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New Jeep owner, cooling system questions


 
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jcrouse
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Joined: 23 Jul 2006
Location: AZ

PostPosted: Tue Aug 01, 2006 10:09 am    Post subject: New Jeep owner, cooling system questions Reply with quote

I was recently given by my in-laws an '89 Cherokee with the 4.0 engine. It had the water pump replaced a few years back and has had constant overheating issues ever since. My father-in-law took it to a few indepentent repair shops and also a Jeep dealership. Over the past couple years the thermostat has been replaced a number of times, it has a new radiator, new hoses, and the plastic reservoir is new. The in-laws got fed up with nobody being able to fix the problem so they just gave the thing to me. A call to a Jeep mechanic gave me the idea that the air in the system had never been properly purged. He suggested I remove the upper radiator hose and the heater hose on the thermostat housing and add water to the thermostat housing opening until water came out of the upper radiator opening. I did this until the water ran clear. This did fix the overheating problem and I drove it almost 300 miles in 100+ temps to get it home. There were no overheating issues at all. I went out four-wheeling yesterday for an hour or so and it began to run warm once again but not like it did. Originally it would reach the red zone on the gauge in 3-5 minutes and yesterday it never did reach the red zone but it came close. I drove around town this morning for only 15 minutes or so and it again ran almost up to the red zone. I flushed the system again this morning and again, it seems to have solved the problem.

A few questions: How can I get coolant\anti-freeze into the system when I flush it like this? I was able to add a little to the reservoir but it wasn't but a quart or so. Also, why did it begin to run warm again when wheeling? Was it because the lack of coolant? If so, I'm not sure why it ran quite cool (only approached the ~200 temperature mid line on the gauge once) in over 100+ temps for nearly 300 miles. Why did it run too hot this morning after only a few miles? It seems there must be an air leak in the system. Does this sound reasonable?

Any advice would be greatly appreciated. I did read the 'sticky' on overheating issues. The air purging method described was different from what I was told so I'm wondering if the advice given to me by a "professional" Jeep dealer mechanic was completely sound. This Jeep is in incredible shape and I'd like to be able to use it without worrying about a heating issue.

Thanks.
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ThePhantum
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Joined: 23 Jan 2004
Location: I knew it...I'm surrounded by Assholes!

PostPosted: Tue Aug 01, 2006 12:58 pm    Post subject: Reply with quote

What proably happened is that air was still trapped someplace in the system. After a couple of heat cycles, it finally made it's way to the top of the engine and started causing problems. Welcome to the wonders of a closed cooling system. They are a royal pain.

Since it's giving you problems my first suggestion would be converting it to an open system. There's a number of writeups out there on different ways to do it, but here's one. http://www.off-road.com/jeep/cherokee/98/12_dec/radiator/radiator.html

Here's a way to purge air out of a closed system. I forget where I found it so I can't give you the link. I will say this, when loosening the the hex fitting, make sure to not unthread it to much...otherwise it will achieve a low earth orbit and you'll end up spending you're saturday afternoon shopping hardware stores for a new one.

Quote:
If you had a copy of the FSM (Factory Service Manual) or equivalent (Haynes, Chiltons, etc.), you wouldn’t need this web page but it would give you the following procedure:

1. Fill the system as normal with your antifreeze mixture. Always use a mixture of antifreeze and water (distilled works best) of at least 50%, though you can go as high as 70% antifreeze. An in-expensive tester available in most auto parts stores or the auto parts section of larger stores (Wal-Mart, etc.) that will tell you the concentration of antifreeze in your system.
2. At the top of the water box where the upper radiator hose enters the engine there is a small threaded plug with a hex fitting. Using the correct Allen wrench loosen the fitting to the point where air starts to escape. Ensure the heater is left on to allow water into the heater core.

NOTE: Before you fill the system completely it may be a good idea to remove this plug and apply some anti-seize or thread sealant to the threads. Over time the steel plug tends to seize to the aluminum head and so step two above may prove just shy of impossible without explosives. If you do manage to remove it, some anti-seize or thread sealant should make it easier to remove next time.

3. Continue to add antifreeze to replace the air being expelled through the plug.

4. When fluid starts to seep out of the plug tighten it up, top off the overflow tank, and you’re done. If you get erratic temp readings, or lack of heat from the vents in the car, re-open the screw and allow any residual air to escape.

Some people have replaced the plug with a brass one that is less likely to seize to the head, others have adapted a small valve or petcock into the threaded hole, allowing them to vent the system by simply opening the valve. A good hardware or plumbing supply store should have the parts needed for either of these modifications. Be sure that anything you adapt can withstand the temperatures and pressures under the hood.

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97 XJ Sport with a bunch of stuff
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jcrouse
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Joined: 23 Jul 2006
Location: AZ

PostPosted: Tue Aug 01, 2006 5:12 pm    Post subject: Reply with quote

Thanks a bunch for the information. It sounds like the conversion to an open system is the way to go. I searched for the hex fitting but I'm not sure where it is located. Is it near the thermostat housing?

Thanks again for the help.

Joe C.
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ThePhantum
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PostPosted: Tue Aug 01, 2006 5:42 pm    Post subject: Reply with quote

It should be right where the upper hose enters the engine. If you can't find it, an alternative method would be to jack up the rear of the Jeep until the cylinder head is either level or just slightly up at in rear. Then loosen the temperature sensor on the driver's side rear of the cylinder head and leave it loose until coolant starts to drip out. If it doesn't, keep adding coolant until it does. Then just tighten the sensor.

I also found a tip to help self purge air trapped in the block:
Drill two 1/16" holes in the thermostat flange (180* apart) and install the drilled unit with one hole at 1200, and the other at 0600. This makes the system "self-purging" as far as air in the engine block goes, and you just need to keep an eye on your coolant level for the first couple days or so.
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Never argue with idiots, they drag you down to their level and beat you with experience
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TheBrat97
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Joined: 28 Jul 2006
Location: Dallas, TX

PostPosted: Wed Aug 02, 2006 5:39 am    Post subject: Reply with quote

Quote:
when loosening the the hex fitting, make sure to not unthread it to much...otherwise it will achieve a low earth orbit and you'll end up spending you're saturday afternoon shopping hardware stores for a new one.


what do you mean by this?
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ThePhantum
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PostPosted: Wed Aug 02, 2006 8:39 am    Post subject: Reply with quote

TheBrat97 wrote:
Quote:
when loosening the the hex fitting, make sure to not unthread it to much...otherwise it will achieve a low earth orbit and you'll end up spending you're saturday afternoon shopping hardware stores for a new one.


what do you mean by this?


Remember that the cooling system is under pressure when it's hot. If you loosen it up to much, the pressure behind it will cause it shoot out like a BB and you will never find it.
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97 XJ Sport with a bunch of stuff
Quote:
Never argue with idiots, they drag you down to their level and beat you with experience
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TheBrat97
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Joined: 28 Jul 2006
Location: Dallas, TX

PostPosted: Wed Aug 02, 2006 8:58 am    Post subject: Reply with quote

Gotcha
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88WOWJ
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Joined: 12 Aug 2006
Location: Hinesville Ga

PostPosted: Sat Aug 12, 2006 4:07 am    Post subject: Cooling System Reply with quote

Owning 1988 XJ. I have walked your path many a time.Convert to the open system.You need to get a new radiator for a 1991 or above.
One thing that I found out that the 1991 rad has or may not a place for the coolant switch found in the rad for the closed system. If you do not
purchase a rad with the switch you will loose your electric coolant that acts
as aback up for cooling and you must rewire to correct it.Adavnce Auto parts sells a metal 2 core rad for $135.00 that has a plug that is removed
for the coolant switch.Secondly you must get rid of the coolant botltle.
That $45.00 dollar piece of French technology that breaks every 9 months.Buy you one at Advance Auto for $10.00.Also you must replace the heater control valve with a 1991. I didnt, I used the 1988 cut it up for parts to make it work.Cheap I guess.Also I removed my stock fan
and installed an electric fan 14 inch. With 100 degree heat in GA.
I have not gone above 206 degree.
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jcrouse
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Joined: 23 Jul 2006
Location: AZ

PostPosted: Sat Aug 12, 2006 11:11 pm    Post subject: Reply with quote

Thanks to everyone for the responses. I once again purged the air from the system and it ran nice and cool.......for a few days anyway until the waterpump began to leak like crazy. It took a few hours to replace it but I certainly am more familiar with my XJ now.

One question though. Is it really necessary to re-install the plastic splash shield that covers much of the lower front half of the engine? I've never had another vehicle that had one. The heavy metal skid plate seems like it would do a good job of keeping water etc. off the engine.

Thanks again.
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88WOWJ
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Joined: 12 Aug 2006
Location: Hinesville Ga

PostPosted: Sun Aug 13, 2006 1:29 am    Post subject: Cooling system Reply with quote

The skid plate is not there to keep water out its there as its name is skid plate.
As for the plastic or rubber shield it does help keep mud and water out.
I havent had one on mine for 7 or 8 years.
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Bucks Owin
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Joined: 12 Aug 2006

PostPosted: Wed Aug 16, 2006 9:25 am    Post subject: Reply with quote

By all means, do NOT get a stock plastic tank rad, go with an all metal setup. It doesn't take a lot of body flex to split the stock rad as you will probably find out at the worst possible time! Luckily mine let go crossing a ditch in front of my house....
(I can't believe that Chrysler ever put that plastic POS in there in the first place!)

FWIW,

Dennis
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