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      08-13-2013, 06:47 AM   #1
Mustard3
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Weird noise from pressure converter

On turning off my car I've noticed a strange noise coming from the vacuum control area (engine bay above exhaust manifold).

The sound is an underlying hum, with a louder, irregular buzzing noise, a bit like morse code. I goes on for up to a couple of minutes until the vacuum releases and the actuator rod releases with a loud 'sigh'.

I took it to my usual BMW specialist, who after listening to it (no fault codes) said they had only come across it once before and it was a faulty large turbo actuator which can only be bought with a new turbo at a cost of 1600 fitted.

However, I removed the engine cover and scuttle panel and it appears to be coming from the rear pressure converter. You can feel it vibrating in time to the noise. Can these thing fail in that way? There is no loss in performance.

Funny thing is, that pressure converter was replaced recently by above specialist. When they did it I was expecting both to be replaced along with the modified mounting bracket, but they said it wasn't necessary. When I inspected it earlier I noticed the two PCs are of different design, and the new one does not appear to be fixed securely to the bracket, it can be twisted a bit. Odd?

I would be grateful for any thoughts on this before I go back to the garage.
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      08-13-2013, 07:18 AM   #2
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If its a non standard part they fitted then I'd be back there demanding they fixed it FOC.. Then I'd never use them again.

If similar to the 335i, the boost actuators are very easy to replace and are secured by a couple of screws. Replace the vacuum hoses too, may as well.
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      08-13-2013, 07:57 AM   #3
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It''s the same shape as the standard part, I think it's likely they did use OEM.

On the 335d, you can just about see the pressure converters with the scuttle panel remove, but accessibility to remove the look far too daunting for me.
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      08-14-2013, 03:13 PM   #4
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I had one of my pressure convertor replaced due to power loss (low end) was fine for a weekand then power loss at high end. Other one replaced and all was well again. My car makes allsorts of funny noises as it shutsdown, my indy has never made a point of it. Large turbo actuator attached to large turbo =1600quid to replace, dont think so. Mine was about 3/400 for part and labour. Find another indy
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      08-14-2013, 10:47 PM   #5
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Quote:
Originally Posted by Mustard3 View Post
On turning off my car I've noticed a strange noise coming from the vacuum control area (engine bay above exhaust manifold).

The sound is an underlying hum, with a louder, irregular buzzing noise, a bit like morse code. I goes on for up to a couple of minutes until the vacuum releases and the actuator rod releases with a loud 'sigh'.

I took it to my usual BMW specialist, who after listening to it (no fault codes) said they had only come across it once before and it was a faulty large turbo actuator which can only be bought with a new turbo at a cost of 1600 fitted.

However, I removed the engine cover and scuttle panel and it appears to be coming from the rear pressure converter. You can feel it vibrating in time to the noise. Can these thing fail in that way? There is no loss in performance.

Funny thing is, that pressure converter was replaced recently by above specialist. When they did it I was expecting both to be replaced along with the modified mounting bracket, but they said it wasn't necessary. When I inspected it earlier I noticed the two PCs are of different design, and the new one does not appear to be fixed securely to the bracket, it can be twisted a bit. Odd?

I would be grateful for any thoughts on this before I go back to the garage.
I have the exact same noise coming from my converter/s and and I have recently changed them both. I think it's normal because it made exactly the same noise with the faulty ones and also the entire time I've had this car (about 3 years).

If you had problems with your big turbo actuator you would have some serious lack of power.

The reason why you can move the new converter by hand is because they haven't replaced the mounting bracket and in that case it can only be attached with one screw. It's the front one they have replaced, right?
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      08-15-2013, 01:53 AM   #6
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The pressure converter replaced was for the big turbo. I had lost all power above about 2000 revs. The one that's only fixed with one screw is the one nearest the bulkhead, which I assume is for the big turbo.

Interesting that you had the noise before and after replacement, suggests that some other faulty component is causing the PC to make the noise. All was completely silent with mine until recently.
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      08-15-2013, 02:01 AM   #7
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Quote:
Originally Posted by rsmallwo View Post
large turbo =1600quid to replace, dont think so. Mine was about 3/400 for part and labour. Find another indy
So did you have the actuator replaced separately from a new turbo?

Actuator as opposed to pressure converter, some people seem to give them the same name.
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      08-15-2013, 08:13 AM   #8
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Actually, there is no "big turbo converter/actuator" or "small turbo converter/actuator".

There is 3 actuators ( round sylinters with a rod coming out of them) that control: the turbine control valve, compressor bypass valve and the wastegate.

The biggest actuator which is located directly under the pressure converters is the turbine control valve actuator. This one is controlled by the first pressure converter from the bulkhead side.

The second actuator, which is located under the bigger turbo, controls the wastegate valve.

The two pressure converters that control these two above, can be adjusted to any position between fully open to fully closed.

Third actuator is located in front of the engine, under the vacuum pump (where the red hose goes to) and this actuator controls the compressor bypass valve. This is an on/off actuator which is controlled by an electric changeover valve that is located right below the first pressure converter from the bulkhead.

The actuator which controls the compressor bypass valve, is opened when revs exeed 3250rpm.

So, the converter that has been changed, controls the turbine control valve. If this control valve stays fully closed, the exhaust gasses have to go thru the small turbine at all times and therefore the big turbines speed is defined by the small turbine (so, lack of power on higher revs). Normally this valve is opened continuously as the engine speed increases so that eventually the small turbine will be bypassed completely.

So usually you have problems either with the first pressure converter or the electric changeover valve. If you had problems with the wastegate actuator/pressure converter then you would have overboost and limp-home-mode

Some say that these actuators can also be "stuck" and limit the normal movement-range off the valve but you can easily check the actuator/valve by moving the rod by hand, if it moves normally it's okay

Just to clarify things (or mix them even more)

Last edited by JP-76; 08-16-2013 at 12:48 AM. Reason: Edited some bits to more understandable form
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      08-15-2013, 08:29 AM   #9
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Wow. I had to read that several times!
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      08-15-2013, 08:55 AM   #10
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Quote:
Originally Posted by Mustard3 View Post
Wow. I had to read that several times!
Is that a good or a bad thing
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      08-15-2013, 09:08 AM   #11
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Well, I thought I had a slight grasp of what was what, but now I'm doubting it!

Still have to figure out what's causing the pressure converter to make the weird noise when switching off the engine - i.e. is it faulty, or is there another faulty component causing it to do this. Although you think it's normal, but it didn't do it previously.
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      08-16-2013, 12:51 AM   #12
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Quote:
Originally Posted by Mustard3 View Post
Well, I thought I had a slight grasp of what was what, but now I'm doubting it!

Still have to figure out what's causing the pressure converter to make the weird noise when switching off the engine - i.e. is it faulty, or is there another faulty component causing it to do this. Although you think it's normal, but it didn't do it previously.
I'm going to check it also again when I got the time. You got me interested about the noise.

I'll let you know if I find something.
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      08-17-2013, 03:18 PM   #13
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Quote:
Originally Posted by JP-76 View Post
I'm going to check it also again when I got the time. You got me interested about the noise.

I'll let you know if I find something.
Mine also makes whining noise from both solenoids for approx 30 seconds after the engine is turned off (They are both the new type)

The actuator rod also starts to drop around 30 seconds after engine turned off and then the whining stops/rod fully dropped(im guessing the whining noise is vacuum being lost through the solenoids).

The electrical hum lasts for approx 1 min after engine switch off, finished with a final 'relay click' at the end (i dont get any actuator movement or vacumm 'dump' as they already ran out after 30 seconds)

So i checked both solenoids and when i manually create vacumm they make the whining noise. Engine is running fine so i dont know if it is a 'feature' of the new type solenoids ?

What is the time on others ?
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      08-18-2013, 03:36 AM   #14
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Quote:
Originally Posted by new 335d m sport owner View Post
Mine also makes whining noise from both solenoids for approx 30 seconds after the engine is turned off (They are both the new type)

The actuator rod also starts to drop around 30 seconds after engine turned off and then the whining stops/rod fully dropped(im guessing the whining noise is vacuum being lost through the solenoids).

The electrical hum lasts for approx 1 min after engine switch off, finished with a final 'relay click' at the end (i dont get any actuator movement or vacumm 'dump' as they already ran out after 30 seconds)

So i checked both solenoids and when i manually create vacumm they make the whining noise. Engine is running fine so i dont know if it is a 'feature' of the new type solenoids ?

What is the time on others ?





Good post there mate. Well detailed.
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