Just recently bought an '86 928 with a manual transmission. I'm no mechanic, but enjoy poking around and learning. This site has been a godsend already. I'm currently trying to figure out why I can't get heat directed to the footwell and why the cruise control doesn't work. From all of my reading here, sounds like vacuum lines. I took a look at my vaccuum check valve as per http://members.rennlist.com/pirtle/svc.html and found the attached picture. The obvious thing to do is to reconnect the loose end to to valve, but I wanted to be sure I didn't do anything stupid. Should I reconnect the loose end and try things out? Why would the PO have disconnected and capped it off? What should the line with the light blue tip be connected to? Thanks!

 

the capped off line is most likely your cruise control, a little hard to see which way the lines route to be sure

 

welcome to the world of 928's.

somebody here probably has a vacuum hose route schematic (I don't right off hand).

as you will find out, vacuum a big trouble spot for 928's. once you start replacing vacuum lines, you should just replace them all. several complete kits are available.

good luck---


--Russ

 

Actually, the "capped off" connection is the one that comes off of the brake booster. I'm thinking that since the brake booster supplies the vacuum, anything connected to any of the other lines won't work. Right?

 

The blue plug is a factory test location.

The disconnected hose goes to the HVAC system. It also goes to a vacuum storage tank and the cruise actuator, both of which are in the driver's side fender. The brake booster tank only stores vacuum for the brakes. The HVAC actuators go bad, so don't be surprised if connecting the hose does not restore your heat.

My '86 has no footwell heat, either, because of a bad diaphram somewhere.

 

I guess luck is on my side today. I reconnected the hose and... heat in the footwell!!! It's rainy here today so a cruise control test will have to wait. Thanks for the help everyone!

I have to say though, I'm still wondering why the PO had the hose disconnected and the connection capped off. Why would you purposely want your HVAC system to not work properly? Could there be some other reason to do this??? This is bugging me...

 

Reason for PO might be vacuum leaks in activators or lines, he didn't want engine getting air into manifold from any place rather then air filter housing

 

Art20c - let me see if understand: since the engine is "sucking" to create the vacuum, any leak would allow the engine to suck in air from the spot of the leak. In addition, this air would be unfiltered which is undesirable. Do I get it? Sounds like I should get one of those Mityvacs and do some testing to be sure of what's going on.

 

Yes, that is what i meant. Getting vacuum tester is a good idea. This is link to vacuum test page on internet
http://members.rennlist.com/pirtle/svc.html

 

Thanks again. I'll do that and post my results.

 

Bought a Mityvac and did the tests as per http://members.rennlist.com/pirtle/svc_act.html. The problem was the actuator bladder for the center comb flap. The tear was in a spot I thought was fixable. I used some black silicone sealer and it worked. Might be in there again to replace the part in a few months, but figured it was worth a try.

I also figured out why the PO disconnected the line in the engine bay and capped off the brake booster connection: The tear in the bladder caused an extremely annoying screaching sound, but it didn't happen right away - only after restarting the car a few times.