Dave,
We only have an auxiliary tank, but I can see how the pump might be better
in some cases. Some of this is speculation, and some of it has been stated
by other GMCers here that already have the pump.
The pump will let you know if you have a booster/vacuum line problem (with
engine still running) because the pump will cycle on. This will give you
some advance warning that you might be having a problem which the tank
would not. It would also ensure that even if you pumped the brakes a
couple of times (panic) that you would still have vacuum being developed.
It might also let you coast to a better/safer spot while still knowing that
you will be able to stop when you get there even if you have already used
the brakes to slowdown.
You are, of course, correct that the pump could fail, but I would think the
chances of the pump failing mechanically at the same moment you lost the
engine would be pretty slim. The pump would cycle every time you started
the GMC (if wired that way), so you would know if you had a pump problem or
not at that point (this may be a good reason to wire it up to the ignition
switch). In most cases, if the pump sounded ok at the start of the trip, I
would think it would also be ok when you needed it. One time, I can think
of, that there might be a problem is if an electrical problem caused the
engine to die. If this were the case, there might also be no power for the
pump. A system wired off the ignition for normal operation with an
emergency switch to switch over to house power might solve this potential
problem though.
I like the idea someone else had to combine both the pump and the tank.
That really seems like the best of both worlds. I guess cost and space are
really the only obstacles to this idea.
Just some thoughts,
Zak
PS - So far, the only places we have had the engine die on us in any of our
tow vehicles were pretty flat sections where we were actually hoping we had
enough speed to get off the road rather than enough brakes to stop. I can
see how having a failure on a mountain would change those priorities pretty
fast though
.
>Help! I've been told that adding an auxiliary vacuum TANK will easily
>provide me with enough reserve vacuum for 3 or 4 stops after the engine
>quits. This advice comes from an experienced and trustworthy mechanic. If
>he's right, adding a no-maintenance tank seems much smarter than another
>electro-mechanical device (reliability) to provide braking reserve.
>
>Is he wrong? What makes the pump a preferred solution?
>
>I'm going to have one of these solutions installed before our trip next
month.
>
>Comments from the GMC brain trust will be greatly appreciated.
>
>Dave (& Dege), Santa Barbara, '76 Royale 26'
>
