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Unread 07-07-2005, 10:11 PM   #1
GDSQDCR
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How do you burp the cooling system in a 4.0

I have a 90 4.0. I believe I introduced air into the system while I was changing some parts.

How do I burp the system to get the air out? The only opening I have is the reservoir cap.

Thanks!

Anthony

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Unread 07-08-2005, 09:25 AM   #2
MJDriver
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There are a couple suggestions for this. One is to warm it up with the cap closed, then drive it around with the reservoir cap cracked enough to let out excess pressure. Close it when you are satisfied it has balanced at a good pressure.

I did it the rather stupid way, as I forgot about about built up heat after shut off. I replaced all the hoses, filled it as much as possible with coolant, then let it run for 15 minutes. It seemed fine so I shut it off. That's when it almost blew apart the reservoir with excess coolant and pressure. I used a rag and opened the cap and let it burp out all the excess coolant (a whole lot of it), and used a turkey baster to drain more and bring it back down to a decent level.

The first couple times after that, when I got home I would lightly open the cap and let out the excess pressure. Now it works just fine.

Good luck.
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Unread 07-20-2005, 09:24 PM   #3
Tonka
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I pull the heater hose, at the thermostat, fill through bottle it till coolant is at the top of the thermostat neck, replace hose, top off coolant motor running, bottle cap off
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Unread 07-22-2005, 08:18 PM   #4
Ed in North Ga
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foolproof method->

park jeep with rear end higher than front- that gets the rear of the engine higher than the front.

with jeep off- loosen the temp. sending unit on the rear of the engine block-- looking inside from the front bumper, located right rear of the engine/just right of the valve cover/firewall area/above the intake/exhaust. One wire hookup.

loosen, but dont remove--just a couple of threads holding it in. (removeing causes volcano of coolant).

with the jeep sitting with the rear of the engine higher than the front, that sending unit is now the highest point- the air that gets trapped in the head that no one can ever seem to remove is now sitting right under there-- Fill engine and plastic "piece of junk" coolant bottle with antifreeze goo- start engine and watch for coolant to start leaking from the sending unit hole- shut engine off and tighten it back down when it does flow out.

there be no air in dere no mo.
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[URL=http://groups.msn.com/RattsNest]Ratts Nest [/URL] 1989 Jeep MJ- 200,000- 28mpg. If its a Renix, its all good. 1989 XJ (sold) 310,000- 29mpg. Renix. See the pattern?
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Unread 07-22-2005, 09:39 PM   #5
Dana44
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ah, the joys of a closed loop cooling system. not very smart

hmm.. i didnt even know air would affect it.

i know when you do like a water pump, or lose water in any way. dont rely on the tank, gotta pop a hose off and fil it manually.
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Unread 07-22-2005, 10:14 PM   #6
Ed in North Ga
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Quote:
Originally Posted by Dana44
ah, the joys of a closed loop cooling system. not very smart

hmm.. i didnt even know air would affect it.

i know when you do like a water pump, or lose water in any way. dont rely on the tank, gotta pop a hose off and fil it manually.

hehe- the joys? naaaa, I wouldnt even go that far. the "pains" maybe...
ah well- Ive had two- both have gone at least 200,000 with the XJ topping 320,000....both closed systems. One radiator apice...well, one anyway, Im waiting on the MJ to blow its seams.

the "air" that "affects" it, is the wonderfull design of the old 4.0s head...its like a RAID bug trap. Air gets in, and never gets out- it dutifully resists gravity and heads to the front of the engine(since its higher normally anyway) away from the sending unit...excellent design(flaw).. -- some decide that the coolant tank heat/cool/heat cycle will rid the head of its air, some decide to pull hoses and fill to their hearts content. ALOT of people live with it....and wonder why the guage wanders so...must be ghosts.

Ive done it for years(both ways)- I`ll stand by my way. Burrrrrpppppp. No mo air.
Dam coolant tanks are over $30 again..at this rate, i`ll have to convert to the open system in, ohhhhhh....another 75,000 or so....naaaaaaa. I`ll buy a metal tank next go-round.
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[URL=http://groups.msn.com/RattsNest]Ratts Nest [/URL] 1989 Jeep MJ- 200,000- 28mpg. If its a Renix, its all good. 1989 XJ (sold) 310,000- 29mpg. Renix. See the pattern?
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