2021 VDO Water Pump A2C59514607 and bolt question

[dan2342]

Good evening Addicts,

My thermostat went at just over 49,000 (yellow warning to red) last week, leaving us stranded an hour from home with a newborn in the middle of the night. Good times.

I decided to replace the water pump if I was going in for the thermostat, so I ordered the often referenced "kit" from FCP (11517632426KT3) and was surprised to see a pump with isolation mounts when it arrived:



I was initially confused and thought I had received an old pump, since my understanding is they had isolation mounts prior to my car, but the date on it was brand new (02/21):



I then found this service announcement from VDO regarding the change: UPGRADE – Electric Water Pump BMW (A2C59514607)

But the bolts included in the kit were the same 26mm old bolts (11517602123), so with the new pump mount being 4mm thicker (17mm), that leaves us with only 9mm (4 threads) to attach to the crank case:



For reference, here is the same bolt in the water pump I removed that had hard mounts:



I reached out to FCP and a few others, but they all reported that I should use the shorter bolt (11517602123, 26mm) instead of the longer bolt (11510392553, 36mm), that would seemingly fit perfectly in the crank case mount point. It seems likely they're all checking the same database and repeating back to me what the recommendation is for my car, which doesn't account for this new revision.

This is the same problem, but in reverse, that people had when they switched from isolation mounts to hard mounts back in 2013/2014, but people would still get the longer bolts and have to cut them.

I had to get it done, it being our only car, so I went to the hardware store and bought 3 M8x30 stainless bolts, which worked great. The M8x40 just barely bottomed out. It's almost like an M8x36 would be perfect...

Has anyone run into this yet and received a better answer? It just seems like a bad idea to hang anything off your engine block, let alone a heavy water pump, with 4 threads when the hole is a good 23mm deep.

[dtla1]

That's an interesting find. The literature you linked to just says "The screw set M8x26 (B) is particularly relevant for the UPGRADE of the pump." but doesn't really say HOW it's relevant.

And then it continues to go on to say that the aluminum screws (36MM long) must be replaced if a pump using aluminum screws is being replaced.

And the final clue, "We also recommend swapping the steel screws (A, B)." Which I guess might mean if you have A, you should swap to B? At least that's how I read it.

I feel like some if not most if this can be attributed to maybe some fuzzy translation, and the intent is that you should use B spec screws, and if you previously had A length, swap to B length now. But then again, who knows for sure. I would say it's probably ok to use the 26MM long screws (rule of thumb for steel is usually 1:1 bolt diameter to thread length for good engagement).

Also for extra funny, I found a VDO version of that bulletin that include english and german side by side, note the dimensions given for the flange thicknesses... https://us.continental-aftermarket.c...nfo_Update.pdf

[dan2342]

Great find. The bulletin you found is from when they switched FROM using an isolation mount to a solid mount (11517632426) back around 2013, so we have the complete VDO mount history here.

My understanding is that the original unit with the isolation mount used the longer bolts (bolt C, 36mm), and if this latest revision is 1mm thicker than the original, you'd think the latest revision would also use the longer bolt.

I've found multiple comments from years ago that the 26mm bolt is only for pump 11517632426 (the one that first had the hard mount, introduced in the pdf you linked to). At that time, the concern was people using the short bolt on the original pump with the thicker isolation mount or trying to use the longer bolt on the hard mount (which would bottom out).

VDO wouldn't make a recommendation on which specific bolt to use, just that one of the three bolts should be used. They only state that the aluminum bolts MUST be replaced and the steel SHOULD be replaced. BMW would have to make the recommendation on which bolt to use and my impression is they haven't yet, but that's where I thought I might find someone here that knew better.

FCP said they would ask BMW NA, but "it might take awhile". I won't hold my breath. It's hard to look at the pictures and think those 4 steel bolt threads are the right answer in that soft aluminum crank case.