mikekantor

iTrader: (5)

All the other signs point to a yes, but I'll have to do some more driving before forming any final opinions.

I am not sure why it seized up like that, the effect came on gradually towards the end of a decently long drive. Driving and braking after I released the pressure was completely normal.

internetautomar

iTrader: (30)

whoever bled the brakes SHOULD have caught the bleeder screws being in the wrong location

mikekantor

iTrader: (5)

I put the calipers in their correct positions now. The brakes still seize up after very little driving/braking. It seems to come on very gradually at first and soon just bites so hard that the car barely moves, if at all. The pedal becomes completely immobile.

I've been able to deal with it by relieving pressure at the bleeder... so it sounds like a Master Cylinder issue, right? Because if the caliper pistons were freezing then they wouldnt relieve pressure on the disc after I relieve fluid pressure, right? Someone please confirm my logic here.

I think I'm going to install the old M/C back into it tomorrow, the one I put new pistons into. I'm calling the shop tomorrow to have a chat about this, maybe I can get some of my $ back because this is ridiculous.

Greeny

iTrader: (43)

Seized up slide pins maybe?

mikekantor

iTrader: (5)

The Z32 calipers dont have slide pins, but there are two bolts on each one that the pads ride on, maybe I'll look at those.

mikekantor

iTrader: (5)

Could a resedue on the rotor or the pads cause this? Maybe I'll clean the rotors with brake parts cleaner just to be sure.

mikekantor

iTrader: (5)

So this is interesting...

When it seized tonight, I just let it sit isntead of messing with the bleeders like I did every other time. After cooling off it has become unseized on its own. Maybe it is just a dirty rotor..?

LvR

Dangerous but easy experiment to see if its the calipers ............

On the MC, swap the front and rear outlet lines - if you now drive be aware your brake take-up and distribution is all non-optimized and you may very well end up locking the rears immediately if you apply "normal" pedal pressure.

If the calipers still lock up its the calipers, if they don't - well - so much for friends and humanity.

mikekantor

iTrader: (5)

Not sure how that would be possible. They are all fragile, small metal lines, bent to align into the exact place where they enter the m/c.

I'm going to try cleaning everything thoroughly. After that I might swap my stock brakes back in. After that I could swap the stock m/c back in.

Whats funny about all this is that I've now become quite adept at the brake bleeding and brake work in general.

LvR

In general, on most vehicles there is often enough "give" in the lines to affect this without too much trouble or damage. In the Max's case I guess you would need the 2 spare flexible extender hoses I have for exactly this task.

Just trying to suggest easiest way to get to the right conclusion with the least amount of work and money involved

internetautomar

iTrader: (30)

are the calipers rebuilt or used?
if used, you may have rust/pitting in the piston bores that becomes an issue as the metal expands.

mikekantor

iTrader: (5)

Used, but were rebuilt 3-4 months ago.

internetautomar

iTrader: (30)

were they on a car for those 3-4 months?

mikekantor

iTrader: (5)

SurraTT told me he took them off the car just before the sale.

internetautomar

iTrader: (30)

were they rebuilt by him? or someplace else that may have a warranty or a tech line to talk to?

shoult

iTrader: (1)

Here's the ultimate test.

Put the STOCK calipers back on. Bleed. Test.
Work?
Yes -> Z32 Calipers are hosed
No-> Problem not isolated to Z32 calipers, reinstall stock MC, Bleed, Test

Work?
Yes-> BBK Master hosed. Either leave STOCK on or fix or source new BBK MC
No -> Isolate Front and rear brakes by building ONE MC plug. Using plug, block either front port and test rear or vice versa. Bleed. Test

Back Work?
Yes-> must be isolated to front
No-> Must be isolated to rear.

mikekantor

iTrader: (5)

Yeah, I know... this is more or less what I was planning:

mikekantor

iTrader: (5)

After messing around with it last week, I started to suspect the brake booster more and more. I was out of town during the weekend, and finally got to the booster today.

I managed to remove it without messing with the brake lines at the m/c so that saved a lot of time. Measured the output rod, and it was out of spec. Adjusted it to spec, test drove, no more seizing!

Tomorrow I'll have to do another quick bleed on it though, I let a bit of air into the system last week. I bought some bleeder screws with check valves... 2 for $0.95, so that will be a good chance to install them.

LvR

"Out of spec" being too long?

Was this thing working properly before you started the caliper conversion?

So its working with the new calipers on the vehicle now too yes?

mikekantor

iTrader: (5)

It is only supposed to protrude a little over 10mm from the brake booster. It is threaded for adjustment. Mine was out at like 14-15mm. It resisted the pistons moving backward as far as they needed to, which caused the seize.

The brakes worked properly before the conversion, the pedal was a tad soft though. At this point, I dont even know how the output rod used to be. I never measured it initially, and then the shop the car so I dont know what they could've done with it, if anything. Over these many weeks, with all tinkering I've been doing to solve the various issues, I cant even be completely sure that it wasnt something I did to it.

I compared the new and old master cylinders. Their dimentions are identical in all respects, the pistons have the same locations, and the springs have the same rate.

Yes, all is well. Stops very nicely.

renzokuken1227

I'm also having trouble with my brakes. My abs unit has had a leak for a while, so I just replace the fluid every 2 weeks and it works fine, but the other day suddenly after a hard stop I practically lost at brake pressure, pedal would go to floor. It was then i decided to replace the abs unit from another one from a junkyard. I tried bleeding from the tires, I get very little to no fluid coming out, I even took it to my mechanic and they tried using a vacuum still no luck. What should I do?

CapedCadaver

iTrader: (8)

sounds like you've exploded a brake hose. check all your rubber brake hoses. You started with a pin-hole leak, which is why they "worked fine" but you had to keep topping it iff, and then all the sudden it ruptured, causing a total brake system failure.