75ohm

Making a long story short -- I am over the idle bouncing between 800 and 1200 all the time. So, off comes the throttle body, intake, fuel rail, injectors, etc. Throttle body gets a rebuild, intake gets powdercoated, injectors get cleaned up and new o-rings, etc. Whilst in that far, I figured I'd finally replace that rear cam tower cork gasket. Nice to know that the PO or latest "mechanic" put two out of three bolts in it... no wonder.

In any case, while putting everything back together I am shocked to find something while looking straight down on the rear of the cam tower. I've replaced the engine compartment vacuum lines probably about 6 months ago and never saw anything connected here:



Ah, yeah, forgot to mention that I replaced the heater valve thinking that would actually work. Mine was constantly closed. As in, always under vacuum control regardless. Interesting.

So, what's supposed to go those two connections? I've checked all the diagrams I can get my hands on, including the WS manuals and PET, here, and others boards. Nothing to positively identify what goes there.

Secondly, is an '88NA supposed to have a "venturi"? Mine apparently does not.

Thanks all,
75ohm.

aribop

The one you have pictured goes to a 'T' splice. One end goes to the vacuum canister by the battery and the other end splits into the vacuum lines that go to the Fuel Pressure Regulator.

The hidden one that is not shown goes straight to the heater control valve.

75ohm

Aribop, the connections that you reference are already in place. These are lower than those on the firewall... perceivably running through the same spot as the A/C lines.

75ohm

BUMP...

Come on now, hook a brother up!

camelot

Clarks garage , under heater malfunctions. It mentions the 2 lines . I'm in work or I would help you further. Scroll down The paragraph starts with" The second problem" Hope it helps

75ohm

Thanks camelot - something doesn't add up though. I've got the connection going through the very top of the firewall next to the battery directly to the heater valve. I do have a connection to the brake booster but honestly it feels like old drum brakes... hmm. I honestly think that the engine vacuum is correct but the ancillary stuff is fubar. I need to see it correctly mapped on someones ride. It is proposterous to think that anything is working correctly this way but the car runs!

75ohm

Here's what I now know after referencing headhunter's 86NA and searching posts @ clark's...

The line running by battery compartent (vac can) goes through the upper firewall and T's off and one side goes directly to the brake booster. The other side feeds down to the input side of the picture shown above. The other side connects to the heater valve.

This explains two things:

1. really poor braking booster performance.

2. zero heater control valve, control. (allow myself to introduce, myself!)

Thanks previous owner and previous non-porsche mechanic! You both are A$$CLOWNS!

Zero10

There should be a small regulator/check valve on the line feeding the climate control.
The circled line feeds the climate control, and there should be another line coming out which leads to the heater valve.
The feed for this whole section should be from the little T/Y valve on the brake booster, which is fed by a large line coming off of the intake manifold.
You are correct no proper venturi, but there are some messed up hoses on the NA's

75ohm

Zero10,

Now you've got me questioning something else...

You are stating that the feed to the climate control, the one circled in the picture, is being feed from a "T" off the brake booster...

Here's what I think you and I are both saying:

From the vac cannister near the battery, a line comes through the firewall. From there it splits down to the climate control input and to the brake booster.

Right?

Where does this regulator/check valve come in? I see one of those possibly next to the fuse panel... but since I am not in front of the car, can't say for sure what hooks up to it. I think it actually goes to the fake venturi hookup, does that sound right? I don't know how on my car the regulator/check valve would get in line before the climat control input.

Thanks for your help,
75ohm.

Zero10

Hmm, vacuum canister near the battery.... It has been a long time since I worked on a N/A, but here's how I remember it.
There is a small vacuum system (5/16"), that is fed from a nipple on the throttle body, it controls the FPR, FPD, and possibly some other small things.
There is also a large line that feeds the ISV, it essentially bypases the throttle body.
Thirdly there is a large line that comes from the bottom of the intake manifold, that feeds the brake booster. From where it attaches to the brake booster, there is a fitting, that has 2 large hose outlets (5/8"?), and 1 small one (5/16"). The small one feeds a small in-line cylinder with a blue stripe on it, that goes to the climate control.
From the climate control it runs straight to the heater valve.
There are 2 lines attaching near the A/C lines, they are for the climate control.
I can't recall which is which. Do you have the vacuum diagram on your fender?

aribop

Here are the two lines coming out of the firewall. The left is orange while the right is green (if you are looking at the firewall)


The green line goes directly to the heater control valve.


The orange line 'T's off. One end goes to the vacuum canister by the battery.


The other end goes to the brake booster with the check valve in place.


I was looking at my S2 when I gave you the specs last night...basically the same.

75ohm

Thanks guys, I appreciate the information and pics. Here's what I found out. The last person to touch the vacuum lines screwed. The hooked the heater valve directly to the orange line coming out of the firewall, essentially bypassing all HVAC controls. Thanks again!

I won't have an opportunity to test this for a couple of days... still putting other pieces back together!

Thanks!

75ohm.

75ohm

Wanted to follow up with everyone -- this indeed fixed the issue! Thanks!

Zero10

Good to hear

89AZ944

Rennlist saves the day!