I have an 93 ZJ with the 5.2L that I rebuilt about 1 year ago. I have noticed the coolant level going down. I found that 1 of the freeze plugs on the drivers side has a real slow (hardly noticable) leak, the second one is on the passengers side and I notice it on the bottom of the bell housing. I have tried to feel around on the back side of the intake and head, but no luck. I have also pulled all the intake bolts and put thread sealant on them, nothing.

Any ideas? <img src="/forums/images/graemlins/confused.gif" alt="" />

Thanks
Tim

I guess being in Arizona you have added water to the coolant over the years.. Water is a curse to iron. Specially to those so called "freeze plugs" I always use BRASS when rebuilding an engine. But Here in the warmer climate of Austin I always use PURE ethylene glycol also and it don't rust up an engine.
There are expansion rubber freeze plug inserts that can be used to replace the rusted out ones.
Be advised it will only be a short time before the 16lb pressure starts squirting out the small hole you have now.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Your "hardly noticeable" leaking freeze plug is probably leaking more than it looks like, thus causing your coolant level to go down. When the engine is warm, most of the coolant coming out of a freeze plug will evaporate right away, so it won't look like much is coming out.

Here's a TEMPORARY solution that may work to help determine if the freeze plug is the sole cause of your coolant loss. Most holes in freeze plugs start out as a small pin hole. It is often possible to screw a small sheetmetal screw into that hole. Put a small rubber gaskeet on the screw first, and only tighten it up enough to secure it. Be very careful that you do not get any contaminants in the engine doing this. Then fill the fooling system and drive it a while (just close to home). If your coolant level stays the same, or goes down much slower than before, you're found the problem.

DO NOT leave that temporary fix in place. The hole in the freeze plug will undoubtedly get bigger. It is possible then for a cooling engine to develope a little vacuum and suck the screw into the engine, with unwanted results!

In any event, I'd strongly suggest changing the freeze plug ASAP. If you can get to it well enough to insert a brass freeze plug, then I'd recommend that. If not, you might try one of the expanding rubber-edged ones mentioned in another response. However, if you ever remove the engine, I'd recommend that you replace the expanding one with a regular brass one at that time.

As another thought: Anytime I get a cooland loss, I check the crankcase dipstick very carefully for signs of water or coolant. Any little bubble on the dipstick usually means oil contamination by coolant.