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I was changing the fuel filter on my 82CE and, as usual, I was giving everything under there a good look over.
I noticed there was a plug with a brown/white wire on top of brake proportioner. The plug was pulled out and sitting on top. I plugged it back in.
I have been having no issues with the brakes. They have been working great since I got the car several weeks ago. I test drove the car for several miles Nanking numerous slow and sudden stops. No difference - still great brakes.
I think this has something to do with the brake warning light and giving a warning when there is a problem.
please correct me if wrong. How did the plug come off, is the question.
It could have fallen off accidentally or someone pulled it off to turn off the warning light.
If someone did pull it off intentionally the original problem may have been corrected afterwards and nobody plugged it back in.
It's not a proportioning valve in our cars with 4-wheel disc brakes. The experts call it a "distribution block" or something like that. The electrical connection provides a ground to the brake light if there is a significant pressure imbalance between the front and rear systems.
It's not a proportioning valve in our cars with 4-wheel disc brakes. The experts call it a "distribution block" or something like that. The electrical connection provides a ground to the brake light if there is a significant pressure imbalance between the front and rear systems.
Got it. It was kinda of a PIA to get it to snap in. The block looks like it has been replaced at some point. May not have gone in all the way.
It would be good to know that the re-connected wire was truly functional. If you remove it from the distribution block and rig a way to make electrical contact between that wire connector and chassis ground, the BRAKE warning light should light on your dash. If so, reconnect it normally. You should be fine.
If it does not illuminate (ignition on, engine off), that explains why the wire was disconnected. It isn't operational.
All the vendors label it as a Proportioning Valve and rightfully so.
A distribution block is usually a brass fitting or junction with EQUAL brake line pressure going in, and going out in two or three directions. Equal distribution. Its a very common part near the rear axle when both rear calipers feed off of one line.
A Proportioning Valve does exactly that. It detects a brake failure and loss of pressure in one direction or line and Proportions the brake fluid to another line.
This keeps the vehicle from loosing the entire brake system. The little spring / piston or shuttle inside proportions brake line pressures.
One parts name makes sense, one doesn't. But you can call it what you want.
Last edited by HeadsU.P.; Jun 21, 2020 at 08:06 PM.
There are three grounding paths for the brake light on the dash. Make sure they all work. The VA inspector was familiar enough with C3s to make sure that it operated correctly.
1. Ignition switch: During startup, the brake light should flash on the dash. This ensures that the bulb is functioning (avoids false negatives).
2. Combination valve switch (or whatever you want to call it). As suggested, pull the plug back off, and ground to chassis. The brake light should light.
3. Parking brake switch: If you pull up a notch or two, the brake light should light.
A "proportioning valve" sets the brake bias for the vehicle (proportion of braking pressure that is sent to the back wheels vs. the front wheels). It can be 'fixed' percentage or it can be adjustable bias valve. The DISTRIBUTION BLOCK in the C3 sends 50% to the front and rear. But, the purpose of that block is to shut off brake fluid flow to a section of the system when a leak is detected.
The section with a leak will have some brake fluid flow, so the shuttle valve in the distribution block will move with that flow to close off further pressure to that part of the system. NO BRAKES in that half of the system; but no further loss of brake fluid & no loss of braking in the other half of the system.
The vendors can call it whatever they want....but that doesn't mean they are correct with their terminology. But, as C3 owners, WE should know what it really is.....shouldn't we????
Yup. I found some other "errors" in my 77 repair manual also.
Combo Valve has a nice ring to it though.
PropCom?
ComProp?
Combo-Propo?
Yes, the later C3 repair manuals retain some of the generic nature of the shop manuals (covering all models) that came before them. With the Corvette the only Chevrolet with 4-wheel disc brakes in the C3 era (excepting the 1982 Camaro as a rare option) the manual was correct for millions of cars.
The vendors can call it whatever they want....but that doesn't mean they are correct with their terminology. But, as C3 owners, WE should know what it really is.....shouldn't we????
Plug on brake proportioner
