Coolant & Engine question

I have a slow coolant leak but don't know exactly where its coming from.
There is no visible leak looking from the top of the motor. I snapped this picture from the bottom of the engine bay.

There is coolant dripping down where the arrows are located in the picture and it collects down below where I drew the square.

What is the part connected to the drive belt directly below the water pump? As far is I can tell from the Bentley manual it is not a part of the cooling system. Perhaps coolant is leaking from the water pump which is directly located above.

Any thoughts?

Most likely you're leaking from water pump seal or crack in thermostat or hose connections.
You need to get in there to get an up close look at things.

Object below wp is the crankshaft pulley.


Arrows and square missing from your pic here.

It could be leaking from the bottom of the block. I did a cooling system overhaul a few months ago, and I want to say there was a bleed screw we had to remove to drain all coolant from the engine. If so, the crush washer may need to be replaced, but that's a bit of a task, just for one screw. You'll have to bleed the system entirely to replace one washer.

Check out step 9-12 for reference. http://www.bmw330ci.net/maintenance/completecoolant.php

Thanks for input. I updated the pic as well. It appears the coolant droplets form from the center of the crankshaft pulley. But again I wonder if its just coming from the water pump above.

The thermostat & water pump look pretty dry and clean from all visible angles, without taking everything apart. The car has 190k and I had the thermostat and water pump replaced around 80k. I wonder if its time to get in there and do it again. I just wish I could see the source of the leak.

You said it.
Take things apart to see what's going on and use a mirror to really get a good view.
Unless you want to do the recommended cooling system overhaul and build in some reliability.

There's a gasket seal around the thermostat that may be going bad, too. It's a pain inthe ass to get to as well, but could be bad, especially with that mileage. How's the rest if the car, any signs of higher temps, longer than usual warm up times?

That is an interesting question. My wife always complains in the winter that the car takes so long to get to temperature and produce some heat in the cabin. Perhaps its related.

Once up to temperature, the temp guage is always pegged in the middle. I add coolant every couple of weeks.

Coolant from the "center of the crankshaft pulley," is really from the water pump. This is no big deal. You need to replace the water pump. Smart money would replace the t-stat and the hoses, and the belts and pulleys all at the same time. You might want to consider a new viscous couple (fan clutch) at the same time.

Further consideration should be given to the radiator and the expansion tank, since these items are made of plastic, and the plastic tends to crumble and break apart without any previous warning.

I'd agree with jdstrickland -- it sounds like your thermostat is staying open too, otherwise it'd only take 10-15 mins for your engine to warm up and start cranking out warm air.

Since you have that high of mileage, it probably wouldn't hurt to replace the t-stat, waterpump and expansion tank, just as preventative maintenance. I'd double check the hoses as well, as my upper radiator hose was rubbing against one of the belts and was almost worn completely through. Just make sure to clamp the hoses back on until the snap, otherwise they could come loose if you hit a hard bump and leak -- speaking from personal experience :\

I have a 2000 323ci - I am have a pretty major leak coming from what looks like just behind the water-pump.. Any thoughts would be greatly appreciated.. I am probably gonna start with taking out the water-pump and checking it out - anything I should know before starting? Never have taking one out in a BMW. and it looks like its a be mess

Changing the waterpump isn't too bad, but you'll have to pull the airbox, radiator, and aux fan, just to get to it. Since my car didn't have the aux fan, I didn't have to remove that. Once you get those parts out of the way, it's a matter of loosening a few bolts and pulling it out. It'll take a bit of force, but should come out fairly easily.

You'll also need more coolant.. obviously. One gallon of BMW coolant and one gallon of distilled water, mixed together.

All said and done, it'll take the better half of an afternoon from start to finish.

Originally Posted by dauble2k5

Changing the waterpump isn't too bad, but you'll have to pull the airbox, radiator, and aux fan, just to get to it. Once you get those parts out of the way, it's a matter of loosening a few bolts and pulling it out. It'll take a bit of force, but should come out fairly easily.

Take out the rad?........I don't think so. Should clear.

Don't pull on the pump to get it out, just use two jacking bolts to ease it out as is designed into the system. Have you done this before?

With any car experience, should take a couple of hours. Unless you have an auto and aren't skilled getting your fan out.

Originally Posted by cbritton

I have a slow coolant leak but don't know exactly where its coming from.
There is no visible leak looking from the top of the motor. I snapped this picture from the bottom of the engine bay.

There is coolant dripping down where the arrows are located in the picture and it collects down below where I drew the square.

What is the part connected to the drive belt directly below the water pump? As far is I can tell from the Bentley manual it is not a part of the cooling system. Perhaps coolant is leaking from the water pump which is directly located above.

Any thoughts?

The pulley directly below the water pump is the crankshaft pulley. How many miles are on the car? Is your car a manual or automatic (can't see your fan in the picture)? The bearing in the water pump can wear out over time and coolant can leak out around the pump shaft. I would imagine this is more likely to happen sooner on cars with the engine driven fan, as there is extra weight being supported by the water pump shaft. If you're at or over 100k miles and the water pump hasn't been replaced, you are likely due for a cooling system overhaul. You could probably get away with only replacing the water pump, but if possible I would suggest replacing all of the components dauble mentioned.

Originally Posted by Stinger9

With any car experience, should take a couple of hours. Unless you have an auto and aren't skilled getting your fan out.

For someone that's done it before yes, a couple of hours is about right. For a first timer, it's going to take them longer depending on how mechanically inclined they are and if they have help.

EDIT: missed the part where you mentioned mileage.. my bad. Sooo yeah, I think it's time to get in there and do it again.