V6 Vac Tank Survey

[Marks DTM Calib]

For all those with a later (post 96/97) V6 which has the additional VAC tank mounted on the set of trumpets just in front of the alternator.

Here is something to try.....

The vac tank has two pipes, a feed and an output, the fed is the one on the right or bottom (or at least should be) which connects to a large rubber elbow piece.......

Here is the test I would like you to try.....

Follow the pipe from the vac tank feed to the rear of the engine bay where it connects to the brake servo pipe (normally via a T piece).

Disconnect the pipe here and suck on it, place your tongue over the pipe and check it holds vaccum.......

Reconnect the pipe and now remove the output from the vac tank (you can do this at the front multiram solenoid if its easier).....does it hiss for a short period or not?

I suspect it will take a few days to get some responses but, there is a good reason behind this question.....which could help your economy, low rpm acceleration.....and all for under a fiver...

[Admin]

Interesting, you could get to try it on 2 cars tonight!

[TheBoy]

Interesting, you could get to try it on 2 cars tonight!

Alas, M_DTM won't be testing that on mine tonight    

[Taxi_Driver]

Interesting, you could get to try it on 2 cars tonight!

Alas, M_DTM won't be testing that on mine tonight    

And mines only a 4 pot .....so i carnt contribute  

[Omegatoy]

if its the fault i think it is the quick easy fix is a one way valve fitted in line from a windscreen washer system takes 2 mins to plug in and cures all the vacuum leakage!!
Omegatoy

[Paul M]

Will try and do the test at the weekend

[TheBoy]

Go on then M_DTM, I'll let you test it on mine tomorrow...

[Paul M]

Checked mine today, yes to holding vac and yes to hissing.

[TheBoy]

Err, uhmm, no comment  

But it does hiss now...

[Paul M]

So what's the script? If it holds vac and hisses does that mean all is OK?

[TheBoy]

So what's the script? If it holds vac and hisses does that mean all is OK?

[Marks DTM Calib]

The vac tank has a one way valve.....if this is now a two way valve and you give it some gun at below 4000rpm....the vac dissappears (very little inlet vaccum at wide throttle openings) and the multiram cuts out making it flat until 4000rpm is reached.....

More noticeable on a manual but, also impacts the autos to....

[The Barge Captain]

Holds vacuum ok at reseroir supply, but no hiss at front multiram.  Both my multirams worked last time i checked operation on the driveway though.

[Marks DTM Calib]

Holds vacuum ok at reseroir supply, but no hiss at front multiram.  Both my multirams worked last time i checked operation on the driveway though.

In which case your one way valve is knackered.....this will not be noticeable under the usual test conditions because you only blip the trottle..

What you need is a one way air valve as used on aquariums (about 2 quid delivered on ebay) and insert it into the vac line (in the correct direction!) and the jobs a good un....much better low down torque under normal driving conditions....

[TheBoy]

It does indeed make a small, but noticible difference....

And M_DTM, IOU a 1 way valve... ...I forgot...