Coolant woes..
 

So my wife's X5 M54 has been leaking coolant lately from the drivers side front. I replaced the hoses, expansion tank, and automatic transmission thermostat. The leak still occurs. It leaks down to a point overnight and won't leak anymore. I add about a quart of coolant, bleed it, and the car is fine until it has to sit overnight again. Then it leaks down 1 quart and never more than a quart. After it has leaked, the heater doesn't work well even though the temp needle is rock solid in the middle.

I've looked and can't figure where the French toast the coolant is leaking from! Is there anything else that leaks around there or is it probably a ninja hole in the radiator? Any suggestions help!

my bet is the water pump is leaking from the weep hole

The water pump much closer to the middle of the motor though. I've never heard of the weep hole.. What's that?


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The small auxiliary water pump is on the drivers side, close to the radiator. All plastic, so they crack. The heater valves are on the drivers side firewall near the strut tower. Also have plastic parts.

If you really can't find it, get a uv dye kit and put some dye in the coolant.

A word of caution, it took many (like 10) fill, warm up, drain, repeat cycles to get the dye out when I was done, so I would suggest using 1/10 bottle of dye to start and not the whole thing. I did use straight deionized water for this flush and then filled with proper coolant at the end.

How about just getting a pressure tester and doing it that way.

I think it's pretty obvious we are losing pressure so not sure what that would help.

I'm mostly looking for items outside what I mentioned in that area that can fail.

The pressure tested will reveal your leak. Top off the coolant, hook up the pressure tester, take it up to 15-20psi (should be good) and start looking around for your leak.

There are a bunch of plastic parts at the bottom of the rad that could be your culprit... as well as numerous hoses.

http://www.realoem.com/bmw/images/diag_3ebw.png

http://www.realoem.com/bmw/images/diag_3sl1.png

:iagree:

Ah, increase the pressure - Great idea. Thanks! Looks like that's my Saturday chore..

When this all started my wife told me she heard a pop! noise followed by some spraying of coolant, but just a quart. That's why I went straight for the expansion tank and the "usual culprits" in that area as I've experienced on my E46's. Even if they were ok, we're at 100k and needed replaced regardless.

Is there anything else down in that area that has been known to go POP?

Sounds like the pressure hits the 2 bar max on the expansion tank and vents the excess coolant to lower the pressure - I would probably park it until you can fix the problem