928autobahndreamer

I started to replace the heater control valve this past week due to heat coming out of the vents at all times. I removed the old one and applied vacuum to it and the valve works and seals. So, this is a vacuum issue.

I know there are some great threads on the HVAC vacuum diagnosis and plan to follow this. However, I can't seem to pull vacuum with my Mityvac on any of the lines in the engine compartment. I purchased the silicone vac line replacement kit from 928 motorsports. However, I am not really sure what to do with the lengths of tubing. Is the smaller diameter line to replace the hard plastic lines? If so, I don't see how you make the connections. Do I use the silicone line to replace the rubber "elbows"? What do I do about the 3 and 4 way connectors? I may be making this much more complicated than it needs to be, but before I start cutting lengths of line I want to be sure I am heading in the right direction.

Anyone who has done this job already can you post some pictures of how it all gets replaced?

Thanks for your help. Being a seriously newbie mechanic I need all the help I can get. I have several other questions regarding other systems I am working on at this time and you will see other threads. I am afraid someone may drive down and take my tools away to keep me from doing any more harm to my shark, but I am bound and determined to learn how to do all of this.

Accomplishments so far oil change, transmission fluid, filter and gasket change, fuel line replacemet (most of them) and removal of cam end plug pins (found floating in amongst my cams-yikes). The list of things still to do just keeps growing.

SeanR

This is exactly what Rennlist is here for, members helping members. Just think, in a couple of years, there will be newer owners looking to you for information because you've been there done that (BTDT)

As far as your vaccume, check to see if the blue valve coming off the brake booster is holding vac, I noticed on one of those the other day at Rog's house, that it wasn't. This pretty much fixed his vac issues.

It looks like this, and you should only be able to blow through it in one direction.

JHowell37

The connections are via friction. In other words, simply press the line into the soft fitting. I was just speaking to Tom (I believe) at 928 International and he told me that the 4-way fitting in the picture above costs about $150 from Porsche. That's no bull****. The black and blue check valve is only about $15. What I found on mine was that the 4-way fitting had become loose over time so I pulled the hoses out, rotated it 90 degrees and plugged them back in. It's not perfect but it works well enough. My source of leakage was the small y-connector. Stuffing it into a tighter fitting seems to have worked.

928autobahndreamer

I understand how the current lines fit together, the problem arises with the new silicon tubing. If the silicon tubing is to replace the hard plastic lines, the external diameter of the tube will no longer fit into the connectors. Basically I just need to see which tubes people replaced with the silicone lines.

And seriously $150 for the 4 way? If I'm going to spend that much, 4 way better mean something entirely different.

I think the blue black check valve may be part of the problem but I haven't completely removed it from the system to fully check it.

Thanks for the replys.

VehiGAZ

928intl.com has the 4-way fitting for $4.50.

SeanR

I was gonna say, I'd sell you 3 of them for $100.00

Hilton

I haven't done my vacuum lines yet (I have the hose sitting around.. just about to order intake gaskets, seals etc. as I'm doing the whole intake).

However, my understanding is that the 3mm silicone hose replaces the hard lines. I've seen recommendations that you re-use the existing elbows, and use short lengths of the original hard vacuum line to connect the silicone hose with the elbows.

If there's a better way of doing it, hopefully someone will post it here.. I'm interested too

BrianG

I did the vacuum line replacement routine on my '87 S4 while I had the intake manifold and cam cover off for painting. It is my experience that the hard-lines seem to survive 20+ years without much degeneration, and they are routed along the body in nice solid fittings, for the most part. So I just used silicone tubing to replace the rubber junction pieces. Many of the rubber elbows and spiders were cracked and leaking. There are a few places on the car where this isn't easy because of the acute bends. I bought a dozen OEM rubber elbows for these situations. I also replaced a number of the hard lines on the engine just for effect because I have red cam covers and manifold and got red silicone tubing.

Do test each line you work with, with your mity-vac. This will help you identify leaking control valves and actuators, dampers, and such. There is no sense replacing the tubing that goes to a leaky end-unit.

928autobahndreamer

Thanks for the replys. I kind of figured that the 3mm line was for the hard lines. I had also considered using lengths of the old hard line to connect the new silicone to the rubber elbows. However, I did not want to start cutting lenghts until I was sure. Also, I don't think I will replace most of the hard plastic lines. I found that a lot of my leaks went away with zip ties on the rubber connectors. My remaining leaks are from the lines that disappear under the intake and one line up front.

Now on the big lines, here are some pictures of what I think needs replacing. Let me know it I am wrong. I was a little unclear on the med sized lines.

Mrmerlin

you might remove the cross brace it makes removal of the cam cover and any other intake work much easier, just remember to reattach it with both front wheels on the ground and if you want to see what it holds together remove it with both front wheels off the ground by loosening one side, also consider new fuel lines

928autobahndreamer

I thought about removing the cross brace, but honestly that didn't seem to pose too much of a problem when removing the cam cover. But, to make things easier I will probably take it out prior to replacing though. As far as the fuel lines. See my other thread titled "Fuel line replacement" Thanks.