dontherogue

Hi all, I need some fresh thoughts on a coolant leak. My '99 4.2l is in prime shape and I park it in my 86 year-old mother's garage for the cold, snowy, and road salty Manitoba winter. When I garaged it last October, the floor was dry as a bone. When I opened up the garage this week, I noticed a good-sized puddle under the truck. Coolant, diagnosed by taste. The recovery reservoir is down slightly, maybe a cup. The mystery is: what the heck started to leak over the winter when the truck sat there and was never started? I've done a visual search of all hoses and connections and cannot find anything that looks wet. I fired it up and let it get to full operating temperature and then the leak seemed to quit! It was a very slight drip from the oil pan, right where the oil drain plug is. I thought at first that maybe with the extreme cold over winter (we got as cold as minus 40 this year) maybe a rad hose clamp contracted enough to cause a leak and of course the stuff will run down to wherever gravity takes it (oil pan drain plug). Then, I hoped, when I fired it up that clamp would expand and the leak had quit. Wrongo. I took a look this morning (we're in above-freezing temps now) and the leak was back. Thoughts, anyone?

white89gt

Just a thought.... do you have your mixture correct at 50/50? If there's too much water, maybe it expanded when frozen?

The most common leak, just out of the blue, would be the weep hole on the WP. Do you see any evidence of coolant near the weep hole?

dontherogue

Thanks for the reply. Mixture is 50/50 and should be fine. I did check the water pump and couldn't see any evidence of leakage but I agree that's a good place to start. One question though: if it wasn't leaking in the fall when I parked it, would a water pump seal break without it running and would it just keep leaking without any actual pumping? Seems unlikely to me.

fordguy2100

A seal or hose could've dried up and started to leak. I'd drive it for a few days, keeping an eye on any more leaks. If not, I'd top it off and run with it. If not... you'll find your leak lol

white89gt

When it is just sitting for that long, nothing is really common. But the weep hole is the easiest out for it, especially if it were to freeze.

dontherogue

Just to close the loop on this thread. Once I put the truck back on the road this spring, the leak stopped. I even had the coolant changed, and the shop that did the work found no leaks. There has not been a drop of coolant on my driveway all spring/summer. So I guess my gravestone will read "Nice guy, but never diagnosed intermittent F-150 coolant leak."