Common problem with M50 vacuum connector

By · July 10, 2014 · 2 comments

There's a common problem with the BMW M50 engines as fitted to the E36 320i and 325i, and the E34 520i and 525i.

On the intake manifold there is a air pipe connection that over time can come loose. Then, usually when starting the car, this connection can blow off resulting in a large vacuum leak. The car will be reluctant to start and run, idle badly, and have no power brakes.

The fix is to replace this connector and o-ring, but for a temporary fix you can usually just plug it back in. On my 325i the previous owner had ran a cable tie around the intake manifold to secure this connector in place. I suffered the problem twice in only a few months but didn't get around to replacing the part before I sold the car.

The connector is located on the engine side/underside of the intake manifold almost opposite of where the air intake goes into the manifold. The connector is held in place by a clip only on one side.

For replacement the part numbers are below. Note that there are different part numbers for pre and post February 1992 models. My car was a 1991 model and I don't know if the problem effects the post February 1992 models, or possibly even the M52 engine too. I also don't know if the later part is improved and interchangeable. Do you know? Please leave a comment.

Part numbers

Connector, up to 02/1992 11611730265
Connector, from 02/1992 11611738629
O-ring, 24×3.5 11611730725

BMW M50 intake manifold problem
My 1991 325i

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Comments (2)

# Posted by Brian P. · August 21, 2015

Hello John Avis,
Thanks a lot for posting this blog. After pumping gas, I started my car and it made a loud pop noise then started idling really bad and showed a check engine light. I tried giving it gas then it would make a whistling noise and the CEL would flash off then back on. Also, after moving it from the pump, I noticed the brakes had no power. I thought I blew the engine and all hope was lost. After searching the Internet for tips, I guessed it was a hole in the plastic intake manifold or gasket(s) broke. Then I stumbled upon this blog and all the symptoms matched. After work, I went to check it out myself and sure enough, it was the connector hose disconnected. I reached my hand through and reconnected it and voila, back to life. I appreciate helpful blogs like this. It saved me time and $. Thanks again John!

Brian P.
Las Vegas, NV
Calypso Red 1992 E34 525i Manual transmission


Brian P.
# Posted by John Avis · August 26, 2015

Thanks for the feedback, Brian. It's always good when you can fix a problem cheaply and quickly yourself, isn't it? You are best to replace that part or secure it somehow otherwise it's probably going to keep happening to you.

Just saw you have a manual E34 - that must be a rare car in the USA?


John Avis
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About me
John Avis I am a bit of a 3 series fanatic, having owned a couple of E30s and a few E36s, plus a few parts cars. I like the combination of the compact size, good performance and handling, and that they are more sports sedan than an impractical and extrovert sports car. This blog is a place to share my experience and knowledge.

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