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post #1 of (permalink) Old 11-19-2002, 10:07 PM Thread Starter
 
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4.0L Head gasket problem????

Hey guys,

I have a 98 TJ with a 4.0L. My radiator started leaking around the top tank so I pulled it out and had the gasket replace... 2 days later its leaking again around the same gasket only in a different spot... I bring it back and tell to guy that his gasket didnt take... no problem he says and fixes it for me... but he tells me that maybe my cap has gone bad and the system is building up too much pressure...okay I can buy that... So I replace the cap and the thermostat while I am at it... I bring it home put the radiator back in and go for a ride. I assume all is well until I head out to move it again in the morning and see antifreeze on the ground... Same gasket around the top of the tank and radiator core. I talked with a back yard mechanic and he said that he has heard the Jeep 4.0L radiators blowing the gasket on radiators and this was a sign that he head gasket is starting to go...

Now I am not professional mechanic but I am not an idiot when it comes to vechiles either... How would it be possible for the cooling system to be building too much pressure and blowing this gasket if the cap is working properly? Doesnt the radiator cap regulate the pressure in the cooling system along with the overflow tank? I specifically asked the guy at the radiator shop if he pressure tested the radiator for leaks. He said he did both times with 20 psi. Has anyone ever heard of head gasket problems in the 4.0L? I have researched Jeeps for years on the internet and never seen anything mentioned about a head gasket problem. Could a bad head gasket be causing a surge in pressure in my cooling system that would be blowing this gasket out?

The Jeep isnt running hot, nor is there any water in the oil, or white smoke out the exhaust... all typical signs of a head gasket problem. I am stumped.

Any thoughts on the situation???
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post #2 of (permalink) Old 11-19-2002, 10:33 PM
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Re: 4.0L Head gasket problem????

Something doesn't add up here. This apparently never happens while you're driving it .......just after you're driving it. I would think that any head gasket problems would be far more apparent under load. I would also expect that if it was severe enough to exceed the handling capacity of the radiator cap (to vent it) that you would have some indication at the temp gauge while driving. You indicate NO temperature anomolies.

I would FIRST do a few things. Have the rad guy pressure test the rad BEFORE he tears it down again to refit the gasket. After the gasket is refitted and you're all set to go through this again I would drive around for a while and end up at the rad shop. I would then immediately open the hood .......and turn off the engine and watch it.

I think that the gasket refit is the faulty link in this event.
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post #3 of (permalink) Old 11-20-2002, 06:21 AM
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Re: 4.0L Head gasket problem????

im not sure this is related at all, but here the one experience i had with my 40 radiator....
i was stuck in a mud hole and really getting on the 4.0..eventually i heard a pop and steam rolled out from under the hood. Upon fuether inspection I saw that the radiator cockpit blew out of the bottom tank. that wasnt so bad as a new cockpit was $3 and it just popped in, however, less that a week later I broke a connecting rod. The engine shouldnt have gotten hot, i shut it down immediately after the radiator blew and towed it home.
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post #4 of (permalink) Old 11-20-2002, 10:58 AM
 
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Re: 4.0L Head gasket problem????

I just recently replaced my rad on a 98 TJ. You should have the aluminum/plastic rad that came stock with the vehicle. I had the same problem you are describing - leaking from the top tank. I had numerous people tell me that when that happens on a alum./plastic rad - that you replace it. Repairing doesn't really extend the life that long. From the sounds of it they were right.

My advice - replace the rad - you won't be able to find an aftermarket replacement for the alum. plastic, a dealer will sell you one for mucho markup, get an aftermarket copper/brass for half the price and twice the durability.

Rob
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post #5 of (permalink) Old 11-20-2002, 12:02 PM
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Re: 4.0L Head gasket problem????

any great ideas on catalogs or websites to get a new rad at a deal, I have been conidering this for a while, I get an antifreeze smell everytime I turn the heater on, I only loose about a half a quart of liquid every there thousand miles, any way, I feel this smell may be precursor to bigger problems down the road, or trail, or lost off the trail no clue where you're at, trying to get a fire started so you don't freeze to daeth but your mathc3es are floating in the sloosh on your floorboard.
post #6 of (permalink) Old 11-20-2002, 12:14 PM Thread Starter
 
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Re: 4.0L Head gasket problem????

I figured it was probably the surface where the tank and the core meets. It looks like they cant seem to get a good seal. Its good to hear that its probably not the headgasket.

I noticed that I have an 18 lb cap on the radiator. I checked the specs thats what its supposed to be. It seems kinda high... Are there any side effects to putting a lower pressure cap on your radiator?
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post #7 of (permalink) Old 11-20-2002, 04:17 PM
 
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Re: 4.0L Head gasket problem????

I here this place is pretty good and inexpensive for rads. I bought mine from a local shop, only because I live in Canada, and with shipping, taxes, exchange and everything else it isn't worth my while.

www.radiator.com

Rob
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post #8 of (permalink) Old 11-20-2002, 04:52 PM
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Re: 4.0L Head gasket problem????

You can lower the pressure of the cap until the coolant boils. As long as the temp stays in the 200-210 range, you should do fine with about a 6# cap.

The pressure raises the boiling point of the coolant. Nothing bad will happen until it boils.
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post #9 of (permalink) Old 11-20-2002, 11:36 PM
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Re: 4.0L Head gasket problem????

If you use Evans coolant you can go with a NO pressure cap. Propylenegychol boils @ 375

Now it does cost over $20 a gallon. non aqueous cooling
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