dave1123

This is on the 4.0 and I'm not sure about the 4.7. We all know about the "weep" hole on the bottom of the water pump bearing, right? Well, it seems that OEM water pumps have a weep CHAMBER, a small well that holds a slight seepage amount, about 1 tablespoon full, and allows it to evaporate as the engine runs. When the seepage gets bad enough, this chamber fills up after the engine shuts off and is slung off on start-up. I discovered this after doing some brake work then starting the engine while on the lift and seeing coolant pour out of the front of the engine, then stop dripping. Looking on-line for a water pump, the listing for AC Delco pumps talked about this chamber. A bell went of in my brain! Sure enough, after getting the new pump, I saw this chamber thing.

THAT'S why I could smell coolant but never find the leak. SO, if you have this slow disappearance of coolant, replace the water pump.

dave1123

Gee, I'm surprised nobody jumped on this one with criticism. I found it amazing that engineers would build something like this into the system.

basegrinder

I thought you just always smelled coolant around american cars

93_xjcherokee

Xjs are American? Lol

dave1123

Update on my slow coolant loss, it ain't there no more!

cherokeexj21

that's great info I've been noticing a small amount of coolant everyonce and a while. I'll check that weep hole thank you!

Cherokee_Mike

I've had my 2000 Jeep GC 4.0 for almost 4 1/2 yrs now, still only done 72k miles and around every 5-6 months have had the 'Low Coolant' warning - topped it up each time till it happened again - just put it down to normal evaporation as a leak would surely cause much more rapid coolant loss.
Around 2 weeks ago the warning came up again, topped it up and it was back 2 days later so topped it up again and looked for leaks - checked hoses, hose clips, etc...nothing obvious found.
Yesterday checked coolant level - it had lost a bit and was almost down to the 'Min' mark so topped up again but this time I noticed a drop of water on the ground right under the front of the engines.
With the engine switched off - for obvious reasons - I held the fan and rocked it gently sideways to see if there was any movement in the bearings, sure enough there was and water continued to slowly drip onto the ground.
I think I could hear a slight rumbling from the water pump when the engine was running but not so loud as to be too obvious.
New water pump ordered - not too expensive, under £40 delivered here in the UK.
So, if you are experiencing slow & erratic coolant loss from your 4.0 Jeep, #1 suspect is the water pump starting to fail - much cheaper to fix than a blown head gasket or cracked head !

dave1123

You've already bought the pump, but I'd like to suggest you don't put one in with a plastic impeller. That impeller spins about 1/16" from the cylinder barrel and if the bearings get worn, can strike it and shatter. My 97 ZJ 4.0 water pump was very worn and when I replaced it, the cylinder barrel had a shiny groove in it from the impeller. Shattered pieces of plastic are near impossible to get out of the block! Make sure your water pump impeller is METAL! JMHO.