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Thread: Help me diagnose where my coolant leak is coming from?

  1. #1

    Default Help me diagnose where my coolant leak is coming from?

    Ok gang, total jeep newbie here.

    I just got my WJ, 1999 Grand Cherokee Laredo, 4.0L engine, a few weeks ago, and first off... I LOVE IT, but it did come with a couple of small issues.

    Here's the first one I'm trying to tackle. It has a slow engine coolant leak. By slow, I mean the "Low Coolant" ding comes up every 2 weeks-ish. As soon as I fill the overflow to the full line, after another 2 weeks it comes back on.

    I got underneath the jeep, and can see coolant dripping down from right below the fan pulley. There's two connections there, one smaller coolant line that runs to the side of the radiator and has a hex style screw in connection. That's the one that I think is leaking, but it's hard to tell. I can't tell if there's anything above it that could be leaking down on it. It's on the driver's side of the engine compartment, close to the pulley's and the front edge of the oil pan.

    I did some searching but turned up nothing. I was hoping someone with more experience might be able to point out of this is a common fault, or just a one-off problem I'm having.

    I've attached two pictures (quality isn't too great), but you'll see where it's leaking from at least. The pictures are from me underneath the car, on the driver's side, looking up towards the pulleys.

    Any help is GREATLY appreciated. Thanks a ton.
    Attached Images Attached Images

  2. #2
    Patriot Guard Riders Drem's Avatar
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    You could have a water pump seal leak. When the seal starts to go it allows coolant to come out of a weep hole on the bottom end of the water pump. If you have an inspection mirror or you can reach in with a small mirror take a look. Or once the engine has cooled down enough reach your hand up in there to touch the bottom of the pump to see if it is wet.

    I am not really sure as I do not have a 4.0, but those lines appear to be for the transmission cooler since you said they go into the radiator.
    Last edited by Drem; 07-03-2010 at 09:57 AM.

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  3. #3
    Stock Is NOT An Option mdoffroad's Avatar
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    X2 on the waterpump..
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  4. #4

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    Water pump leak I imagine is not good, and clearly something I should get fixed asap. I'll have to look at the manual to see how big of a PITA it is...

    Correct me if I'm wrong, but I have a 2WD Jeep, so those wouldn't be trans cooler lines would they?

  5. #5
    Patriot Guard Riders Drem's Avatar
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    Quote Originally Posted by coheed View Post
    Water pump leak I imagine is not good, and clearly something I should get fixed asap. I'll have to look at the manual to see how big of a PITA it is...

    Correct me if I'm wrong, but I have a 2WD Jeep, so those wouldn't be trans cooler lines would they?
    Leaking water pumps are strange. I have had them start leaking and last for months. But I have also had them start to leak and fail big time.

    I have not seen anything other then trans cooler lines running into a radiator. Just trace them back from the radiator to their termination point and you will know for sure.

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  6. #6

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    check the timing case cover gasket as well...My ZJ was leaking from there and NOT the waterpump gasket...the dealer even thought it was the waterpump gasket (after they tried to fix it) then i took it home in disbelief and tore it down and it was the timing case cover gasket

  7. #7
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    Icon928

    Could be the water pump and it probably is, but check to make sure. The trany fluid is cooled in a 2wd Jeep in the radiator. That is probably the lines you see.

  8. #8
    Registered drgonzo's Avatar
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    Check the thermostat housing. Mine rotted out and needed to be replaced. That was where my leak was from and it was the same as yours with the low coolant sensor coming on.
    03 WJ Laredo

  9. #9
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    I've had the same problem. Water pump and Thermostat are a pain to change. You have to take the fan shroud off and really get in there to clean it all up so it seals correctly. I've had to do this 3x so far.

    Bob

  10. #10
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    Wipe of that connection hose with paper towel or rag. I suspect its being dripped on. It does not look like a cooling line but a tranny cooler line to me the way it goes back. If you follow those aluminum lines they likely go to the tranny. The water pumps have rubber pressure hoses on them.

    Wipe all the other areas that a currently wet. Depending how long it takes to drip. You can maybe slip a piece of cardboard above those hoses and it will catch the drip from above and you'll know. The have to look for the source.

    Pump shaft at the front, weep hole in casing or other cover gaskets on the engine face as mentioned by others. Put it up on steel drive on ramps start it up and go under with a good bright light and see if you can see it. Have someone turn off the engine as soon as you see fluid and track it back before it get too wet everywhere if you can.

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  11. #11

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    I replaced my water pump on my 4.0L at 140k. I had a similar problem where I was refiling it every few weeks. It is very difficult to tell where something is leaking from. It really was a PITA even in my buddies shop on the lift on a Sunday. I have a factory tow package and the trans cooler made removing the fan shroud a nightmare. If this is something you are going to do yourself I would definitely replace the thermostat and you might as well get a gator-back serp belt while your at it.
    ~Jason

  12. #12
    Fails at Jeeps mverne's Avatar
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    Looks like you got a slow leak from the water pump to me.
    Mine went all at once. I drove it to my garage and was just chillin and when I went to leave there was a river under my front end.
    I just pulled it in and stuck a bucket under the front and drained the coolant then got a ride home.
    The next morning I got a pump and slapped it on there.
    I did it with the fan shroud on, it's definately doable, though it would give a lot more room if it was off.

    The only good tip I have for you is if you do it yourself, buy some Hi-Temp gasket silicone, and use it on both sides of the waterpump gasket.
    I had to take my waterpump back off a couple times because it wasn't sealing right.
    Then I put some silicone on it and all was fine.

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