How to bleed the Cooling System

[Jeepcom23]

I have an open cooling system in a 1991 MJ 4.0 HO.

How do I bleed the cooling system, Ive looked and looked but I've yet to find a solid answer.

 

Thanks!

-Cody

[ParadiseMJ]

You shouldn't have to. It's an open system, meaning open to atmosphere.

 

Coolant is added through the coolant overflow bottle. In a perfect world, when the coolant heats up, it expands and moves into the overflow (along with air bubbles). When it cools it should suck coolant back in to the radiator (without air bubbles). It should be self "burping". If your overflow runs empty it will suck air but filling it back up usually remedies that in a few cycles.

 

Just to be sure you can a.) buy an OEM t-stat with the little toggle hole in it or b.) drill a 1/8" hole in the t-stat flange (inside).

 

Check the level of the coolant overflow when cold and then again when hot, should be a difference

[Jeepcom23]

Hmm, alright.

Just trying to rule things out.

 

But where exactly do i drill the hole on the Tstat?

[ParadiseMJ]

Take the t-stat out. Drill on the flange, the round part that surrounds the meat of the stat, think of it as the ring around Saturn (the planet, not the car). Drill anywhere EXCEPT close to either edge. Install t-stat with the hole at 12 o'clock position (not the time).

 

Also get yourself a new 16lb. radiator cap without the lever.

 

On a closed Renix system you can drill a hole at 12 and 6 o'clock.

[RLCollins]

If you do not want to drill a hole, than purchase a OEM 1-83501426AC AKA SF 8952001797, which is the Part number stapped on the flange. This is a 195 degree thermostat with a small hole which appears to be a check valve, because there is a small silver ball inside. This hole is to be installed at 12 o clock position. I only paid $10.92 for it at Chrysler. :yes:

[avnsteve]

and if all that still doesn't work, back your rig up onto a set of ramps, you want the rear most portion of the head sitting higher than the rest of the engine, you can then remove the temp gauge sender and burp from there, I almost ALWAYS have an air pocket back there and thats how i clear it.

[Nixels]

and if all that still doesn't work, back your rig up onto a set of ramps, you want the rear most portion of the head sitting higher than the rest of the engine, you can then remove the temp gauge sender and burp from there, I almost ALWAYS have an air pocket back there and thats how i clear it.

That worked! Thanks from 3 years later!  :doh:

:rotf: