Brake Lockup/Drag Racing Application

[supraguru05]

Well I have hit a road block so I need some help. Last year I had some issues with the brakes dragging and then the fronts in particular locking up after racing for a certain period of time. We were able to isolate the problem to the master cylinder because when I came to a stop with the brakes locked, we could crack the line from the master cylinder to the front brakes and the wheels would instantly go free, even when hot. This told me it wasnt a caliper sticking etc. Clearly the master cylinder piston was sticking in the bore. We replaced the then toyota master cylinder with a spare toyota one I had off a parts car. All was well for a couple races then the same problem cropped up again. At this point I had to buy parts store master cylinders. The Oriely's cylinder leaked, and now the pep boys (new) cylinder has the same lockup issues. I just called a toyota dealer and the Non-ABS master cylinders are not available anymore. My plan was to buy a new toyota cylinder and then heat wrap it using the DEI cool-tape but I need to find a good high quality cylinder first. Also the rear piston on these failed master cylinders is impossible to get out of the bore which is what is leading me to believe the rear pistons is scuffing bad.

Does anyone know of a good source for master cylinders?
Rock auto has a bunch of different brands but seeing how I already sunck 140 bucks on a crapping pep boys cylinder I would love some input on which brands people have used that worked.

Also this couldn't be a stuck or sticking proportioning valve could it? The problem last go around only affected the front two wheels, and the car does not have ABS

 

[IndigoMKII]

Isn't there another master cylinder that we can use that is bigger? It's off a land cruiser or something, I can't quite remember but I do remember seeing it. I'll see if I can dig it up.

I believe it was off a 4runner.

 

[Backlash2032]

Would a rebuild be possible?

Sent from my HTC6435LVW using Tapatalk

 

[supraguru05]

based on the rear piston being so difficult to remove I believe the bore would be damaged beyond repair. Also some older threads indicate the rebuilt kits have leaking orings. There is a Beck/Arnley (new) master cylinder on rock auto. I am leaning toward trying that one. I will wrap it in the reflective tape to help keep the heat off of it. Also will go through and readjust the pedal, and booster to ensure the right plays are in place.

 

[gats]

Are you able to get any of your faulty master cylinders re-sleeved?!

I have had a few re-sleeved with a stainless steel insert. Then you effectively have a cylinder with a brand new bore...
I know you are in the US, but this is the place I've used in Australia: https://www.powerbrakes.com.au/index.php/selectedContent/2000398759?currentDriven=2147259961&currentContent=430756718&PHPSESSID=9eba47b64055cb606f127dcb09610949

 

[supraguru05]

found a place in US that will do sleeveing. Found a old toyota cylinder that was bad. Now I just have to figure out how to identify a ABS vs non-ABS master cylinder. the line positions are the same so I am not sure how to tell yet.

 

[supraguru05]

Found my own answers back in this thread. Amazing how much you forget. Looks like from Jeffs post that the early ABS and Non-ABS cylinders are probably interchangeable however the later ones have an additional orifice.

http://www.supramania.com/forums/sh...ove-ABS&highlight=master+cylinder+differences

I will dig through the cylinders I have to see if I can clarify this.

http://www.applehydraulics.com/brakes.htm
They will do the sleeving and I ordered the rebuild kit from rock auto which is for a non-abs cylinder.

 

[Dylan JZ]

I'd recommend the T100/4-runner unit because its beefier and will assist with better pedal feel. They are also widely available.

 

[3p141592654]

Are you sure its not the brake booster sticking on?

 

[supraguru05]

we replaced the booster last year. Also its only effecting the front brakes not the rear brakes. And the wheels go free when I loosen the line at the master not behind the proportioning valve. I plan on readjusting the booster and pedal when I get the best master cylinder in just to make sure. I wont be able to really try anything out until march because that is when the races start

 

[3p141592654]

Yeah, I'm wondering if its pushing the piston in a little, which is then only hanging up the front circuit. Have you considered getting the rebuild kit from Toyota for the master cylinder. I bought one a while back but I guess it could be discontinued now.

 

[Dylan JZ]

Driftmotion rebuilds them and apparently does a pretty good job. I'd get mine rebuilt just for peace of mind in this particular situation.

 

[supraguru05]

using a rock auto rebuild kit. since toyota wants way to much for one. The rebuild kit goes with the cylinder to the machine shop and they will set the clearance in the new sleeve correctly. should get the cylinder back in under two weeks.

 

[super51fan]

Once you have a known good master cylinder. You need to make sure you properly adjust the brake booster pushrod. Page BR21 in repair manual shows how with SST09737-00010. The process can be done with other measuring tools. It sounds like compensating port is blocked or restricted in master cylinder or push rod adjustment is wrong. Just my 2 cents. Good luck.

Btw I would only use a Toyota rebuild kit regardless of price. They will last longer.IMO>

 

[3p141592654]

I agree. The pistons are an amazing engineering marvel. I think they are worth the price to get them from Toyota.

 

[supraguru05]

New master cylinder from driftmotion installed. Took it out and the brake pedal sinks practically to the floor with little brake power. No matter how many times I pump it when the car is running it sinks. brakes were not dragging. I started the brake booster checks.

Operational checks per

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=BR&P=6

a) seems like it goes to the same spot everytime pedal gets firm but low
b) when car starts pedal sinks a bunch. I dont know what the tsrm means by slightly going down. I would say mine sinks practically to the floor.

air tightness
a) seems like to goes to the same spot each time
b) doesnt sink any after car is turned off. may actually rise some.

So seems to me like it fails operational check b and possible air tight check a. Should I try a new booster? I bled the brakes multiple times using a power booster so I wouldn't wear out the master cylinder. Also I don't think its air in the system because I should be able to pump the brakes to get the pedal firm if it was air. Another note is when I adjusted the booster piston for the master cylinder the piston pulled out from the booster slightly but I think I got it back in its right place. This is driving me crazy I have a race in less than a month and I have to get this thing fixed.

rock auto has this booster for 161
CENTRIC Part # 16088684 Reman
Engine VIN M; With Aisin Booster


EDIT: heading back out to check the check valve between engine and booster. Also will reperforme air tightness check B which is leave car on for 2 minute. press pedal. turn off and see if pedal moves up or down.

 

[supraguru05]

checked check valve between manifold and booster. it sealed when I put positive pressure on it and only allowed vacuum in. I redid the 30sec engine off test and the pedal definitely rose quite a bit and I was pushing pretty hard trying to keep it down. Does this mean the booster is leaking? Also I removed the vacuum line from the booster and drove the car quite a bit without the booster working. Obviously I had to push super hard to stop but I got the brakes up to temperature and the pedal was really firm and didn't sink. I really don't think there is air or the master cylinder leaking. I could push as hard as I wanted and it was still a great firm pedal.

 

[super51fan]

Have you ever checked your booster to master cylinder clearance. Based on your original complaint it could have been a smiggen to long. Like holding the brake pedal down slightly. Made since, only happens at max thermal expansion. It really needs checked if you use a different master cylinder. BTW I thought drift motion only has non ABS master cylinders. Good luck.

 

[supraguru05]

Fixed the clearance when I installed the new mc. Car is non abs I converted it years ago as the abs wasn't great on track. Brakes are not dragging anymore. May have broke the booster when it's piston fell forward a bunch

 

[nctexan]

Did you ever fix your brake issue? Even though I'm running Wilwood kit in the front, and also removed my abs, it sounds a lot like a problem I've been dealing with for a long time now.