[Hevath]

Car in question 2007 335i Coupe 164 k kms

Okay so I have been scouring the forum since Friday and despite how I rephrase my searches on Google, I don't seem to be finding anything at all related.

I recently replaced my OFHG, serpentine belt and flushed my coolant/oil but noticed a very small coolant leak on my driveway. I took my car to BMW for an alignment Friday and asked the techs to check my engine mounts and to diagnose where the coolant leak was in fact coming from. The came back with a small leak in the rad and the water pump. Now I have had the water pump replaced by this dealer in 2017, then almost a year to the date in 2018 (they warranted it) and now a year and 3 months to the day again I need a new water pump... They said it failing do to excessive oil leaking down from the OFHG.. plausible?

My biggest problem is that my water pump was working, might have been slowly leaking but it was working, i had the car running almost the entire day before with zero issue. when i left the dealer i hit the highway home and my serpentine belt just came off, i decided to keep going to home, wasn't far, running on battery only power, until i got a engine temp warning and pulled over.. the pump was no longer working at all...

Long story short is there anything anyone can think of the dealer might have done that caused the water pump to simply stop? Im on my way out now to check the fuses, voltage and anything else i can think of but any direction would be certainly appreciated!

Dealer wants $1400+ to do the pump

[Emilime75]

Anything's possible - Murphy's law. Water pump and thermostat are electronic, so voltage could have dropped significantly while driving on battery only, causing it to quit. Maybe when the belt came off, it knocked the water pump connector off or damaged wiring. Maybe your leak isn't as slow as you think and you're low on coolant...

There are plenty of possibilities. How did you determine that "the water pump wasn't working at all"? These cars are power hungry. It doesn't take long to drain the battery when the alternator is not charging.

I think step 1 would be to check/charge the battery.
Step 2 is to determine why the belt came off. Oil from previous leaks on pulleys? Bad pulley/s? Bad tensioner?
Step 3, check coolant level.
Step 4, run the coolant bleed procedure. This will determine if the pump actually is/not working, and if the reservoir ever went dry because of any leaks, you could have an air pocket in the system. Water pumps are not good air pumps.

[gds52]

Originally Posted by Emilime75

Anything's possible - Murphy's law. Water pump and thermostat are electronic, so voltage could have dropped significantly while driving on battery only, causing it to quit. Maybe when the belt came off, it knocked the water pump connector off or damaged wiring. Maybe your leak isn't as slow as you think and you're low on coolant.

There are plenty of possibilities. How did you determine that "the water pump wasn't working at all"?

I think step 1 would be to check/charge the battery.
Step 2 is to determine why the belt came off. Oil from previous leaks on pulleys? Bad pulley/s? Bad tensioner?
Step 3, check coolant level.
Step 4, run the coolant bleed procedure. This will determine if the pump actually is/not working, and if the reservoir ever went dry because of any leaks, you could have an air pocket in the system. Water pumps are not good air pumps.

Step 5. Find a local BMW shop and not the dealership

[Hevath]

Originally Posted by gds52

Step 5. Find a local BMW shop and not the dealership

***UPDATE***

Dealer had the electrical connector to my water pump unplugged.... checked my fuses and everything was good, got under the car and voila! This will warrant an aggravated call to my dealer but I'm happy its at least pumping again.

Step 2: I just replaced the belt and I have a slight squeal coming from it that I'm trying to diagnose. I did replace the tensioner when i originally changed the belt and that seems to be working well. I checked the other pulleys and there doesn't seem to be any play.

Step 3: This was the first thing I checked, was all topped up!

Step 4: Running this again now just because

Step 5: Yuuuuuppppppp!!!!!!!

[Hevath]

I was told by my friend at the parts store the belt was a cheap one, not like the original i bought... this one was only $22 Canadian :P

Question: Should i let the belt and engine get up to operating temp now that i can and see if the squeal goes away?

[Tambohamilton]

The serpentine belt shouldn't squeal, ever. If it's squealing at all, something isn't right.

If you replaced the tensioner as well as the belt, my money is on the alternator pulley being worn out...that wouldn't explain the belt hopping off though, so definitely more investigation needed.