Ok, makes sense.  So question then,  would the 30min regular highway drive
prior not have created the boiling to make me lose pressure or are we
thinking it's a combination of high vacuum with boiled brake fluids?

On Mon, Sep 25, 2017, 9:40 PM Stuart MacMillan <stuartmacm@gmail.com> wrote:

> The standard test for the booster is to depress the brake pedal and start
> the engine. Pedal should drop a bit on startup.  Like Dennis said, you
> might have a stuck brake caliper piston. The friction could cause the fluid
> to boil (or absorbed water to vaporize) which results in loss of braking.
> Time to have the brakes checked.
>
> Stuart
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
> Of Ryan Perry
> Sent: Monday, September 25, 2017 5:55 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Stumble and Loss of Brake Pressure Heading Up a Pass
>
> Thanks Dennis, checked the level and was at max. I can't say how old the
> brake fluid is so maybe it's time to change it?
>
> Is there a definitive test anyone knows for master cylinder and brake
> booster?
> Thanks
> Ryan
>
> On Mon, Sep 25, 2017, 3:27 PM Dennis Haynes <d23haynes57@hotmail.com>
> wrote:
>
> > Check master cylinder fluid level. Combination bad cylinder and brake
> > booster can let engine vacuum suck the fluid out of the master.
> > Next would be brakes dragging or otherwise overheated and you vapor
> > locked the brakes. Problem could be compounded by the fluid being old
> > and saturated with water.
> >
> > Dennis
> >
> >
> > -----Original Message-----
> > From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
> > Behalf Of Ryan Perry
> > Sent: Monday, September 25, 2017 3:14 PM
> > To: vanagon@GERRY.VANAGON.COM
> > Subject: Stumble and Loss of Brake Pressure Heading Up a Pass
> >
> > This one is new for me, taking it to the collective brain trust!
> >
> > '84 Manual with a newly installed 2.2l GoWesty. Runs fine in all
> > normal driving conditions. When heading up a pass for camping this
> > weekend, think Western NC, couple thousand feet elevation over 4 miles
> > or so.  The van was under moderately heavy load in 3rd gear, RPMs on
> > the high side but nothing outrageous, was holding steady in power.
> >
> > About 4 mins in the power hiccups slightly then continues on. I had a
> > bit of a corner so tapped the brakes lightly and find no pressure.
> > Really weird.  Made it to the top for a short flat and found I had to
> > pump brakes to get pressure.  This was short lived for a single
> > application. As soon as I let off back to no pressure, had to pump
> > again. Then back up the next section of the cut under similar load and
> > had the same stumble at about 3-4min in then carries on fine. Top of
> > that cut and the end of our trip out the van is running fine, though a
> > bit hot as expected, but no brakes without pumping.
> >
> > Parked,  camped,  had a great time celebrating or 4th wedding
> anniversary.
> >  (Someday I'll show you all or vanagon wedding pics, you'll like them)
> > Anyway, leave Sunday and brakes are fine, engine is fine.
> >
> > What do you think? Related? Coincidence? Vacuum line or booster? Fuel
> > pressure or pump?
> >
> > Thanks for any ideas, i try to keep stopping at the top of my list of
> > fixes!
> >
> > Ryan
> > Asheville,  NC
> >
>
>