So winter's around the corner and I decided to drain the water out of the coolant system of my 87 Cherokee and add antifreeze. Somewhere along the way I got air in the system and the thermostat won't open. I've tried burping the system by leaving the cap off the reservoir, turning the heat up, and letting it idle. Lots of air came out but the thermostat still won't open. I've been doing this for the past two days. It's driving me crazy. Can I get any suggestions?

this funnel is a real life saver

X2 on the funnel. $25 well spent. I usually just do what I can, drive the Jeep, keep the overflow up to level, and in a couple days all the air has burped out. With this funnel dead on from the get go. Did you replace the thermostat or is it the old one? If new would not be the first time a part was defective out of the box. If old maybe just needs to go?

Turn the heat full on, take off the bottle cap, and run it up to about 1500 RPMs and hold it there for a while.

If you still have the closed cooling system, you can peek through the gap where the hood is open and see the air bubbles burp out of the system through the coolant bottle. When they stop, you're done.

I replaced the water pump, thermostat, radiator, and reservoir cap over the summer. Filled the coolant system with water at the time and everything worked fine. I Now decided to drain the water and add antifreeze and air got in the system. I tried burping the system and didn't work. Is there anything else I can do?

This can be a huge pain with the closed system on the Renix engines. I've not tried this but, park on a hill with the nose down. Remove the temperature sending unit on the head at the back of the driver's side.
This should allow all the air to escape.
Like I said, I've not personally done this but have experienced the frustrating "air in system" in my old MJ. I was ready to drive it off a cliff.

This is driving me insane. I've done everything and the thermostat still won't open. I don't know what else to do. I GIVE UP.

Note from DJ
First do you have the original closed system; no radiator cap on the radiator?
Next remove the thermostat and place it in an old pot of water on the stove apply heat and see if it opens.

Note from DJ
Have a look at this for coolant flow and closed loop pressure bottle.

Assuming your thermostat is good, doing what I suggested earlier should do the trick.

It worked every time for me on my '87 with the closed cooling system.

It won't get hot enough at normal idle to burp.

Its been a while since I commented on this thread but I just got the Lisle Spill Free funnel to burp my 87 xj but none of the fittings fit on the reservoir. What do I do?

Ditch the funnel and use a vacuum filler to bleed the system.

About to try this this weekend. Everyone use 50/50? There is no bleeder valve on our Jeeps right?

I learned of this from ChrisFix on YouTube. This is a wrost case scenario for me, but you can drill a small whole near where the edge of the head meets the thermostat into the thermostat. There will always be some flow, but it won't be high flow until the thermostat opens. You won't have to worry about air and burping on your closed system.

If the resevoir cap is good, it should self bleed.