M52 with M50 Intake Manifold Whistle Noise

[DiamondschwarzE30]

Noticed after I swapped a M50 intake manifold on my M52 that I am hearing a whistle noise that changes with throttle input. It only occurs at a specific throttle position, regardless of engine speed. The noise was not apparent before the manifold swap. I used a kit from Kassel performance that included a new M50 manifold vacuum connector. I also deleted the ASC throttle body with a Mishimoto intake elbow. Thinking it was a bad CCV based on previous posts, I replaced the valve but the noise is still prevalent.

I checked for vacuum leaks, but did not find any. All the hoses and seals for the intake were replaced with the swap anyway. Could it be possible that the noise is just a characteristic of the M50 intake manifold or ASC throttle body elbow, or is something else wrong with my setup?

Thanks!

[ZekeTheSneak]

That big ol vacuum that is the m52 is sucking alot of air through that tiny intake system. In other words its either the air filter or any other obstruction in the plumbing before the throttle body that is causing it. You have the asc unit installed but no plate in it? its probably that doing something with the air as it passes by. I have the m50 manifold with m50 TB and it whistles a little bit but nothing horrible. Changing air filters might shut it up a bit.

[DiamondschwarzE30]

That big ol vacuum that is the m52 is sucking alot of air through that tiny intake system. In other words its either the air filter or any other obstruction in the plumbing before the throttle body that is causing it. You have the asc unit installed but no plate in it? its probably that doing something with the air as it passes by. I have the m50 manifold with m50 TB and it whistles a little bit but nothing horrible. Changing air filters might shut it up a bit.

I may have sounded misleading, but it has an ASC delete elbow by Mishimoto currently. Funny thing is, before it had the ASC throttle body and stock elbow with the valve removed and did not make that noise with the same universal filter.

Is it possible that the IAT in the elbow is creating that noise? The Mishimoto elbow has 2 ports on it, one for the idle control valve and the other for the intake temp sensor.

[AndrewBird]

If you're IAT sensor is in the boot, what is in the hole where it would normally go in the intake manifold?

[DiamondschwarzE30]

If you're IAT sensor is in the boot, what is in the hole where it would normally go in the intake manifold?

That hole on the M50 manifold is plugged with the threaded OBD1 sensor currently. Left it in when I pulled the manifold from the junkyard, but its not plugged into the engine harness.

[ZekeTheSneak]

Does the mishimoto elbow have two holes? One for iat sensor and one for the crank case vent? Also how are you venting the crank case? With the car parked can you rev the engine to make it whistle? You can take a prybar and hold it to your ear and listen on things.


I have one other theory as it happened to me, which primary chain tentioner are you using?

[DiamondschwarzE30]

Does the mishimoto elbow have two holes? One for iat sensor and one for the crank case vent? Also how are you venting the crank case? With the car parked can you rev the engine to make it whistle? You can take a prybar and hold it to your ear and listen on things.


I have one other theory as it happened to me, which primary chain tentioner are you using?

Crank case oil separator is connected directly from the manifold with a silicon adapter from a M50 manifold swap kit (connects to the vacuum elbow on M50 manifold). Still have the OEM crankcase tube from the valve cover to the oil separator. Checked the tube for leaks and it seems fine. I should also point out that I replaced the oil separator too, thinking that was the source of the whistle based on previous posts.

I cannot make it whistle while parked. I did notice the tone of the whistle does change depending on RPM, but it still occurs at the same partial throttle input.

Not sure what primary timing chain tensioner is installed, I haven't touched it so I assume its the factory one still. Engine was pulled out of a 1996 328i.

[ZekeTheSneak]

Did you vacuum cap off the little Barb on the connector that plugs into the m50 manifold? Also have you tryed a different filter? Maybe some pipe between map sensor and filter might help?

I'm really drawing a blank to be honest. Wish I could be more help. Picture or two might help. That m50manifolds kit is a good one and I doubt that's what is doing it. There is also small vacuum port under the obd1 tb. I don't know about the obd2 tb.

[DiamondschwarzE30]

Did you vacuum cap off the little Barb on the connector that plugs into the m50 manifold? Also have you tryed a different filter? Maybe some pipe between map sensor and filter might help?

I'm really drawing a blank to be honest. Wish I could be more help. Picture or two might help. That m50manifolds kit is a good one and I doubt that's what is doing it. There is also small vacuum port under the obd1 tb. I don't know about the obd2 tb.

Yeah, I'm drawing a blank too. The small barb on the m50 connector goes to the purge valve (ran it capped until the valve was hooked up, no difference made), the small barb under the manifold goes to the fuel pressure regulator. I retained the OBD2 throttle body, did not see any vacuum line directly attached to it like the OBD1 one.

Let me see if I have any pictures that might be helpful. I'm starting to think the noise is just air turbulence over the throttle body at a specific position, more noticeable now with with a smooth throttle body elbow.

[ZekeTheSneak]

11611738629 BMW pn.

You cap that little Barb? I'm all out of ideas.

[DiamondschwarzE30]

11611738629 BMW pn.

You cap that little Barb? I'm all out of ideas.

Yup

[DiamondschwarzE30]

Here’s a quick photo of the intake. I can take more detailed photos later if needed

[bradmer]

OP perform a smoke test, it will find the leak every time. Sounds like a small leak if it's not doing it all the time.

[DiamondschwarzE30]

OP perform a smoke test, it will find the leak every time. Sounds like a small leak if it's not doing it all the time.

Yeah that's next on the to do list. Wish I had a smoke machine though.

[ZekeTheSneak]

You just need a metal container with a lid. Place burning rag into it that's slightly wet. Low psi Compressed air in and air out is smokey. There's tons of videos on YouTube. Or the old spray break cleaner at it method.

Make sure the TB is propped open. I used rubber gloves to seal off the intake tube. Plus you can see it inflate to make sure it's pressurizing the intake. You only need a few psi.