mytrplseven

I replaced the rubber brake lines with stainless, and one from the firewall to the front pax side frame mount. All new pads, rotors, and checked the booster for input vacuum (10 psi) and checked that the booster holds 10 psi vacuum. I bled all the lines in the proper order and yet, I still have to stand on the brakes and they are very ineffective. They don't feel boosted and it takes about 1 1/2 inch play before engaging. What could I be missing?

T&T Racing

[QUOTE=mytrplseven;15544078]I replaced the rubber brake lines with stainless, and one from the firewall to the front pax side frame mount. All new pads, rotors, and checked the booster for input vacuum (10 psi) and checked that the booster holds 10 psi vacuum. I bled all the lines in the proper order and yet, I still have to stand on the brakes and they are very ineffective. They don't feel boosted and it takes about 1 1/2 inch play before engaging. What could I be missing?[/QUOTE
What procedure was used to bleed the brakes. The "play" indicates to me there is air in the brake system.

Otto Mechanic

I recently replaced my lines with stainless while doing a clutch job on the car as well. I did have to make several circuits around the car bleeding the calipers as well as bleeding the clutch slave cylinder. Getting all of the air out of it was challenging and repetitive work. At the time it was still possible to buy blue fluid to swap with amber to make sure I got a complete exchange of fluid on each try. I also used a hard plastic mallet to knock the calipers while bleeding them.

To get the last of the air out I bled the clutch slave cylinder from below, using a squeeze bottle to force fluid from the bleed nipple to the reserve tank. I also raised the rear of the car, bled all the calipers, then raised the front and bled them again.

mytrplseven

[QUOTE=T&T Racing;15544156]Motive Flow pressure bleeder.

mytrplseven

This used to be easy. Never thought I'd have to "burp" the system as well. Bleeding the clutch was challenging but in the end, successful. I guess I'll have to buy a gallon of dot 4 to finally and hopefully finish the brakes part of the restoration project.

T&T Racing

The Motive system is the way to go. If done per procedure all the air is driven out. Make sure your caliper bleed valve is open enough to get good fluid flow. If all that was done with at sufficient new fluid added to brake system

Maybe the issue is Brake MC.

mytrplseven

Looks like it's back up on the jack stands....again. I'll pull all the wheels, check the pads for possible glazing, and then kick myself for not replacing the master cylinder while I had it and the booster off. I may have to buy dot 4 by the case at this rate.

T&T Racing

If I was in your situation, try brake bleeding one more time before replacing MC. The Motive pressure should be about 10 psig and ensure the brake fluid is covering the pickup tube at all times. I place the Motive tank so it is on an incline with the pickup tube on the downward slope so all the brake fluid is at the end of the pickup tube

mytrplseven

I've been buying ATE 200 and plan to do occasional Xcross. Do you think normal Dot 4 would be ok or should I stick with the higher temp stuff? My plan is to try a few more bleeds and pull the pads to check (since I'm in there anyway) to see if there's any glazing of the pads. Replacing the MC would be my last resort if nothing is resolved by then.

Otto Mechanic

This is a pet peeve of mine; one I fret over ever since the "Bureau of Automotive Fluid Colors" took over in the US.

Buy the cheap DOT 4 stuff to bleed the system. In practice, I just recover the stuff I've already used with a catch bottle, it reduces cost significantly. Once you have good brakes, clean the Motive and fill it with the good stuff. Go through one more complete cycle of bleeding the calipers and clutch with the high grade/high temp fluid you plan on using and discard the cruft you've used to bleed.

When you could buy two different colors of ATE, it was easy. Now you need to do it by volume since there's no obvious color change in the fluid.

mytrplseven

Yeah, I know. We're the DOT.....were here to help. Seriously, it shouldn't matter if the brake fluid has to be a specific color. That's what labels are for.

T&T Racing

DOT4 for autox is a good choice. if you mean higher stuff as synthetic or silicone, DO NOT use. These brake fluids entrap air bubbles when vibrated and the air bubbles do not escape back to the reservoir

GPA951s

I Sort of had the same problem with My Turbo-S … I used to have to STAND on the pedal, and that is not a comfortable feeling at Watkins Glen, and It really will mess with any heel-toe Downshifting.. Anyhow, I ended up getting a Caliper rebuild Kit, I did all 4 calipers.... 16 pistons.. Took my time and was very detailed in the cleaning all new o-rings, got 30 years of junk and varnish out of the calipers. Put it all back together... Took it for a rip on the street and was a TOTALLY different car at the track.. It was amazing the difference the rebuild made... they work awesome now.
Look on YouTube, Van has a great Video on how to rebuild/clean them...I got my rebuild kit from Racers Edge. I took my time and it was about an 8 hour job. FYI You Don't need the scraper rings.. just the seals..

GPA951s

Buck "the system" I just put some dye in mine anyhow.. much easier to change fluid..
1. open bleeder
2. pick up beer and drink
3. Put beer down when color changes close bleeder
4 Repeat 7 more times

mj951

Don't forget to bleed the clutch.