[MoeTE87]

Hey everyone..I don't post here much but I am in need of some help and input from you guys. Here's what is going on.

I have a 2011 335xi, N55 engine with 51.6k miles on it and there has been some intermittent issues that I've noticed recently.

1. When I start the car if the engine is cold or hot, the idle likes to fluctuate up and down for about 5secs and then stops. Very weird and was told it can be a soon to be failing fuel injector..I don't have any codes on my dash.

2. This one is most recent issue and noticed it this past Saturday. When the car was parked over night and started it cold, the radiator fan kicked on then off, then on again and kept doing that then eventually stopped. It got pretty loud..like the car was overheating fan speed. So this morning it did the same thing and it still was going on and off my whole commute until I reached downtown from Newtown.

So I'm not sure what's going on..any help would be much appreciated.


Thanks,
Jeff

[robthewrench]

Related to #2, the fan on/off can be a symptom of a failing water pump and at 51K your at pretty much the exact same mileage of my 2011 N55 water pump failure.

You should get the codes scanned with BMW specific software to look for both emission related and shadow codes. If the water pump is failing, you'll probably have 1,2, or 3 codes stored related to it. You may not have a lot of time here, so I'd do this quickly before it leaves you stranded one day.

You can either get software and a cable and do it yourself, have a friend do it, go to an independent, or go to the dealer. Note that a standard OBDII scanner will only show you emissions related codes and will not show you the rest of the codes and this will not help you with this problem.

[MoeTE87]

Admin right now I don't have any codes or check engine light on (haven't scanned the obd2 yet) how much would it cost to change out the water pump?

[MoeTE87]

Here's what my SA from my local BMW store said:

"Sounds like a possible fuel injector or carbon buildup (google walnut blast) OR it could just be fuel/air mixtures adapting (especially if it only happens for 5 seconds and clears out)

The fan noise-Sounds like a possible electric coolant pump on its way??"

[jgoens]

Almost certain your water pump is on it's way out--mine did the same thing for a couple weeks before going out. Your idling thing could be related to that--sounds weird but if faults(not codes) are being stored because of pump other things can act weird. I posted a thread a month ago relating to this and how my transmission was acting up due to water pump failure.

[CookMaster]

Your engine idle could be related to the version of software for your DME. I had problems with my car with idle fluctuations. When I installed the PPK, they also flashed the DME with the latest software. You may want to ask your SA to get an updated software for your DME.

[BashShah]

1. When is the last time you had a Walnut Blast?
Before changing really expensive injectors......first and for most.... Get a walnut blast done.

2. Look at your plugs and coils also before injectors....
I know no codes.....so change them all at the same time.

3. Your rad fan is most likely water pump and tstst.
Not sure if you have CPO or not, but if you do, pay the extra and tell SA, you want to replace the TStat also..
Meaning replace both water pump and tstat.

Don't forget to do a full adaptation reset.

DN

[CookMaster]

Originally Posted by DarkNemesis

1. When is the last time you had a Walnut Blast?
Before changing really expensive injectors......first and for most.... Get a walnut blast done.

2. Look at your plugs and coils also before injectors....
I know no codes.....so change them all at the same time.

3. Your rad fan is most likely water pump and tstst.
Not sure if you have CPO or not, but if you do, pay the extra and tell SA, you want to replace the TStat also..
Meaning replace both water pump and tstat.

Don't forget to do a full adaptation reset.

DN

N55 Engines have build-up on their intakes at 1/2 mileage of the N54. You could think about having a walnut blast sometime in the 80K range.

Don't waste your money on doing the hunt/peck routine for fixing problems. Flash your DME with the latest software first, then look at whether you need to replace parts.

TSTAT or fan logic is bad. Let the experts do the troubleshooting.

[MoeTE87]

Thank you guys for all the help. I did the walnut blast on my 08 135i before I sold it and wow what a huge difference that made.

I just emailed my SA about updating the DME software. I guess that's a good place to start.

If it is the water pump / tstat..how difficult is it to replace those two parts? I'm pretty good at wrenching.

[MoeTE87]

So it's for sure the water pump and tstat? Just wonder before I pull the trigger on a new set.

[robthewrench]

The fan coming on/off is very likely the waterpump. Have you pulled the codes yet? This could confirm that you are in fact having the early signs of waterpump failure.

If there are no codes, you could probably wait a while to see if it repeats or gets worse. If you aren't taking any long trips, even if it fails completely, you could wait until it cools off and drive it very short distances to get it home.

You are right at about the right age / mileage for the waterpump. Mine went at 54K. And a lot of other N55s seem to go near that mileage.

[mxchris727]

The bad idle sounds like a failing mass airflow sensor.

[MoeTE87]

The thing is, I don't have any codes that have popped up. Maybe some secret faults have been stored but I'm not sure.

[AllBlackBimmer]

The fan and on off most likely ISN'T the water pump, its more likely the thermostat failing. Obviously these components do go hand in hand, and yes it could be the pump, but I would def think it's the thermo. If youre replacing the thermo, replace the pump while youre in there.