Heat issues again

I have a 90 cherokee. I recently changed out my thermostat again, I went from an Auto Zone 195 t-stat, to an OEM Mopar Stealership 195 t-stat. This one has the bleed valve at 12 'o clock, this how I installed it too with the bleed valve at 12 'o clock. After installing this I filled the expansion bottle up with anti-freeze and left the cap off and started the car. It started to get over 210, so I shut it off and let it cool down, then I started it again and all the coolant left the container and went through the motor so I added more. I shut the car off once it was full. I did notice that huge bubbles came up from the tank. But after driving around I found that my car has air in the cooling system once again. Is there anyway I can go about bleeding this without pulling the t-stat out again, or jacking the rear of the car up and pulling the temp. sensor? Can I just drain my anti-freeze, and pull the upper radiator hose off and fill it up with coolant until it overflows then quickly connect it to the radiator, and then fill the bottle up with anti-freeze? Would this effectively remove air? I'm about to give up on the closed cooling crap and do the poor man's open conversion.

I am in the same situation as you are. I have tried evrything with the same temp readings. I need advice on air pockets and bleeding as well.

I know what you mean, this is annoying as heck, the open system is way easier to maintain.

Any advice from anyone else would be helpful.

I changed over, but in researching all the threads about the turtle tank before I changed, I ran across some stuff.

The tank is supposed to be 1/2 full when cold, not filled completely. The cap is a pressure cap and does go bad, allowing no pressure to build and causing overheating just like a regular cap.

Use a water wetter to eliminate the bubble tension and move the air out of the system. This stuff works even on a open system and I experienced a 15-20 degree reduction in temp even with my open system - which had no recovery tank and was gulping air. I plumbed in a Comanche fender tank and that problem is now solved.

Jacking the car to fill it and pulling the rear temp sensor can help - I'd do it if I knew everything else had been done. The turtle tank being the highest point should still gather up the air if it's not stuck in the head unable to get out. High flow pumps are not guaranteed to move bubbles, and may even make the problem worse as the coolant passes through everything too quickly to pickup heat from the engine or lose it in the radiator.

Swapping in a good two core rad will help, as it has more heat loss capacity. I went to a three core and it takes some time to warm up, leaving the computer in open loop and costing a little more in mileage theoretically.

Cherokee coolant systems are more about getting the air out than swapping thermostats - as you have discovered. Draining/swapping/etc. never gets the air out, it just leaves you back at square one about a gallon short.

So will it work to pull the upper rad. hose and fill it up and put it back on and fill up overflow tank?

check with your favorite xj 4x4 parts people and get a kit to convert your closed cooling system to an open one. As some of you have stated the closed system xj's are very common to develop your same over heating (air pocket) problem. I think Quadra Track sells em and there not to expensive?

In my case this is an overcooling problem

On my 90, I used a factory thermostat, changed all the hoses and valve. To bleed it, I pulled the sensor out and made sure coolant came out while running. Then screwed the thing in, top off the tank, and it has been good to go ever since. I did, also, park it on a incline, but you could jack up the back.

The original system works fine, if all is in good condition. This thing has 260+K on it and runs cool everywhere.

If you use a closed or open system, just make sure everything is in good shape and you should not need to make a change,

Bob

I thought you weren't supposed to have it running while unscrewing the sensor:nono:

In my case this is an overcooling problem

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now I am really confused...are you saying your coolant doesn't come up to temp...around 210*...or are you saying your heater doesn't work?

Your first post said you shut it down because you "started to go over 210*"

Let me clarify,,,,

With the thing off, and at operating temp, I pulled the sensor, then restarted it, waited for fluid to come out, then shut it down. Put back the sensor.

IF it was wrong to do that, well it worked fine for me! I did the same when I put in my block heater too.

The original system works fine.

yes it doesn't come up to temp which affects heater output. I was talking about when I first filled it up with coolant after the t-stat change out. I had to shut it down because it was on the brink of overheating and when I did that the t-stat kicked in, and took all my anti-freeze.

This is the closed system right, the one with the turtle on the firewall ? most every problem on that puppy can be traced to the bottle, it holds pressure, if it's old it's probably warped and you are not getting a good seal on the things pressure cap.
I seem to remember seeing them in the quadratec catalog for like $17 or so. There is nothing wrong with the closed system when it works, they have been used for years by all the manufacturers and in fact Ford uses them to this day on a few models.

megabyte5689 said:

So will it work to pull the upper rad. hose and fill it up and put it back on and fill up overflow tank?

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That is all I ever did to my 87, even when I replaced the radiator. Slowly Filling the elevated upper radiator hose (disconnected at the thermostat housing) lets air out the upper radiator hose while flodding the radiator and engine. It also lets air out the poly bottle opening, and eventually fills the poly bottle as well.

I hear a lot of complaints about poor heat and I suspect some of them are due to failed damper door actuators that fail to shut off outside air and switch to inside air circulation. I also think some people have accidently swapped the upper and lower heater core hoses and flow path thus causing problems, I nearly did it on my 87 recently when replacing hoses. Also the '90 has a notorious heater control valve IIRC in the heater hose line!!!! So don't be too sure its a thermostat problem.