I need to hook up the very small diameter yellow vacuum hose that runs
from the cabin through the firewall to the hot water valve on our L48.
Some PO removed it from the valve, sealed the end, and left it dangling. (I
posted some time ago, trying to figure out what this line was; electrical or
vacuum--and learned from the forum that it is in fact a vacuum line).

The metal nipple on the valve itself feels rough-edged, like it's been
slightly damaged in some way. And it doesn't seem like this diameter
hose would fit over it, even if it was in the right condition. Plus, although
the hose will just reach the valve, it doesn't seem as though I have quite
enough hose left to make the connection properly--but I could be wrong
about that. It's tough to get my hands down far enough into that location
to know for sure.

I saw a photo somewhere of another L48 that appeared to show a black
hose rising up from the area of the valve, and then connecting with the
yellow line at about manifold height. The shot was from too far away, and
too small an image, for me to be sure though.

Can anyone tell me what this hook up is supposed to be like? I figure I'll
have to replace a lot of vacuum lines, and if this is one of them, fine.
Same with the valve. But the hose itself seems OK, and if I can hook it up
as is, even temporarily, it'll be a help as I drain and flush the cooling
system, and just generally try to get the non-operating heating and AC
system working again.

Thanks for any insights on this--

I have a 78 L-48 also and it has a small diameter yellowish hose going to the heater shut off valve.  There is a small black piece that actually connects it to the valve (about 1 inch long with a small loop at one end that secures it to the heater valve).  I also believe that in order to shut off the valve it needs to have vacuum applied to it.  With no vacuum the valve is wide open all the time.  However, I'm not really sure on this.  I imagine that if put a short piece of vacuum hose on the valve and then stuck the yellow line into the other end, it would work, provided you had a tight seal. 

 

There should be a short section of rubber hose on the end of the hard plastic line. The factory did use a moulded piece, with the "loop" on the end as ammo6 described. It is just there to keep the line from working it's way off, over time.
A short section of hose will work just fine.

Thanks, ammo6 and Joel. Now I know the secret to this setup, and it puts
me one step closer to getting this baby back in working shape.

Can you tell me what size vacuum hose I need to make the connection? It
seems as though the 'regular' size used elsewhere on the engine would
be too large to fit the metal nipple on the hot water valve tightly enough
to seal. Plus it's got to be a small enough ID for the yellow line to seal to
at the other end...

Appreciate any further info you could provide on this!