'77 911 MC Vacuum hose location

[tonyduc]

All

Trying to locate the vacuum hose on my '77 where it attaches in the engine compartment. All pics I've seen are on SC and later models. This is the only larger hose (14mm) I see on the left side (see arrow in attached), the other is located by the WUR. The 19mm OD hose referred to in prior posts goes from left and behind the engine along the firewall, and ends up in the right side of the engine. Any advice for the 77 is much apprectiated.

Thanks
Tony

[KMoore68]

I think the hose you are pointing to is the fuel return that connects back to the fuel tank.

One of the connector's on the "T", the "top" one is back to the Fuel Accumulator, IIRC

[rwest]

I think your picture is of a fuel line. I converted my ‘77 to EFI, so going off memory, but I believe the booster hose is coming from the lower section of the air box between the intake runners on the driver’s side.

[boyt911sc]

Tonyduc,

Please post a picture of your engine showing cylinder #1-#2-#3 and the CIS airbox. I will try to identify the vacuum line to the MC. Thanks.

Tony

[tonyduc]

Originally Posted by boyt911sc

Tonyduc,

Please post a picture of your engine showing cylinder #1-#2-#3 and the CIS airbox. I will try to identify the vacuum line to the MC. Thanks.

Tony

Tony, thanks will do soon. After probing a little more I found that the 19mm line was just tucked behind the engine unconnected. So there must be a vacuum port somewhere that was plugged, otherwise the engine would likely run rough. So the PO probably did this rather than replace the hose.

Tony

[Pelicamways023]

Thanks for assisting

[tonyduc]

I think I found the problem. According to my records the PO had a shop install a new airbox. They apparently never connected that lose 19mm OD hose I found tucked away behind the engine. It reaches exactly to this brass plug in the left side of the airbox - pictured. The shop likely never replaced the plug with a 19mm male fitting. I tested the hose with a smoke tester and it goes all the way to the booster - no leaks. I am assuming this is the intended port and will try to locate a a proper male fitting. Curious as to why the PO never recognized the vacuum never being reconnected, perhaps the faulty airbox resulted in a loss of power brakes ?

[PeteKz]

Correct me if I'm off, but I believe 1977 was the first year with power brakes. Does yours have the power booster in the frunk? If so, the large diameter hose should go to the brake booster from the left side of the airbox. That brass plug is where there should be a nipple for the brake hose. I'll bet your brakes are pretty stiff.

[tonyduc]

Yes, from what I have read 77 is the first year for the booster. This is my first air cooled Porsche and I just thought old sports cars had stiff brakes. Now I have been going thru the process of checking all the vacuum lines and that's how I caught this.
Thanks