Jethro4days

Hey everyone. I recently bought a 99 xj sport and I believe there is air in the coolant system. The heat comes on but doesn't get really really hot. It gets really warm. I was on the highway today. And the Jeep was running at 220. Which is abnormal seeing how it's October and in New Hampshire the air is very cold my last jeep would run about 195-200 on the highway. Even on warm days. I purchased a new waterpump and thermostat. I'm debating pulling the trigger on a new radiator seeing how they are only $100 with a life time warranty. Just curious on everyones thoughts.

cliffy

Did you think about flushing the heater core ? I did mine and it made a world of difference.

Jethro4days

So today after work I flushed the heater core. Got some pretty dark stuff out. But the heat still doesn't blow hot. Is this the symptom of a bad thermostat? I bought a new t stat aswell as water pump so I plan on replacing both this weekend. Was just curious if warm air is a sign of a bad tstat. Or if I didn't flush the heater core enough. But the high Temps on the highway the other day leads me to believe the thermostat is to blame.

Jethro4days

Produced another gallon similar in color.

toasterknight

You need to keep flushing the entire system until the water comes out as clean as it went in.

Jethro4days

I went back and fourth between flushing water into the inlet and the outlet. The water was clear when I stopped.

ehall

When the car is cold, start the motor and keep feeling the upper heater hose coming from the thermostat housing, and compare it to the other hose coming back out of the core. If there is a big drop in temperature between the two, then coolant isn't flowing through the heater core very well or at all, possibly because the valve is stuck, or because air pocket in the core. If they feel about the same then something else is the problem, maybe clogged fins in the core, or weak fan motor, or blend door is not working properly.

toasterknight

It's a 99. No hcv.

quneur

Thermostat and radiator left. I'm inclined towards radiator. If thermostat was stuck, you would get overheating problems.

BlueRidgeMark

No, a blown-up engine from overheating is the symptom of a stuck thermostat. No coolant flow = overheat QUICKLY. The thermostat has nothing to do with your lack of heat, UNLESS it's stuck OPEN, in which case you'll get heat eventually, but it will take a while.

Your heater core is probably still gunked up. It needs more than just a quick flush - you need to get the gunk loosened up.

Try an old mechanic's trick: Toss in a quarter cup of Amway SA8 laundry detergent, and run with that in your cooling system for a couple of weeks. Then flush. You should now have a squeaky clean cooling system. I've done this with several vehicles and it works.

If the PO used a stop-leak product in it, expect to develop some leaks as the detergent washes it out. Repair leaks as needed.

Some say Dawn dishwashing liquid will do the same thing. Dunno, haven't tried it myself.