Low power / erratic fan speed issue. Help!

450pirate · 01-21-2018, 02:51 PM

Im having a intermittent low power issue on my 2011 n55 335i STOCK (~55k). This all started after I replaced the coolant expansion tank, but may totally be unrelated. I did the bleed procedure and it seemed like it was taking more than 10 minutes and thought it was taking longer than it should so I cancelled it before it finished. (silly, I know). All these issues started shortly after this, but may be completely unrelated, just noting. The car has no codes, although my scanner can't read shadow codes. Im looking for some advice on where to move forward from here.

The Problem: Im getting low boost / power at times, at medium to high throttle. It seems totally random, comes and goes even during pulls. Ive done a 3rd gear pull and felt the reduced power and then have it kick back to full power during the pull. I also have an erratic cooling fan speed. I can hear it kick on to full blast at times when it shouldn't be, like pulling into a drive through after mellow cruising. Last time i pulled into my driveway it was on full blast, I restarted the car and it was normal, so it makes me think the car isn't really getting hot. There are NO dash lights at all.

Is my car stuck in the bleed procedure somehow? Is my fan relay going bad possibly? Would that give me low power at times when the fan is on HIGH? Would reading the shadow codes give more info?

I had trouble searching for this issue. Im more of a motorcycle / off road mechanic, newer cars are kind of new to me to work on. Im looking for some advice before I start throwing parts at it. Thank you for any info or links you can provide!

opjose · 01-21-2018, 03:05 PM

Has the water pump and thermostat been replaced?

450pirate · 01-21-2018, 03:08 PM

Original water pump and thermostat.

EB89 · 01-21-2018, 10:56 PM

Check codes.....

opjose · 01-22-2018, 09:40 AM

He said the car has no codes.

A water pump that is on the way out may not throw codes until it has completely failed.

Mine threw no codes but I got the racing fan at times about two weeks before it finally died.

450pirate · 01-22-2018, 01:05 PM

Im willing to believe my water pump could be on its way out at that mileage, but then what would the low power issue sound like then if the problems were unrelated? Its very noticeable when it happens. Could my diverter valve be sticking?

OP3NAIR · 01-22-2018, 03:10 PM

The power reduction is the safety mechanism for the car overheating. Your water pump is on it’s way out. Scan for BMW codes and you’ll probably see the codes for the pump failure. If you don’t, you will soon. Fan on full bore and a non responsive gas pedal is an impending overheat.

450pirate · 01-22-2018, 04:29 PM

Ok this sounds like we’re getting somewhere. Thank you everyone!!!

01-21-2018, 02:51 PM	#1
450pirate Enlisted Member 3 Rep 42 Posts Drives: '11 E90 335i (stock) Join Date: Oct 2015 Location: Socal iTrader: (0)	Low power / erratic fan speed issue. Help! Im having a intermittent low power issue on my 2011 n55 335i STOCK (~55k). This all started after I replaced the coolant expansion tank, but may totally be unrelated. I did the bleed procedure and it seemed like it was taking more than 10 minutes and thought it was taking longer than it should so I cancelled it before it finished. (silly, I know). All these issues started shortly after this, but may be completely unrelated, just noting. The car has no codes, although my scanner can't read shadow codes. Im looking for some advice on where to move forward from here. The Problem: Im getting low boost / power at times, at medium to high throttle. It seems totally random, comes and goes even during pulls. Ive done a 3rd gear pull and felt the reduced power and then have it kick back to full power during the pull. I also have an erratic cooling fan speed. I can hear it kick on to full blast at times when it shouldn't be, like pulling into a drive through after mellow cruising. Last time i pulled into my driveway it was on full blast, I restarted the car and it was normal, so it makes me think the car isn't really getting hot. There are NO dash lights at all. Is my car stuck in the bleed procedure somehow? Is my fan relay going bad possibly? Would that give me low power at times when the fan is on HIGH? Would reading the shadow codes give more info? I had trouble searching for this issue. Im more of a motorcycle / off road mechanic, newer cars are kind of new to me to work on. Im looking for some advice before I start throwing parts at it. Thank you for any info or links you can provide!
	Appreciate 0 Tweet Quote

01-21-2018, 03:05 PM	#2
opjose Major 242 Rep 1,354 Posts Drives: 335xi Join Date: May 2016 Location: Md iTrader: (0)	Has the water pump and thermostat been replaced?
	Appreciate 1 450pirate3.00 Quote

01-21-2018, 03:08 PM	#3
450pirate Enlisted Member 3 Rep 42 Posts Drives: '11 E90 335i (stock) Join Date: Oct 2015 Location: Socal iTrader: (0)	Original water pump and thermostat.
	Appreciate 0 Quote

01-21-2018, 10:56 PM	#4
EB89 Brigadier General 541 Rep 3,131 Posts Drives: 2011 335i e92 DCT Join Date: Sep 2015 Location: Australia, NSW iTrader: (0) Garage List 2011 BMW 335i e92 [0.00]	Check codes..... __________________ / MHD Stage 2+ / AR CATLESS DP / PE MOD 4 INCH TIPS / BMR FMIC / K&N DROP IN / BMS CP /
	Appreciate 1 450pirate3.00 Quote

01-22-2018, 09:40 AM	#5
opjose Major 242 Rep 1,354 Posts Drives: 335xi Join Date: May 2016 Location: Md iTrader: (0)	He said the car has no codes. A water pump that is on the way out may not throw codes until it has completely failed. Mine threw no codes but I got the racing fan at times about two weeks before it finally died.
	Appreciate 1 450pirate3.00 Quote

01-22-2018, 01:05 PM	#6
450pirate Enlisted Member 3 Rep 42 Posts Drives: '11 E90 335i (stock) Join Date: Oct 2015 Location: Socal iTrader: (0)	Im willing to believe my water pump could be on its way out at that mileage, but then what would the low power issue sound like then if the problems were unrelated? Its very noticeable when it happens. Could my diverter valve be sticking?
	Appreciate 0 Quote

01-22-2018, 03:10 PM	#7
OP3NAIR Second Lieutenant 68 Rep 211 Posts Drives: '11 335i e93, '03 325xiT Join Date: Jan 2015 Location: NoVA iTrader: (0)	The power reduction is the safety mechanism for the car overheating. Your water pump is on it’s way out. Scan for BMW codes and you’ll probably see the codes for the pump failure. If you don’t, you will soon. Fan on full bore and a non responsive gas pedal is an impending overheat.
	Appreciate 1 450pirate3.00 Quote

01-22-2018, 04:29 PM	#8
450pirate Enlisted Member 3 Rep 42 Posts Drives: '11 E90 335i (stock) Join Date: Oct 2015 Location: Socal iTrader: (0)	Ok this sounds like we’re getting somewhere. Thank you everyone!!!
	Appreciate 0 Quote