Mk 1 Brake Master Cylinder Switches - Why are there 2?

[Garbon]

Why is there 2 brake switches on my master cylinder?

1 has 3 prongs (towards the front of the car) and the other has 2 (towards the rear)

Anyone know why the difference and what they do?

[GRN_VAGN]

just another reason for your brake lights to randomly not work...
I believe they both work on fluid pressure, both work together on both circuits to work properly. I had one burn out and my brake lights wouldnt come on intill i was half way on the stop pedal.

Gone a pedal switch now and havnt looked back

[Peter Jones]

In case one pressure circuit fails your brake lights will still work.

In some wiring scenarios a loss of pressure at one switch will also light the brake warning light on the dash.

[Garbon]

Hi Pete

My brake lights still work, which is great however the top dash brake light came on yesterday, I just pulled the passenger side wheel off and the disc is loose what do I need to tighten to get this snug again? I had a grinding noise yesterday on this wheel when driving the car.

[Garbon]

I think I worked it out, I tightened the centre nut which seemed to have fastened it again

[Garbon]

I think that I need to tighten the driveshaft nut some more as it is still grinding on the passenger front wheel? Is this correct?

I disconnected the battery for a few minutes and the top red brake light on the dash went off as well. I also adjusted the rear brake shoes and hand brake cables on the weekend, brakes feel a little better now but still a bit spongey

Time for a brake bleed...

[Golfer_76]

if your front center nut was loose you might need to fork out for a new wheel bearing. they dont like to be driven on when they're loose.
how tight did you do the front nut up out of curiousity?

Tim

[Preen59]

If your axle nut has come loose (and they shouldn't unless the bearing fails), your wheel bearing is now shot. Unfortunately you don't get a second chance with them..

[gldgti]

^^yup

needs to be VERY tight. What works for me is my weight (105kg) on my long breaker bar (500mm) with a decent bit of "bouncing" until its RFT.

And, it will certainly be failed now, you'll have to replace unfortunately.

[wai]

I think I worked it out, I tightened the centre nut which seemed to have fastened it again

More importantly you need to work out why it has come loose.

These nuts are either castelated or have some other locking mechanism to stop them coming loose. You could well have worn bearings or something else. My recommendation would be to have it checked out by a mechanic. Better to get it checked and fixed now rather than it suddenly breaking down.

[Spyda]

Id say it would have come loose from a bad wheel bearing in the first place or someone not tightening it correctly to begin with.

The pressure switches on the master cylinder suck, according to most people they fail often and replacing them requires brake bleeding.

http://www.vwwatercooled.org.au/forums/f13/how-wire-mechnical-brake-switch-your-mk1-55356.html

[Garbon]

Hey thanks for all of the replies

Looks like I'll have to replace the wheel bearing, I could only hand tighten the centre nut so thats probably why it came loose again. I cannot see anything to hold it tight on the drive shaft...

Could it be missing something, I noticed on the rear drums that there was a cotter pin (or something) that was bent to hold the nut on the shaft

I guess I need to ensure it does not come loose again in future, what do I need to look for exactly?

Thanks

[Golfer_76]

dont know about everyone elses but the center nut on my mk1 is slightly out of round which almost acts like a lock nut.
it needs to be done up really tight. you need someone with their foot on the brake and a decent size breaker bar to do it up to whats recommended.

[Preen59]

They utilise squash nuts as a way of locking. If it is done up correctly (like Aydan said, RFT), it should not come loose. The only time they loosen is when the bearing fails, if everything has been done right.

Good move to just replace it, Garbon. Wheel bearings aren't a "I'll get to that next service" type of item.


FYI, the other day I had to use a 2 metre long length of 50x50 RHS on the end of my old man's 3/4 drive breaker bar to get the drive shaft nut undone on a Volvo station wagon while he sat in the car with his foot on the brakes as hard as he possibly could push.. So that'll give you an idea of how tight they can be.

[wai]

They utilise squash nuts as a way of locking. If it is done up correctly (like Aydan said, RFT), it should not come loose. The only time they loosen is when the bearing fails, if everything has been done right.

Good move to just replace it, Garbon. Wheel bearings aren't a "I'll get to that next service" type of item.

This being the case, shouldn't the nut be replaced each time as the ability to deform to lock is lost?