What is this thing?

[msksann]

Ryan:
It is a Pressure Protection Valve. There should be some part numbers
located on the 'cap', which, in this picture, is located underneath.
It is probably the same ones used between the air tank and the spring
brakes. Those are Midland part #N15759C (N157590) BB part #0522508.
This has been replaced by the Haldex KN31000, available at napa for
aprox $38. Or online for less:
http://tinyurl.com/24ngm4
I do not have the bulk oil fill on my Bird, so I can not check, but I
had the diaphragm rupture on one of mine last week, (for the drive
axel spring brakes). It opens at 65psi, and closes at 45psi, and it
protects the air system from loss of pressure. On the 3 used on the 3
axels, I believe the application is different, they keep us from
releasing the brakes until we have at least 65psi, and close down if
air pressure drops below 45psi(?) Perhaps someone else will jump in
here and confirm this applications use, since a failure could be
critical(?)
I begin to suspect that the diaphragm material is cracking in all of
them from age(?)

Michael Kramer
86 PT-40 8V92
San Diego, CA

--- In WanderlodgeForum@yahoogroups.com, "Ryan Wright"
wrote:
>
> Picture here: http://www.ryanwright.com/tmp/thing.jpg
>
> What is this thing? It's on the right side of my engine, tied into my
> air system. It's leaking air like a sieve, on all sides where the
> upper and lower pieces meet. I'd like to either replace the seal,
> rebuild the thing, or replace it all together. But I need to know what
> it is first.
>
> -Ryan
> '86 PT-40 8V92
>