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heater isn't blowing as warm as it used to

S

scott00tj

NAXJA Forum User
Location
Medina, OH
Normally I turn on the heat and about the time I'm half way to work I'm roasting and need to open the window. Today I realized I was still cold when I got to work. I felt the air coming out of the vents and it just didn't seem very warm. Of course this happens just as its getting colder. I'm not good with HVAC systems, but would like to try and fix this myself. Where do I start troubleshooting?
 
Always post year/engine for most accurate responses.

What is the history of routine cooling system maintenance? IE: coolant changes?

What is the engine running at on the coolant temp. gauge on the dash?

Oftentimes, the heater core begins to get clogged up with very small particles which reduces the amount of heat getting into the cab. Reverse flushing with a garden hose can "sometimes", but not always restore function.
 
Maybe its a low T problem. :laugh:
 
birchlakeXJ said:
Always post year/engine for most accurate responses.

What is the history of routine cooling system maintenance? IE: coolant changes?
Click to expand...

I think it's been flushed once in its life, but I'm not 100% sure about that. It's a '99 with the 4.0L.


birchlakeXJ said:
What is the engine running at on the coolant temp. gauge on the dash?
Click to expand...

Once warmed up the temp gauge is right on 210*.

birchlakeXJ said:
Oftentimes, the heater core begins to get clogged up with very small particles which reduces the amount of heat getting into the cab. Reverse flushing with a garden hose can "sometimes", but not always restore function.
Click to expand...

Anyone have a writeup on doing this?
 
I was not getting any heat in my 1999 a few years back. A friend took off the two small black hoses under the hood by the firewall that connect to the heater core and blew them out with an air hose I believe.

After that my heat has been fine. You may have a clogged heater core.
 
Does the 99 have a heater control valve? If so my bet is on that. If not I'd say it's a plugged heater core from lack of flushing the system out.
 
No it doesn't, I would look at the thermostat and then pull the heater hoses off at the firewall and flush the heater core to see what comes out, it should flow pretty well if its not obstructed. Do the heater hoses get hot? if all that checks out, I would think it would have something to do with the blend door and vacuum inside the vehicle under the dash.
 
I have a similar issue on my 98... but I flushed he heater core twice in the last month. A lot of crap came out but the heat isn't much better (well it was for one day, then got bad again) so I'm thinking blend door now after reading this thread. Where is that located on the 98? Is it a standalone valve that I can replace or something?
 
I just did this on my 98xj. Take both heater hoses lose at the front of the engine. Start the engine and turn the heat on. I used a pneumatic fitting to reduce the water hose down a little and put a little more pressure through hoses. Alternate back and forth. Flush one hose and see what comes out then back flush the other way on the other hose and see what comes out. Continue to do this until you get clean water coming out of both hoses. I did this last weekend and today I had to turn the heat all the way down about 3 miles from my house. I had already used a cleaner and flushed last month and that didn't do it. Give it a try, water is pretty cheap.
 
I haven't flushed the cooling system yet, but I'm wondering if I should just have that done as part of a heater core replacement. I want the right fix, but don't want to have to pay for the system to be flushed twice if I do it once now then again with a new core. What do you think is the likely hood of the heater core being the main issue and just bite the bullet and do that now?

Also, could this have anything to do with my AC not blowing very cold when it was summer?
 
Replacing the heater core is a PITA. The part is cheap, but the labor will kill you if you have a shop do it. It will almost kill you if you do it yourself ! :)

Flush the heater core first.
 
birchlakeXJ said:
Replacing the heater core is a PITA. The part is cheap, but the labor will kill you if you have a shop do it. It will almost kill you if you do it yourself !
Click to expand...

I've been checking out the process. Paying a place to do it just isn't going to be in the budget if that ends up being the issue. Better get a 12 pack now for the home install.
 
Unless the heater core is leaking I would try to flush the one you have now and see if that works. Heater Core replacement as some have said already is a major pain and I'm not talking about Damon Wayans. If you disconnect the heater hoses at the front of the motor you don't lose much coolant. Someone at some point in my xj's life before me had run radiator stop leak through it and I had to flush my entire coolant system 3 time and flushed the heater core by itself 3 more times after that. That was still cheaper and easier than replacing the heater core.
 
I have done heater cores in my 97 and 00 xj's and for customers. I went by the fsm,I didn't take the seats out no need to and on the steering column I just pulled the steering shaft a part instead of unbolting for the column much easy to put back togather. I'm doing a grand cherokee for a customer this weekend hopefully not to bad. Back flushing is a band aid fix but I have done it to help customers. I put iron out or clr in the core with hot water and let it sit for a hour or so and back flush it. It does work for a while.
 
yjnick95 said:
I have done heater cores in my 97 and 00 xj's and for customers. I went by the fsm,I didn't take the seats out no need to and on the steering column I just pulled the steering shaft a part instead of unbolting for the column much easy to put back togather. I'm doing a grand cherokee for a customer this weekend hopefully not to bad.
Click to expand...

As you have done a few of these, what would you estimate for the time to complete the job? Or do you know what the flat shop rate for hours is??
 
birchlakeXJ said:
As you have done a few of these, what would you estimate for the time to complete the job? Or do you know what the flat shop rate for hours is??
Click to expand...
My 06 motors time manual says 7.0 hrs with a add of 1.5 for evac and recharge. So a total of 8.5 but I can do them pretty easy so i just charge $350.00 plus parts. It still takes me the about 6.5 hours to do.
 
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