[chalkboss]

Well, it's only odd to me cause I don't understand :roll: . 87S4, about six years ago and 40K miles I did the WP (Laso, plastic impeller), I also freshened up everything on the car since then. New radiator, coolant tank, hoses, etc on and on. Always ran fine on the temp side, fans work correctly. Zero leaks.

So I moved from Cali a few years ago to Colorado. Last winter was very cold here (single digits often). I kept the car in the garage for the most part but did drive it on clear dry days. Started noticing after letting it sit for a few days I would lose a a cup or so of coolant, seemed to be below the WP or in that area (pans on, never pulled them to look closer). Pretty bummed, thinking WP bad, but then spring arrived and I drove it some more and suddenly no more leaks. I even drove to South Dakota last month for Rendezvous and I have not lost a drip of coolant since winter.

Sorry for the long-winded story, but can the extreme cold cause a leak to surface in the WP? I have pulled the front pan off a few months ago and see no evidence of past leak. Shrinkage factor on the impeller bearing?

[worf]

but can the extreme cold cause a leak to surface in the WP? I have pulled the front pan off a few months ago and see no evidence of past leak. Shrinkage factor on the impeller bearing?

Yes. But...

With a 6yr/40k pump, I would first suspect everything else starting with any of the hoses that are more than 10-15 years old.

Borrow/rent(*)/buy a coolant system pressure tester. It might show you the source when everything's warm. If not, repeat in the winter when you see that it's leaked a bit.

* Most chain parts stores offer tool rental.

[chalkboss]

Thanks, I'll try that out. I don't think it will show a leak until it gets butt-ass cold again but it's free to rent the tool and I'm sitting on my duff these days so why not.

[worf]

Thanks, I'll try that out. I don't think it will show a leak until it gets butt-ass cold again but it's free to rent the tool and I'm sitting on my duff these days so why not.

You may be surprised at how well it works for showing you leaks in the liquid-handling portion of the system.

Directions:
Test the release pressure of your reservoir cap and note that pressure. If in good shape it should hold 12-14 PSI.
Do not exceed the release pressure of the cap when you test your cooling system. Unless...
... the cap holds less than 5-7 PSI.
In that case test the system at 6-7 PSI.

Note that exceeding the release pressure of the cap may 'surprise' portions of the cooling system. The expensive portions are the radiator side tank seals and head gaskets. If your radiator is pretty new and your gaskets have been replaced then you can go to 10-12. But start at a lower pressure and see what happens. In any case, finding out that you have rad or HG leaks now, is, possibly, better than finding that out when you are on the road.

If the system is leaking only a little bit, it may take 5- 10 minutes at 6+ PSI for you to notice the 'wet spot.' When you do find the wet spot the next step is to trace it to its origin. A small leak at the water bridge may result in a false indication of a water pump since both can result in a puddle on the oil pan. Inspection mirrors, LED pen lights, paper towels under suspects work well. You may end up wanting to take the center belt cover off and double check the test if you decide the pump is leaking; you'd be really pissed if you R&R'd the pump only to find out you didn't find the correct wet spot origin.

[worf]

Thanks, I'll try that out. I don't think it will show a leak until it gets butt-ass cold again but it's free to rent the tool and I'm sitting on my duff these days so why not.

One more thing, a small trickle of coolant will evaporate on a running motor and will continue to do so until the motor is cool. And while it's leaking and cooling system pressure will be going down.

So, doing the test now while it's still warm outside may work better than you expect. And it may not. But, can't hurt if you keep the test pressure consistent with operating pressure.

[chalkboss]

Thank you Dave for the detailed instructions. I was away for a few days ...