Brake switch
Thread Starter
Race Director
Joined: Apr 2003
Posts: 17,699
Likes: 1,667
From: moraga ca
Brake switch
My brake switch on the master cylinder is starting to leak pretty well. I am not using it and I don't even have the connector plugged in. Is there a simple plug I can use to replace the thing? If so, what is the size and thread pitch? Otherwise, I will have to buy another switch to use as a plug. Thanks.
Team Owner
Joined: Sep 2003
Posts: 25,375
Likes: 2,734
My brake switch on the master cylinder is starting to leak pretty well. I am not using it and I don't even have the connector plugged in. Is there a simple plug I can use to replace the thing? If so, what is the size and thread pitch? Otherwise, I will have to buy another switch to use as a plug. Thanks.
The switch is still available and a GM #10074131. You might see if a dealer in the area has one on the shelf and check it with a screw pitch gauge or maybe someone here will accommodate you with one from a master. It does all C4's '84 - '95. I don't have a master to check or a switch to check.
Last edited by WVZR-1; Apr 6, 2013 at 07:38 PM.
Team Owner
Joined: Sep 2003
Posts: 20,176
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
The brake switch your refer to is the white switch screwed to the MC.?
There are no seals on the brake switch.
It detects movement of the shuttle valve between the front and rear pressure chambers of the MC.
If there is a pending failure of one of the systems, the shuttle will move causing the switch to engage and illuminate the brake warning lite.
If the warning lite is not illuminating, then the o-rings on the shuttle valve are leaking.
In your case the later is most likely the problem.
When the shuttle valve moves, it will block the fluid delivery to weak side.
Simply plugging the hole will not resolve problem.
There are no seals on the brake switch.
It detects movement of the shuttle valve between the front and rear pressure chambers of the MC.
If there is a pending failure of one of the systems, the shuttle will move causing the switch to engage and illuminate the brake warning lite.
If the warning lite is not illuminating, then the o-rings on the shuttle valve are leaking.
In your case the later is most likely the problem.
When the shuttle valve moves, it will block the fluid delivery to weak side.
Simply plugging the hole will not resolve problem.
Last edited by JrRifleCoach; Apr 6, 2013 at 11:38 PM.
Thread Starter
Race Director
Joined: Apr 2003
Posts: 17,699
Likes: 1,667
From: moraga ca
The brake fluid is leaking around the two terminals in the center of the switch. What does that mean? Is the switch shot or is it something in the master cylinder? Why can't the opening be plugged?
Team Owner
Joined: Sep 2003
Posts: 20,176
Likes: 673
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
#20 Combination piston O-ring seals are leaking, moving fluid out thru the warning switch #19
Just pull the switch on any normal MC and you'll find the bore dry.
Just pull the switch on any normal MC and you'll find the bore dry.
Last edited by JrRifleCoach; Apr 7, 2013 at 12:05 PM.
Safety Car
Joined: Aug 2009
Posts: 3,749
Likes: 275
From: Melbourne, Victoria, Australia
When my switch got broken the master cylinder did not leak at all, was a good couple of weeks before the new switch arrived.
Maybe better of getting a new master cylinder, if one seal is leaking there may be corrosion in the master cylinder. Only a matter of time before another problem pops up, like the dreaded sinking brake pedal at traffic lights(or drag strip in your case)
.
Thread Starter
Race Director
Joined: Apr 2003
Posts: 17,699
Likes: 1,667
From: moraga ca
When my switch got broken the master cylinder did not leak at all, was a good couple of weeks before the new switch arrived.
Maybe better of getting a new master cylinder, if one seal is leaking there may be corrosion in the master cylinder. Only a matter of time before another problem pops up, like the dreaded sinking brake pedal at traffic lights(or drag strip in your case)
.
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