I notice recently that occasionally my 85 30sd would not shut off with the ignition off and the key out. Had to use the STOP handle under hood. While driving thereafter, I realise that the brakes would go hard. What could be the problem.

Drew

If you or someone else changed the oil recently. You have a disconnected vacume line. Even if you haven't changed the oil you have a vacume problem.
Will need Mighty Vac gauge to chase down vacume leak. You should have 20 to 24 merc. from vacume pump. Check archive under vacume leak.
Charlie

Try a ruptured diaphragm in the vacuum pump.

I had this happen once. You can get a rebuild kit for the vacuum pump. it contains three little check-valves (odds are one of those died) and a wide rubber band looking thing, and a funny looking rubber o-ring. (I know my description isn't the greatest, but you'll see what I mean when you open the box)

If I remember right, you will need 3 or 4 different tools...nothing special. If you are going to do it yourself, you should be able to do it in way less than 3 hours the first time. If I had to do this again, I could probably do it comfortably in 90 minutes; now that I know what to do.

Important! Make sure the allen bolt holes are Clean, or you could have your allen wrench slip/strip, and then you will be really irritated (to say the least).
Also, it would be a good idea to note which directions the check valves go - two go in one direction, the other one goes in the other direction.

There might be a post where somebody can give decent details on replacing the pump parts....do a search.

Have fun & good luck

-Larry

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

Make sure you at least double check all the connections.

My car started to hesitate to shut off (stumbled till it died) like 3 times luckily I was going to the dealer that day and picked up some vaccuum line. Turned out the vaccum line from the ignition to the shut off valve came loose and eventually popped out on the shut off valve side. I replaced the little rubber connecting piece with a chunk of Diesel braided fuel line ( I had extra laying around) and re routed the vaccuum line through the dash. Problem solved

__________________
2005 Audi A4 1.8T CVT -Silver/Black "Siegfried"

1982 300D - Silver/Blue "Ralph" -For Sale:
http://www.peachparts.com/shopforum/showthread.php?p=852260

1989 VW Diesel Jetta Blue/Blue "Bodo" RIP

I had this happen to me in the summer. I first noticed the hard brake and on the trip back home the car wouldn,t shut down. THe latter was the clue I needed. I, as Capt. Kirk suggests, checked the vaccuum connections. That was the problem. One had become disconnected at a joint.
I would first suggest that you just eyeball all the small vaccuum lines to see if anything looks disconnected. Then take a look at the lines coming out of the master cylinder and make sure they are connected. Good Luck.

THANKS GUYS, I WILL RUN A CHECK LATER TODAY.

DREW

My '79 300SD did same thing. The nut that connects the large vacuum line to the vacuum pump came loose.

Tightening this nut fixed the problem.

P E H