MC Shift, Exhuast stuck on LOUD mode!

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vanman1936

Junior Member
Messages
77
So I have this a bit - I have a manual valve override remote, works fine when at town speed but when it is in the motorway it will open up but not close until I am back at sub 40 speeds and have been for a few minutes?
 
CatmanV2

CatmanV2

Member
Messages
48,727
vanman1936 said:
So I have this a bit - I have a manual valve override remote, works fine when at town speed but when it is in the motorway it will open up but not close until I am back at sub 40 speeds and have been for a few minutes?
Click to expand...

So it stays noisy until you slow down?
The valves are pulled closed (i.e. quiet) by vacuum.
The vacuum is generated by manifold under pressure. This is why they always start noisy. There is no vacuum on a stopped engine.
There is a vacuum bottle, which 'stores' vacuum.
The vacuum bottle is connected to the box valve actuators via an electric solenoid valve. I can't see it likely that this fails other than totally (i.e. won't open, car is always noisy, or won't close, car is always quiet)
So my view on this is that at high speed cruising, where manifold pressure is *higher*, vacuum is not being maintained at a sufficient level to keep the exhaust valves closed against the springs.
So tl;dnr you've probably got a vacuum leak. I'd suspect a hose has perished. Can you tell if it's one side or both that are opening? If it's one side it'll be near the back. If it's both it could be anywhere leading to and or from the vacuum bottle.

I think.

C
 
B

bigbob

Member
Messages
8,965
vanman1936 said:
So I have this a bit - I have a manual valve override remote, works fine when at town speed but when it is in the motorway it will open up but not close until I am back at sub 40 speeds and have been for a few minutes?
Click to expand...

Always nice when the problem happens somewhere else too! For mine I know it is only one side so it
can only be about a metre of tubing. Could be the same for you or is it definetly both sides?
of you
 
CatmanV2

CatmanV2

Member
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48,727
vanman1936 said:
Catman....interesting, so at motorway speed the vacuum is lower?
Click to expand...

Pretty much (or at least less). WOT is going to have most depression I recall. The bottle there is to act as a buffer. I can't really think that you are ever going to 'run out' of vacuum unless there is a leak. For example I can go for hours (Ooooerr) at motorway cruising with no valve opening.

C
 
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vanman1936

Junior Member
Messages
77
The valve doesn't ever open if I am on the motorway when its closed, it's just I can't close it until I get back down to town speed if it's open. In my mind I was think some sort of heat contraction was causing the valves to stick, however its both valves that are affect as no change to sound when I hit the button on the MWay. It typically stays loud until I come off the motorway then the usual "clunk" of the valves closing and quiet again??
 
CatmanV2

CatmanV2

Member
Messages
48,727
vanman1936 said:
The valve doesn't ever open if I am on the motorway when its closed, it's just I can't close it until I get back down to town speed if it's open. In my mind I was think some sort of heat contraction was causing the valves to stick, however its both valves that are affect as no change to sound when I hit the button on the MWay. It typically stays loud until I come off the motorway then the usual "clunk" of the valves closing and quiet again??
Click to expand...

Sorry, you've lost me but I've been up for eeek hours now.....
C
 
stewarttownsend

stewarttownsend

Junior Member
Messages
469
CatmanV2 said:
There are two valves. Make sure they both move freely. If they do they you can have an assistant press the sport button in the cabin while you lie under the car and see if they move at all.

If not, my money would be on the solenoid valve having failed, which is a comparatively cheap fix. £35 from Eurospares for the part plus a couple of hours max labour I'd have thought.

C
Click to expand...

Hi

could you point me at the part, think this is what could be broke on mine
 
Ryandoc

Ryandoc

Member
Messages
1,842
I posted on this last year. Could operate the flaps piece of p1$$ by hand but not operating correctly via sport button. About £45 for the vacuum solenoid and replaced the hoses and been great ever since.

Probably been mentioned but as was said to me on here the difference between loud and quiet is huge. Church quiet to spitfire mode it's that different.
 
stikey

stikey

Member
Messages
556
after noon all i had a h pipe removed and a cross pipe fitted on my strad last week ran it for a few days then the valves stopped opening in race mode got under the rear
and both actuator rods were hanging off the valve flap pins so cliped them back on and they still don't open when i pull on the actuator rods they both have really strong resistance but they don't change in either mode any ideas
 
Zep

Zep

Moderator
Messages
9,229
stikey said:
after noon all i had a h pipe removed and a cross pipe fitted on my strad last week ran it for a few days then the valves stopped opening in race mode got under the rear
and both actuator rods were hanging off the valve flap pins so cliped them back on and they still don't open when i pull on the actuator rods they both have really strong resistance but they don't change in either mode any ideas
Click to expand...

Disconnect the actuators from the valves and start the car, put it in race mode. If the actuators move they are working fine. Then try and move the valve themselves, if they are stiff then you can try lots of lube and working them open and closed until they free up, a common problem.
 
Sam McGoo

Sam McGoo

Member
Messages
1,758
As what Zep says.
Also, just another check. you could pull off the vacuum tube from the actuator and put it in normal mode, make sure that there is a strong vacuum.
Then put in race mode and make sure there is no vacuum.
 
stikey

stikey

Member
Messages
556
Sam McGoo said:
As what Zep says.
Also, just another check. you could pull off the vacuum tube from the actuator and put it in normal mode, make sure that there is a strong vacuum.
Then put in race mode and make sure there is no vacuum.
Click to expand...
Thank you sam will try that
 
stikey

stikey

Member
Messages
556
just been out under it valves are free release the vacuum pipes and the actuators dropped
vacum pie permanently sucks regardless of mode
 
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