conwaylale

Woke up to 1 degree this morning and started the jeep/ 96 xj. 4.0/ wanted to let it warm up before I took off to work. About 10 minutes later I went out and got in. The heater was blowing cold air and then I noticed it was overheating. Turned it off emmediatly and took the wides car. Any idea what could have happened?

Firestorm500

It's probably not a blown head gasket. At what temperature is your anti-freeze good down to?

If you don't know, take wifemobile and get a tester.

CCKen

Coolant in radiator might be frozen.

Roler

Yep, heater blowing cold and overheating....something is not flowing properly
(Just thinking along here, not that I've ever had that issue here in Oz, hehe.)

Firestorm500

That's why I told him to check coolant strength first. Or lack of strength.

The first thing everyone wants to do is jump in there and replace the poor thermostat. I wonder how many good thermostats have been thrown away?

His antifreeze is likely the problem.

salad

Yeah thermostat won't do much for that, the heater core bypasses it. Lack of antifreeze sounds most likely.

CCKen

How ya doing mate. Haven't heard from you in awhile.

conwaylale

I'm not sure about the anti freeze strength. But I'm going to say very weak. She's. Parked in the garage with a heater on the radiator now. Hopefully going to thaw it out and do a flush and fill to see if it helps. Is draining the fluid from the block recommended?

Firestorm500

All the old coolant needs to go, including in the heater core.

conwaylale

Ok. Radiator is thawed and empty. How do I get the fluid out of block and heater core?

Roler

Heater core is drained by removing the heater hoses of the thermostat. Take the opportunity to flush the heatercore while you're at it (reverse flush, so flush opposite direction of how it ususally flows, to flush the crud out the heatercore.

Block has drain'plug' on the side, but not sure if this is depending on year (and model).
Somebody will likely chime in regarding this.

conwaylale

Well I was unable to find the block drain plug and I couldn't flush the heater core because my garden hose was frozen. The problem was a frozen radiator. I drained it and flushed with hot water. Then filled with 50/50. Not the best flush but it gets me back on the road and I have heat. Hate I couldn't do a full flush but its surely better than nothing. Id still like to redo it and find the block drain so if anyone knows exactly what it looks like on a 96. 4.0 let me know.

CCKen

Post #3.

The drain plug is on the left side of the engine near the rear, and above the oil pan. The plug takes a special size square drive. They've been reported as being available at Harbor Freight as a set but I went to my Harbor Freight and couldn't find them. Go on line and see if they're listed.

highmileage

Aside from the coolant issue, I had my thermostat lock up on me one time in the bitter cold -26 a good rap with a screwdriver on the stat housing opened it. Just another thing to look for in the "hard" winter.

CCKen

Additional reading...from the dark side.

http://www.jeepforum.com/forum/f11/e...in-plug-16632/