Best way to purge closed system?

[ibjeepin821]

Hey guy and gals im having overheating problems and I have been doing everything to elminate causes. my next step is gettting all the air out of the system It is a closed system (89 4.0.) It seems the thermostat isnt opening (brand new along with a new water pump) but there is a lot of air. Is there a good way to get it out...I was told that tapping a valve into one of the hoses might be a good idea cna someone please help

 

[JJacobs]

Pull the temp sensor from the rear of the head. Be prepared for a small geyser when it's full. That seems to get most of the air out. Tools are also available to pull a vacuum on the system and burp all the air without the mess.

 

[XJXJ]

Hey guy and gals im having overheating problems and I have been doing everything to elminate causes. my next step is gettting all the air out of the system It is a closed system (89 4.0.) It seems the thermostat isnt opening (brand new along with a new water pump) but there is a lot of air. Is there a good way to get it out...I was told that tapping a valve into one of the hoses might be a good idea cna someone please help

I fill it by removing the upper hose from thermostat housing, hold it up and pour. With the vehicle level the coolant will fill the radiator, engine and eventually make it's way up through the bottom of the tank. I've never had air trapped in the system using this method to refill the system.

I've read about folks loosening the CTS (coolant temperature sensor) in the block but have no experience doing that.

Overheating? Probably need a new radiator. Do the tank/cap and rubber at the same time. Watch-out for worn/loose motor mounts if you go with aftermarket because the rads are usually thicker and the engine fan may rip a hole in it.

 

[PETEY]

When i replaced my radiator I just took off the hose from the top of the radiator, and the little hose of the thermostat housing. I poured the fluid into the little opening of the thermostat housing until the fluid came out of the top of the radiator. Not sure if this is the best way but it worked.

 

[drifto77]

Pull the temp sensor from the rear of the head. Be prepared for a small geyser when it's full. That seems to get most of the air out. Tools are also available to pull a vacuum on the system and burp all the air without the mess.

Should this be done with it running? I just bought a ' 91 and it got hot on me on the way home, (test drove it 2 times and it never got hot) so I got one Iam trying to fix now too.

 

[churky89]

Swap out to the open system

 

[gr8tires]

Just did the same procedure as XJXJ:
After re-installing radiator, hooked lower hose on first, then poured liquid thru upper hose until it showed at hose end, then re-attached upper hose to t-stat housing. Burped the system by squeezing the lower and upper hose, then filled reservoir with fluid.
Will check levels today, but last nite seemed OK.
:sunshine:

 

[ibjeepin821]

Where is the tcs on my jeep?

 

[BSD]

It is at the top rear driver's side of the block. It sets right next to the valve cover, back by the firewall and has one wire coming off it. I have an 89 4.0 also and this method works great. two suggestions. Frist, do it with the front end pointing slightly down hill - like at the end of the drive way. Second, you do not need to take it all teh way out. Just slowly loosen the threads. You will eventually get it loose enough were the air can make it by. It will also be easy to tell when it is just radiator fluid. Also, make sure it is at operating temperature. good luck
BSD

 

[drifto77]

Should this be done with it running? .

DUH........... my bad. Not running = no geyser.
Boy do I feel stupid now, should have thought about that before asking.

 

[XJXJ]

DUH........... my bad. Not running = no geyser.
Boy do I feel stupid now, should have thought about that before asking.

LOL... At least you know the water pump's pumping good. Helluva surprised on a quiet Sunday, I bet.

This is also "the way" to flush a system except you remove the thermostat and lower hose too. It'll drain the big stuff out and you can stick a garden hose in the thermostat hole in the head. I've even ran the engine with the hose flowing but I was very careful to keep everything clear of the fan.

It's always a good idea to think EVERYTHING through because things like that can have much worse results. Luckily, this was more of a wake-up call while you and your Jeep are okay.

Once, I spaced-out and yanked a HOT heater-core hose off a chevy 350 engine fitting before realizing I'd forgotten to remove pressure. That resulted in a nasty trip to the ER where I was given the strongest pain killers I've ever heard-of and endured the doc removing blistered flesh from my arm. Ouch!!!