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[TheBoy]

Smacks of a multiram issue - sure they are working. Any vac leaks?

[VXL V6]

8. Gearbox has been behaving a little oddly – holding it in gear for too long, and then changing into the next gear with a very small ‘thump’ – this is intermittent, not sure if related, as this is the first A-Road run I’ve done with her.

I did think that the seals on the inlet bridge, plenum O rings etc looked a bit past their best, but, there is no noticeable air leaks.

Fix the known problems first.....

[JamesV6CDX]

Smacks of a multiram issue - sure they are working. Any vac leaks?

Exactly my thoughts TB....

But, I've had the car revved - and they both work.

Can't find any vac leaks - and - you get a good 'hiss' if you pull off the rear multiram connection after it's been running - indicating the front tank is holding a good vac?

VXL - although the intake seals looked past their best, I don't think there is an air leak, else it'd idle quick, etc etc?

And ref the gearbox, I really don't think it's related, just a bit tired...

[VXL V6]

Smacks of a multiram issue - sure they are working. Any vac leaks?

Exactly my thoughts TB....

But, I've had the car revved - and they both work.

Can't find any vac leaks - and - you get a good 'hiss' if you pull off the rear multiram connection after it's been running - indicating the front tank is holding a good vac?

VXL - although the intake seals looked past their best, I don't think there is an air leak, else it'd idle quick, etc etc?

And ref the gearbox, I really don't think it's related, just a bit tired...

Has the Brake vacuum pipe to plenum rubbed on the Aircon pipe at all? My first one did that.

[JamesV6CDX]

Smacks of a multiram issue - sure they are working. Any vac leaks?

Exactly my thoughts TB....

But, I've had the car revved - and they both work.

Can't find any vac leaks - and - you get a good 'hiss' if you pull off the rear multiram connection after it's been running - indicating the front tank is holding a good vac?

VXL - although the intake seals looked past their best, I don't think there is an air leak, else it'd idle quick, etc etc?

And ref the gearbox, I really don't think it's related, just a bit tired...

Has the Brake vacuum pipe to plenum rubbed on the Aircon pipe at all? My first one did that.

You mean the thick one that comes from the servo, to the passenger side of the plenum - 19mm hex connection?

I'll double check it.

You know this has got me thinking. Although there is a 'hiss' when you pull off a vacc pipe when it's been running - it's not a POWERFUL hiss, like some Omega's I've seen...  :-/

[VXL V6]

Yep, where the vac pipe passes the top corner of the plenum it runs parallel to the aircon pipe. Can rub through the vac pipe.

[Entwood]

Have you checked that funny shaped "o-ring" .. the one with the bar across it .. that sits in the centre of the plenum I seem to recall it being broken on my 2.5, so blocking the 2 tiny breather holes and causing a serious power loss ... I know it breaks very easily when old.....did you replace it when you did the breathers ??

[JamesV6CDX]

Have you checked that funny shaped "o-ring" .. the one with the bar across it .. that sits in the centre of the plenum I seem to recall it being broken on my 2.5, so blocking the 2 tiny breather holes and causing a serious power loss ... I know it breaks very easily when old.....did you replace it when you did the breathers ??

Hi Nige - I haven't touched that one - not got around to doing the breathers yet 

[Kevin Wood]

You mean the thick one that comes from the servo, to the passenger side of the plenum - 19mm hex connection?

I'll double check it.

You know this has got me thinking. Although there is a 'hiss' when you pull off a vacc pipe when it's been running - it's not a POWERFUL hiss, like some Omega's I've seen...  :-/

Other thing to check is that the non-return valve in the reservoir is working - otherwise your vacuum will disappear on full throttle.

Kevin

[Cliffo B]

has anyone thought of useing a vac gauge to check vac quality? I bought one several months ago and never got round to useing it because couldn't find any positive "vac should be" info

[Kevin Wood]

has anyone thought of useing a vac gauge to check vac quality? I bought one several months ago and never got round to useing it because couldn't find any positive "vac should be" info

Yes, I often do. If the vac is a little low it's a good indication of a leak in the system and watching the post-reservoir vacuum decay after stopping the engine (it shouldn't) can also give clues to what's going on with the non return valve and / or leaks.

Kevin

EDIT: to answer the "what it should be", at idle with a warm engine I would say about 18-20"Hg / 30kPa absolute (70kPa / 0.7Bar  of vacuum below atmospheric).

[JamesV6CDX]

Just an update.

I tried plugging the line from the front vacc tank outlet, directly into a spare multiram, with the engine running.

I turned off the engine, and the ram stayed open, and didn't slowly return to it's original state, so it would appear it's holding a good vac?

I've also tried

- pulling off the feed line into the vacc tank after idle - no hiss. then pull off the outlet line - a good hiss - this indicates the return valve is OK, I guess?

I've also done a thorough inspection of vac pipes, removing them one by one - no damage or leaks evident  :-/

[JamesV6CDX]

took her out for a run on a quiet road tonight

at 20mph - floor it - there is a good kick of power around 4000rpm, but - even in sport mode, it changes gear just under 5800 rpm - this can't be right??? 

[TheBoy]

took her out for a run on a quiet road tonight

at 20mph - floor it - there is a good kick of power around 4000rpm, but - even in sport mode, it changes gear just under 5800 rpm - this can't be right??? 

Grow longer legs, or move seat forward

[hotel21]

Don't want to sound condescending but you are using the full length of travel of the accelerator pedal, as TB suggests, including into the kickdown switch??