I have a 77 c3 and I bought it from an estate sale and It was quite a mess and sat for a year or two, anyhow I replaced all the brake calapers and had problem with the rear not working, so I replaced the master and they are working but not to well , getting the brake light in the dash I have gravity bleed and did the pumping thing and there is no air in the system I removed dismantled and inspected the paportioning valve and cant see anything that could be wrong with it, if I just drive the thing around will it come around, I have had about 6or7 c3's and have done brakes on allmost all of them and never had this problem any help would be Great Thanks>>>>>>>>>>>>>> Greg

 

Keep in mind, that what you're describing as a proportioning valve is not really a proportioning valve. It does however control the brake light in that when one side of it experiences a loss of pressure, it pushes the valve in that direction and turns on the brake light.

The procedures on how to center the valve (turn out the light) are in any of the better service manuals. Essentially what you do is open a bleeder (front or rear as required) while depressing the brake pedal and the valve should center and the light go out. Have your pedal "depressor" watch the light as you open the bleeder.

You didn't mention if your car has power brakes, the condition of your flexible brake hoses or if you used silicone brake fluid (sorry I used that contentious word).

If you have manual brakes by some fluke, as power was standard on 77's, you will not experience the typical braking action. While the manual brakes are more than adequate, they require an unexpected amount of pedal pressure and most are either surprised or disappointed in the braking action. Before I get jumped, let me say I have manual brakes on my 1973 and am very satisfied with them, but they do require getting used to.

What is the condition of your flexible brake hoses? If they are the original ones (it's possible), they could be weak and expanding as you use your brakes. This will result in a spongy brake pedal. The braided steel lines from almost any of the vendors are a great upgrade for little more than the cost of original ones.

If you used silicone brake fluid then you could be encountering some of the difficulty that others have run into when bleeding their brakes with silicone. Because silicone aerates much more than hydraulic brake fluid, you need to depress the pedal more deliberately to avoid agitating the fluid. It's also a good idea to wait a day after completely bleeding the brakes and doing it one more time.

I have used silicone brake fluid for more than 20 years in my vehicles where I feel it's appropriate and have never encountered a problem. I am a bit more vigilant and attentive in doing so, but the results have always been worth the effort in zero maintenance on cars that sometimes sit for a year or more.

GUSTO

 

don't mean to hijack the thread, but GUSTO had a lot of good points so I thought I would ask a question as well. Last night I tried to adjust Parking brake and ended up pulling the caliper and rotor to get to it. Once I got it all back together the "BRAKE" light was illuminated and I had no brakes.

Did I dork something up? or

do I just need to bleed the brakes?

thanks for the help,
Oscar

 

Oscar,

Unless you removed the brake line from the caliper when you removed it, I'm not sure how pulling the caliper and rotor would lead to this problem. Because your brake light came on, I would guess either you did disconnect the brake line or you somehow introduced air into the system.

I would certainly start with a good brake bleeding, in the correct order. Remember the rear calipers must be bled from both bleeders. Have your assistant watch the brake light while you're doing this and you should see the light go out at some point. If it doesn't, you can also turn it off by "cracking" the fittings at the master cylinder one at a time. If you try this at the master cylinder, crack the fitting gently and be prepared to close it quickly so the valve doesn't move to the other side. (The light will go out then come right back on.) If it does, try it again, but use the other fitting. Also be sure to place some paper towels or shop rags under the master cylinder if you do this to keep the brake fluid from making a mess.

If all else fails, you can call Bill Poggi in Aquia Harbor 720-6230 and he can help.

GUSTO

 

Well the flexable hoses are the original so you meen they could be balooning?? and making the brakes spongy I will have to check that one out tonight And the brakes are Power I think the fluid is just dot 3 or 4 I don't think it is silicone I will check that

 

Yes, that is what will happen if they are original.

If you decide to replace the lines it is a good time to flush the system with new brake fluid in case you didn't flush it completely when you did the brake job.

There was an earlier post on how much trouble it was to remove the flexible lines from the hard lines, especially on the front. I have had problems on older cars with original lines that had corroded severly. Use a good lubricant like PB Blaster, CRC 5-56 or any other quality product well before hand to make the project go easier. I can't stress enough how important it is to use a top quality fitting wrench first. Since these are always tight, they are particularly prone to rounding off so do not start with a regular wrench, even a quality one. Start with the best fitting wrench you can buy (there is only one that comes to mind) and you will stand the best chance of removing it without having to replace the line and fitting. I hear people complaign all the time about the cost of these tools, but rounding off bolts or fittings can be expensive and time consuming and it just doesn't happen when you use them.

Sometimes the line and the fitting will rust together and in spite of your best efforts, the steel line will be so weakened by rust, it will twist off. You can try bending your own new line, most good autoparts places carry everything you need to do this, or you can purchase a new from one of the forum vendors. I would recommend if you go this route, only buy the stainless steel lines.

Good luck...

GUSTO

 

Your brake lines should be suspect since they are at least 28 years old. I would replace them before I drove that car again. If you have the 1977 GM Service Manual, most of the things you need are in that. You may not find the Haynes or Chilton's adequate for the quality and depth of material you are looking for.

Gayr

 

Gusto,

thanks for all the info- I just got back from 4 hours in the auto shop on base and now the brake pedal is nice and firm - went around the car twice - also managed to remove and clean both adjusters for the P brake and now it works as well. Last night really sucked leaving my car sitting outside at the garage. Today was lucky day. I ran into a guy at the shop who had a 79 and he showed me everything. Nothing like having a someone with experience to lend a hand.
anyway, thanks again for the tips.

Oscar