Dual master brake switch hookup ???

[wildcat077]

Hey guys,

For those of you who installed Fabcar or other brand dual master cylinder assemblies,how did you hook up your brake switches ?

My guess is i would need an inline tee but how would that connect to the master ...

Thank you !

Cheers
Phil

[175K911]

If you're using the Tilton 74 master cylinders, you have two choices:
The MC has two threaded inputs- you can use one for your brake line (off the back) and one for a separate Tilton brake light switch.

Or I got one of these:
https://www.pegasusautoracing.com/productdetails.asp?RecID=5028

Had my new brake line for the front brakes made up with a banjo fitting on one end, then this bolts through the banjo fitting into the back of the MC. Then just wire the switch to the two wires that go to the brake lights.

[Cory M]

I put a tee in the line and used the factory switch. Got the parts I needed from http://techna-fit.com/ and was pleasantly surprised at the prices. You need a 10x1.0 thread.



Here's my old thread on it:

Dual master cylinder help - thread size?

[wildcat077]

Thank you guys !
Looks like for now i have enough hardware to go with Cory's suggestion.I got all the fittings from Patrick Motorsports including two tees and the required AN/10mm adaptors from the master ...
I was wondering if the wire loom for the brake switch was long enough to hook it up farther from the Fabcar master cylinder,looks like it is
Cory,did you hook up both switches or only one ?

Cheers !
Phil

[Cory M]

I only have 1, I would have had to cut and flare the other factory line to add a second. It's probably a good idea to have 2 though for redundancy. If you only do 1 you might want to keep a spare switch in the toolbox because if it fails your brake lights won't work. I had one go bad on me at the track and I had to replace it before the next session, luckily I kept the other as a spare. So the factory ones do go out from time to time. The OEM switches are a lot more expensive than aftermarket but are supposed to be superior.

[Bill Verburg]

Originally Posted by wildcat077

Hey guys,

For those of you who installed Fabcar or other brand dual master cylinder assemblies,how did you hook up your brake switches ?

My guess is i would need an inline tee but how would that connect to the master ...

Thank you !

Cheers
Phil

I'd use a mechanical switch activated by the brake pedal, 911 used these thru '76 and 964/993 too.

[wildcat077]

On to question 2 ... i have a G50 with hydraulic clutch and there is a braided hose that runs from the OEM master to the clutch cylinder at the pedal cluster,the Fabcar unit has two Tilton reservoirs but no provision to run a fluid line to the clutch cylinder ...

Do i need to use this line or can i cap it at the clutch cylinder ?It's a blue cloth braided line so i doubt it supports much pressure.

Cheers !
Phil

[KTL]

Originally Posted by Cory M

.......If you only do 1 you might want to keep a spare switch in the toolbox because if it fails your brake lights won't work. I had one go bad on me at the track and I had to replace it before the next session, luckily I kept the other as a spare. So the factory ones do go out from time to time. The OEM switches are a lot more expensive than aftermarket but are supposed to be superior.

Cory brings up a good point here. I experienced this with a friend a few years back. His '87 911 has a brake light problem and we went over to the Eurosport shop at the track to ask for a switch. No such luck.....

So in his infinite wisdom, being a Jeep/Dodge/Chrysler dealer tech, he decided to swap the wiring on the switches. Wouldn't you know it, brake lights back in action! No need to replace the switch.

So my point is, I think one switch is for the brakes and the other is for the brake warning light on the dash?

[175K911]

Originally Posted by wildcat077

On to question 2 ... i have a G50 with hydraulic clutch and there is a braided hose that runs from the OEM master to the clutch cylinder at the pedal cluster,the Fabcar unit has two Tilton reservoirs but no provision to run a fluid line to the clutch cylinder ...

Do i need to use this line or can i cap it at the clutch cylinder ?It's a blue cloth braided line so i doubt it supports much pressure.

Cheers !
Phil

You're correct, that blue line supports no pressure. It's just to gravity feed fluid to the clutch master cylinder. You will need a reservoir to feed the clutch though. I suppose you could fab us something to hang the original reservoir off to the side and continue to use it as the clutch reservoir, capping off whatever fittings went to the old brake master.

Or you could get a simple Tilton reservoir and fab a bracket to hang it and feed the clutch.

Reservoir:
https://www.pegasusautoracing.com/productselection.asp?Product=3558

Bracket to attach reservoir to, and hang in the car:
https://www.pegasusautoracing.com/productdetails.asp?RecID=1111

Total investment- $17 for both parts

[KTL]

Originally Posted by wildcat077

On to question 2 ... i have a G50 with hydraulic clutch and there is a braided hose that runs from the OEM master to the clutch cylinder at the pedal cluster,the Fabcar unit has two Tilton reservoirs but no provision to run a fluid line to the clutch cylinder ...

Do i need to use this line or can i cap it at the clutch cylinder ?It's a blue cloth braided line so i doubt it supports much pressure.

Cheers !
Phil

No don't cap it. That blue hose is the clutch fluid supply line that is connected to the brake fluid reservoir.

Get an extra reservoir somewhere and use that for the clutch. I've got an extra one from a 915 car if you want it. Perfect size for the clutch and you know it'll fit your Motive bleeder to bleed the clutch!

[Cory M]

Originally Posted by 175K911

....Or you could get a simple Tilton reservoir and fab a bracket to hang it and feed the clutch.....

That's what I did:

[wildcat077]

Thank you for the feedback guys !
As far as the brake switches go,a couple of pre made 8 and 12 inch brake lines from the masters did the job and i'm very grateful regarding the clutch reservoir info,i'll see what i could come up with to hook up a third one.
I have one brake switch hooked up to the rear system and i'll do the same for the front so both switches will be hooked up.I'm going to make a bracket and secure both tees and brake switches together.

I guess it's pretty simple after you've figured it out

Cheers !
Phil

[wildcat077]

OK,both switches and brake lines to masters are done...hard on the fingers to turn two 8 inch brake lines into pretzels ... lol ... Just need to make a small bracket to secure the tees and the lines !
Ed,thank you for the Tilton P/N's for the extra reservoir,i will order those tomorrow and now comes the final install.

Kevin,Cory,Bill,is there a recommended procedure as far as getting everything filled up or should i just fill up the reservoirs and use my Motive to pressure bleed the system.I'll be using the cheapo fluid to run through the whole system before i put the Motul in.
That's the procedure i used for the 23mm master and all went well !
Time to take the dog for a walk

Cheers !
Phil

[Cory M]

Looking good. Is that the proportioning valve on the rear line? I think you want to remove that since you will now be adjusting bias with the knob. I just filled my masters and used the Motive bleeder. The stock Porsche attachment on the Motive won't fit the Tilton reservoirs, I had a spare Tilton cap that I modified to work with it but Motive may sell one that works too. There is a bleed port on the master cylinders too if you need it, can't remember if I did.

[wildcat077]

Cory,

The proportioning valve is already gutted as i've been running my 996TT brakes for two years now and i already have the Motive adaptor for Tilton caps.Is the small (4oz) reservoir good enough for the clutch or should i get the medium (6oz) one ?

Cheers !
Phil

[175K911]

Looks like Cory is running the medium 6.8oz reservoir.

[Cory M]

Yeah, I've got the medium. I don't think it really matters too much though, there isn't a lot of fluid in the slave cylinder system.

[KTL]

The amount of fluid the clutch moves is really small. This is why you have to pressure bleed it. The master doesn't push enough fluid for you to be able to pedal bleed it. Been there, tried that, failed.

So you could have a super small reservoir and it wouldn't matter. Plus, the fluid level doesn't even change much at all. Clutch reservoir is not like the brake reservoirs where you need some reserve space in there to accommodate fluid level going up due to heat.

[Geneman]

Hi kevin et. Al. I am also interested in the brake switch issue. I am totally rewiring my car with an isis custom module system. I assume it needs a simple on-off input from the stock brake switch to work properly. In my 88 carerra there are 2 wired sensors on the master cylinder. Are they the ones? And are they identical. ? Ie: As kev says does one activate brake lights and the other go to a dash sensor or idiot light?

I assume there is no other mechanical brake switch in pedal cluster correct?

Btw, there seems to be a mechanical switch near pedal cluster which is sensing clutch movement. Anyone know what this is? Will send pictures if need be.

As always thanks alot and apolpogies for hijacking

frank

[KTL]

Hey Frank,

I'd take Bill's advice & do a mechanical switch. Since you're rewiring entirely, I see no reason to use the pressure switches. The brakes lights are indeed a simple on-off switch on the master. The switches are both connected to the brake lights but also connected to the brake warning light.

The other guys, apologize speaking for them if i'm mistaken, chose to use the pressure switches because they can take advantage of existing switches & wiring right there where the old master cylinder sat. Coincidentally their new dual master setup resides there too, which is nice.

In your case since you're starting fresh, might as well get it set up in a way that best serves your wiring layout. If you're sticking with the original master cylinder location, no reason to use those pesky pressure switches if you don't really want to run wire to them. Run a switch off your brake pedal and wire from there. If you have a dual master setup like theirs, you still don't need to use the pressure switches.


That mechanical switch by the clutch pedal is for the cruise control. When you push in the clutch, it disables the cruise. The brake pedal has to be able to disable the cruise too. Brake pedal deactivates cruise via the brake switch which conveys its signal to the cruise control "brain"