Serpentine belt thrown

[Salty B.]

Ugh. I was heading up to Louisville, about 300mi, and heard a weird flappy sound and seconds later battery warning, no power steering, you know.

Serp belt is now wound around the crank pulley. I had it towed to the closest place in Monteagle TN that said they could fix it. I have roadside assist but they never showed up and I had to pay $100. Not terrible for a flatbed tow.

REALLY hoping it did not get sucked into the crank seal... guess I'll find out tomorrow. I'm kinda stuck here. Luckily it happened right before an exit and I was able to get to a gas station before the temp gauge maxed out, but it did go to about the 2:00 position. Hope that didn't overheat.

Oh and it took out something that caused a coolant leak. Not massive, but enough. The radiator looks OK, and the leak seems to be down towards the PS pump area but I can't see where it might be coming from.

The belt isn't old. It was replaced about 25,000mi ago. Maybe it got oiled when I had a leak from the filter o-ring?

I have all my tools with me, but without parts, I'm stuck. Hope these good ol' boys can figure it out. It's going to be a very expensive tow back to Atlanta...

[andrewwynn]

F30 or e53? Not aware of fms ingestion concern on any e53 motors but I've seen a handful of cascading problems with coolant tank or hoses.

With that new of belt, if the tensioner isn't at fault I'd suspect the coolant leak damaged the belt not the other way around.

My car insurance roadside will reimburse for out of pocket tow.

[Salty B.]

Mine will too, just kinda mad they didn't come through.

E53. I know about the N54/55 issue so I was concerned the M54 was susceptible too.

Had no signs of a coolant leak prior, temp was steady @ 12:00 until it went. Expansion tank was replaced about 30K ago. Funny enough I ordered a new one just to have on hand but it didn't show up in time. The current one shows no signs of leaking. Fan does not wobble, water pump and tensioner have about 25K on it, spins freely no grinding or noise.

Wonder if FCP honors their warranty for the subsequent owners... probably not.

No red light on temp gauge.

[andrewwynn]

Temp @ 12 is fake unless you reprogrammed. It does light up red if it overheats which you'd prob have noticed. My theory on coolant is temp got hot enough to build enough pressure to vent. No harm done.

[Henn28]

Been there for sure, sorry to hear. My belt shucking and overheating issues came down to a very slight deformation in the alternator pulley (like it had been dinged in shipping), and mostly, I think, a tensioner assembly kit where the bolt holding the pulleys on hadn’t been torqued properly so there was a slight wobble. It took 2000 miles, but when it let loose it picked the worst spot possible to do so.

Both parts came from out of the box with these problems I assume, so I’m an idiot for not checking when I installed it all. Not sure if the 6 cylinder has the same tensioner arrangement as the 8, but if so definitely check that the pulleys are secure to the snubber/tensioner unit.

I think you’ll be fine on the temp. Mine got hot enough to blow the radiator reservoir seams (full hot needle for a couple minutes before I was able to get off the interstate bridge it happened on) but happily no bad report cards from blackstone…3 oil changes later.

[Salty B.]

Tensioner was replaced with the belt around 25K ago... I just called them and he says the main water pump is grinding and the aux pump is leaking. Swell... $$$ but he's pretty sure he can have it done this afternoon.

The two pumps aren't that old... maybe 35K miles on both. I didn't even know it had an aux pump. I'm gonna see what FCP can do for me if anything, since it was the prior owner who bought those parts.

[andrewwynn]

Originally Posted by Salty B.

Tensioner was replaced with the belt around 25K ago... I just called them and he says the main water pump is grinding and the aux pump is leaking. Swell... $$$ but he's pretty sure he can have it done this afternoon.

The two pumps aren't that old... maybe 35K miles on both. I didn't even know it had an aux pump. I'm gonna see what FCP can do for me if anything, since it was the prior ornate who bought those parts.

Im pretty sure FCP policy is for the same person but if you're friends with the original owner have him do the exchange. Aux pump is right next to the disa valve.

[Bdc101]

Remember that FCP warranty now just gives you store credit for the original price of the old one, NOT a refund and not a free part. You have to buy the new part, send them the old one and then you get store credit. Not really a good deal at all anymore.

[BimmerBreaker]

If the needle was only at about 2 o'clock position, the engine will be fine. It got hot because the water pump stopped spinning.

M54's are not known to have the same issue as N5x where they suck belts into the crank seal. I've been around M54 cars a long time and never heard of this happening.

Originally Posted by andrewwynn

Temp @ 12 is fake unless you reprogrammed. It does light up red if it overheats which you'd prob have noticed. My theory on coolant is temp got hot enough to build enough pressure to vent. No harm done.

Temp at 12 isn't "fake" - TDC represents the range of acceptable operating temperatures for the engine. The electrically assisted thermostat causes the temperature to fluctuate, thus the gauge is buffered otherwise the needle would constantly be bouncing around.

Considering the engine is typically operating at 1.0 bar, it is safe to say that it did not reach 2.0 bar to vent coolant. The temperatures to do so would be quite excessive - this occurs deep into the red on the temp gauge, not a little past TDC where OP's car reached.

Originally Posted by Bdc101

Remember that FCP warranty now just gives you store credit for the original price of the old one, NOT a refund and not a free part. You have to buy the new part, send them the old one and then you get store credit. Not really a good deal at all anymore.

If you plan on owning your BMW for a long time - or maintain several at a time - it ends up being a wash. After a return or two you just end up using store credit to buy the replacement parts, then get the exchange and return the old one to replenish the store credit.

[Fifty150hs]

Originally Posted by BimmerBreaker

If the needle was only at about 2 o'clock position, the engine will be fine. It got hot because the water pump stopped spinning.

M54's are not known to have the same issue as N5x where they suck belts into the crank seal. I've been around M54 cars a long time and never heard of this happening.



Temp at 12 isn't "fake" - TDC represents the range of acceptable operating temperatures for the engine. The electrically assisted thermostat causes the temperature to fluctuate, thus the gauge is buffered otherwise the needle would constantly be bouncing around.

Considering the engine is typically operating at 1.0 bar, it is safe to say that it did not reach 2.0 bar to vent coolant. The temperatures to do so would be quite excessive - this occurs deep into the red on the temp gauge, not a little past TDC where OP's car reached.



If you plan on owning your BMW for a long time - or maintain several at a time - it ends up being a wash. After a return or two you just end up using store credit to buy the replacement parts, then get the exchange and return the old one to replenish the store credit.

True, except you have to pay to ship the old part back. It actually ends up not being such a great deal anymore.