[tomwadek]

Hi everyone,

I have a 2011 335i N55 and I've been chasing both issues for some time. The first issue is a squeaking belt and the second a coolant leak.

First issue:
I've changed out the tensioner, belt, and both Idle pulleys twice. The sound is immediate with new parts.

I've tightened the power steering pulley.

Ran the car with the belt off ( sound goes away)

I don't know what is causing this sound and I'm afraid of driving it and the belt shredding. There seems to be a small oil leak coming from the OFHG which I had changed last year (only lasted a year) but like I said the sound is instant even after a belt, tensioner, and idle pulleys change. All parts are from the dealer.

Video link:

Second issue:

I have a pretty bad coolant leak coming from the passenger side. I can see a trail from under the car but nothing from the top of the car which makes me think this is somewhere in the middle.

6 months ago I put in a new radiator (because it was cracked from the top hose inlet) and new coolant reservoir. I didn't have any leaks until now. any idea of where it could be coming from?

Video link:

[BSM n54iS]

[Jackma119]

Originally Posted by BdSM n54iS

+1

[tomwadek]

I have a stethoscope.

seems to be coming from the tensioner area but I've changed it twice...

[tomwadek]

Any help on troubleshooting the coolant leak?

[weehe126]

Probably a bad PCV valve in the VC. Search and you will find plenty of threads.

[kkasson]

Squeaking could perhaps be the alternator pulley. Search for "alternator decoupler pulley" to find a few methods of testing it. Gates has a video on it.

[tomwadek]

I have chased the sound and it's coming from the general location of the OFHG and belt tensioner. It almost sounds like a vacuum leak when I rev the motor up but then goes away above 1500 RPMs.

As far as the leak goes, I cant find where it's coming from. Sometime sit leaks and sometimes it doesn't. Only thing that I can think of is a cracked radiator.

[tbirdboy]

Had my 2013 e92's OFHG replaced on 4/10.
Just purchased the thing on the 4/4 w/77k odo from Mercedes of Monterey.
Immaculate in and out. Not a blemish.
Same problem your having and just noticed it pulling into the garage. Please post an update when you nail this gremlin. Thanks.

[lowrydr310]

Originally Posted by tomwadek

Any help on troubleshooting the coolant leak?

It's really tricky to diagnose an intermittent coolant leak. Your best bet would be to use a UV dye test to poinpoint the source.

But first take a look at some of the obvious places. I once had a mysterious coolant leak. After I bought my car, I did several drains and fills of my radiator with distilled water to flush out all the (incorrect) green coolant that the previous owner installed when he had the water pump and thermostat replaced. After I got clear water draining out the final fill was with the correct BMW coolant. I drove around for weeks with no problems then one day while I had my car idling in the driveway I noticed a steady stream of coolant dripping onto the ground. I thought it was a cracked radiator but it ended up being the drain plug at the bottom of the radiator that I overtightened. I loosened it then retightened it, and all has been good since then. I found it strange that I didn't touch the drain plug and it held fine for weeks, then randomly one day it started to leak. However after I properly torqued it, it hasn't leaked since.

[tomwadek]

Originally Posted by lowrydr310

It's really tricky to diagnose an intermittent coolant leak. Your best bet would be to use a UV dye test to poinpoint the source.

But first take a look at some of the obvious places. I once had a mysterious coolant leak. After I bought my car, I did several drains and fills of my radiator with distilled water to flush out all the (incorrect) green coolant that the previous owner installed when he had the water pump and thermostat replaced. After I got clear water draining out the final fill was with the correct BMW coolant. I drove around for weeks with no problems then one day while I had my car idling in the driveway I noticed a steady stream of coolant dripping onto the ground. I thought it was a cracked radiator but it ended up being the drain plug at the bottom of the radiator that I overtightened. I loosened it then retightened it, and all has been good since then. I found it strange that I didn't touch the drain plug and it held fine for weeks, then randomly one day it started to leak. However after I properly torqued it, it hasn't leaked since.

Thank you, i'm going to try another go at it next week.

The coolant leak looks like it's coming from just above the inner cooler hose on the driver side. There is a smaller return hose that bolts onto the radiator using a T25 screw and at first I thought it was coming from there but now i'm not sure.

[OnlyDriveGerman]

Originally Posted by tomwadek

Hi everyone,

I have a 2011 335i N55 and I've been chasing both issues for some time. The first issue is a squeaking belt and the second a coolant leak.

First issue:
I've changed out the tensioner, belt, and both Idle pulleys twice. The sound is immediate with new parts.

I've tightened the power steering pulley.

Ran the car with the belt off ( sound goes away)

I don't know what is causing this sound and I'm afraid of driving it and the belt shredding. There seems to be a small oil leak coming from the OFHG which I had changed last year (only lasted a year) but like I said the sound is instant even after a belt, tensioner, and idle pulleys change. All parts are from the dealer.

Video link:

Second issue:

I have a pretty bad coolant leak coming from the passenger side. I can see a trail from under the car but nothing from the top of the car which makes me think this is somewhere in the middle.

6 months ago I put in a new radiator (because it was cracked from the top hose inlet) and new coolant reservoir. I didn't have any leaks until now. any idea of where it could be coming from?

Video link:

I'm dealing with a similar squealing sound. I believe the pulley on the AC condenser was the cause so I got a smaller belt, deleted the ac from the belt system and it went away, for a while. I was using a 435K6 but the squeal came back as I don't think it puts enough tension on the system. I'm hoping to get a 433K6 and that it's tight enough.

[tomwadek]

Interesting, My brother noticed a whistling sound coming from the engine bay when I was pulling out of his parking lot.

[tbirdboy]

Well, kinda solved it...

I just got back from a visit to Monterey Motorworks (BMW indy)here in Monterey, CA. Having a chirp, chirp myself but exactly sure where it was coming from, Jeff, the owner had his stethoscope w/ silicone lube spray and went through the belt and pulley system.

The diagnosis was the belt edge rubbing against the side of the harmonic balancer. Liberal shots of silicone spray on the balancer reduced the squeal/chirp to nothing for a few minutes.
Drove 20 minutes home and saw the chirp come back but to a lessor degree. He told me these balancers in his experience are not perfectly straight and over time cause this issue. Never heard of that before but he has been around BMW's for 30+ years so I'm taking him at his word.

[tomwadek]

Originally Posted by tbirdboy

Well, kinda solved it...

I just got back from a visit to Monterey Motorworks (BMW indy)here in Monterey, CA. Having a chirp, chirp myself but exactly sure where it was coming from, Jeff, the owner had his stethoscope w/ silicone lube spray and went through the belt and pulley system.

The diagnosis was the belt edge rubbing against the side of the harmonic balancer. Liberal shots of silicone spray on the balancer reduced the squeal/chirp to nothing for a few minutes.
Drove 20 minutes home and saw the chirp come back but to a lessor degree. He told me these balancers in his experience are not perfectly straight and over time cause this issue. Never heard of that before but he has been around BMW's for 30+ years so I'm taking him at his word.

I gave up and will be taking it in to the dealer on Thursday but a Indy shop told me the same thing. Actually you can see some wobbling in my videos and the balancer seems to be out of alignment.

[juld0zer]

They all have a bit of a wobble to them. N20 are even worse but N20 uses a different belt from Gates.

I wonder if it is worth flipping the belt? Or giving the balancer a bit of a shave with some sandpaper? It's not rare for a belt to be a bit uneven on the edges.

Of course, if your balancer actually wobbles more than 'normal', you may have no choice but to replace it. It's a very expensive part though

[juld0zer]

The coolant leak is most likely the radiator end tank. Get it pressure tested and the origin should become apparent

[lowrydr310]

Originally Posted by juld0zer

They all have a bit of a wobble to them. N20 are even worse but N20 uses a different belt from Gates.

I wonder if it is worth flipping the belt? Or giving the balancer a bit of a shave with some sandpaper? It's not rare for a belt to be a bit uneven on the edges.

Of course, if your balancer actually wobbles more than 'normal', you may have no choice but to replace it. It's a very expensive part though

There are quite a few independent guys who rebuild these balancers, significantly cheaper than a new part. I don't have any experience with them but I discovered them while looking at options when I noticed my pulley wobble. Apparently 1-2mm of wobble is acceptable and that's what I see on my car so I'm just driving it as is.

[tomwadek]

Dealer found the leak, the new radiator which I bought from FCP euro and installed only 6 months ago is cracked and leaking...

also leaking from the coolant cap which was bought from FCP euro and arrived that day before taking it to the dealer and installed.

The squeaking sound is the belt tensioner also bought from FCP euro and warranted 3 different times now.

tech recommended to buy genuine parts and install them, of course the bill is $3000 with the dealer but he knows I can do it myself so he suggested I work out a deal on genuine parts and install them myself.

Has anyone had this bad experience form FCP euro?

I didn't buy the genuine versions of the parts and went with OEM to save some money but this is crazy. Tech sent me a video of each issue, i'll post it when i get home.


BMW Radiator - Behr 17117547059
BMW Drive Belt Tensioner - INA 11287582946
BMW Expansion Tank Cap - Rein 17117639020

[juld0zer]

Radiator - definitely not the click on fittings? Orings can get damaged. Unlikely in your situation to find motor oil up there but if motor oil was used to aid reinstallation, the orings can swell from oil contact. I have installed Behr radiators before without issue. It also appears radiators can come from various origins. The last one i fitted was a South African made one. I believe the OEM is Modyne but again this can depend.

Belt tensioner - hmmm. INA is the OEM. The product is good in every time i have fitted one. Was the bolt torqued up correctly? No corrosion on the engine?

Expansion tank cap - difficult to test properly using the BMW pressure tester. It easily fails good caps if you are not aware. I have never used a Rein cap before though but some of their products are borderline passable in terms of oring dimensions.

[weehe126]

Originally Posted by tbirdboy

Well, kinda solved it...

I just got back from a visit to Monterey Motorworks (BMW indy)here in Monterey, CA. Having a chirp, chirp myself but exactly sure where it was coming from, Jeff, the owner had his stethoscope w/ silicone lube spray and went through the belt and pulley system.

The diagnosis was the belt edge rubbing against the side of the harmonic balancer. Liberal shots of silicone spray on the balancer reduced the squeal/chirp to nothing for a few minutes.
Drove 20 minutes home and saw the chirp come back but to a lessor degree. He told me these balancers in his experience are not perfectly straight and over time cause this issue. Never heard of that before but he has been around BMW's for 30+ years so I'm taking him at his word.

Just to think this through, the harmonic balancer is right over the front main seal. Spraying the area with silicone spray most likely sealed the front main seal stopping the vacuum leak/chrip.

[juld0zer]

That is also plausible. You could try drenching the area with brake cleaner/carby cleaner while the engine is idling. If it revs up on its own, then it is leaking.

Then you have the possibility of other issues like a bent crank causing the pulley to oscillate and stretch the seal lip. It is best diagnosed from underneath as access and vision is better. Unfortunately it is not easy to diagnose and you usually have to go through the process of elimination starting with a new seal, then pulley, then crankshaft.