confused... servo vacuum feed on webber 34ict?

my bus has just failed an MOT on a number of points, one of them that the brakes have no servo assistance. the garage suggested that i check the vac feed off the manifold in the first instance.

however, i've just had a look on google for info and then with this a look around the engine and i cannot see any hose coming off the manifolds (they are empi manifolds) or even a pipe to fit a hose too.

i know for definite that there is nothing coming off the carbs themselves as i've had them out myself in the last week or so.

sorry if i'm being thick, working on brakes are the new chapter it would seem in the VW book that i need to read, but quickly can anyone tell me if i'm looking in the right place?

 

If you don't have a servo you won't have any vacuum feed... iv got braided hoses and works much better now.. no servo fitted to mine

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If you have a servo but missing vacuum feed...you will need to drill the manifolds and fit a pipe

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Do you have a big metal cake bolted to your front beam? That's your servo. It's powered using a vacuum, which can be provided either using your intake manifold vacuum or an electric brake bacuum pump. If you don't have one, your MOT man doesn't know fish from frogs. If you do have one and there's no hose to it, as has been said, you need to run a hose to the engine and tap into the inlet manifold somehow (or get creative with a pump). Make sure you only use hose rated to J1403A- Any other type of hose can collapse under the vacuum and leave you with no brake assistance, you need the reinforcement that vacuum hose has.

 

i have a brake assist servo, i just don't seem to have a hose off the manifolds, that is what confused me.

the webbers were installed by a previous owner.

 

Your brakes must be incredibly heavy if you've got a servo, but nothing powering it

Easy enough to tap one of the manifolds. Is there a vacuum pipe to the front under the van?

 

When I got my van, the servo didn't work and you had to stand on the brake pedal and pull on the steering wheel to stop it!

It had obviously been like that for a long time, but still had an MOT.

Is a faulty servo unit an MOT fail?

Fixed it now btw and the brakes are as good as they're ever gonna be.

 

If they're in good shape, your Bay's brakes are as good as, if not better, than any modern vehicle...

 

thats how mine is, i just thought it was the way old vans are. it had an mot when i bought it (from a vw specialist) and definitely the brakes have not changed for worse over the last year.

the guy i used today is a good bloke, he does my other classic car, sensible MOTs.

i just wanted to establish if i was looking for the right hose in the right place. sadly, knowing what i do of this van after a year, it would not surprise me if the carbs had been fitted and the hose not taken off the manifold.

 

As stated above, you need to drill and tap one of the intake manifolds. They should have a boss for this as part of the casting. When you do it, try to bias the pipe up and away from the spark plug, or its a pig to get the plug out, or the HT lead on.

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they do have a boss so i assumed that was where the feed should come from should one have been fitted.

i'm not sure though how do-able it is to remove the manifold to add the pipe, whether its engine out or not, and frustratingly its pouring with rain so i can't have a decent look.

i also want to get under the bus and have a good look, see if i can trace a pipe at all.

the other option, and i'm trying to find answers on google as to what is involved, is removing the brake assist servo completely and putting it back to standard.

 

If you've got a servo, keep it (assuming it's working). Just tap the manifold.

 

I think '72 on had servo's as standard.
Just another thought. Mine has two pipes, one for vacuum and the other is open ended (atmospheric pressure?) Could your MOT guy have looked at that one?

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the fail was that it wasn't working as it should, he suggested i check the feed off the manifold and thats where it started because i looked and no feed.

i want to get under it tomorrow and find the pipe and try and follow it to get more of an idea.

 

If you have a balance pipe fitted between the manifolds, you can T into that.

 

Yeah, make sure it's in good shape (and the master cylinder). My servo fell apart when I took it off !

 

'If you have a balance pipe fitted between the manifolds'

there was a balance pipe between the carbs themselves, but not from the manifolds. this balance pipe now feeds into the svda distributor i fitted.

i did wonder if i had unwittingly disconnected something so that was the first thing i checked.

if this damn rain would stop i'd jack the van up and get underneath, its driving me mad not being able to have a good look and figure it out.

 

You just need a reasonable diameter tap off and a non return valve from the manifold.
No its not an engine out job everything is on top.

Get a big polytarp and throw it over the bus then climb under it. Or become so focussed on the job the engine hatch keeps enough rain off..

An alternative to drill and tap in a proper spigot is to drill and JB weld some microbore CH tube in . You can go into thinner walled parts of the manifold as you do not need the thickness of metal for a decent thread.
I fitted a vacuum takeoff from the manifold on my progressive for the air cleaner vacuum feed like this. 40k miles later its still there.

 

here's mine on my old type 4, they connected into a tube shown in the first photo joined by a piece of hose

 

I did this on a T25 for servo and vacuum feed.

Many naysayers said it would never work, but it worked just fine. Commuted daily in it, 60 mile round trip.

As you say you can drill anywhere that suits.

So easy, whip one (or both if you must) manifolds off, select a handy point, drill a hole and cold weld a bit of tube in. Bolt manifolds back on (new gaskets ideally) and hook up the vacuum hose that's hanging around at the back of the engine bay somewhere...

I reckon 4 hours tops, assuming you need to go and buy the bits first!!