DUBarado

Ok, so as some of you may know, my '90 2 door xj overheated in june, and since then I got it back running fine with a new thermo/water pump and belt...

Unfortunately now that it's cold out, I realized the heat doesn't blow hot anymore like it used to... it tries to get warm but never does...

Also the temp guage floats around 150... I guess that's a tad cool? I'm not sure if the motor temp has anything to do with the heat.

SilverHaze

Heater may be dirty. Your temp gauge is more than likely stuck in the open position not allowing the jeep to get warm which is in turn not allowing the air to get hot. So change it.

highmileage

flush it out with water then with air through one way then the other. Do it a few times, and make sure you diverter valve is in good working order.

DFlintstone

"I'm not sure if the motor temp has anything to do with the heat. " YES! That IS your heat. Goes in the heater core, (like a small radiator in the dash), via the upper small hose, out the bottom. Watch the little lever on the vacuum controlled valve on the heater hose while someone switches it from hot to cold, ect. Make sure it's working. BACK flushing would be running water in the bottom hose and let the gunk run out the top one. (not back into the engine). Just squeeze the garden&heater hoses in your hand. You can go both ways, but start with the bottom one. Full house pressure might not be good for your heater core. If that gauge is right you need a new 195* thermostat.

Pets like antifreeze, even a little can kill. Good luck.

gthbryce

I ran a gallon of vinegar through my system and my heater is so hot it now Burns your hands. Its a mild acid so you should put a little baking soda through when your done to neutralize it. Another method I would have done was fill it up run it for like 10 minutes then let it sit all night but its too damn cold!

tjwalker

Good advice above by Dflintstone. Cab heat is simply a byproduct of engine heat. If the engine coolant isn't at the right temp, you'll never have good heat inside of the cab. Your goal should be to get the engine coolant to around 200 degrees, give or take a few. You can verify coolant temperature by pointing an infrared point and shoot thermometer directly at the thermostat housing of a hot engine.

What brand stat did you put in a while back; having a stat fail or not work properly out of the box is not unusual for many aftermarket units. A new OEM Jeep thermostat (195 degree) might be a good start. I'm not a big fan of aftermarket stats and considering how many thousands of cycles that thermostat is going to be asked to do during it's lifetime, spending $8.00 for a high quality one from Jeep is money well spent.

DUBarado

Hey, sorry for the delay, was in Christmas-mode... I bought a 180 degree thermo, but it rarely ever gets to 180 on the guage, usually floats around 160 when I'm driving... idk why I thought the jeep had electric heat... durr... but alas, I never had a heater that ran cool.

I guess I'm gonna have to swap the thermo out again for a 195* one, any good brands out there? Or are they a "get-what-you-pay-for" deal?

RTorrez1

Yea. I would also say a good place to start is a new thermostat 195deg. My 98 XJ, 4.0. runs at 210 deg no matter what the weather is If it's 110 deg or down to 34 deg it stays a constant 210 deg

DUBarado

it will also give me an excuse to replace my idler pulley, which has gotten rather noisy when I got the Jeep on the road again. Also, (sidenote) how do I know if I got the 9in or 10in rear brakes?

DFlintstone

Some drums are casted "Max Dia. xx.xx" on them so the lathe operator will know what size to stay inside of. You may have a faulty temp gauge as well as a flow issue in the heater core btw. You could feel the heater hoses relative to a radiator hose....If the radiator hose is hotter than the heater hose it probably isn't circulating that well. You can also put a thermostat in a pot of water on the stove....if you where inclined!

cruiser54

Get a new stat from Jeep,part number 83501426 and your problem will be solved.

generalcrawl

sounds like you t-stat is stuck open, i would swap it out first being that its only about 10 bucks with a gasket

DUBarado

Also side note. After driving it when I take the oil cap off smoke comes out like someone blew out birthday candles. And the oil on the air filter from blowback seems a bit much. Like a good 3rd of my filter has been sopped with oil. From watching the guage the oil pressure would be around 50 then drop to 20. I run 15w40 diesel grade stuff too.

DFlintstone

Bummer. How many miles on it? That "blow-by" is basically combustion gas that got past the rings. You might want to check that rear tube on the valve cover, it provides positive crankcase ventilation by sucking. The tube on mine was completely clogged, then disintegrated when I tried to clean it. What it doesn't get goes out the forward tube to the air cleaner.

Don't know about using oil made for a diesel. If there where an advantage, oil for gas engines would be diesel oil!

DUBarado

At almost 170k. The tube is working fine as far as I can tell. Im just not exactly sure what's causing the oil to be so tempermental. And im just running the heavier grade to help the old *** motor and the lack of pressure after a couple of miles driving.