Master Cylinder Replacement Challenges, Reservoir Lines and Single Pole Contact Options

[DennisV]

I've run into a couple challenges while replacing our brake system.

The new master cylinder has a single pole contact, whereas the original had 2-pole. I read somewhere that you just leave one wire detached. Do you lose some functionality doing that?


I am having a hard time getting the plastic lines that run to the fluid reservoir to naturally land in a position where they would connect. The old lines appear to be identical to each other. Whereas the new lines are different from each other with different part numbers found in the factory parts catalog. Has anyone else run into this? These came from Porsche and I triple checked the numbers on the bag against the catalog. I inserted them into the master cylinder per the indication of the factory parts catalog. I have done all sorts of twisting and contorting but would have to bend one of them substantially to get them to align with the reservoir hoses.


Thank you.

[mepstein]

“The new master cylinder has a single pole contact, whereas the original had 2-pole. I read somewhere that you just leave one wire detached. Do you lose some functionality doing that?”
Yep. Just as you described. Tape off the 2nd wire. Functionality is the same.

And make sure you have the metal washers under the rubber grommets. Not all new MC’s come with them.

[914Sixer]

Dennis,
I have a NOS 2 pole switch if you want OE. I have not seen new black lines but do they match the old lines when you lay them side by side?

[Superhawk996]

Just a guess

I would think the line with the arrow that has more “reach” (red arrow) would go to the master in the hole that is furthest away from the mounting face of the master and through the slot in the body that is furthest from the reservoir mounting point.

Can’t imagine it will make much difference (IMG:style_emoticons/default/confused24.gif)

Shame Porsche can’t be bothered to make proper parts given how spendy those lines are.

[DennisV]

I have not seen new black lines but do they match the old lines when you lay them side by side?

One of the new lines matched the old ones. Old ones were two matching lines. Not certain they were original or correct, but they were connected. New ones are each a unique part number and bend.

[914Sixer]

Just my thinking , but they maybe selling the one made for 911 thinking they were the same as 914. Seems no goes back and checks stuff.

[87m491]

I just went through this trying to track down some braking issues. Have literally had my MC in and out over half a dozen times last 2 weeks. In the process I finally broke one of the Nylon MC fluid feed lines. I think it was just as well since they had taken such a set after 50 years that I had to pull the tank to run them back up to the reservoir. Let me say that Tygon vinyl tubing from NAPA is your friend here. Resistant to all petrochemicals and brake fluid. Way cheaper than hard nylon replacements, More flexible than a rubber band and will fit through the body panel grommets without collapsing and save tons of cursing and you can fish it easily around an installed gas tank.

Now, on aligning the feed pipes below the car from the MC. My short, hard lines at the MC were symmetrical and I believe factory vs yours that are clearly different from each other. Because I'm still running 1 factory nylon feed line I also had to "crisscross" mine like seen in the parts catalog to get them to better line up with the body holes. When i swap in another Tygon line, I'm sure this won't be an issue.

My switch connector was capped off to one connector decades ago by the PO and brake warning works fine.


(IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-14731-1692108349.1.jpg)

I've run into a couple challenges while replacing our brake system.

The new master cylinder has a single pole contact, whereas the original had 2-pole. I read somewhere that you just leave one wire detached. Do you lose some functionality doing that?


I am having a hard time getting the plastic lines that run to the fluid reservoir to naturally land in a position where they would connect. The old lines appear to be identical to each other. Whereas the new lines are different from each other with different part numbers found in the factory parts catalog. Has anyone else run into this? These came from Porsche and I triple checked the numbers on the bag against the catalog. I inserted them into the master cylinder per the indication of the factory parts catalog. I have done all sorts of twisting and contorting but would have to bend one of them substantially to get them to align with the reservoir hoses.


Thank you.

[Dave_Darling]

The two-pole switch has a signal and a ground. The signal wire connects to one pole, the ground to the other. When the switch gets tripped, it connects the two terminals.

The one-pole switch does not have a separate ground. It grounds through its threads. You tape up the brown ground wire, and plug in the brown/white signal wire.

--DD

[DennisV]

I would think the line with the arrow that has more “reach” (red arrow) would go to the master in the hole that is furthest away from the mounting face of the master and through the slot in the body that is furthest from the reservoir mounting point.

This logic makes sense, so I gave it a go. Note that this contradicts the placement shown in the factory parts catalog, but it wouldn't be the first time there was an error in the catalog. The shorter metal bend seems to match the footwell contour better. Still not a great fit though. I looked back at some photos I took before disassembly. It appears the line from the master cylinder to the right brake ran forward of the reservoir tubes. So maybe I need to move that.

Up above, the tubes seem too tall where they should mate with the reservoir and are not parallel. The reservoir is not mounted in the photo, but standing a few inches too high. I thought they should follow the floor of that compartment, but they didn't in my before photos either.


This really tried my patience and sucked up much more time that it should have. They seem to have been very deliberate in the bends on these pieces, so I would have expected them to fit the contours of the car much better. Feel like I'm missing something. Maybe my expectations regarding fit and finish are too high for 1970 914.

I may take a heat gun to these and see if I can massage them into a better position.

[Superhawk996]

Maybe my expectations regarding fit and finish are too high for 1970 914.

It’s not a 914 thing. The original lines fit nice.

It’s a Porsche (IMG:style_emoticons/default/sheeplove.gif) thing. They screwed up something - just like they did with the whole CV joint fiasco.

I think 914Sixer may have hit upon it in earlier post - they are probably substituting a 911 line as a 914 part. They already proved how incompetent they were with the CV joints.

I almost wonder if you would be better off comparing the new lines to the old; pick the one that is closest and then order a 2nd one of those. If I’m not mistaken it’s that line with the hard 90 degree bend that doesn’t belong. If you’re lucky maybe argue for a refund of the one that is clearly different. They did refund CV’s to at least 1/2 dozen members here due to that screw up.

I think it might all work out once you do that and move the brake line to the front.

Frustrating though since you’re trying hard to keep it original as a /6.

EDIT: if you would be so kind, please post for others which part number is the one that matches the original line

[DennisV]

EDIT: if you would be so kind, please post for others which part number is the one that matches the original line

I will try to remember to do this next time I am have access to the car.

Was the original orientation correct? The line from the master cylinder to the right brake should be forward of the reservoir tubes? Opposite of my photo.

[Superhawk996]

Honestly - it doesn’t matter as long as lines aren’t touching and rubbing other things

I wouldn’t leave it the way you have it with hard lines touching and it looks like the brake line is putting stress on the reservoir feed line and rubber grommet.

You’ll either have to tweak the lines where they are at or move to the front.

I looked for pictures both of my own car (strike 1), PET (strike 2), and the factory service manual (strike 3) and didn’t come up with a clear definitive routing picture.

The bottom line is that the hard lines must not be touching / rubbing other things. That is a definite no-no when it comes to routing brake lines. You’d be amazed at how quickly two metal lines rubbing each other will wear a hole in one or both.

Google search of the site:

[DennisV]

EDIT: if you would be so kind, please post for others which part number is the one that matches the original line

Part number PCG-355-063-10 that I received from Porsche is the closest in terms of the metal pipe length and plastic tube bend to the lines I took off the car.