Need help replacing the pressure
Thread Starter
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Joined: Sep 2004
Posts: 505
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From: Guntersville Alabama
Need help replacing the pressure
differential warning switch. It is located on the master clylinder. The old one was leaking tremendously. I bought a new one and it leaks as much as the old one. Does anyone have any tips on how to stop this leak. It is hard to believe I installed wrong. The car is a 93 vert with LT1. Thanks for your help.
93cruiser
93cruiser
Le Mans Master
Joined: Mar 2004
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From: Ft. Lauderdale Fl
differential warning switch. It is located on the master clylinder. The old one was leaking tremendously. I bought a new one and it leaks as much as the old one. Does anyone have any tips on how to stop this leak. It is hard to believe I installed wrong. The car is a 93 vert with LT1. Thanks for your help.
93cruiser
93cruiser
Intermediate
Joined: Apr 2007
Posts: 35
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From: Sandusky Ohio
switch
I don't know, I've been through 4 of these and all leaked. on another thread someone mentioned buying a plastic bolt like they use on toilet seats and putting it in the spot, gonna try this when i get time. I ordered a sevice manual on this car and hope I can figure out what I'm doing wrong.
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From: Guntersville Alabama
The service manual says not remove the spring from the housing and only hand tighten the assembly in the master cylinder. If my latest attempt does not work I will plug mine also. If I have to make this I will make you one as well. Thanks for the reply
93cruiser
93cruiser
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Maybe this part isn't supposed to be see high pressure, and one of the seals on your combination valve is bad.
I may be completely wrong about this, I'm just speculating that maybe the pressure switch isn't the problem. After all, it's just a little piece of plastic, is it supposed to be subjected to 1200 psi? It's worth checking into at least.
Does the brake light come on the dash? Does pressure cause this warning switch to ground out?
It's best to make sure you know what you're talking about before making an *** or yourself.
I may be completely wrong about this, I'm just speculating that maybe the pressure switch isn't the problem. After all, it's just a little piece of plastic, is it supposed to be subjected to 1200 psi? It's worth checking into at least.
Does the brake light come on the dash? Does pressure cause this warning switch to ground out?
Originally Posted by elefkow
Differential warning switch located on the master cylinder leaking? Thats a good one. Thanks.
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Joined: Sep 2000
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From: The Top of Utah
Originally Posted by CentralCoaster
Quote:
Originally Posted by elefkow
Differential warning switch located on the master cylinder leaking? Thats a good one. Thanks
It's best to make sure you know what you're talking about before making an *** or yourself.
Originally Posted by elefkow
Differential warning switch located on the master cylinder leaking? Thats a good one. Thanks
It's best to make sure you know what you're talking about before making an *** or yourself.
When used in reference to a brake system, "differential" is short hand for PRESSURE DIFFERENTIAL. It refers to the difference in pressure between the front and rear brake hydraulic systems. Making fun of the term "differential warning switch". Ha Ha.
"Thats a good one"!RACE ON!!!
Team Owner
Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
On many straight axle vehicles, it also functions as a differential warning switch. If the differential falls off of the vehicle the warning light will come on, this is because your rear brakes lines are attached to it, (and thus no longer attached to the car.)
Last edited by CentralCoaster; May 3, 2007 at 06:56 PM.
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Thread Starter
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Joined: Sep 2004
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From: Guntersville Alabama
The Brake light does come on only when the enough fluid has leaked out of the reservoir for the fluid level detector switch to trip the light. The ASR and ABS service light comes on as well. After adding fluid the service lights and brake light go away. Again, I believe this is caused by the fluid level in the resevoir.
I hear what you are saying about the proportional valve causing a problem. Can you expound on the symptons that would be prevalent with this type of problem. The manual says that if there is a failure in the brake system that causes the warning switch to latch and indicate a fault then the fault would need to be repaired and then apply a high braking force to reset the switch. I do not believe the switch has been triggered by such a failure. The car brakes and stops very well. I am just loosing a lot of fluid through the switch, not around the threads but through the switch connector. This tells me that the seal on the switch is not sealing. It will require removing the MC to investigate this area.
The next logical step is to remove the MC and check the sealing surface for the warning switch. Thanks for your reply.
93cruiser
I hear what you are saying about the proportional valve causing a problem. Can you expound on the symptons that would be prevalent with this type of problem. The manual says that if there is a failure in the brake system that causes the warning switch to latch and indicate a fault then the fault would need to be repaired and then apply a high braking force to reset the switch. I do not believe the switch has been triggered by such a failure. The car brakes and stops very well. I am just loosing a lot of fluid through the switch, not around the threads but through the switch connector. This tells me that the seal on the switch is not sealing. It will require removing the MC to investigate this area.
The next logical step is to remove the MC and check the sealing surface for the warning switch. Thanks for your reply.
93cruiser
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Joined: Sep 2004
Posts: 505
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From: Guntersville Alabama
Maybe this part isn't supposed to be see high pressure, and one of the seals on your combination valve is bad.
I may be completely wrong about this, I'm just speculating that maybe the pressure switch isn't the problem. After all, it's just a little piece of plastic, is it supposed to be subjected to 1200 psi? It's worth checking into at least.
Does the brake light come on the dash? Does pressure cause this warning switch to ground out?
It's best to make sure you know what you're talking about before making an *** or yourself.
I may be completely wrong about this, I'm just speculating that maybe the pressure switch isn't the problem. After all, it's just a little piece of plastic, is it supposed to be subjected to 1200 psi? It's worth checking into at least.
Does the brake light come on the dash? Does pressure cause this warning switch to ground out?
It's best to make sure you know what you're talking about before making an *** or yourself.
To answer your second question. The switch seems to be shorted under normal circumstances. The spring makes the connection. I will check continuity this weekend to confim this belief.
93cruiser
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From: Guntersville Alabama
93cruiser
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From: The Top of Utah
I think what CC is saying here, is that while the switch is leaking, it isn't so much that the switch is defective, but that the switch is being subjected to pressures it wasn't designed to contain. I'm not sure of this, but I tend to agree. I think the REAL problem may be with the seals on the combination/proportioning valve piston, inside of the master cylinder.
RACE ON!!!
RACE ON!!!
Last edited by CFI-EFI; May 3, 2007 at 08:11 PM.
Thread Starter
Pro
Joined: Sep 2004
Posts: 505
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From: Guntersville Alabama
I think what CC is saying here, is that while the switch is leaking, it isn't so much that the switch is defective, but that the switch is being subjected to pressures it wasn't designed to contain. I'm not sure of this, but I tend to agree. I think the REAL problem may be with the seals on the combination/proportioning valve piston, inside of the master cylinder.
RACE ON!!!
RACE ON!!!
Yea, I agree that the switch is not the problem. I was hoping maybe that I installed it wrong. Anyhow, I will check out the MC. I do appreciate the constructive replies. This forum is a fantactic tool for shade tree mechanics to work on a fairly sophisticated vehicle.
93cruiser
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From: Phoenix AZ
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differential press switch
I broke the end off of mine removing the booster. I went to a wrecking yard, with the end still broken off, no leakage, and replaced it at home when I could get a proper tool in there to remove it.
There's a spring, a piston follower, and the switch body.
There is no pressure there unless your master cylinder is leaking at the combination valve.
When I broke it off, there was no fluid, and still, it's a plastic switch body. The plastic might be good for maybe 100 psi if that. If yours is leaking, you need a master cylinder!!!
BTW, it's not a pressure switch. The little rod rides in a groove. if the pressure is not correct to either the front or back, the groove slides one way or the other, and the rod moves up, and touches the wire pin, and grounds the light so the bulb can illuminate. no pressure involved in the switch operation.
There's a spring, a piston follower, and the switch body.
There is no pressure there unless your master cylinder is leaking at the combination valve.
When I broke it off, there was no fluid, and still, it's a plastic switch body. The plastic might be good for maybe 100 psi if that. If yours is leaking, you need a master cylinder!!!
BTW, it's not a pressure switch. The little rod rides in a groove. if the pressure is not correct to either the front or back, the groove slides one way or the other, and the rod moves up, and touches the wire pin, and grounds the light so the bulb can illuminate. no pressure involved in the switch operation.
Last edited by coupeguy2001; May 5, 2007 at 01:31 AM.
Le Mans Master
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From: Less Talk, More WOT | Houston TX
Don't plug that switch! Its important for your safety it can be the difference between having 50% braking and 0% braking if you have a failure. Trust me, I know. 
Team Owner
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
