[AFLRO]

Couple weeks ago, my car started to develop what best can be described as throttle cutouts during shift changes. The condition was more prevalent shifting from 3rd to 4th or 4th to 5th gear via moderate/hard acceleration after driving the car normally for about 10-15min. This started to drive me insane as couple days ago this condition appeared going from 1st to 2nd. The clutch engages, I give it gas, nothing happens. ~2 seconds later, throttle is responsive again.

2 days ago, I came off the highway after driving for about an hour at speeds between 60-75mph and immediately noticed that my fan was going batsh!t crazy. Oil temp was normal, pretty close to 240 F; however, I did not know at the time how to check my coolant temp. I turned the engine off, let it sit for a minute or two, restarted, and everything was back to normal. I did not get a SES or yellow coolant temp message.

Yesterday, I found out how to get into the hidden cluster menus and monitored my KTEMP in menu 7.00. In the morning, coolant temp never got hotter than 87 C, no matter how long I drove the car for. My oil temp also was unusually low, I'd estimate around 180-190 F. Meanwhile, the fan kept cycling on and off every 10 seconds or so while the climate control was completely off.

Today, I decided to monitor the temps during more aggressive driving. Again, I started off in the unusual mid-80 C range. After pushing it past 4-5k RPM for about 5min, the temp suddenly started shooting up, eventually reaching 120 C, triggering the yellow coolant message. Of course at this point, the fan was working in overdrive and I stopped the car and turned off the engine. Restarted 5min later, drove lightly, and the temp was at mid-80s C yet again.

This all makes sense however. Since water pump and thermostat are controlled by ECU and if one of them was defective, ECU would intervene in order to preserve the engine from overheating. I am just glad I was finally able to isolate the water pump/thermostat as my problem. At 86k miles, I am due to replace both anyway.

[seccsc]

Originally Posted by AFLRO

Couple weeks ago, my car started to develop what best can be described as throttle cutouts during shift changes. The condition was more prevalent shifting from 3rd to 4th or 4th to 5th gear via moderate/hard acceleration after driving the car normally for about 10-15min. This started to drive me insane as couple days ago this condition appeared going from 1st to 2nd. The clutch engages, I give it gas, nothing happens. ~2 seconds later, throttle is responsive again.

2 days ago, I came off the highway after driving for about an hour at speeds between 60-75mph and immediately noticed that my fan was going batsh!t crazy. Oil temp was normal, pretty close to 240 F; however, I did not know at the time how to check my coolant temp. I turned the engine off, let it sit for a minute or two, restarted, and everything was back to normal. I did not get a SES or yellow coolant temp message.

Yesterday, I found out how to get into the hidden cluster menus and monitored my KTEMP in menu 7.00. In the morning, coolant temp never got hotter than 87 C, no matter how long I drove the car for. My oil temp also was unusually low, I'd estimate around 180-190 F. Meanwhile, the fan kept cycling on and off every 10 seconds or so while the climate control was completely off.

Today, I decided to monitor the temps during more aggressive driving. Again, I started off in the unusual mid-80 C range. After pushing it past 4-5k RPM for about 5min, the temp suddenly started shooting up, eventually reaching 120 C, triggering the yellow coolant message. Of course at this point, the fan was working in overdrive and I stopped the car and turned off the engine. Restarted 5min later, drove lightly, and the temp was at mid-80s C yet again.

This all makes sense however. Since water pump and thermostat are controlled by ECU and if one of them was defective, ECU would intervene in order to preserve the engine from overheating. I am just glad I was finally able to isolate the water pump/thermostat as my problem. At 86k miles, I am due to replace both anyway.

Did you get the codes? Sounds like a thermostat.

[DaZuc]

Lucky, I got no warning except when the fan kicked (in a parking lot idling) on as if the car was prepping for flight.

56k my pump lasted.

From what I've read on the forums once you hear your fan kick on get ready to start ordering parts.

[AFLRO]

seccsc, negative. ATM I have only the regular OBDII engine code reader. I've ordered a K-CAN D-CAN cable and will see what I can dig up using INPA and/or EDIABAS.

[seccsc]

Originally Posted by AFLRO

seccsc, negative. ATM I have only the regular OBDII engine code reader. I've ordered a K-CAN D-CAN cable and will see what I can dig up using INPA and/or EDIABAS.

Roger!

[tdavis42]

I JUST had my thermostat replaced for this exact reason. I never had any lights come on but I did get the crazy fan noise in the cabin even when it was 50 degrees outside. The water pump stayed but the thermostat had to go. I got the thermostat, belt, pulley, and oil change done for 790 at an indy shop. 760 is what the dealership quoted for just the thermostat.

[vapore0n]

^^
I would have done the water pump too, considering they are tied to each other.
Unless youve already done it.

[tdavis42]

I thought about it but I really didn't feel the need to. I caught the thermostat soon enough to not have it continue to push the water pump in a constant on position for to long. From what I have read the problem is with the thermostat going bad not the water pump. What I mean by that is if you don't replace the thermostat soon enough it will wear the pump out prematurely by over working it. But time will tell!

[John 070]

For some reason I don't look forward to this job....I may do one of those, well, I saved $3,400 minus $250 on the DSC hydro by DIY, I'll pay an indy to do the water pump? My only thing is I hate not having control over what part they used to do it....or go to dealer and hope for a 20% coupon...lol

[AFLRO]

I sourced the water pump, the hose (t-stat to pump), a quart of Pentosin coolant, and 3x aluminum bolts for $445. All OEM bought through WORLDPAC. Unfortunately, they ran out of OEM t-stats, which go for ~$60. I had to go to the stealer and fork out a whopping $121.50 for it. I'll be DIYing this project on Friday. Should be a pretty easy job with all the documentation available online.

[tdavis42]

I am comforted by the fact that my shop uses OEM parts default. You can request cheaper but he doesn't like to. It also helps that my shop is owned by my girlfriends uncle and has been around for 40 years.

A few pics of his garage at home.

[luckyJ]

Did BMW update/change these parts for MY2012 e90/91s? If so is there a part number for the updated/newer versions please?

I just purchased a 2012 e91 w 52k miles and was going to inspect the water pump/temp sensors. Thank you

[muncie21]

My water pump was intermittent and getting progressively worse when I decided to change it. You can see the problem in the pic below. Not sure if a bad T-stat was the cause or a design defect of the pump

[AFLRO]

Changed my thermostat and water pump today. Quite a pain to get the hoses off and back on. On a positive note, no more throttle cutoffs and the temps stay in 105-110 range. I had the original thermostat with production date of 06/2010.

[luckyJ]

Originally Posted by AFLRO

Changed my thermostat and water pump today. Quite a pain to get the hoses off and back on. On a positive note, no more throttle cutoffs and the temps stay in 105-110 range. I had the original thermostat with production date of 06/2010.

Hi Alfro. Would you happen to have the part numbers for the water pump and t-stat please?

[AndreyT]

Originally Posted by AFLRO

Couple weeks ago, my car started to develop what best can be described as throttle cutouts during shift changes. The condition was more prevalent shifting from 3rd to 4th or 4th to 5th gear via moderate/hard acceleration after driving the car normally for about 10-15min. This started to drive me insane as couple days ago this condition appeared going from 1st to 2nd. The clutch engages, I give it gas, nothing happens. ~2 seconds later, throttle is responsive again.

In my case very similar symptoms appeared in a different order with different (albeit related) consequences.

First I noticed my radiator fan going crazy, spinning non-stop at full RPM, which was a sure sign of an impending water pump failure. However, there was no negative impact on throttle response. The car was driving normally.

One day the pump finally failed, giving me the standard orange and then red warnings. The dealer replaced the pump, and what I got my car back - that's when intermittent issues with the throttle began. And they were very similar to what you describe above: the feeling of strangely "weak" upshifts.

Trying to describe these issues to the dealer (the car was still under warranty) resulted in nothing - they "Could not reproduce". However, in a course of a year it was getting worse and worse, and at some points started throwing fuel pressure codes.

So I ended up with HPFP replacement, which immediately fixed the throttle response problem.

The throttle-related symptoms you describe can mean a loty of different things: turbos, HPFP (as in my case), and, apparently, water pump (as in your case).

[AFLRO]

Originally Posted by luckyJ

Hi Alfro. Would you happen to have the part numbers for the water pump and t-stat please?

luckyJ, part numbers are as follows:

11517632426 - Water pump
11537601158 - Thermostat
11517602123 - Bolt (sold individually, need 3)

I also replaced the thermostat to water pump hose. Part number is 11537545665.