From where is this coolant actually leaking?
 

I found coolant under the belt covers, assumed the WP was leaking, ordered a new one, and in the mean time I've stripped down the front of the engine, cleaned it up, and left it a few days.

Here what's strange: I can see where the coolant drip forms before it drops, right on the bottom of the WP where the hoses connect. Pink drop in photo below:

http://forums.pelicanparts.com/uploa...1258256696.jpg

Now, here is what strange: I was expecting the coolant to be leaking from the WP seal, and then perhaps dribbling down to that point to form a drop. But there's no evidence of that. In fact, it looks like there absolutely no trace of coolant actually escaping from the WP seal:

http://forums.pelicanparts.com/uploa...1258256763.jpg

And one last one:

http://forums.pelicanparts.com/uploa...1258256864.jpg

Could be from the plastic fitting on the front of the pump. There is an o-ring that seals it against the pump housing that may be leaking.

Also looks like the lower rad hose is not completley seated on the pump, or atleast that's how it looks from my tiny phone screen :)

Thanks, Mr Duck -- I looked up the PET to get a part no for the 28 x 2.5 O-ring: 999.707.283.40

I'll replace the O-ring in any case.

I noticed from the PET diagram that there is actually another thermostat under that plastic housing -- what's that for? I notice it's listed as only for model M44.52 (which one is that? S2 or Turbo?) Does it need replacing as well as the main one for periodic maintenance?

Turbo only, it is for the turbo water jacket.

There is small hose on top of the WP that may have loose clamps or a bad hose.
GL
John_AZ

I agree.........looks like the plastic hose fitting is where it's leaking from. Correct me if I'm wrong, but it appears that the actual plastic fitting is cracked in your second picture? Looks like there's a split just below the hose and ends at the mounting face of the water pump. I have seen these crack before like that. I would suggest removing the part and inspecting it to confirm.

+1 bxtech I also think the fitting is split on top you can it it very clearly.

I had a closer look... that's not a crack, it's a ridge in the plastic moulding where some dirt has been trapped. There's a matching ridge on the other side as well... there doesn't appear to be anything in the way of cracks at all, although I can see why the photo makes it look that way.

The O-ring was pretty flattened, however. Techno-duck's suggestion that the O-ring has failed seems most promising at this stage. The hose connections don't seem to be obviously contributing to the problem, even though the large rad hose probably could have been pushed on a bit more, as Techno-duck observed.

Since I've ordered a new pump, I'll be refitting the hoses and the plastic housing anyway... I suppose it will just be case of putting it all back together with new seals and see what's what.

Thanks all for your advice. I suspect I've ordered a new pump when a $2 O-ring would have done the trick. Oh well. Over-maintenance can't be all bad, I suppose (except on the wallet...)

I'd put on the new one and save your mystery leaker as a spare.

Yep, it looks cracked, but since you say it is part of the moulding, i would throw a new one on anyway

Just to report back: Techno Duck nailed this one, it was the o-ring.

Thanks all!

That large hose likes to leak unless the clamp is torqued down nice and tight as well, so be sure to when you put it all back together.

once had a problem with the large hose contacting the ps pulley when warm, and it eventually caused a leak. you could only see the the hose touching the pulley when the car was warm. embarassing.

This car is the worst for ffinding ways to grind through those hoses. My lower hose has marks from the PS pulley, the expansion tank hose has duct tape all over the corner near the alt pulley to prevent further damage as it's about 2mm from being done in, and same deal with the top rad hose...zip tied to keep it out of the way...and was a replacement because the old one got burned through!!!