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slow overheating issue


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Lets start of with: I have a 1988 Comanche with a 4.0L Renix mated to a 5spd transmission. Everything is stock in the engine bay.

 

I am having a slow over heating issue. I over filled the expansion tank and it boiled over, I replaced the cap with one that was on a newer '90 cherokee and it did not stop the issue. I can drive for about 20+ miles before the needle passes the 210 mark, but it doesn't stop until just before the red. My antifreeze is bright green, and is fresh.

 

I did jack up the truck and pulled out the sensor in the back of the head, and got a mouth full of hot antifreeze. I assume I did something wrong there. When I turn off the truck I can hear a sizzle from the expansion tank cap. I am going to swap the tank with the new cap and see if it is just a mating issue.

 

How much do I fill the expansion tank up? What could I be doing wrong, and could someone illustrate a little clearer how to bleed the cooling system?

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Are you sure the bottle isn't cracked? The system needs pressure to keep the boiling temperature up. Afterall, the boiling point of water is 212 degrees. By keeping the system under pressure, it raises the boiling point.

 

I guess what I am getting at, is if you can hear hissing around the bottle, there is pressure getting out. It will not perform like it should until the pressure is sustained. I might take a closer look at the bottle.

 

Rob L. :cheers:

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There's a little post directly below the filler neck, as you look inside the pressure bottle. On all the bottles I've seen, the bottom half of the post is round, and a semi-circular portion sicks up above that. Fill to the top of the round part of the post. Any more than that, and it's likely to overflow. Bleeding the system...raise the rear of the truck a ways, engine cold, remove the temp sensor at the left rear of the cylinder head, fill until coolant runs out the hole, replace the sensor, check coolant level in the bottle as described. If you're seeing coolant around the cap or elsewhere on the pressure bottle after running at normal temps, assume it's got small cracks and won't hold pressure. At the temps our trucks run, if it won't hold pressure, it will boil and overheat. As automan pointed out, the bottle is always suspect.

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...By the time summer's over there will be 1,009,453 posts similar to this. :peek:

Like this?

http://www.comancheclub.com/forums/viewtopic.php?f=2&t=23276&hilit=coolant

 

 

Finding a clearly depicted bleed process is not easily found in a search. I did searches and I got choppy and conflicting information.

 

 

Thank you for your help guys.

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Finding a clearly depicted bleed process is not easily found in a search. I did searches and I got choppy and conflicting information.

"Bleeding" is for brakes.

 

"Burping" is for the cooling system.

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Finding a clearly depicted bleed process is not easily found in a search. I did searches and I got choppy and conflicting information.

"Bleeding" is for brakes.

 

"Burping" is for the cooling system.

 

 

What do we do to clutches?

 

:) Sorry, if we're arguing semantics, I can't resist.

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