Coolant Leaks
 

My wife tells me that her X5 is telling her that the coolant is low when she starts it. I drove it Mon., 02/27 and again on Tue., 02/28. The trips were short, no big deal to have to walk home, but that didn't happen. Both times, I put the car in the driveway so I could see where it was leaking from, but it took 1.5 hours to leak anything at all.

It's hard to tell so far, but I'm going with the water pump because that's a common problem with the M5x engines.

This engine has an auxiliary pump that I have not had in any of the earlier engines. How prone is the aux water pump to leaking, and why would any leak take 1.5 hours from when I park to when the leak appears on the ground under the car? The HVAC system does not have any indications that it will cycle coolant -- the job of the aux pump -- so I have no idea how to make it work, and I don't really care. But the aux pump is there and I'm having a leak so I have to wonder what conditions would make it leak after 1.5 hours of turning the car off.

Check on the exhaust side of the engine. The lower coolant hose has a temp sensor that likes to trickle coolant from the o-ring

The plate under the engine makes it hard to see, but the drips are front and center, and if they were on the side, it would be the intake side.

You probably need to put the car in the air and take off the plate to see clearly where they are coming from.



Just a matter of finding the leaky parts and replacing them, but to be honest, if you have a fair amount of miles on the car it's probably time for a cooling system overhaul. If everything is the same age and one part is leaking, other parts are probably soon to follow.

So if you can't find the leak and have an automatic transmission....

Check the transmission coolant block o-rings, also the tanks get old/brittle and can have a small crack at the header plate near the bottom hose.

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I can find the leak and fix it, that's easy. I want to get the parts on hand before I take the car apart.

The question is about, what leaks an hour and a half after turning the car off?

All of the "normal" stuff that leaks will leak all of the time. My car does not leak for a long time after parking it, then it only seems to leak for an hour or so. Because there is an auxiliary water pump that I am not familiar with, my specific question is whether it does something after the car is parked that ends up on my driveway.

+1 It's in the lower side of the radiator. I had to put UV dye in my system to find it as it was a very small, slow leak.

It could be anywhere. I do understand how you want to be prepared, but just find the leak and then order the parts to fix it.

The last leak I had was coming out of the heater control valves. I found it using UV dye.

"where are my coolant leaks coming from...." Really??? How about all 46 (sic)places that a coolant joint/attachment point is!!!!! And the 1.5 hour part is that as things heat up, they expand, when they cool, they contract. 4th grade science class. There are so many Orings, gaskets, etc etc on this engine that you have to do some work to find it.

From my experience no.

The aux water pump only comes on when the key is in the ignition