Help! Drove car to work. Towed back home

[rbryce]

Beginning to think that the simplest thing to do is to just throw money at it !!!

 

[JohnZ]

Do you have any pedal free play from its rest position to where you feel initial resistance when you press on the pedal? You MUST have 1/16" to 1/4" of pedal movement before you feel resistance; if there's no pedal free play, the master cylinder pistons may not return fully and open the compensating ports. The pushrod from the booster (or from the master cylinder if you don't have power brakes) to the pedal clevis is threaded to provide this adjustment.

 

[JohnGrawcock]

Let me ask this question. It seems like the discussion is either hoses (not likely to me that since each caliper has it's own hose, more than one hose would be failing at the exact time to cause the locking of both front brakes), the proportioning valve, the master cylinder or the booster. Since it was also brought up that this year corvette does not have a separate proportioning valve, that sort of eliminates that! One comment was that the brakes were both locked up and the brake pedal could not be released. What is the one thing that will cause BOTH to occur? Since the master cylinder and the booster are two separate parts, will a failure of the master cause a lockup in the booster to prevent the pedal from returning? I'm not an expert on all of these, but it seems to me that if the master has locked up, the booster, not being internally physically connected to the master cylinder, would return to it's previous state and release the pedal. Since the pedal was reported to have been locked up as well, would that point to the booster more than the master cylinder? :confused

rbryce,

You are correct. The brake pedal connects to a push rod that controls the valves of the booster. It is not mechanically connected to the master cylinder. The pedal should return to the off position even with the master cylinder stuck fully on.

That said, a good test would be to recreate the lock-up condition and then pull the check valve out of the front of the booster. I'm betting the brakes and brake pedal will both be released.

 

[White75]

I haven't got to play with it much over the weekend because my local parts suppliers were all closed. I have full pedal now that things are cold and it has the correct pedal travel according to the replies on here. I haven't pulled the cylinder or disconnected it from the booster. (I have done the booster before in the 75 and it was a bitch but I can do it again if necessary although I don't want to).
After I pumped the brakes a few times, I definitely think there is some BAD fluid in the system. The stuff that came back into the reservoir looks worse than the stuff washing up on the gulf coast and has just about the same consistency. I am pretty certain that stuff is not a good viscosity for brake fluid and could have clogged any number of valves or lines. I'm going to give it a good flushing and probably swap the MC out for good measure since it's quite rusty when I get some time. I'll have to take a pic of the fluid and post it up.

 

[White75]

rbryce,

You are correct. The brake pedal connects to a push rod that controls the valves of the booster. It is not mechanically connected to the master cylinder. The pedal should return to the off position even with the master cylinder stuck fully on.

That said, a good test would be to recreate the lock-up condition and then pull the check valve out of the front of the booster. I'm betting the brakes and brake pedal will both be released.

I did pull the check valve when the brake wouldn't release and it did nothing.
The only thing that released the brakes enough to drive it off was to loosen the lines from the MC and release the pressure from the lines, they spewed like a geyser and came from the lines, not the MC)

 

[Vettehead Mikey]

So I guess getting this diagnosed and fixed is not a priority huh?

 

[White75]

So I guess getting this diagnosed and fixed is not a priority huh?

Not really. Not a daily driver. Also have to pick up/order the parts. Plus lack of time to work on it, got a little one that takes up a lot of my time and a wife that is having to spend time away from us do to a family emergency so I have to watch the baby who crawls and gets into everything.
On top of that, I have a BMW that is giving me fits with a sparkplug that won't stay threaded and it's blocking the other vette. I want to get it fixed up so I can get it sold and focus on the vettes. Got 5 cars and only 2 can be driven.

 

[White75]

Here are the pics:

 

[petes74ttop]

YUK! That M/C is shot. The pistons inside thar M/C are getting stuck on all that rust.

 

[rbryce]

I agree. I wouldn't even consider trying a rebuild on this puppy. REPLACE IT. And flush your brake lines to remove any goo. I would also rebuild both front brake calipers as this could be contributing to causing the brakes to lock up as well if this stuff is preventing the pistons from moving freely. Flush the rear lines to check for any contamination in the rear circuit and deal with that also. Corvettes stock brake lines are steel, not stainless steel, and yours could be practically rusted through from the inside out. After all the troubleshooting to date, can't believe this pile of goo in the master has just been noticed. Even if there is a problem in the booster not related to this, the master and possibly the rest of the brake system must be dealt with at any cost.

 

[White75]

I agree. I wouldn't even consider trying a rebuild on this puppy. REPLACE IT. And flush your brake lines to remove any goo. I would also rebuild both front brake calipers as this could be contributing to causing the brakes to lock up as well if this stuff is preventing the pistons from moving freely. Flush the rear lines to check for any contamination in the rear circuit and deal with that also. Corvettes stock brake lines are steel, not stainless steel, and yours could be practically rusted through from the inside out. After all the troubleshooting to date, can't believe this pile of goo in the master has just been noticed. Even if there is a problem in the booster not related to this, the master and posibly the rest of the brake system must be dealt with at any cost.

When I got the car, I checked all the fluids and the brake fluid was clear. The calipers were replaced a few years ago and I am almost positive they are SS lined.
What's the best way to clean the lines since I want to to get all the junk out?

 

[Hib Halverson]

"rbryce" is correct.

You need to replace the master cylinder.

You can't clean the rust out of brake lines. I'd get one of them off and look at it. If the interior is badly rusted, you probably ought to look at replacing the brake pipes with stainless steel lines.

Even though your have sleeved calipers, I'd split all of them and clean them out because only the bores are sleeved. The rest of the interior of the the calipers which is exposed to brake fluid is cast iron.

Good luck on this project.

 

[rbryce]

I would (and have) replace all of the front and rear brake lines with new stainless steel brake lines. The front to rear line is a different story. It passes between the body and the transmission crossmember. You actually do need to lift the body from the frame to replace it if you want to do it in one piece. There are bendable stainless steel brake lines that can be flared for fittings, which you could build a two piece brake line with, but I have never tried it. In my case, it was a body off restore and I had access. If your car has a removable transmission crossmember, you may be able to replace it with a new one piece line, not sure. At a minimum I would replace all the other lines with stainless steel lines though, extremely cheap insurance, especially on a 35 +/- year old car.

 

[GerryLP]

White75,

this is one of those situations in which a picture would have been truly worth 1,000 words. Yes, I would agree with most in here that this is perhaps the culprit of your problems.

You would probably have to bite the bullet as they say and replace thos components. Good luck!

GerryLP :cool

 

[White75]

well I replaced the Master Cylinder and flushed the lines. Everything bled out good. The front fluid was really nasty with sludge but ran a bottle through and everything was clean about halfway through the bottle of fluid. I can now brake well and ran it through its paces up and down the street with no problems at all. I got a good, strong, full pedal so I am very happy.

Now I need to get the brake lights to turn off. any ideas?

 

[rbryce]

The brake lights work from a switch under the dash that can be adjusted by screwing it in or out. Look up under the dash on the brake pedal, it's a long cylinder looking thing about 3" long with a wire on it. It's probably out of adjustment now that the brake pedal is tight, staying shut and keeping the brake lights on.

 

[White75]

Well I jsut got out from under the dash and it appears that the switch has come loose from the bracket. the threads appear to be OK but they wont grab onto anything they should screw into. I can't get a better look at what I'm dealing with. What shoud it be screwing into? I tested the switch and the switch is fine electrically.

 

[rbryce]

Look at the link below. There should be two adjustable lock nuts on the switch. The switch does not thread into the bracket, the two lock nuts hold it in place and allow adjustment of the switch. Sounds like you may have lost one of the nuts.

https://www.paragoncorvette.com/p-350096-brake-light-switch.aspx

 

[White75]

Look at the link below. There should be two adjustable lock nuts on the switch. The switch does not thread into the bracket, the two lock nuts hold it in place and allow adjustment of the switch. Sounds like you may have lost one of the nuts.

https://www.paragoncorvette.com/p-350096-brake-light-switch.aspx

Thanks. Looks like I'm missing both nuts gonna see if I can find those nuts locally this weekend. Had a blast driving it today when I was checking the brakes, even if it was just up and down the street.
Gotta get it ready for the Collector Car Appreciation Day.

 

[tracksnblades1]

Glad you got her figured out. Just pick up a remanned master cylinder for a 79 with a different brake problem. Be careful, No numbers on the new casting, if your into the numbers. Good debate. I not stirring it, But I recall the well discussed check valves primary functions as a means to preserve and maintain stored vacuum to allow for full vacuum assist in conditions of little or no engine vacuum. This allows for full braking if you kill her on the hill an she's rolling down it. It allows for full braking after you ran her WOT to top speed and then gramma pull out of her lane. As well as Hib's mention of the next morning in the drive on the hill when you step down on the clutch to hold her there while firing her up.