NO HEAT! Where to start? '00 XJ

No heat in 2000 XJ
had this problem last year too but it was intermittent, now is all the time

1) jeep gets up to operating temp fine

2) heater core hoses seem to both be warm (seem to be the same as radioator hose)

3) controls properly change flow from defrost, to floor, to dash, etc.

4) checked the blend door actuator today...it turns REALLY slowly and you can hear it trying to move the door. it turns 1/4 of a turn, is that ok?
should it move fast?

saw the heater core flushing post...should this be my next move?
also saw a post on re-lubing actuator. i'd do it if you guys think its turning too slow.

help! need to attack this problem this week..its COLD out

thanks
mike in ohio

This happened to my 2001. Almost exactly the same symptoms. Ended up bring a plugged heater core. Pull your heater hoses and flush the core good with a garden hose. It's all mine took. Maybe you'll get as lucky.

just a water rinse or use some chemicals?

really hard water here, wondering if theres scale buildup.

i've been told that it's a somewhat common thing to reverse the heater hoses at the heater core side and backflush the heater core for like 15-20 min or something, should dislodge any blockage and if you're lucky, maybe even dump it off into the coolant overflow tank, i'm not sure if it's true, or if it actually works, so don't try this unless someone can confirm it works, cause i'd feel like an arse if you did this and it wrecked something

Just a garden hose back and forth.

that would probably be the best way to do it, but i'd advise not doing it in your driveway, i've seen the crap that comes outta there and it looks like it would stain a driveway something fierce

anyone have any thoughts on whether that actuator is doing its job?

i will try the flush this week and repost.

dumbagain said:

just a water rinse or use some chemicals?

really hard water here, wondering if theres scale buildup.

Click to expand...

I installed two of those garden hose adapters that go inline on the heater hoses. Put a hose on one, opened the other and then used two pairs of vice-grips to pinch off the hoses in front of the adapters so the water wasn't contaminating the rest of my system. Opened up the tap, let it flow for a few minutes then swapped hoses and repeat. When no more gunk came out I tightened the caps and no more cold. No chemicals were used.

Stick your head under the dash on the right side and move the hot cold knob. You can see the arm moving. I just finished flushing my heater core 10 minutes ago. Had little heat on an arrand I was running yesterday. This is in my new to me 98. Yanked both hoses at the T stat housing and water pump. Stuck the garden hose against the top hose had little flow, stuck it on the bottom hose had a little more. Back and forth it was clean water at a decent flow rate after 3-5 minutes. I blew the water out of the heater hoses. My coolant was nasty looking so I rinsed it out and refilled it also. Less than 45 minutes for the whole project. Ive got lots of heat now.
Ron

Sometimes I will disconect the actuator and move the door manually to make sure

The last thing you want to do is take the chance of moving whatever is plugging the heater core into the radiator. Unless you are in the market for a new one.

Are both the hoses at the core connection point betting hot? If both of them are hot, most likely the blend door is not working correctly to make the shift from cold to hot. If the one from the T-Stat housing is hot and the one to the water pump is not, the core is plugged. Disconncet the lines and attempt to flush.

did a flush today (the best i could without actually hooking up garden hose to heater hose, i had to spray into the heater hose) but it didnt help the heat situation.

my coolant is extremely brown! is this normal (2000 xj)?

when you flush into heater core is there a lot of resistance or should the water flow through rather easily?

double checked core hoses and they seem to both be hot.

my blend door actuator turns very slowly, and changes air from cold to lukewarm but never hot.
the shaft on actuator has 2 notches and it seems to turn 1/4 of a turn.
can anyone confirm if this is enough?

do shops have a better machine to flush with?

The '98 has a push/pull cable for the blend door, on the '00 it has a rotary actuator that turns the shaft. I recently replace the evaporator on my '00 and didn't get the upper pivot of the blend door in the top molded in socket. If you remove the three screws and drop the actuator off the shaft, you should be able to easily rotate it with your fingers, if not it's jammed up. I think it was a 1/4 turn hot to cold and the actuator dose move slowly.

Brown rust coolant isn't good. Prestone has a kit with some T fittings that works well to hook up your garden hose to flush it out. Just don't leave the T installed as they seem to fail over time. Pull the thermostat and replace it too.

I had the same issue about a week ago. I too just ran hose pressure water through it until it came out clear, but it did nothing. I posted up here and was told to try vinegar and water, it worked! First I blew out all and any water in the heater core (just held the hose up to my mouth and blew out the water...didnt take much) Then I did a 50/50 mix of vinegar and water and filled the heater core wore with it. I let it sit for a few hours and then blew it out with my air compressor. The amount of crap that came out of there even after I had "flushed it" with hose water was unbelievable. Once I got the vinegar mix out I just filled it again with water and kept blowing it out with my air compressor in both directions. It fixed my issue, nice and hot now!

Vinegar works to remove mineral scale as it is an acid and will disolve the build up. Off the shelf Vinegar is already 95% water so keep that in mind when using it as a flush. Just make sure you get as much of it out as you can before adding back coolant. I pull the lower hose... To use an acid bath on the core, I would recommend that both hoses be disconnected and the ends raised well above the core. After draining the core, fill it with Vinegar straight from the bottle and let it sit. Let the acis work for awhile and repeat until it comes out looking like what it did going in. Use white vinegar to get a better reading.

Some of us here practice aggressive cooling system maintenance. Every two years, I use a commercial flushing agent (the type you drive around for a couple of days), flush repeatedly and fill with new coolant. Also, I never use tap water, just steam sistilled water. Tap water is chock-a-block full of minerals that will happily plate out of solution onto all of the metal it can find. Every year the coolant gets changed.

Expensive? Maybe. Then again the Heep operates between 195 degrees and 201 degrees all day, every day. See my signature on how to get there...

The XJ cooling system is known to be marginal. The vehicle was designed for a 2.5L or the optional 2.8L engine. Cooling needs are low for those engines. Unfortunately, those engines are also short of power. So, the 4.2L 6 gets de-stroked and then bored out to make a 4.0, Jeep crams in the largest radiator that can fit and Voila', marginal system once it ages. All we can do is to attempt to get it at least back to factory condition.

"Excessive" maintenance, it's an old guy thing...

"Pull your heater hoses and flush the core good with a garden hose"

Excuse the newbie-ism... but where/which are the heater hoses to do this flush? I've got a similar issue.. my heat takes forever to actually get more than lukewarm and by the time I get to my destination it's still lukewarm. Maybe I've got a plugged core as well.

They are the two smallish (about 3/4 id) hoses that run down the right side of your valve cover and into your firewall. One comes off the tstat case and one comes off the water pump.

o-gauge-steamer said:

Every two years, I use a commercial flushing agent (the type you drive around for a couple of days), flush repeatedly and fill with new coolant. Also, I never use tap water, just steam sistilled water. Tap water is chock-a-block full of minerals that will happily plate out of solution onto all of the metal it can find. Every year the coolant gets changed.

Click to expand...

Do you flush the agent and coolant out of the system with water, or just drain it? If you flush it, how do you use distilled water rather than tap water?

I always fill mine with distilled, but there's always some tap water left in the system from flushing with a garden hose.

had a good flush with chemicals done at the shop...heat's back on.
not sure if it was a semi plugged up heater core or not.

question for you guys..
coolant was very very muddy / rusty looking.
wouldnt that maybe cut down on the efficiency? which could of been a problem.
how does it get so murky looking? my 97 has never had a problem with discolored fluid.

thanks