Hello all, I have a 1998 XJ8. I have no heat and have exhausted all of the areas to search that I know of.

For starters, I had a leak around my water pump, so I put in some Barr's Leaks cooling system stop leak. I drove from DC to Williamsburg and back (approximately 225 miles) with no heat issues. Now, I have no heat.

I have checked all the fuses (two under hood blocks and trunk) and all fuses are good. My horn sounder works when the alarm goes off. I have good coolant level and no leaks. I have no fogging inside, so I'm assuming no heater core leak. My heater pump is working fine and my AC is working fine. My fog lights work, so I'm assuming that the shared circuit is fine.

I just checked the voltage to the heater valve and it seems to only have 6 volts on HIGH. Is it supposed to have 6 volts or 12 volts?

Please help! I can't really tell if the aux pump for the heater is working, what is the check for that? Will a radiator flush push any gunk possibly clogging the heater core out?

Because I drove with the heat on for several hours after putting in the Barr's Leaks, I'm reluctant to blame the stuff, but I'm just not sure.

Any takers?

Thanks.

 

MrTrouble, A quick check that I would do is to break into the coolant system for the heater core and attempt to blow some air through those lines. There is nothing inline that is blocking the fluid path so, you should get a healthy stream of air to flow through. If you don't get anything, then that is telling me that you clogged up your heater core and if you are lucky, you can remove the blockage. But, if not, you are looking at a new heater core.

After this, I would play with the heat/cooling system and run it through a gambit of temperature extremes and see if you can hear the temperature damper moving. Not being extremely versed on your car, I am not sure if you can see a shaft that shows the position of the damper (near the bottom of the dash in the center). As you go from say hot to cold, you should see the shaft rotate some. it is possible also that you had a coincidence and that damper failed at the same time. But, I am also willing to go out on a limb and say I think it is the heater core.

Hopefully I am wrong and it is simply the damper has failed. That is a much cheaper and easier thing to fix than the heater core itself. If you do have a blocked heater core, then I would suggest getting your hands on an air compressor (capable of up to 120 psi) and then add a little bit of water to one line and then shoot that slug of water to the heater core. Then repeat using the other tube. Repeat until the blockage clears or it is pretty obvious that the clog is not going to clear itself. What you are doing is using the slug of water as a hammer (actually called water hammer in steam lines, probably heard it as steam pipes in the older building would bang and clang periodically).

If you need some more help, let me know. Sounds like you live not to far from me. I am in Great Mills, MD. I am just on the other side of the Potomac River bridge off of 301.

 

Many thanks Thermo. I have had a whole slew of stuff go bad working on this thing...LOL...today. I was going through looking for clogs in the lines and while heating the car up, the radiator hose going into the thermostat housing blew off.....ARE YOU KIDDING ME!!!! The radiator wasn't really hot, the fans never came on and it had been up to operating temperature for at least 10 minutes. Now granted, I am in Springfield, VA and it is about 25 degrees outside, but I still think that idling for that length of time should have set the fans to spinning.

So, I have gone through the JTIS and traced out everything. I know the directions that every thing should be running. I have eliminated any air lock. I will now try the water hammer to see if it clears out the core hoses.

Question: at what point in the hoses should I try to get into the core? Can I inlet hose just behind the pump and the outlet just before the valve?

I will have to check and see if I can see the door moving behind the vents. I ran the cooling system self test earlier and it ran through everything with no issues.

Right now, I have to get a new o-ring for the thermostat. when the hose blew off, I figured I should test the thermostat to make sure it was still functioning. It is working fine, but the o-ring has stretched out and will not fit into the thermostat housing correctly.

 

BTW, Yeah, I'm about 15 minutes outside DC just south of Alexandria.

 

MrTrouble, I would go as close to the heater core as you can, but the hoses will handle the 120 psi air (provided they are in good shape). The motor will handle it too. Just, just to make sure, as close as practical is better.