Exhaust valve - it continues and i cant explain this

[Ryandoc]

So my exhaust valves are playing up and at present seem to be stuck in quiet church mode. From my previous thread (http://www.sportsmaserati.co.uk/sho...ck-exhaust-valve-open?highlight=exhaust+valve) i'm aware that ....

Car off valves are open
Turn engine on (not in Sport mode), after 2-3 seconds vacuum will build up and close the valves
Press sport button, hear them operate and valves open and exhaust gets noticeably louder

So tonight I've been under the car and unless I have the only GTS in existence that does the opposite of the above then I'm stumped, and I consider myself a clever lad. This is what I get.

Car turned off valve is in position A
Turn car on valve stays in position A
In position A car is quiet
press sport button and although they dont go very far, valves at least start to operate and move towards position B, can clearly see them moving a bit.

So how they weren't in position B to begin with is beyond me, the valve mechanism isnt hard to figure out, a bonnet with a diaphragm and a spring which returns it to its natural position, ie open when car is off.

My valves move freely I can push them easily. To take this further if I get under the car and the valves are in position A, if I push the stem / mechanism myself to position B then you hear the exhaust get deeper.
To take this even further I removed the vacuum hoses from both valves, they stayed in position A and this was quiet mode.

Either i'm loosing the plot have suffered hearing loss or I have an **** about tit exhaust valve setup!

I kid you not I was under there half an hour trying to figure it out and I can't, unless the mechanism bonnets were in upside down etc which I very much doubt is possible then god knows.

Also the pic thats in the attached thread shows the natural position on my car, ie position A and that's the stem at full length.

Feel free to point out the obvious I'm missing or have i made a complete **** of my understanding of it

 

[CatmanV2]

Turn the car off
Prod valves to position B
Turn car on
Wait for vacuum to build

Do the valves move to position A

Sounds to me like the spring my be broken as my understanding is that the vacuum holds the valve closed against spring pressure. This would also explain that they don't open fully in Sport.

Once vacuum has built, leaving the engine running, can you (try to) push the valves into position B?

Odd that both have failed though

C

 

[Ryandoc]

I would have expected that ther is a single Spring one side of the disphragm and pushing from position A you can feel you are pushing against s spring and it does return. They actually feel smooth and good to operate by hand.

I'm going driving tomorrow for a few days so going to try and get the mechanisms secured into open.

Really can't figure it out I was under there ages and had a mate with me doing the start / stop / sport etc

 

[CatmanV2]

I would have expected that ther is a single Spring one side of the disphragm and pushing from position A you can feel you are pushing against s spring and it does return. They actually feel smooth and good to operate by hand.

That sounds wrong. Because they should go to position B under no vacuum, or effectively spring pressure. As far as I can work out they shouldn't need anything (assuming the vacuum is off / disconnected)

C

 

[Ryandoc]

I know, I should have taken a video.

Sounds like I'm talking bollox but I cannot figure it out against what it should do. Going to try and get them secured into loud mode tomorrow to go driving the weekend then already spoken to my garage who will get a lot hopefully next week

 

[safrane]

So if I read this correctly if the vacuum pipe is disconnected on the GT you get quiet mode?

On the GS if you do that you get loud mode...are the two that different? And why.

On the GS you do not have a vacuum on start hence the slight bark on start, which if you are not in sport mode the car then settles into a quiet mode as the vacuum has now built up negative pressure forcing the vlaves to the quiet position.

 

[Ryandoc]

Basically yes, but seems to be on both sides, I've given up its going the opposite of everything it's supposed to !

Going to try and get the valves secured open today for the weekends driving and then will stick her in the garage next week

 

[voicey]

If I've read your description properly it sounds like you have a mechanical issue with the valves rather than a problem with the control. If you have a mityvac you can test the operation of them by hand.

 

[Ryandoc]

That's what I think, that the valve bonnet is doing strange things on both by coincidence. My garage next week will text everything, today my other garage (I'm away from home) who services my 320d is going to secure them open for me, that'll see me through the weekend

 

[Ryandoc]

So with the help of two friendly mechanics and both valves pushed turns out whilst despite the fact the vacuum system isn't working and closing them, they are in open poosition.

It definitely doesn't sound quite the same, still amazing. I have a theory that the solenoid is goosed and before failing completely was possibly only moving a little and partially blocking off he vacuum and that the bitterly valves were in a midway position, there were more prominent pops and bangs previously, exhaust flow around a partially opened bluff body may have actually depend it more than fully open

Will get it sorted next week anyway