Wilwood MC Float Switches
 

For those of you building CR kits with dual Wilwood or Tilton brake Master Cylinders wiring in a brake fail light is a pain.

Ian reccomends fitting float switches to the master cylinders to detect the fluid level drop when a brake circuit fails.

I just completed my float switch setup and thought I'd doccument it so that it may save someone else the stress of how to nut out adapting the float switches.

I started at my local Pick-A-Part wrecker and went down the lines of cars looking for ones with brake master cylinder float switches. There were several to choose from but the most easily adaptable looking were in mid 80's Holden Barina or Suzuki Swift. These have a remote brake reservoir with a switch built into the cap. There were a few at this yard so I pulled the switches from 2 cars and took them home for $10 each.

Here's what the Barina switch/cap looks like:

http://www.clubcobra.com/photopost/d...rina_cap_1.jpg

It looks like it's made by NABCO

http://www.clubcobra.com/photopost/d...rina_cap_2.jpg

The first step is to remove the switch assembly from the cap. It clips in place and can be levered out with a screw driver. You can clip the side of the cap with some side cutters to loosen it and make it easier to get out.

http://www.clubcobra.com/photopost/data/500/Float_1.jpg

There are three wires to the switch. We only need two of them, the Black and the Red/Black. Clip off the White/Red wire.

The float switch has a reed switch inside it. The contact of this switch is normaly open. The float is a torus shaped magnet coated in foam to make it float. As the float drops down the spindle the magnet passes over the reed swich inside closing it's contacts. The black and red wires are the two switch contacts.

http://www.clubcobra.com/photopost/data/500/Float_2.jpg

The switch needs a bit of modification before it'll fit inside the cap of the Wilwood master cylinder. Remove the rubber seal first. Just hook under it with a thin screwdriver and lever it off.

http://www.clubcobra.com/photopost/data/500/Float_3.jpg

Next clip away the flange around the top of the switch being careful not to damage the center part.

http://www.clubcobra.com/photopost/data/500/Float_4.jpg

Using a file or preferably a linisher clean up the part where you removed the flange. You will also need to remove some material from the two ribs below it so it will fit in the neck of the Wilwood reservoir. Work slowly and linish it down to the strengthening ribs.

At his point you should also drill a small vent hole in the side just above the top rib. I used a 1 mm drill bit and just drilled through the outside wall. The vent is needed to equalise pressure as the fluid level drops or rises.

http://www.clubcobra.com/photopost/data/500/Float_5.jpg

Take the wilwood cap and look at the underside. There is a plastic disk that's clipped into the center that acts as a baffle for the vent hole. This stops fluid splashing out of the vent hole.

http://www.clubcobra.com/photopost/d...wood_Cap_1.jpg

flip the baffle out with a screw driver and then carefully pull out the rubber seal under it. Hang onto the seal as we'll re use it later.

http://www.clubcobra.com/photopost/d...wood_Cap_2.jpg

Now we need to drill some holes in the cap for the wires to come through. I used a 2 mm bit and drilled out th vent hole and put another hole next to it. We'll be adding a new vent hole later.

http://www.clubcobra.com/photopost/d...wood_Cap_3.jpg

Surprisingly the inside diameter of the top of the float switch is a snap fit over the lip inside the cap where the baffle clips in. It's a fairly tight fit so you could probably get away with just clipping it all together. I thought I'd make it a bit more secure as I don't know how it'll cope with vibration over time and the cap being unscrewed to top up.

When using epoxy glue it's a good idea to roughen up both surfaces with some coarse sand paper. This will give the epoxy something to key into.

http://www.clubcobra.com/photopost/data/500/Float_6.jpg

http://www.clubcobra.com/photopost/data/500/glue_1.jpg

Run some glue around the inside of the top of the float switch.

http://www.clubcobra.com/photopost/data/500/glue_2.jpg

A pool of epoxy around the wires where they exit the cap will secure them.

http://www.clubcobra.com/photopost/data/500/glue_3.jpg

Pull the wires through and snap the float switch into place. Wipe off any excess glue from the inside of the cap and where the wires exit the cap. The 2mm in the cap holes are a snug fit around the wires so the glue shouldn't leak.

sit them upside down somewhere whilst the epoxy cures. I left mine over night.

http://www.clubcobra.com/photopost/d...ed_Float_1.jpg

When the epoxy has cured you can run some heat shrink tubing over the wires and terminate them with your choice of connector. You can also pop the seal back into the cap. It will stretch over the float switch and settle back ito it's original position with some careful help from a screw driver.

http://www.clubcobra.com/photopost/d...ed_Float_2.jpg

You will also need to drill a new vent hole in the cap near where the wires came through ito the space in the top of the float switch. The hole we drilled earliar in the side of the switch also goes into this cavity so we have a vent and baffle.

http://www.clubcobra.com/photopost/d...ed_Float_3.jpg

The Wilwood reservoir may have a filter element in the neck. This will have to be pulled out for the float switch equipped cap to be installed.

http://www.clubcobra.com/photopost/d...ed_Float_4.jpg

The float switch can now be wired up to the idiot light on your dash. If you are running two switches connect them in parrallel.

http://www.clubcobra.com/photopost/d..._Cylinders.jpg

Hope this helps

Cheers

Wow
 

Mike,
Incredible!!!!


Well done.

Phil

Great work Mike - I pinched one of those float switched off an old barina a while back - and tinked a little with inserting into the willwood cap - but put it all in the too hard basket. Might have another crack at it now....looks like a bought one :)

Cheers.

If you struggle to find Suzuki/Barina switches, you could also try Subaru Leone of about the same vintage. Look to be the same switches and you can add another make of car to the component list that makes up your Cobra.
Great job Mike.

Cheers.

Mike you truely are a master !!!!!!

Very Impressive Mike, Well done.
Did you/will you also wire up the hand brake switch in parrallel with these float switches??

Luke.....

Thanks Guys,

The hand brake switch has a seperate idiot light on the dash. It was pretty straight forward to wire up as there's provision for mounting a push button switch on the MG hand brake lever. The wire is just gaffer taped to the side of the tunnel and will be hidden under the carpet. I'll snap a pic of it it if you like.

Good tip on the Subaru switches. It figures there must be a few cars out there that share these components.

Cheers

Nice work Mikey

Mike,
This is almost exactly how we decribe it in the wiring instructions. However, you have made one slight error that I feel we should rectify so other do not follow these instructions. DO NOT CUT OFF THE WHITE/RED WIRE.
Under the ADR's the light MUST come on when the system fails & when you turn on the igition. This function is performed by the white/red wire when it is wired into the alternator light circuit.
Your current installation will not pass engineering & will need to be changed.
Cheers,
Ian

Fantastic post Mike,

People like you make this forum great. Your post will certainly save some people time and money and give people the confidence to try things themselves.:)

Thats a great post guys, nice detail.
I'm new in here and stay on for a while , haven't looked at porn for three days. Its great !

Keep it up

Hi guys, the reservoirs on my Wilwoods have bayonet fittings and not thread like Aussie Mike has. That means that the float caps from an 85 Barina or Swift will fit directly into the reservoir without modification. Im ordering some on Monday morning for Gavin Irvine so if anyone wants some let me know and Ill order more. They cost under US$10 each plus delivery.
Ph. 0407 80 70 60.

Regards.

Nice work Mike, where did you get the MC from and what sort of $$ are you looking at?

Todd

I've found about the best price locally for the Wilwood MC kits is $108 from VPW http://www.vpw.com.au

Some of the guys have bought them from the US and got them cheaper but if you don't want to wait for the post $108 isn't too bad.

What are you thinking about fitting them to Todd?

Cheers

I have this to go in my '02...

http://www.massivebrakes.com/pictures/pop_2002-1.jpg

I have to update the M/C to split system and have to work out what is the most cost affective way of doing it... a new BMW part or aftermarket...

Cheers,

Todd

Very nice Todd. I'd probably look at getting the whole wilwood pedal box. They do a couple of 2 pedal combination units that do the clutch and have a dual MC and ballance bar setup for the brakes. Look pretty trick too and only $298 from VPW plus master cylinders.

With the booster and existing clutch MC gone there should be plenty of space to mount something. They have versions you could sandwich the MC on the outside of the fire wall and the pedal box inside.

If you are running a cable clutch then the single pedal assembly is only $166.

Food for thought.

Cheers

Thanks Mike... I will look into it.

Cheers,

Todd

I haven't seen anything in any of the manuals I have that describes how to do this. It must be in another manual
I haven't seen.

I've been thinking about the way you suggest wiring it up and can see a bit of a problem. What happens when you get a charge fail problem and the charge light comes on? It seems to me you would get a brake fail warning as well.

I think a better way would be to use a delay circuit much like the seat belt warning light to short the float contacts for 10 seconds when the key is turned on.

Cheers

Makes sense to me Mike.
If you have no charge then you can't drive the car, hence you won't need brakes. Alternatively, if you have no brakes it doesn't matter if you don't have charge, you can't really drive the car anyway.... :p :LOL:

Mike,
The reason you have not see this in any manual is because you have not purchased the wiring harness with the manual!
No, the fail light does not come on when you have a charge problem. This is the way most of these lights are wired on production vehicles.
Cheers,
Ian