Exhaust valve on Granturismo S query(mc shift)

Brendan

Member
Messages
1,163
From what I understand, the valves are open on start up, and as the vacum builds they close.(How long does this take?). I've noticed more smoke comes out of the NS exhaust and hardly any out of the OS one. Upon checking, found that the valve has seized, but it is the NS one and not the OS which doesn't make sense.
 

CatmanV2

Member
Messages
48,352
I find the valves close quite quickly, never timed it……… but I would say 30secs

Also depends on how long it's been standing since it was last fired up.

Perhaps more of the 'smoke' (actually steam I hope) condenses in the innards of the OS silencer, and on the NS, it passes straight through. Bit of a guess, though

C
 

Zep

Moderator
Messages
9,095
Mine close within 2-3 seconds - some take longer.

The NS one might have got more crud (not the felonious type) from the road, making it seize. I don't think they should seize in any particular order, its down to luck (of the bad type).
 

Sam McGoo

Member
Messages
1,710
Yeah, as zep says, no rhyme or reason to which one or what way.
My OS valve was stuck when I bought it, in the closed position! Which to me suggests that the previous owner rarely had it in sport. What a waste lol.

As much as I've tried, it won't free up enough to function properly. So I forced it open disconnected and blocked the vacuum pipes from both sides, so they're both open all the time.

Suits me fine as my nearest neighbours are about 100m away and I press the sport button as soon as I turn the key anyway.

One day, I will get some new valves welded in, just incase I want to one day be stealthy.
 

Bebs

Member
Messages
3,188
Yep, 2-3 secs I think. I’ll get AV to double check when it goes in for the big 4 year service next month.
 

ChrissGT

Member
Messages
341
Mine was sort of seized, removed the muffler, dropped in some wd 40, forced the valve open and close quite a few times untill things started moving freely. Back on and working without an issue.

Other one had a valve related rattle, so that one got a new valve welded in.

Guess previous owner did not use sport mode, so now it is mandatory on each run to open and close the exhaust.
 

CatmanV2

Member
Messages
48,352
Mine was sort of seized, removed the muffler, dropped in some wd 40, forced the valve open and close quite a few times untill things started moving freely. Back on and working without an issue.

Other one had a valve related rattle, so that one got a new valve welded in.

Guess previous owner did not use sport mode, so now it is mandatory on each run to open and close the exhaust.

Similar issue that I had. Of course the valves will open and close on each run (assuming you don't hit Sport before the close). It's standing, wet, when you shut down, I believe that causes them to corrode in the open position. Of course as the corrosion increases it's not impossible for them to close, and get stuck there.

C
 

strictly

Junior Member
Messages
44
As you have already worked out one or both actuator arms will be rusted in the open position, see it all the time.
Awesome that you know that so well. Is there a grease you would recommend to keep them freely moving. Something high temperature? Silicone grease? Copper slip? Pagid brake grease? I've not even looked at mine, but if it can rust "open" then some sort of lubrication sounds like good preventative maintenance. My GT is off the road for winter, so jobs like this, when the valves are getting little use are perfect to do
 

CatmanV2

Member
Messages
48,352
Awesome that you know that so well. Is there a grease you would recommend to keep them freely moving. Something high temperature? Silicone grease? Copper slip? Pagid brake grease? I've not even looked at mine, but if it can rust "open" then some sort of lubrication sounds like good preventative maintenance. My GT is off the road for winter, so jobs like this, when the valves are getting little use are perfect to do

Probably something highish temperature, but needs to be penetrating. I *think* I used lithium spray

C
 

Ebenezer

Member
Messages
4,392
Since we now know that there are internal actuators in the 4.2 back boxes that open up with exhaust pressure, I wonder if these invariably seize up, since there's going to be no lubrication in there.
Eb
 

Zep

Moderator
Messages
9,095
You need some dry lubricant, as grease will attract dirt and case wear by making a grinding paste. Something like dry graphite lubricates but does not stick.
 

strictly

Junior Member
Messages
44
You need some dry lubricant, as grease will attract dirt and case wear by making a grinding paste. Something like dry graphite lubricates but does not stick.
OK thanks! I'll look into it. I'm hoping to put my GT on the ramp in the next week or two