My LB9 has 108k on it. Couple weeks ago, noticed a puddle of coolant under the car. Upon inspection (didn't go under the car), I saw it dripping off the lower radiator hose. Figured it was from the water pump, maybe the 20+ year old hose was cracked by the water pump neck. Replaced it, still leaked. Suspected it was from the water pump, as I could see something dripping from the back of the pump. Replaced the pump, and still leaks. So I'm guessing the water pump and lower radiator hose are not to blame. What possible causes are there that I should also look at? A couple people I asked locally mentioned could be the freeze plugs, one mentioned the water jacket in the block may be cracked, and another said perhaps the new pump (cheapo Advance Auto $30 pump) could be faulty right out of the box. Nothing above the water pump level of the engine is leaking, I can be certain of that.

Mainly curious to how common it is for the engine block to be the source of a coolant leak.

As SOP, I always make sure the bolts securing the back plate on the water pump is tight before installing it.

You need to buy, rent or borrow a cooling system tester. Take the guess work out of locating cooling system leaks.

http://www.harborfreight.com/radiato...kit-69258.html

That's a nice kit...
but I recently found a coolant leak that has eluded me for a long time.
I should have bought this much earlier.

Just put the dye in and run the car to let the dye circulate through the system.
Then when its very dark put on the glasses and use the little UV Flash light to scan the most likely spots first.
You will most likely have to raise the car so you can get a really good look at the underside.

Don't stop when you find it.
Keep looking every where because its possible to have a second leak.

Good luck.

Read the dye kit and make sure its the right one for your system.

Heres the links.=
http://www.autozone.com/test-scan-an...artNumber=true

http://www.autozone.com/test-scan-an...artNumber=true

By the way, pets love to taste/drink antifreeze for some reason. Just a little bit will kill them, so please do not leave any around where they can get to it.
Thank you

Excellent. Thanks Ron. I'll go grab that here in a bit and will report back with my findings.

Found the leak. It ended up being one of the gaskets that was crunched up when I first installed it. But when I removed the pump, I re-tightened the back plate just to make sure, and bought a pair of Felpro gaskets and bolted the pump back in. Definitely solved the issue.

Thanks for the help fellas, at least I can apply all this knowledge to my Xterra that has a small coolant leak somewhere.

So did you find the leak with the kit ?