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Darn Brakes Again

 
Old 06-04-2019, 07:25 PM
  #21  
Techoca
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That seems reasonable Craig, looking forward to hearing from you after the MC rebuild, I believe it’s likely that will solve your issue.
Eddy
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Old 06-04-2019, 08:17 PM
  #22  
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Originally Posted by Street Rat View Post
mrvette I have been contemplating adding the Wilwood mc and control valve to the system. I think that would do away with the prop valve and allow front to rear brake bias adjustment.

BUT

What am I looking at price wise for a Hydroboost set up? I'm simply curious as I have been reading threads where guys are doing this conversion.

Craig
My HB came from a junkyard pick, too long ago for me to remember what vehicle it's from....

sorry, but another thread will get you an answer for sure.....
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Old 06-04-2019, 08:37 PM
  #23  
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Originally Posted by Street Rat View Post
This afternoon I got the rear of the car in the air as in the video link in cagatzman's post above.

The first thing that I noticed when I opened the master cylinder was dark fluid in the rear reservoir.

One of the points in the videos were to check the interior reservoir ports for blockage.
Hell I couldn't even see the ports in the rear reservoir. I had to take some brake fluid out to see the ports. I poked a paperclip in the ports and everything felt clear.
I'm suspecting something is wrong with the master cylinder seals in the rear at this point.

I go ahead and check for bubbles coming from the rear interior mc ports with the rear of the car up. No bubbles are released.

I went ahead and bled the right rear caliper with the Motive bleeder. Everything seemed to be going well until I came back to check on the pressure bleeder.
There was a puddle of fluid under the front of the car.
I checked the prop valve connections. All were dry.

The culprit seems to be the master cylinder as I see fluid being released from the rear of the mc mounting area.

I purchased a mc rebuild kit from CSSB and it has arrived.

So the next chapter is to rebuild the mc tomorrow and try things again.

Craig
When you have the M/C apart, look for pitting in the bore of the M/C. It must be smooth and pit free.
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Old 06-04-2019, 09:58 PM
  #24  
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Originally Posted by Fredtoo View Post
When you have the M/C apart, look for pitting in the bore of the M/C. It must be smooth and pit free.

Cheap to buy a new chrome Master cylinder as well. That cured my brake issue.
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Old 06-05-2019, 09:36 AM
  #25  
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Originally Posted by Fredtoo View Post
When you have the M/C apart, look for pitting in the bore of the M/C. It must be smooth and pit free.
The cylinder looks perfect and by the way so did the rubber on the pistons.

I hope I'm headed down the correct path.

Craig
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Old 06-05-2019, 05:53 PM
  #26  
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Default Another Set Back

I put the mc kit in today and bench bled the master cylinder. Got the mc on the car and proceeded to the rr caliper to start the bleeding process. As soon as I applied pressure to the mc with the Motive bleeder I had a puddle under the car. It's coming from the rear of the mc OR the seal on the Motive adapter plate is leaking. Mine is in pretty bad shape but has been working fine. I ordered a couple of new adapter gaskets from Motive today.

So no bleeding until I plug the mc ports and stomp on the pedal a few times to see if it holds or leaks. I'm just a little burned out to proceed today.

Hell who am I kidding?

I'm ordering a Wiwood mc kit right now.

I am so tired of this crap.

The saga continues on.

Craig
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Old 06-05-2019, 06:13 PM
  #27  
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Sorry to hear of your continuing brake troubles.

When you get your new MC (or want to bang your head against the wall a bit more), I found that the Motive system always leaks, unless it's clamped. The chains are worthless. I've used a wood clamp (pictured), but now I use a big one-hand pistol-grip clamp. Equally important, I don't put brake fluid in the Motive reservoir. I just use it to provide (air) pressure, and I keep taking the lid off to add more fluid, hence the one-hand clamp instead of the (stronger) wood-clamp.

I hope it helps, and I hope you get to the bottom of this soon!

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Old 06-05-2019, 06:18 PM
  #28  
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On my 75, I had a similar problem. TWO...yes TWO faulty master cylinders. The third one fixed the problem. I went nuts because the first thing you mentally eliminate, is anything you just bought.
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Old 06-05-2019, 07:21 PM
  #29  
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Originally Posted by Bikespace View Post
Sorry to hear of your continuing brake troubles.

When you get your new MC (or want to bang your head against the wall a bit more), I found that the Motive system always leaks, unless it's clamped.
I have to purchase a different adapter plate for the Wilwood master cylinder that I just ordered. Go figure.

I use a two by four and a large c-clamp to mount the cap. I think that's the problem with my gasket. I put too much pressure on the cap and destroyed the gasket.

I'm going to try to get this factory system going one more time. If I get frustrated I'll just open the Wilwood kit and start some real fun.
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Old 06-05-2019, 07:34 PM
  #30  
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Is there any reason that you can't modify a spare master cylinder cap to use with the Motive bleeder?
They seem to seal pretty tight with the spring clips.
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Old 06-05-2019, 07:42 PM
  #31  
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Originally Posted by Street Rat View Post
I have to purchase a different adapter plate for the Wilwood master cylinder that I just ordered. Go figure.

I use a two by four and a large c-clamp to mount the cap. I think that's the problem with my gasket. I put too much pressure on the cap and destroyed the gasket.

I'm going to try to get this factory system going one more time. If I get frustrated I'll just open the Wilwood kit and start some real fun.
Sorry to hear about your brake problems Craig. I did not upgrade but rebuilt all my calipers when I did the suspension 2 years ago and replaced a leaking MC. Had a failure on one rear caliper 6 months ago and just bought a rebuilt locally. I used a similar brake bleeding method, starting with the right rear outer, inner, same on left rear, then front right and front left. All using a one man brake bleeder and my foot pumping the pedal. Got the brakes really hard and not spongy. I did upgrade all of the brake hoses to SS which really firmed things up as well.

Good luck, keep that 81 beauty going!

Randy
1981 Vette
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Old 06-06-2019, 09:22 AM
  #32  
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Originally Posted by Fredtoo View Post
Is there any reason that you can't modify a spare master cylinder cap to use with the Motive bleeder?
They seem to seal pretty tight with the spring clips.
I certainly could do that.
I'm getting ready to use some closed cell foam on the Motive bleeder cap. I'll see if I can get it to work prior to my new gasket arriving.
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Old 06-06-2019, 09:32 AM
  #33  
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Originally Posted by Street Rat View Post
I have to purchase a different adapter plate for the Wilwood master cylinder that I just ordered. Go figure.

I use a two by four and a large c-clamp to mount the cap. I think that's the problem with my gasket. I put too much pressure on the cap and destroyed the gasket.

I'm going to try to get this factory system going one more time. If I get frustrated I'll just open the Wilwood kit and start some real fun.

I found another way to solve the brake problems on the C3

https://www.macmulkin.net/corvette-inventory#close
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Old 06-06-2019, 04:49 PM
  #34  
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Default The Last Straw - Almost

Plan A -Well it's a fact that the gasket on the motive bleeder was worn out. I tried to replace it with some closed cell foam that I had. It spewed fluid out as soon as I applied pressure to it. The factory gasket is on order.Then I plugged the mc ports and applied the pedal. I got a rock hard solid pedal. Master cylinder checks ok.

Plan B -So on to the old pedal method of bleeding. I ended up with a harder pedal than what I have had. I am not satisfied with the still spongy feel though.

Plan C - A new adapter plate for the Wilwood mc (on order) is arriving today. It should fit the factory type mc. When it arrives I'm going to try another pressure bleed on the system.
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Old 06-06-2019, 04:54 PM
  #35  
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If you have new calipers and new pads, the soft ish pedal could be kind of normal.

Assuming the brakes stop the car, you may want to put some miles on it to get the pads bedded in and laying flat on the rotors.
Re-bleed the calipers at that time to remove any residual air.

Once the pads wear off the surface fuzz and bed in, the pedal should get better.
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Old 06-06-2019, 05:04 PM
  #36  
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Originally Posted by Street Rat View Post
I have to purchase a different adapter plate for the Wilwood master cylinder that I just ordered. Go figure.
While I have adequate brakes (Wilwood all around, including the MC), the pedal moves a bit before I get pressure building. Since the Wilwood MC cover has two pinholes and is sort of thick, I too (as in FredToo) am thinking it would be easy enough to enlarge and rethread the holes for compressed air fittings for the next time I bleed the brakes. I don't see why that wouldn't suffice, rather than somebody's adapter plate!

And, again as Fred has noticed, the brakes seem to get better with some use.
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Old 06-07-2019, 08:53 AM
  #37  
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Originally Posted by Street Rat View Post
Plan C - A new adapter plate for the Wilwood mc (on order) is arriving today. It should fit the factory type mc. When it arrives I'm going to try another pressure bleed on the system.
The new adapter plate for the Wilwood master cylinder is too long. The ports on the adapter were too far apart for the factory mc. Fluid sprayed from the top of the mc and seal.

I took the gasket off of the new adapter plate and modified it to fit the adapter for the factory mc. I proceeded with the bleeding procedure. The pressure held and there were no leaks around the lip of the mc.

I got all of the calipers done. Although the right front outer Wilwood caliper bleeder took for ever to evacuate the air.

The pedal feels better but I'm soliciting opinions from my son and wife as to the firmness of the pedal. They both agree that the pedal is much firmer than previously.

Today I'm going to put the wheels back on and go for a test drive.

Fingerers crossed.

Last edited by Street Rat; 06-07-2019 at 08:54 AM.
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Old 06-07-2019, 10:28 AM
  #38  
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Originally Posted by ignatz View Post
While I have adequate brakes (Wilwood all around, including the MC), the pedal moves a bit before I get pressure building. Since the Wilwood MC cover has two pinholes and is sort of thick, I too (as in FredToo) am thinking it would be easy enough to enlarge and rethread the holes for compressed air fittings for the next time I bleed the brakes. I don't see why that wouldn't suffice, rather than somebody's adapter plate!

And, again as Fred has noticed, the brakes seem to get better with some use.
Get some c- channel steel and mount fittings for your air compressor. Use gasket material between the c-channel and the MC. Make holes in the gasket were the air compressor fittings are cut. I have a shutoff fitting which I can move to close off the circuit I don't want to bleed.


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Old 06-07-2019, 12:57 PM
  #39  
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Default Finally Success

Test drove her this morning and the brakes are great.

This is the firmest brake pedal that this car has had in the six years that I've owned it.

The problem was definitely too much air in the system.

I contribute the good pedal to the following...
1. A thorough bench bleed of the master cylinder in a level, tilted forward, and a tilted rear position.
2. A thorough bleeding of the system following the correct bleeding procedure. The system had a moderate amount of air in it. Particularly in the Wilwood right front caliper.
3.Lifting the rear of the car as cagatzmann showed in a previous post, and forcing air out of the rear of the master cylinder reservoir. I actually didn't expect to get anymore air bubbles after the mc bench bleed. To my surprise I got two more air bubbles out of the back reservoir.
4. Patience. Some of the evacuated calipers took quite a bit of time to get ALL of the air out.

Thank you all for following the seemingly endless saga.

Craig

Last edited by Street Rat; 06-08-2019 at 09:39 AM.
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Old 06-07-2019, 01:00 PM
  #40  
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Awesome! Now go drive the hell out of it!
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