Bleeding your closed cooling system

[BLHTAZ]

My method of bleeding works without running then engine and requires it to be cool...

 

1.) Park the truck with the front end pointing down hill or jack the back end up as high as you can if you don't have a sloped area to work with. Allow it to set for a few minutes to get the air to accumulate at the high point in the rear of the head.

 

2.) Locate the temperature sender at the right rear of the head just under the MAP sensor. (I found it easier to remove the MAP sensor to get to it with a socket & extension).

(not a Renix engine pictured, but it shows the location)

 

3.) Be sure that your coolant is propoerly filled and remove the sender, but don't go far with it as the air will bubble out and then the coolant will start to flow so you will need to be ready to put it back in quickly. Be sure to leave the cap off of the coolant bottle during this process.

 

That should have the air out. Check your coolant level again after this process and then take it for a ride and see how it works. It should not heat up again (unless you have other issues), but if it does, repeat this process one more time AFTER IT COOLS DOWN. Mine worked with one try though :cheers:

[IDXJ]

Very good info. It can be an absolutely royal pain to get one bled. What I did was drill a 1/16 hole in my thermostat and instal the stat with the hole at the 12 oclock position. It allows the air to pass to the radiator and vent. Doesn't seem to affect the warmup or running temp either.

[Big_Mark]

On my Jeep it appears that the temp sending unit has been broken off 

Is there another way to bleed the cooling system that does not require removing that sensor?

I just changed the heater core but did not drain the whole system, I think I can get by with just filling the heater core

I understand I should replace all the coolant but it is still bright green and seems to be in good shape. I intend to replace the radiator "soon" with one that has a filler neck on it and likely drill the hole in the t-stat and will refresh the coolant at that time.

I don't want to try to get the sensor base out with a bolt extractor at this time because it is keeping a seal and i need to move the Jeep. 

I suspect I'll need to remove the head to properly remove the sensor but don't have the time to do that right now.

 

Any guidance is appreciated, thanks all

 

EDIT: I was able to burp the Heater core due to the "Prestone" flush fitting in the top heater hose, I simply un screwed the cap, then pushed the hose down (so it's lower than the level of coolant in the reservoir) I did that a few times, added more coolant and viola, she's topped off! At least it's good enough for now. 

Edited September 1, 2020 by Big_Mark
answered my own question, closed loop for others

[Pete M]

oh yeah, if you've got one of the inline bleeders, that's your ticket right there.