Hello Everyone,


I am writing because I want to make sure I understand the air removal process for the open cooling system. You want to run the jeep facing up hill with the cap off. Ideally you want the driver’s side up 1-2” higher (while facing uphill) than the passenger side, ideally having the driver side tire on a curb and the passenger side off the curb. You then run the jeep until it gets hot and the stat opens. You let it run with the cap off and try and fill as much coolant as possible into the system. I’m guessing this would be a good time to have the spill free funnel locked onto the radiator.


If you don’t have the spill free funnel, you fill the radiator so that the radiator is full and its topped off so you can see the coolant moving above just above idle. You then turn off the jeep, let it cool off and when you can squeeze the top and bottom hoses without getting burned. Repeat the process but you don’t remove the cap. Let it run, let it open see the fan cycle on and off a few times then kill it, let it cool then squeeze the hoses again. During the first startup and subsequent startups, its best to have the overflow tank ¾ to full. If you have a new or good radiator cap the building up air should be pushed out through the overflow tank and you should see bubbles. During the squeezing and subsequent startup runs.

I’m guessing I won’t have to worry about the overflow tank line. I might have gotten some air in the overflow hose when I cleaned out the thank. I’m guessing that as long as the cap is good and the hose to tank connection is airtight. The hot engine will be able to push out any of the air that might be in the line from when I disconnected it to clean out the tank.


If you are curious about my overflow tank, the hose to tank connection is at the top of the tank. There is a built in channel that goes down and around almost like a homebrew air lock. Just curious of everyone’s tips because I’m really losing my patience trying to get the air out and conflicting statements I have read. I recall being told to keep squeezing the top hose beyond getting burnt and that didn’t work out to well. I will be replacing the thermostat before I plan to burb it. I’ll make sure to drill the hole at the top and bottom of the stat and fill as much of the hose and t-stat housing before I rejoin them.

I really appreciate everyone’s help and I hope I’ve consolidated everything about burping an open air 4.0L to help others later and look forward to your responses.

 

Me and a friend did it on flat land with a soda bottle with a cut off bottom, put the mouth/cap side into the rad fill it with coolant. start jeep. temp will sky rocket then DROP. watch temp. If temp stays low your good. pretty simple. repeat if necessary.