deeada2004

All winter long my 1999 4.0L Automatic I6 xj has been blowing cold air through the heater vents. I have noticed a minor oil leak and had contributed this to putting a thinner viscosity synthetic oil in for the winter. After checking the AC blend door, and found it to be functioning. I decided to move to the cooling system as the likely source of the lack of heat.

I knew that my radiator fluid was filled with rust, so I thought perhaps the heater core was clogged. So last week I reverse flushed the system several times using the Prestone reverse flush kit. I even added the Peak Flush Cleaner from Advanced Auto, ran the motor as directed, and then flushed the cooling system some more.

While messing around under the hood I noticed that there was a weird noise like water being forced through a small hole and a minor coolant leak coming from the thermostat housing. So, just to be safe I replaced the thermostat, and found it to be faulty, it was stuck half open. Upon replacing the thermostat and starting the car, fluid was streaming out from around the housing. I had to take the whole thing off and redo it with extra gasket maker. Then I allowed it time to harden before returning pressure to the system.

So, I filled the system with antifreeze and distilled water. For about three days the heater worked great, just like it used to, until today. I drove to a restaurant, and after leaving the heat never came on, just cold air... AGAIN. So, I turned off the heat and continued down the road.

About five minutes later the engine overheat warning indicator light came on. I was lucky enough to be passing a filling station, so I pulled in, popped the hood, and killed the motor. I get out of the jeep and BAM there is an explosion of steam from the passenger side of the engine compartment. I was able to deduce that hot coolant filled the non-pressurized coolant reservoir to the point that it blew the cap off.

The liquid that boiled out was the color of chocolate milk, and slick on your fingers. The fluid didn’t smell like oil though, and the tow truck driver says that he didn’t think it was oil in the coolant, but I'm not so sure. I have checked the oil, and found it to be devoid of coolant. But a little low. I have not noticed any steam escaping from the exhaust during operation. Other than the before stated incidents, the jeep runs great. I mean no check engine light, no lagging, nothing.

Can someone please tell me what the issue is here. If it's the head, or head gasket, and how can I check that? Could the thermostat have gone bad again? Also, while I was flushing the cooling system I might have gotten water in the intake, I noticed that the air filter was damp, but not wet. Could this have caused a problem?

Three other issues that are weird, though I don’t know if they apply, as they all involve the warm months of the year.

First, I noticed is an extensive amount of water draining from the car after running the AC in the summer. MUCH more water than I have noticed in the years before.

Second, after running the vehicle for about an hour straight, the pressure of the air coming out of the vents decreases by about 75%. The air is still cold, and the blower motor is still working at the same intensity. After turning off the jeep for 30 minutes or so the air intensity is back to normal.

Lastly, While it was hot out, every time I started the jeep, it would idle normally. Once put into drive it would get up to around 2,000 RPM (I'm guessing, this jeep only has dummy lights) I would loose power, like the engine was bogging down. If you just hit the gas it would hesitate for a moment and then power through it. After this, the jeep would run normally for however long I ran it. The same thing occurred every time I started the vehicle until the fall.

I know this is a lot of information, however, I wished to be thorough. Thank you guys in advanced for any insight you can provide!!!

ehall

You can borrow the block tester from Autozone but you have to buy the fluid

perez1989

Take the oil cap off and see if it has white crud on it. Water and oil makes a white crud that sticks to the cap.