Hunter_

Little bit of useless back story first, I am relocating 2 and quarter thousand miles away and will be driving my WJ that distance, otherwise I wouldn't care about the leak because its not overheating, and not posing any risk in the short in-town drives it normally dose. As such I am preparing the jeep for the longest trip both I and the WJ will ever do, and this leak along side A/C reapers are part of preparation.

On to the issue that I can't seam to figure out on my own. The WJ has a Mysterious water/coolant leak, I replaced the upper rad hose and the T-stat + T-stat housing gasket and have been monitoring it for the last few days, no leaks from there. The leak is farther back from the front of the engine, I believe this because I park on a sloped driveway and the puddle that I believed to be condensation and learned is actually coolant starts closer to the fire wall. I checked the drain-port for the climate control and it is bone dry, and the heater core lines are not leaking as well. I am completely miffed, it is a substantial leak, I read on another thread that it could be the overflow bottle, is there anything els this could be?

Noah911

It could be leaking from the waterpump. From its gasket going bad, or its weep hole if the bearing in it is going bad.

Did you replace the thermostat and its housings gasket as an attemp to fix this leak, or was it because the thermostat wasn't working? I have the same question about the radiator hose you replaced. Was it known and obviously bad, or an attempt to fix this leak? Also to know, was it leaking before these two repairs were done? Or, did the leak start after these two repairs were done?

It can be very very difficult to pin down the origin of a fluid leak by its path taken along the inside an engine compartment! Fluid leaking here can travel and go everywhere, and falsely appear to be coming from anywhere.

There are many different possible reasons for having coolant lost.

If it is not an obvious easily seen leak.. I think you should start with getting a radiator psi diagnostics test kit from the auto store. They should be able to loan one to you. Make sure you understand how it is used for testing. Use it to test and look for any leak(s), and to verify the radiator and cooling system holds the psi.

Hunter_

Hi Noah, you and Dave have been very helpful in my endeavors with both my ZJ and now my WJ.

I replaced the hose because it had a small pinhole leak and no protective cover from rubbing on the alternator, and I did the Thermostat and gasket because there was some evidence of previous leakage, the only reason the T-stat was done was because I was in there doing the gasket anyway so it was preventative. This was a half baked effort to fix this leak, the water pump appears to be be fine its not flinging water off of the pulley so I'm confidant it's not the weep hole.

I have a UV light that I purchased for $12 mostly for the A/C diagnoses but coolant is designed to react with a UV light, this would be of help right? where should I start to look with this?

All of the leaks I have fixed before were obvious so I have never had to use this option, A simple explanation of how this works would be appreciated

Noah911

The psi leak test kit is super simple. There will likely be laminated instructions on the case it comes in. There are adapters used that are fit to size of the radiator filler neck hole for after you remove the radiator cap. You adjust them.. It is like a bicycle air pump. You pump to 18lbs psi on the gauge to see if it appears to hold it there.. Then, pump more to a higher psi to create a flow happening from any possible leak source origins. You will likely need to have a buddy to keep pumping it while you look real closely for leaks, if there are any larger sized leaks causing the psi to be continually lost... But, you have to get to know your cooling system looking it over very well in order to see and determine where at it may be leaking.. Loosing psi..

I would imagine if the coolant glows under a UV light then that tool could very well help you see it leaking better maybe? I'm not sure how that would go?

Coolant leaks are not always straight forward. Different variables affect things here with this system. It could leak a whole lot, but only for a minute or so, at a certain psi, at a certain temperature, etc... Or, just at cool-down.. It could be a constant steady miniscule leak happening over a longer length of time...

Radiator cap?
Overflow resevoir?
Overflow resevoir coolant overflow line?
Radiator hose?
Radiator hose at the connection?
The radiator?
Thermostat housing gasket still?
Waterpump gasket/weep hole?

Heater core?
Manifold?
Head gasket?

Hunter_

Thanks to the Info, I'll take a look at a test like that. In theory because the coolant does appear to glow under UV light if I degrease the engine and cheek again would I be able to locate it that way?

Noah911

Only on days with full lunar eclipses will that theory become relevant, and be possible.

(edited to add):
You're welcome

Cherokee_Mike

I had a mysterious water loss problem on my 2000 WJ 4.0 - needed topping up about once a month for around a year, no obvious sign of coolant loss. Topping up became more frequent until it was an almost daily task - eventually traced it to the water pump bearing.
If you park on a sloping driveway the water could be trickling down the front of the engine and running along the sump before finally dripping onto the ground.

Noah911

The coolant leaking from a water pump can also leak to the sides.. It can run along the frame lip area, and actually appear to be coming from where the heater core is located. It can almost look like it is coming from inside of the vehicle at the front side passenger door region. Almost like the coolant is coming from inside of the vehicle somewhere.. Evidence from the leaking near the waterpump may get blown off and/or evaporated away from the actual source of the leak.

In all reality, replacing a waterpump on these WJ's is soo easy and simple. I think they are only about thirty some dollars too. Those mostly get replaced primarily related to the gasket failing on them. If the thermostat gasket recently failed, or its gasket was in that bad of shape to have leaked.. Then, if the waterpump and gasket is of the same age, it is time to consider thinking about doing the waterpump. It will usually not be far off from failure at this point... behind your thermostat housings gasket failure.

Does the gasket material sealing your waterpump look bad? Does it sort of crumble when you rub it with your fingers? Have you changed a waterpump before? The WJ's is real easy to change.

The most important thing for these - the thermostat and waterpump, is the gaskets and RTV sealant. Should be waterpump/thermostat specific. It should say that on the RTV tube somewhere. It needs to have a certain type of chemical resistance quality for the liquid coolants chemical make-up to it. I have sealed a thermostat housing up before in the past. Only to have it leak after starting up the vehicle after filling the system back up with coolant and trying to burp the air out. It was fully tightened correctly all of the bolts, but the gasket and RTV I used were of horrible quality. I reccomend using Felpro gaskets here for these.

You have a long trip planned. You are driving your Jeep close to 2500 miles? What are you doing that for? When you get going on the traveling, feel free to private message me if you need something too.

Hunter_

Thanks for the information once again, the water pump and gasket appear to be fine I haven't been able to get too close a look at the pump its self, I had to replace the water pump on my ZJ maybe 4 years ago I expect it to be a little easier than that should I need to replace it. The gasket looks almost brand new from what I could tell and looked damn close to the same material as the felpro I used for the T-stat housing.

On another note I am driving the jeep from salt lake city to Orlando because I have a job offer that is paying $25 an hour.

Waynerd

When you say parked in a sloped driveway, was the Jeep facing up or down hill? Maybe try the opposite direction? Also I have had a good amount of water pumps leak and they usually don’t leak onto the pulley it just runs down the block or lower hose.

dave1123

IDK if this helps, but my 2000 WJ has an AC Delco water pump on it and it has a "weep chamber" instead of just a weep hole. This holds just over a teaspoon of coolant as it leaks out of the seal and is held there to evaporate without showing a leak. Sometimes you can smell coolant but not see any leaks. If this leakage gets large enough, it will drip into the back of the pulley and gets thrown off and again you won't see anything unless it leaks after shutdown. Then it gets thrown off on startup. Case in point, we had it up on the lift to bleed the brakes and Kim started it up. Coolant came pouring down the front of the engine and then stopped! WTF? We looked in the Delco catalog for the part number, then noticed the part about the weep chamber. I didn't know about that before then. Apparently other manufacturers do the same thing.

Noah911

Motorcycles have something like that sometimes. The Honda CRFL does, but the 1200 Harley does not. The CRFL is leaky of coolant a little bit, across the board. Some of them are worse than others too.

Hunter_

Update: I know this thread died a little, The leak has mysteriously stoped, I started parking on a flat surface and all evidence of the leak has disappeared, just to double check I marked the coolant level with a sharpie and checked again after a day and it hadn't lost any coolant. could this be a simple case of the slopped driveway causing the tank to overflow on cool down?

Noah911

No. That sounds highly unlikely. I wonder why it was leaking, and how it was able to stop like that on its own?

Noah911

Coolant was never noticed boiling over in the resevoir before was it? Maybe that happening while parked on a slope could cause coolant to overflow, and be lost out the resevoir?