Hi
I have a 2011 Mini Cooper S with a sporadic high pitch squeal that happens after a cold start . When it happens if you blip the gas pedal it goes away , if you don't it will continue to make the noise , if you pop the dipstick it will stop and if you reinsert it the noise comes back . When it is making this noise if you try to pull the oil fill cap off there is so much suction you can barely get it off the valve cover . This continues as long as you don't touch the gas pedal .
What controls how much vacuum it gets at cold start and cold idle ?

Any help or advice would be appreciated

 

All minis have a huge amount of negative pressure while running (at least all the ones I tried) and I don't think this is the issue. Are you sure it is not your belt making the noise? One quick way to test it is to pour water on the belt while it is running, if it stops squeaking then it is definitely the belt. I think perhaps removing the dipstick or opening the oil cap causes the squeak to stop as the engine accelerates when it loses negative pressure.

 

Thanks for the reply.
That was my first thought too so I changed the belt, tensioner and friction wheel but it still does it . It seems like it has way more vacuum at idle when it is making the noise , then you hit the gas pedal the noise stops and the vacuum seems to be less ,more like normal . If you don't touch the pedal it will continue and only when cold on the first start of the day so a bit hard to chase .

 

The best way to correct many of the aggravating noise issues I experience is by asking my wife to step out of the vehicle (kidding, although technically it does eliminate lots of unwanted noise).

All jokes aside, I really don't know what can be causing this noise. I experience a very similar noise and do believe it's highly correlated with vacuum/boost components that may have a small leak. I have an 07 MCS with an intake, BOV and full cat-back exhaust. I suspect these mod may have something to do with this noise. Do you have any engine/exhaust mods?

 

One way to pinpoint where the noise is coming from is this old Mexican way we used to do it. Get a piece of water hose (or any hose really) and put one end in your ear and the other move around the engine while the noise is going on. It will let you determine where the noise is highest at.

 

There are no mods , with 80,000 miles .

 

I know this is an old post, but were you ever able to determine exactly what was causing that squeal? I have what seems to be the exact same symptom as far as the noise goes.


One extra-weird note though - I get the squeal at cold start and then after maybe 1-2 minutes running (or anything just off idle) it goes away. BUT - then it comes back, maybe 5-6 minutes later, and I IMMEDIATELY get a P0343 code for cam position sensor, bank 1 sensor A, and the car goes into reduced power (no boost) mode. Squeal is more prominent then as well and need to actually create some engine load for it to go away. Comes back immediately when load is reduced. Lasts for maybe 3 minutes and car stays in reduced power until the next start. Scanner shows no active code but shows pending P0343.


I already had to replace intake CPS last year, so the first time it threw P0343 I figured the exhaust CPS was failing now. Didn't put together the squeal with the P0343 code until after I REPLACED exhaust CPS and it happened again. Since then, it's happened 2 more times, always after about 6-8 minutes driving when I get the combined CEL and squeal.


What can make the CPS think it's going bad and create the squeal?

 

OK, it happened again this morning on the way to work. About 8 minutes into drive, CEL came on and squeal started. Pulled over and tried the dipstick/oil filler cap removal that SCFIVE0 mentioned. When either the dipstick or the oil filler cap is removed, the squeal stops and (in my case) the car starts idling quite rough, like a big vacuum leak. Replace the filler/cap and it starts idling normally, but the squeal returns. If I shut the car off, the code immediately clears on restart, no squeal and boost/drivability is normal.


Still not sure how the CPS is related to this unless some issue with the cam timing is creating massive internal vacuum and making the sensor think something is wrong.


BTW - 2011 S auto, 66K miles

 

Know this post is a bit dated, but I just bought a 2011 mini cooper s with 75000 miles that seems to be having the exact same issue. It's the first mini I've ever owned as well as the first turbo, so every noise it makes has me on edge at the moment XD

 

Has anyone figured out OR can point to the thread that tells us what fixed the high pitch squeal on startup?

Cheers

 

Same here. I start the car each morning, wait about 2-3 minutes, and the squeal comes on. Loud as can be. Blip the throttle a few times and it goes away. Seems belt related, but I have inspected and cleaned it all and nothing looks to be in bad shape.

It is very strange that it is only the first start of the day when this happens. The rest of the day it is fine.

 

That sure sounds belt related or a component that is fed by the belt. I'm wondering how the alternator is, squeal on start up is common if the bearings are going as there will be heavy load on the alternator after initial start up due to recharging the battery. Also if the battery is getting worn out that could add to the problem. Another squeal source is water pump and on one of our cars it was a bad belt tensioner. Some stores like Princess Auto or Harbour Freight sell something called the mechanics stethoscope, basically a probe with ear pieces that let you listen to various areas of the motor. That might also help track down the sound and they are cheap.

 

What you are experiencing is a failed PCV diaphragm. You can find an aftermarket valve cover online for around $50. The n12 and n14 both have the pcv built into the valve cover and are considered non serviceable. The n12 valve covers are $300+ online. There are companies now that are 3D printing a cap and provide a new diaphragm for around $30.

The person who said its acting like a large vacuum leak is spot on. When the diaphragm is torn the engine is pulling unmetered air into the intake on the downstream side of the MAF. When the diaphragm is in good shape it will seal and open during the event of positive crank case pressure with enough force to overcome the spring. It’s a simple system used by a lot of European manufacturers but they do not last. GM started using it in their turbo 4 cylinder engines too and they had the same issues.

 

I second Rush2252. Definitely sounds like the PCV. Happened on my N18 exactly how you're describing. Got a new one from ECSTUNING, and problem is gone. You're probably also getting horrendous fuel mileage. New Valve cover/PCV valve should fix it right up.

 

The cheap PCV fixed our 2011 as well. The high pitched squeal could also be related to the customers sounding off when the service writer hands them the estimate for $800 or so to replace an otherwise fine working valve cover.

 

EXACTLY. I almost Shat myself when they told me the valve cover replacement would be $780. Did it myself for $300 or so. Could have done the cheaper fix, but I wasn't aware of it at the time. But still, previous owner marred up the factory one, so I felt ok paying that for peace of mind and a prettier engine bay. lol

 

The PCV solution eliminated my squeal as well. Many thanks to the folks who post answers to our issues.