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Leaky coolant


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So this is on a 96 zj 4.0, but figured it applied to MJs too since it's a 4.0

 

Jeep was leaking coolant for a while, finally got around to replacing the leaky lower radiator hose, fixed it for a day, then the water pump started leaking. Replaced the pump, noticed the radiator was rotting out and had a pool in the bottom of it, so replaced that too. Fast forward about a month, jeep is still leaking coolant, has been all month, it's dripping from under the lower rad hose, leaks until the overflow bottle is empty, then stops. Doesn't overheat, but what could the problem be? Since it's leaking on the opposite side from the overflow, I can't see that being the problem. Ideas?

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Typically a leak at a rad hose is due to either a compromised hose or compromised seal. If it's a new hose, probably you can ASSume it's the seal, in which case try to tighten up the hose clamp. Cheap hose clamps don't last long, so that could also be a problem. If it helps, a (very long) while back, another member had an issue with a ZJ rad hose leak... IIRC the nipple for one of the rad hoses didn't have a bead around the tip, and the solution was to make one out of JB weld or something similar. But before you check any of this (especially since the latter requires dumping all your coolant), see the below.

 

Your suggestion that it's related to the level of the overflow makes me doubt that the lower rad hose is to blame here. They're just too far apart. Now, I've never studied a ZJ rad in person, but google tells me that like in an MJ, the rad cap is directly above the lower rad hose connection. Wouldn't surprise me if a loose or leaky rad cap was to blame. Once the coolant level drops past the cap, then no more leak. Another thing worth noting is that the overflow connects just below the rad cap, and any issues with that connection could also cause a leak. Any leaks along the overflow hose or even possibly at the overflow tank could also be running down the hose to the rad cap area as well. Again, once the level drops below the leak, it would stop leaking.

With fluid leaks, unless you spend a good amount of time travelling backwards on your roof, it's generally a good idea to look upwards and forwards to find the source of the leak. If you know which fluid is leaking and you know the leaking stops at some point, the level where it stops is often near the level of the leak.

 

My experience with my coolant system (I replaced the entire thing out of my MJ except for the heater core and overflow bottle in a slow process over the course of a year as parts failed and budget allowed) is that it can take a couple days to get everything settled into it's permanent spot and for all the leaks to show up. Things that may not have initially leaked may develop leaks later on.

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See if your local Autozone, O reilly or any other auto parts chain store has a coolant pressure tester you can rent, very easy to use and can pin point your coolant leak dead on just make sure your coolant is topped off completely in order to diagnose it properly or if your a DIY tool maniac like me you can just buy one. I would recommend the kit from Red Line which is the one I have  http://redlinedetection.com/collections/smartfit

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Checked the overflow hose, put a new clamp on it, no change. Lower rad hose had a new clamp and the lip on the edge for a better seal. The reason I made the guess about the overflow bottle was because it leaks until the overflow is empty, then stops leaking after that. But the puddle is always under the lower rad hose, despite new hose, rad, pump, and clamps all around. I'm going to pull off the shroud for a day so I can see if the cap may be leaking down the rad, that's the only thing that makes sense at this point, unless I just got a bad radiator

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