retracting piston for brake pad replacement

My caps are indeed metal, but they have been dry with no sign of fluid on them, in fact the first time I took them off, one was half undone, I was lucky that I hadn't lost it and the splined adjuster it holds in place. The other was well and truly stuck.

Cheers
Scotty

 

I had oil in one of my caps, one time. Pulled both pistons, adjust screws, etc. and replaced all seals, one time. Have never pulled two halves apart. About all that can go wrong is seals so I don't take chances.

I believe cap is aluminum. It has to seal and handle temp of caliper under extreme conditions. Certainly is soft and hex wrench socket is about one size too small for something made out of soft metal. Slot with Moto-Tool works wonders. Watch seal area. Have replaced both front and rear pads about every 20,000 miles-7 times to date. No sweat after the first time.

John

 

i forgot to add that i replaced the second rear caliper on my 308 because there was brake fluid behind the inner cap even though i saw no external leaks - figured it was just a matter of time. all the caps i've seen are mild steel while the outers are plastic. i suspect if the seals are good it doesn't matter what there made of (and come to think of it, if the seals are bad; ditto). jon s.

 

the inner caps are actually aluminium and were totally screwed up on my car when I first had to replace the brake pads. Full of chisel marks and the hex was rounded. After it has been a major pita removing these and since I consider the whole thing as a design fault I fabricated my own plugs designed like the picture shows.
While having no concours ambitions I can live with that originality flaw.
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The 328 is different - the parking brake is not part of the caliper - so you don't have to worry about the info in this thread.

Just push the pistons back like you do on the fronts.

 

That is the way it should have been done. Thanks for the pics.

John

 

John
I'm confused about the full pressure on the caps. I just removed my caps and there was a torn copper washer under mine but no evidence of a fluid leak. I assumed that the caps were just to keep the adjuster clean and dry. Are these caps really designed to hold full hydraulic brake pressure? It seems that the outboard cap as flimsy as it appears would blow out.

 

Chuck - you are correct. On the Dino, and I assume early 308s, the cap simply protects the set screw from road dirt. The Allen set screw and its locking nut do not communicate with brake fluid or pressure. They simply turn the screw which moves the static position of the piston for adjusting the handbrake. Under the set screw and locking nut is a cavity with a cylindrical gear, which I filled with grease. Brake fluid will not get there.

Jim S.

 

Ahh, I tole you so. It isn't just early 308s. My '82 & Steven's '85 also have the plastic cap over the set screws, so I suspect it's at least all 308s thru the QVs.

 

Jim
If I understand this correctly the adjustment I just made on the pistons with a feeler gauge at .004 was only to effect the parking brake. The main braking system is adjusted automatically when the parking brake is used. In other words the main braking system is adjusted automatically and using the feeler gauge is only to adjust the parking brake? I looked in the OM for this .004 measurement and it said only that is was automatic.

 

Chuck - you are correct. The only other adjustment is related to spacers that position the caliber relative to the rotor. When removing the caliber, either mark the individual spacers (that look like thick washers) or be prepared to carefully measure the distance from each piston to the rotor disk. It is imperative that the rotor disk rotate equidistant between the piston faces (or pads - although it is easier to measure without the pads in place). The spacers are available in different thicknesses for adjustment.

The .004 mm (I do not have the book in front of me to verify this specification) is to assure that the pad does not drag on the rotor disk without the handbrake applied, and to provide sufficient travel for the entire mechanical system of the handbrake (the lever bar that the driver pulls up, the cable, the asymmetric actuator mounted on the frame behind the engine, etc.) to apply sufficient clamping pressure.

Jim S.

 

Thanks Jim.

 

Super easy way to remove the inner cap. Mine were also impossible to get off, I first tried the hex (4mm I believe) and it rounded it out. Uugh! Left side, same thing. I tried the "chisel trick" as described above, nothing. Even after I had them off the car in the vice, I couldnt get the bolt to move. One of the caps showed signs of earlier chisel marks:

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So, I tried a trick that I used on my Jeep a while back to remove a rounded out bolt on top of a shock tower. If you have access to a Mig Welder, its very easy to do. Just get a smaller nut (steel) and use a magnet to hold it on top of the cap. Before you weld it, use a grinder and an abrasive pad to get down to nice shiny metal (will weld much better). Tack it in 3 spots around it, and use a wrench or plumbers wrench to unscrew it! I sprayed a bit of PB Blaster onto it while it was still hot from the weld, and it sucked it right in. It was very easy to remove with the plumbers wrench after that... Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

Please dont make fun of my welding skills (or lack thereof!)

And yes, I know this destroys the cap. But its time to put a new, better one in after. Preferably a stainless steel version of it. There are lots to choose from, just google around for an M10x1.0 cap bolt. You can reuse the copper washer (anneal it first). And dont tighten it down too much or someone else will be in the same spot 30 years from now!

 

I just had my rear caliper rebuilt by PMB Performance, besides re-plating them they also provide new and improved caps

 

Just sent off my rear calipers to PMB Performance to be rebuilt and plated. Ill report back on how they do...