Alternator Failing affecting the Water Pump? Do I still need to replace the WP?

ayzzz · 04-13-2019, 04:29 PM

Vehicle: 2007 BMW 335i E92 6MT w/ 122,000 miles (bought with 112k miles, not sure of the maintenance from the previous owner and what all he had replaced)

Brief Intro in the Problem:
I was driving back to campus after a drive and right before I put it in reverse to park, all of my lights just started going off for ABS and TC etc. My infotainment went out and my radar detector said "high voltage" so I yanked it out. Throttle response became limited etc. I suspected it was either the battery or alternator. So I just called a local indy to replace the battery and on my drive there my radiator cracked and my coolant pipe burst and the engine started to overheat with no sign. I had my radiator and battery replaced at the shop, I would have diy'd it but unfortunately, I don't have my tools to fix it myself.

Problems that arose after:

The shop informed me that they tried to start up the car and noticed that the battery was not being charged up properly because of the alternator and also claimed that my water pump went as well. They quoted me at around ~$1600 and I said forget about it since easter break is around the corner and had my car towed back home.

I read somewhere that the water pump will tend to cease functioning if the alternator is not working, which is similar to my case atm. My main question is do I just have to buy an alternator or do I have to buy a brand new water pump as well?

tldr: alternator failed causing the water pump to cease functioning as well. Do I replace just the alternator or do I replace both?

WhosGotTheLoud · 04-14-2019, 02:24 AM

My alternator took a dump on me not too long ago. Lights came on, weird clunking when putting car into drive, but nothing happened with my radiator or hoses.
Anyways, I only replaced my alternator and coded in a new battery since it was time to replace that as well; nothing done to my water pump whatsoever.
Not sure if you overheated the car enough for any damage to happen to yours.

rjahl · 04-14-2019, 09:40 AM

Not sure about the N54, but My N52 had a special databus that was shared by the alternator and water pump. Bad alternator caused a communication loss with the water pump. The pump still worked but ran un-throttled or full speed.

I'd have the shop replace the alternator, clear codes and then check the water pump.

Edit: it was the replacement alternator that caused the communication problem. Advance Auto special..... picked up an OEM alternator and the problem was fixed.

04-13-2019, 04:29 PM	#1
ayzzz New Member 0 Rep 8 Posts Drives: BMW 335i N54 E92 Join Date: Apr 2019 Location: Tennessee iTrader: (0)	Alternator Failing affecting the Water Pump? Do I still need to replace the WP? Vehicle: 2007 BMW 335i E92 6MT w/ 122,000 miles (bought with 112k miles, not sure of the maintenance from the previous owner and what all he had replaced) Brief Intro in the Problem: I was driving back to campus after a drive and right before I put it in reverse to park, all of my lights just started going off for ABS and TC etc. My infotainment went out and my radar detector said "high voltage" so I yanked it out. Throttle response became limited etc. I suspected it was either the battery or alternator. So I just called a local indy to replace the battery and on my drive there my radiator cracked and my coolant pipe burst and the engine started to overheat with no sign. I had my radiator and battery replaced at the shop, I would have diy'd it but unfortunately, I don't have my tools to fix it myself. Problems that arose after: The shop informed me that they tried to start up the car and noticed that the battery was not being charged up properly because of the alternator and also claimed that my water pump went as well. They quoted me at around ~$1600 and I said forget about it since easter break is around the corner and had my car towed back home. I read somewhere that the water pump will tend to cease functioning if the alternator is not working, which is similar to my case atm. My main question is do I just have to buy an alternator or do I have to buy a brand new water pump as well? tldr: alternator failed causing the water pump to cease functioning as well. Do I replace just the alternator or do I replace both? Last edited by ayzzz; 04-13-2019 at 04:51 PM..
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04-14-2019, 02:24 AM	#2
WhosGotTheLoud Enlisted Member 8 Rep 31 Posts Drives: 07 335i Join Date: Jun 2018 Location: Los Angeles iTrader: (0)	My alternator took a dump on me not too long ago. Lights came on, weird clunking when putting car into drive, but nothing happened with my radiator or hoses. Anyways, I only replaced my alternator and coded in a new battery since it was time to replace that as well; nothing done to my water pump whatsoever. Not sure if you overheated the car enough for any damage to happen to yours.
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04-14-2019, 09:40 AM	#3
rjahl Colonel 996 Rep 2,287 Posts Drives: Z4 35is Join Date: Jun 2011 Location: Tampa iTrader: (0) Garage List 2012 Z4 35is [0.00]	Not sure about the N54, but My N52 had a special databus that was shared by the alternator and water pump. Bad alternator caused a communication loss with the water pump. The pump still worked but ran un-throttled or full speed. I'd have the shop replace the alternator, clear codes and then check the water pump. Edit: it was the replacement alternator that caused the communication problem. Advance Auto special..... picked up an OEM alternator and the problem was fixed.
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