[urq] Vacuum supply

[urq]

Yes, I see that now too . thanks for the reference to IST Dennis!  BTW, the
4kQ Bentley has the information you would need to go to the system that
allows locking center or both diffs . I did this to my car YEARS ago.  

 

I have to say that now that I know the diff lock is plumbed this way, I'd
recommend changing it.  If a leak develops in the diff lock system it will
cause flow in the lines going to the boost gauge and ECU under vacuum . and
under boost should the check valve fail.  This means that the ECU's manifold
pressure and boost gauge readings will be incorrect.  The line coming from
the tap on the back of the IM should go to the ECU and the boost gauge.  Tee
the check valve for the diff lock circuit in to one of the other lines
coming from the intake manifold.  I'll have to add this to the list of
things I need to do when I work the MAC-14 into my car . 

 

BTW, there's no need to scan and distribute the IST pages . Martin has them
available on his website.  I have a link to Martin's website (and many
others) on the urquattro yahoo group page:

 

    http://autos.groups.yahoo.com/group/urquattro/links

 

Steve B

San Jose, CA (USA)

 

-----Original Message-----

 

The IST document showing the vacuum hose diagram shows 1 IM tree hose
leading to the ECU that is tee'd to the diff locks and boost gauge. This is
white on my car. Another hose from the manifold tree has a check valve (at
the firewall I believe) and is then tee'd to the A/C Control and the vacuum
reservoir (green).
There is a check valve at the console connection for the diff actuator to
prevent boost from "unlocking" the diffs.
This diagram has been very helpful to me over the years. I can try to scan
it if there is interest, and it wouldn't violate copyright.
HTH

Dennis Graber



-----Original Message-----



The ECU and boost gauge need actual manifold pressure with as little delay

as possible.  The diff locks on the other hand are looking to use vacuum as
a power source ... and so are connected to a reservoir.  Sorry for the long
answer to your question, but I thought I'd explain why the answer to your
question is no.  
 
ISTR the vacuum source for the diff locks on my '83 comes up from under the
carpet on the transmission tunnel.  On my car there is a vacuum operated
recirculation valve for when the AC is on ... if your car is similar you can
tee your supply line in there.
 
Steve B
 
-----Original Message-----
 
I got everything for my diff panel swap hooked up.
 
But, I ran a new hose for the boost gauge and left the old one disconnected
at both ends. 
 
Does the diff lock switch use the factory boost gauge hose for its vacuum
source?