WJ 4.7 Coolant leak between engine and transmission. - JeepForum.com
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post #1 of 7 Old 11-28-2019, 11:30 AM Thread Starter
ArniWJ
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WJ 4.7 Coolant leak between engine and transmission.

Hi. At the beginning I will try to describe the problem with the best english I can. So....couple weeks ago I have noticed a coolant leak....but it dripping from connection between engine and transmission :/ I suspected blown cylinderhead gasket but they are dry and there is no trace of coolant leaking. Coolant hoses are also dry and undamaged. I've found a picture of back of the engine block.
There are two silver plugs and bolt. Is it possible that the coolant might leak from under of those plugs?
Im one step away from take the engine off the car to check out those plugs.....but I'll wait until someone give me a hint. Greetings from PL!

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post #2 of 7 Old 11-28-2019, 12:15 PM
99wjtx
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Yes, it is true. One of the 1.25"/31.8mm casting or expansion plugs (some call them "freeze" plugs) could be leaking. Other than a head gasket or a crack in the block, there's not much else it could be. Do consider the possibility that a head gasket actually IS leaking into the valley between the heads and the pooled coolant is sloshing off the back of the engine that way.

I would certainly suggest first trying aggressive remediation with a block stop leak product like Bars Leaks. Use a high dosage - depending on the product - maybe two bottles.

If that doesn't work and you get tired of topping off the coolant, some would consider it easier to remove the transmission in order to access the back of the engine. At the very least, you will probably have to disconnect the two front engine mounts and lower the engine enough to be able to reach the four bolts along the top arc of the block holding the engine to the transmission bell housing. I believe they are 14mm.

Whichever way you choose to do it, you may wish to consider replacing the rear main seal while you're able. Of course, depending on the mileage or condition of the engine and the budget, if I went to the trouble to pull the engine, I would be tempted to consider doing some rebuild work as well.

Rage! Rage against the dying of the Jeep.

99 WJ Limited 4.7/NP242
01 WJ Laredo 4.7/NP242
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post #3 of 7 Old 11-28-2019, 04:39 PM Thread Starter
ArniWJ
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Thank you for your advice. It's easier to me to take the engine out rather than transmission because I have all hoses disconnected. Intake manifold, exhaust , wiring harness and other stuff are pulled out too. I'll replace the crankshaft sealing of course, this is gonna be the best occasion to do it. I'll let you know when i'm done with all of this. Thanks.
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Greetings from Poland!
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post #4 of 7 Old 12-15-2019, 03:13 PM Thread Starter
ArniWJ
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Hi. My work on garage was delayed for a while because I was sick. But now ,motor is out and this is what I found - rusted expansion plug. So much work because of small, cheap piece of steel sheet....
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post #5 of 7 Old 12-15-2019, 06:31 PM
99wjtx
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It often amazes me where decisions are made to cut costs and where they aren't. I don't know where you are but as I recall, O'Reilly Auto normally stocks that size plug in brass - Dorman brand if I'm not mistaken - and they can also be found online.

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99 WJ Limited 4.7/NP242
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post #6 of 7 Old 12-15-2019, 07:50 PM
HarryH3
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What a job to replace a part that probably cost Jeep about 20 cents during manufacturing. If I had my 4.7 out of the vehicle, there is no way I'd put it back without pulling the heads and having the valve seats pinned. You already did the hard part.
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post #7 of 7 Old 01-25-2020, 02:50 AM Thread Starter
ArniWJ
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Finally my job is done! Those freeze plugs i had replaced - it was difficult to find the dedicated ones, but i found 35mm freeze plugs that comes from....Massey Ferguson tractor They fits perfect and sits tight. For now Jeep runs great, without any leaks. Now my driveway gonna be clean at last.
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