Uno Turbo Front Caliper Install
- Thread starter Rupunzell
- Start date
Rupunzell
Bernice Loui
One other thing to try in a effort to root out the rear brakes could be a problem. Put the parking/hand brake full on, then check for brake pedal travel. Applying the rear brakes full on with the cable essentially takes away most of the potential caliper piston travel limiting the fluid volume used to move caliper pistons to the front.
Bernice
Bernice
fiatfactory
Steve Cecchele
The one constant here, with both Tony and Hussein's problems...is that they both bought the same brand / make of aftermarket (eastern european manufactured?) rear calipers, and they are both experiencing issues with extended pedal travel.... if you haven't pulled the calipers down to inspect that they are assembled correctly yet then maybe you should be doing that first before re-engineering the master cylinder.
Years ago I went out and bought a pressure bleeder, as being a one man operation I sometimes had difficulty fully bleeding X19 brake / clutch circuits, pretty much identical to this one but snap on branded...https://www.toolsource.com/bleeders...p-79024.html?zenid=oulupi2qs6b2t03t0a9ljomun0
Vacuum bleeders I never found very useful.
SteveC
Years ago I went out and bought a pressure bleeder, as being a one man operation I sometimes had difficulty fully bleeding X19 brake / clutch circuits, pretty much identical to this one but snap on branded...https://www.toolsource.com/bleeders...p-79024.html?zenid=oulupi2qs6b2t03t0a9ljomun0
Vacuum bleeders I never found very useful.
SteveC
kmead
Old enough to know better
What does the pedal feel like when you have the e brake pulled up fully? Is there less pedal travel or the same? If the same I would vote on air in the system, if less it is something mechanical in the rear caliper adjustment mechanisms.
(Whoops, didn't see Bernice's post until after mine was posted.)
(Whoops, didn't see Bernice's post until after mine was posted.)
TonyK
True Classic
Thanks everyone for their replies. Just to let you know that when I powder coated the calipers I took them all apart to the castings and reassembled after powder coating.
One thing that I did do when driving the car was to pull the hand brake on hard braking. The car showed improved braking when doing this. Possibly the bevel washers are stronger and require more pressure to allow the rear pistons to move the required distance.
I have the Licence plates now on the car and put on about 60 miles yesterday. Driving with traffic the brakes are okay, but push the car and it now requires a more aggressive stop that sees the pedal go farther to the floor and brings about doubt that the car will stop in time. I may have to install the stock rears or possibly take the belville washers out of the old calipers and install them in the new calipers to see if that makes a difference. Something until now I have not considered. If I have time on the weekend I can try bleeding again as well.
TonyK.
Grimsby Ontario Canada
lookforjoe
True Classic
Just reading the recent posts regarding the eBrake actuation component impacting piston travelm & therefore pedal travel. Sounds like a reasonable cause for the symptom. I doubt I have any air in the system, I have bleed multiple times, both gravity bleed with rear elevated, and with the Mrs. providing pedal pressure. I have not tried adjusting the eBrake tighter to see if that alters travel, or just seeing what the pedal travel is with eBrake engaged. Tony and I do have the same brand calipers, so it is quite possible the issue lies in the eBrake construction of these calipers.
TonyK
True Classic
First off my apologies to Karl as your post really didn't click in my head. I never considered if the E Brake had anything to do with piston travel, well...it does. Learning something here. I pulled the Ebrake and pushed on the brake pedal and the pedal is higher and does not have the mushiness that it had. Well done. So it appears that the mushy feeling is the hydraulic system compressing the rear caliper spring washers. I think what I will do next is remove a set of washers from my old calipers and install them on my new calipers. I made a tool to compress the washers in the bench vise, I am hoping that I can do it on the car with a large C clamp and not have brake fluid dripping everywhere nor have to bleed the brakes again.
Stay tuned, not sure if Hussein will beat me in trying this first or not.
I won't get at this for a few days. I will take pictures of the washers and measure the thickness of them as well.
Thanks for the help.
TonyK.
Grimsby Ontario Canada.
lookforjoe
True Classic
I've never dismantled rear caliper eBrake mechanism, and sold my old rears to MWB for cores
- I'll wait until you have evaluated the situation (hopefully with pics to document ) before I do anything.
ng_randolph
Bjorn H
The piston has to come out to remove the washers, so no way to do this without opening up the hydraulic system. But I would not go this route, as this would largely disable the self adjusting mechanism. I don't think you need to make any modifications to the system to make it work. i think you have proven that the cause of the problem is that the rear pistons retract too far into the caliper after you release the brakes pedal. Ideally, this should work itself out without any intervention, but it seems that it does not.
What I would suggest doing next is to check at the rear how much clearance there is on the rear calipers. Pull the caliper as far outboard as it goes, so the piston is in contact with the back of the inner pad and the inner pad lining is in contact with the rotor. Then check clearance between the caliper and the back of the outer pad. There should be very little, but I suspect that is not the case here. If there is slop, try turning the piston counterclockwise to extend it and take out the slop. This is essentially doing what the self adjuster should be doing. Adjust both sides this way, and make sure the groove in the piston is horizontal and engages the pin(s) at the back of the pads on reassembly. The scribe mark parallel to the piston groove should be above the groove. If it is not, rotate the piston another 180°.
ng_randolph
Bjorn H
Actually, the pistons don't have to come out, but the parking brake plunger does. You could probably do this with minimal fluid spills, but would still need to bleed that corner after reassembly. I still don't think you need to (or should) do this; see my post above.
TonyK
True Classic
What I am saying is that the washers of the aftermarket caliper are stronger than the stock washers. So I want to change the after market washers to OEM washers from a spare set of rear calipers. I would also point out is if I have to manually turn the piston out to adjust for slack then the adjuster is not working and over time the problem will return as the brake pad wears. I suppose an easy fix for this whole experiment would be to remove a pair of spring washers and install a solid washer to reduce the amount of return spring force and distance for it to travel.
I think what is happening here is that the after market washers are requiring more force to get them to compress before the piston starts moving to clench the pads and actually do braking work. All of this has been an interesting experiment, still hoping for positive results.
TonyK.
Grimsby Ontario Canada.
Rupunzell
Bernice Loui
The rear caliper self adjusters are cleaver and more complex than they appear.
Removing the rear piston will reveal a multi lead screw fitting into the caliper body with an O-ring seal then engaging the manual brake level via cam with a matching nut inside the piston. There is a spring wound around this nut which is held on one end and floats on the other end. As the piston is pulled forward, the spring slides on the multi lead nut. This advances the nut and it's support plate inside the piston. If any of these parts stick or dirt is caught in the threads or parts not properly assembles, the self-adjuster will fail to function. The used set of 38mm caliper that was rebuilt had stuck-sticking adjuster screw and nut. This would have prevented the self adjusters from functioning properly.
Take the entire rear caliper piston apart carefully, noting how the parts assemble together. Clean all parts well, lubricate them using non-petro based lubricant like Krytox or Silicon based grease specifically designed for brake assembly work at the screw, special nut and piston body Do not apply anything other than DOT3 or DOT4 brake fluid at the interface between the coiled spring and special nut body. Check to see the adjuster functions by compressing the piston fully into the caliper body then using the manual brake level. Once the piston has been moved forward using the lever, the piston should hold it's set position within a small variation in distance (0.00X inches). If the piston advance then retain test fails, the pads will end up too far from the rotor resulting in excessive brake pedal travel due to pad to disc distance.
Bernice
Removing the rear piston will reveal a multi lead screw fitting into the caliper body with an O-ring seal then engaging the manual brake level via cam with a matching nut inside the piston. There is a spring wound around this nut which is held on one end and floats on the other end. As the piston is pulled forward, the spring slides on the multi lead nut. This advances the nut and it's support plate inside the piston. If any of these parts stick or dirt is caught in the threads or parts not properly assembles, the self-adjuster will fail to function. The used set of 38mm caliper that was rebuilt had stuck-sticking adjuster screw and nut. This would have prevented the self adjusters from functioning properly.
Take the entire rear caliper piston apart carefully, noting how the parts assemble together. Clean all parts well, lubricate them using non-petro based lubricant like Krytox or Silicon based grease specifically designed for brake assembly work at the screw, special nut and piston body Do not apply anything other than DOT3 or DOT4 brake fluid at the interface between the coiled spring and special nut body. Check to see the adjuster functions by compressing the piston fully into the caliper body then using the manual brake level. Once the piston has been moved forward using the lever, the piston should hold it's set position within a small variation in distance (0.00X inches). If the piston advance then retain test fails, the pads will end up too far from the rotor resulting in excessive brake pedal travel due to pad to disc distance.
Bernice
fiatfactory
Steve Cecchele
OK so you removed the piston, hand brake plunger and arm, and the belville washers... but did you disassemble the innards of the piston? That is where the piston / hand brake self adjustment mechanism is...
The belville washer stack is simply a spring that returns the lever/plunger back to it's rest position, it doesn't get compressed by hydraulic force, so that is not the issue here...
SteveC
TonyK
True Classic
Oh Crap.
First off both Hussein and I have the same issue. I took my calipers apart to power coat them, he did not. I did not disassembly the slack adjuster on the caliper piston, but this is where the issue must be. The springs are really not part of the problem at all. I am now wondering if I can change out the multi start screw and the adjuster nut from an old caliper or not. Everything in this caliper looks clean and it was new, however if there is a problem with the mechanism then the calipers adjust mechanism and I cannot refit old caliper parts then they are basically junk and wasted $500 CND on them and will have to put the old rear calipers back on the car.
Not looking forward to this at all. Will forge on to see what it presents.
Thanks all for the direction.
TonyK.
Grimsby Ontario Canada.
Tony,
If I understand it correctly, you can lock-up both front and the right rear brake. That would lead me to believe the problem is in the left rear brake. If it were me, I would probably try the manual adjustment ng_Randolph suggested in his post paying attention to any difference between the rear brakes. If manually adjusting the brakes "fixes the problem" you have found the problem and can address it. To me that seems like a relatively quick and easy test to eliminate one possible reason for the brake problem. You may be able to drive for a while with the manual adjustment before a permanent fix is done to the brakes.
I enjoy reading your posts and look forward to reading about the permanent fix.
If I understand it correctly, you can lock-up both front and the right rear brake. That would lead me to believe the problem is in the left rear brake. If it were me, I would probably try the manual adjustment ng_Randolph suggested in his post paying attention to any difference between the rear brakes. If manually adjusting the brakes "fixes the problem" you have found the problem and can address it. To me that seems like a relatively quick and easy test to eliminate one possible reason for the brake problem. You may be able to drive for a while with the manual adjustment before a permanent fix is done to the brakes.
I enjoy reading your posts and look forward to reading about the permanent fix.
TonyK
True Classic
When I did the powder coating I removed everything from the caliper casting body. I did not take the adjuster out of the back of the piston.
I will be honest here in the 39 years that I have owned and worked on an X1/9 I have never had rear brake adjustment problems and hence my reluctance to listen to anyone about this being the problem. The advice sound, which matches the symptoms. I suspect it is simple what the problem could be. The fast start multi thread screw allows the nut to turn and take up the slack and a spring of special design prevents it from turning backward. My compulsive thought process now tries to break this down into a resolution. Are the threads the same direction for both sides of the car? If not could the springs be installed on the wrong side caliper preventing the spring from holding the nut? Can I swap out old 34 MM adjuster parts into the new 38 MM piston. I think what I will first do is disassemble the old parts car rear calipers and answer the questions above to have a better understanding of how the adjuster words. Then put the car on the lift and see how much clearance is between the piston and the brake pad and cycle the hand brake to see if it decreases. Lastly manually adjust the caliper to take up the slack. My thinking here is if the spring is not installed correctly then manual adjustment will only work once if at all as the piston will compress it's self once I push on the brake pedal because the spring is not holding the nut in the adjusted outward position. I have new rear brake pads so I suspect as the pad wears and the adjuster will not compensate for the thinning of the brake pad, brake pedal stroke will only get worst as the piston keeps retracting back into the caliper to the fully compressed position.
I will have a bit of time to look into this tomorrow morning.
TonyK.
Grimsby Ontario Canada.
ng_randolph
Bjorn H
Yes, same on both sides.
Cycling the hand brake does not exercise the adjuster, only operating the service brake does.
lookforjoe
True Classic
I think the problem (in my case) has resolved itself - I took it out today, and the pedal feels normal now, and doesn't have excessive travel as before. So, it may just be a matter of putting miles on it & using the brakes fairly hard to get the adjusters to set the pistons. I have to dismantle the coolant setup again, so will be a few days before I can try it again to confirm.
ng_randolph
Bjorn H
I don't know how much adjustment happens on a single brake application. For the adjusters to keep up with brake pad wear certainly does not take much, but to bring the piston out the appropriate distance after having been fully depressed could take quite a few cycles.