Hey guys, we've go an 02 MCS that I recently replaced the coolant tank after it exploded. I refilled it with Peak 50/50 gold colored coolant, maybe should have used Zerex? Immediately after and unseemingly unrelated, a coolant leak started in the front of the engine compartment.

It occurs if the engine is started for just a minute. The attached picture shows were it leaks without the front tray attached. It's quite baffling b/c I cannot see the sources. Could this be the water pump or the the thermostat?

https://www.flickr.com/photos/121851728@N03/

i think try to see the filler hole in the front is leaking and the clamps move when the reservoir explodes...

try to use blue bmw coolant..


lemon

Thanks for the reply!

What do you mean by the filler hole in the front?

Look on the thermostat housing, just behind the supcharger. Follow where that big hose connected. Start engine.. You might see water leak.

I had the same with my 1st 02 MCS it was the thermostat gasket, during the cold months I would notice a small amount of coolant, warmer weather no leak, source was gasket, so changed the thermostat and gasket and leak gone.

Standing in front....
The water pump is on the left....the thermostat on the right.....

The pic shows the leak is front right...
Thermostat leak is usually a weap....nobdrip.... Look around...could even be a hose or the radiator...gotta look...YOU are the detective here....
Drips can hit splash guards and travel....so WHERE it lands is usually not an indication of where it might come from....

I've tried, it seems to come from the front of the engine somewhere where I can't see. It does not appear to be from the radiator area.

I was hoping to pressure test it, but cannot find a suitable adapter.

A water pump would not leak this much I'm thinking. I'll get the thermostat & gasket and see what I find.

Thanks guys!

On an 2002 I would look at the hoses closely...even the clamps...10+ years on rubber hoses and spring clamps are getting up there.....

Yup! Zippy is right! Hose or could be the radiator itself. I would put it on service mode though,that way you can see much more on the front end.

go to the local discount tool store. buy a cooling system pressure tester. read the instructions on which adapter cap to use. pump up the system to 16psi and watch for the leak. It's a far more accurate way than guessing and if it is the water pump, that's a very time consuming job (remove supercharger). I had to do this testing the week after I picked up my 06 R53. It needed a thermostat gasket. no big deal.
Tester Kit

I normally rent the kit from O-reillys but I tried and I it does not work with the mini coolant tank. I just used it to find a radiator leak on another one of our cars that took higher priority.

Are you saying the Harbor Freight kit does work with the mini coolant tank?

I used the Harbor Freight kit on mine. Worked great.

Alright I'm going to pick one up.

Thanks again guys for your guidance, it's greatly appreciated