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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > Is it a boost leak or just a bad boost solenoid?



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      02-24-2017, 02:21 AM   #1
WedgePerformance
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Is it a boost leak or just a bad boost solenoid?

In the past month I have been testing pump / meth on my Pure Stage 2 car and started to notice my boost taping off. I was running a map that should have been pushing 21 psi without issue, but I was only hitting 18. Two week later 13 psi. Normally if you had a boost leak and you were dropping almost 10 psi you would hear the leak. I didn't hear anything other than my turbo spooling and logs showing 90% wgdc and only 11 psi to show for it on a Pure Stage 2 turbo.

Last weekend I checked my clamps and all was good so today I bought a new boost solenoid. Install took 20 min because I removed the intake inlet so I had room to work. I still dropped the F'n bottom nut trying to install the solenoid. Murphy's law...

Good news... It was the solenoid and my car is boosting harder than it has ever boosted. Actually need to turn things down a bit. So before you go pulling your car apart looking for a boost leak, do yourself a favor and spend the $ to buy a new boost solenoid. It's a simple fix...

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      02-24-2017, 05:33 AM   #2
maddmatth
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Probably a more common issue than people realise. I only found out after I shared my MHD logs and people pointed out my car wasn't holding as much boost as it should. Had a workshop check for a boost leak and find nothing.
It also never triggered a code on PPK, and only rarely when pushing very hard on MHD.

Swapped the boost solenoid, and suddenly it holds boost perfectly.

It's annoying how hard it is to tell this apart from a boost leak, and without logging, people won't realise their car isn't making as much power as it should.

I broke my old one open to see the issue. It's actually a thin plastic/rubber membrane that had a little tear in it. Seems silly that a tiny bit of plastic, as thin as the plastic used in a balloon, is responsible for this.

I notice the newer parts have a different part number and look a bit different, at least compared to what my 2010 N55 had. I wonder if the internal design is different, maybe it doesn't have the same thin membrane. I don't want to break my new one open to find out.

These might be repairable, if you can figure out a way to repair or replace the membrane.
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      02-24-2017, 09:32 AM   #3
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Quote:
Originally Posted by maddmatth View Post
Probably a more common issue than people realise. I only found out after I shared my MHD logs and people pointed out my car wasn't holding as much boost as it should. Had a workshop check for a boost leak and find nothing.
It also never triggered a code on PPK, and only rarely when pushing very hard on MHD.

Swapped the boost solenoid, and suddenly it holds boost perfectly.

It's annoying how hard it is to tell this apart from a boost leak, and without logging, people won't realise their car isn't making as much power as it should.

I broke my old one open to see the issue. It's actually a thin plastic/rubber membrane that had a little tear in it. Seems silly that a tiny bit of plastic, as thin as the plastic used in a balloon, is responsible for this.

I notice the newer parts have a different part number and look a bit different, at least compared to what my 2010 N55 had. I wonder if the internal design is different, maybe it doesn't have the same thin membrane. I don't want to break my new one open to find out.

These might be repairable, if you can figure out a way to repair or replace the membrane.
Not sure how much it cost in down under currency as I know you pay a premium for parts, but for most it should be a general maintenance part like coils and plugs. If you have 50,000 M (80,000 K) on the car, just spend the $150 to replace it. Even if you could repair it, is it worth the effort? Bottom line it's a inexpensive part that gets overlooked and is not as easy to diagnose as bad coil.
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      02-24-2017, 02:50 PM   #4
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2011 135i  [5.00]
thanks for sharing and glad it was an easy fix.
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      02-24-2017, 05:06 PM   #5
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Quote:
Originally Posted by WedgePerformance View Post
Not sure how much it cost in down under currency as I know you pay a premium for parts, but for most it should be a general maintenance part like coils and plugs. If you have 50,000 M (80,000 K) on the car, just spend the $150 to replace it. Even if you could repair it, is it worth the effort? Bottom line it's a inexpensive part that gets overlooked and is not as easy to diagnose as bad coil.
Indeed we do get ripped off for parts. I imported it myself from FCPEuro though, it wasn't expensive to ship.
I do this all the time, we can save up to 50% on parts by ordering from overseas.
Not sure what BMW New Zealand's excuse is for their prices when we can import stuff ourselves for less
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      02-24-2017, 05:12 PM   #6
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Quote:
Originally Posted by maddmatth View Post
Indeed we do get ripped off for parts. I imported it myself from FCPEuro though, it wasn't expensive to ship.
I do this all the time, we can save up to 50% on parts by ordering from overseas.
Not sure what BMW New Zealand's excuse is for their prices when we can import stuff ourselves for less
Frustrating for sure.
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      02-24-2017, 05:34 PM   #7
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Do you have the part number or links to purchase by any chance? Good for future reference, thanks!
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      02-24-2017, 05:52 PM   #8
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Quote:
Originally Posted by ihazvtak View Post
Do you have the part number or links to purchase by any chance? Good for future reference, thanks!
Mfg Part #
11747626351
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      02-24-2017, 06:17 PM   #9
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11747626351 is superseded by 11747649407.

My car came with 11747626351, I replaced it with 11747649407.
Although you probably get the same thing regardless of which one you order.
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      02-24-2017, 06:28 PM   #10
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A guy on N54Tech had an F-series N55 boost solenoid fail and replaced it with an N54 variant and had no issues, so I wound up purchasing 11747626350 today. Pierburg branded (OEM supplier from the looks of it) and it looks identical to the one that's specified for N55 cars. ECS raised the price from $89 when I bought it earlier to $99, so I suspect it fits the bill just fine. Will hopefully report back next week to verify that it works...
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      02-24-2017, 07:49 PM   #11
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looks like 11747649407 is the most current one according to realoem

http://www.realoem.com/bmw/enUS/part...&q=11747649407
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      03-02-2017, 07:10 PM   #12
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For the past year, my car hasn't been pulling as hard as it had despite my running a JB4. It wasn't boosting consistently, felt "dead" after about 3,000 rpm, and I attributed this to the JB4 because it seemed to happen so gradually. So I ditched the JB4 and did a custom Wedge tune via MHD...only for that to feel similarly. Dead, flat, no pull whatsoever. I was boosting around 7psi or so, but apparently that's not enough of a drop to throw a code, which I never threw.

I knew the boost solenoid was a possible culprit but figured it could also be my vacuum lines or something on the intake track (which I spent quite a bit on for a smoke test at my local shop). Based on this post, I bought a Pierburg equivalent of the BMW part for $90 from ECS (#11747626350) since I read that the N54 part worked just fine on the N55. Installed it this afternoon, and lo and behold, I have my boost back. The hardest part was getting the vacuum hoses off which took me using a pick tool to loosen them up, though the nuts are a bit of a pain to get off and back on. Should take no more than 20-25 minutes.

Bottom line, if anyone's down on boost, isn't throwing a code, and hasn't replaced this thing yet (40k miles on mine), start here and see if it fixes the issue. Big thank you to Wedge.
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      03-03-2017, 05:49 AM   #13
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Quote:
Originally Posted by maddmatth View Post
11747626351 is superseded by 11747649407.

My car came with 11747626351, I replaced it with 11747649407.
Although you probably get the same thing regardless of which one you order.
I bought PN351 from a local vendor (Sydney). Searched on realoem after buying it and saw new PN. Bought 407 off fcp as well. Installed it and my boost oscillations were gone. Very happy with it!!
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      03-06-2017, 11:23 PM   #14
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Hey sorry if this is off topic but I am having a similar problem with my n55 335i not building boost. I recently installed a jb4 and didnt have any codes show up. However when I decided to put the boost on the fuel gauge I got very low readings. Like constant <5 PSI. I was told it could be my solenoid? My car was hit in that area so it seems likely. Any help would be appreciated.

Thanks,
-Mike
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      03-07-2017, 12:19 AM   #15
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Quote:
Originally Posted by xxMike61 View Post
Hey sorry if this is off topic but I am having a similar problem with my n55 335i not building boost. I recently installed a jb4 and didnt have any codes show up. However when I decided to put the boost on the fuel gauge I got very low readings. Like constant <5 PSI. I was told it could be my solenoid? My car was hit in that area so it seems likely. Any help would be appreciated.

Thanks,
-Mike
It's an easy and cheap part. Just change it.
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      03-08-2017, 07:48 PM   #16
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Heck, after reading this I might just change it regardless if it's failed me yet or not.
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