So, I just did a coolant flush on my 94 xj with Prestone brand flush. Drained the old coolant. Put the flush plus water in ran at idle for 10 min. Drained the flush and added the new 50/50 coolant mixture. As soon as I let the car cool down from flushing it I started it back up and in less than 5min at idle my temp gauge was reading 250F!!! What could be causing this? I wasnt having this problem before (although the reason I decided to do a flush was b/c it was running at about 210-220F). I'm checking my thermostat now. But would could have caused it to overheat right after flushing it?

 

If it wasn't doing this before you flushed it, then it's probably air in the line. You need to bleed the system after you flush it.

 

How do I go about bleeding it?

 

Well, i installed a T fitting in my upper hose. You can get them for really cheap at Lowes/ AutoZone. So, all i do is open that t fitting and add coolant until pure coolant comes out of it. On my old WJ i had a bleed screw, which made it WAY easier. I would do a search here on the forum, to find out how other people bleed their systems.

 

Let it idle with the rad cap off, when coolant starts to flow out the neck of the rad, put the rad cap back on. Check the level in the overflow bottle.