if thus is true and/or other chemicals that may work?




Edit-
Found it...
Lower hose is in to the heater core and upper is out, during normal coolant flowing in the system.
 
I also pulled the fan motor from the engine firewall and saw that the lower 1/3 of the heater core Fins were pretty well impacted with crud so I sprayed them out with the low pressure nozzle of the pressure washer being careful not to damage them.

It’s got plenty of heat nice and fast now.
That might be what I missed! Glad to hear that the work should work like a normal car
 
I appreciate it very much.
I'll do some research on how to do the reverse flush and get after it.
I'll report back with the results.
 
Touching base, and wanted to tell the forum that after the reverse flushes, standard flushes, two CLR treatments the daughter said she had a lot of heat on the way to work this morning.
Thankyou for the help, I appreciate it.
How did you reverse flush it?
Hold water hose in top radiator line and let it come out the bottom line? Or did you use pressure washer in top line and come out bottom?

Nice thread btw.
 
You really shouldn't go above about 14psi when flushing, you don't want to create a leak.

I flowed water or cleaner in and then blew it out with my compressor, the regulator set to 12psi. Yes, in through the top, the reverse of normal coolant flow.
 
  • Like
Reactions: JayTJ
I just unhooked the hoses from the waterpump, had a garden hose repair fitting that I stuffed into the lines that allowed me to thread a garden hose to it and let the water run from the tap, no pressure washer! I flushed both top and bottom prob 3 times and in between lifted the hoses and let some CLR sit in there, then flushed some more.
 
  • Like
Reactions: JayTJ and ac_