Alfa Romeo Forums banner

1 - 20 of 27 Posts

·
Registered
Joined
·
1,233 Posts
Discussion Starter #1
After I got the emission sticker, I have been working on the brakes in the past couple of days. The brake fluid was black so I am doing a rebuilt of the calipers. The fronts are already done. The rears gave me some troubles. Compress air was not enough to blow the piston out. So I put the calipers back on the car and use the hydraulic to pump the pistons out and they did finally.

The rear rebuild kit (first picture) comes with some o-rings in a plastic bag. I thought they are used between the two caliper halfs although I kind of suspicious on that since there are two o-ring sizes in the package. The front kit does not have any o-ring so I didn't split the caliper. I now separated one rear calipers and there are square cut o-rings that don't look like the ones in the plastic bag.

What are those o-rings (that came with the kit) for?

Thanks,
Bob
 

Attachments

·
Registered
Joined
·
518 Posts
I think it was a bad call to split the caliper. I believe (but could be wrong) that the seals between the caliper body halves are quite special, your comment about the section bears this out. However, now it is split you will need to check about getting the correct seals. The ones in the plastic bag may well be for a different vehicle as calipers were often used across different cars.
 

·
Out of the office!
Joined
·
11,650 Posts

·
Registered
Joined
·
7,166 Posts
I've rebuilt :eek:Corvette 4 piston calipers since I was a little fellow:). What's the deal with the Alfa calipers that are so special. Is it the O-rings? Can't you get them or somethin'? Plus, how can you rebuild them if you can't seperate them? Or do you just use them for a core deposit for ones that someone else has rebuilt:confused:
 

·
Out of the office!
Joined
·
11,650 Posts
I've rebuilt :eek:Corvette 4 piston calipers since I was a little fellow:). What's the deal with the Alfa calipers that are so special. Is it the O-rings? Can't you get them or somethin'? Plus, how can you rebuild them if you can't seperate them? Or do you just use them for a core deposit for ones that someone else has rebuilt:confused:
You don't split them because it's not necessary and, the "O" rings are not supplied with the rebuild kits. The pistons can be removed without splitting the caliper.
 

·
Registered
Joined
·
7,166 Posts
You don't split them because it's not necessary and, the "O" rings are not supplied with the rebuild kits. The pistons can be removed without splitting the caliper.
OK, thanks:). Going on, Corvette calipers eventially pitted and you couldn't hone them smooth. They (I guess in the late 70's, early '80's or thereabouts) then offered Stainess steel sleved calipers. No more pitting but you did after a while (10-12 yrs) have to put new seals in. What's with the Alfa calipers? Anything like that? How bulletproof are the rebuilts?
 

·
Registered
Joined
·
1,233 Posts
Discussion Starter #8
OK, thanks guys! But ... it is soooo...ooo... much easier to clean the inside :D (I just did that)! It will save me an hour or so and a few cuts and some skin off my fingers :p! The front was not too bad since the caliper is bigger.

The square cut o-ring on the caliper actually is still looking good and is flexible - the caliper probably is a replacement and not a 20 yr old unit. So, I guess I just have to "Thou shall have faith ..." that it will hold after I put it back. I guess if it doesn't, I probably can try replacing it new o-rings such as those big fat one for fuel injectors. I'll report back if it leaks!

Bob
 

·
Premium Member
Joined
·
2,811 Posts
Search for it.

You can split the calipers and re-use the O-rings if they are still intact. It's not that big of a deal. Although they are not supplied with the kits, suitable replacements for the rings are available.

There are many threads on this.
 

·
Premium Member
Joined
·
21,374 Posts
In spite of the absolute commandment not to split calipers, I did it back before I knew any better, and never suffered any consequences. I replaced the pistons seals and dust boots, and just reused the caliper-half o-rings. I drove the car some years afterward without incident.

Andrew
 

·
Trained (ex)Professional, , 1953-2018 RIP,
Joined
·
16,232 Posts
Lost track decades ago on the number of calipers I've split. But not all calipers I do need splitting. After the pistons are removed, the calipers are split only if a light hone/bore clean up is indicated.
 

·
Registered
Joined
·
7,166 Posts
How do you tap the seals in if you don't split them?
 

·
Registered
Joined
·
518 Posts
I really would not advocate reusing the seals, if they fail or leak then you will loose rear brakes. If you measure up accurately the counterbore that the o-ring sits in (diameter & depth) plus the fluid bore diameter it will be possible to specify a replacement seal that most engineering shops would carry.
 

·
Registered
Joined
·
321 Posts
I see that you have the tool to set the pistons in the correct position. When I did the brakes I did not have this tool, and the diagrams I drew were inadequate. Hence the left side of the car has the pistons installed incorrectly, and the right side is ok. I have not noticed any problems in 3000 miles. What's going to happen.....?
 

·
Registered
Joined
·
863 Posts
I see that you have the tool to set the pistons in the correct position. When I did the brakes I did not have this tool, and the diagrams I drew were inadequate. Hence the left side of the car has the pistons installed incorrectly, and the right side is ok. I have not noticed any problems in 3000 miles. What's going to happen.....?
The tools are original Alfa Romeo that I borrowed from my mechanic. I made a set for myself.

Rich
 

Attachments

·
Registered
Joined
·
1,233 Posts
Discussion Starter #18 (Edited)
Rich, that's a beautiful rebuild! Mine are still black and ugly when I finished :eek:!

Here's an update: I have put everything back together yesterday and bled the system. However, I got the low pedal syndrome! The brake was pretty firm but it was at about 2" off the floor when it got firm. It gave me scary feeling when I stepped on the brake because of the "more than usual" pedal travel. I searched the forum and it appears that this is a common problem after MC work etc. I did empty the brake lines and also pulled out the plastic reservoir from the MC to clean it since the old brake fluid was so dirty (black stuff on the reservoir bottom and wall). I guess I have introduced some trap air into the system! I tried bleeding it again this morning by opening up the top two brake line connections at the MC. I raised the left side of the car (so the connection points are higher) and used the (one-person ;)) pressure bleed set up that I've been using (see picture below). The pedal is now probably a couple inches higher but I don't remember whether it was similar to before (I didn't drive this car much). Although the pedal is still not as high as I like (possibly due to booster now) but I think it is acceptable - for now!

Regarding to caliper rebuild, yes I have sinned again and splitted the other rear caliper. Between the possibility of needing new o-rings and to be able to clean the caliper inside better, I decided to deal with the possible caliper leak if it does happen! Splitting the calipers made cleaning the cruds out from the piston seal groves and "polishing" (with 600 grit sand paper) the piston bores much easier. The original o-rings are still flexible and looked thicker than the depth of the o-ring bore. I inspected the calipers this morning and I didn't see any sign of leak so I think they should be good!

I knew about the piston orientation template but I didn't bother to print them out. Since the description says to the set the stepped-down section to "follow an imaginary radial line from the center of the disc", I just eyeballed and installed the pistons. BTW, it looks like using the template would not exactly "follow an imaginary radial line" - it is slightly tilted (a little more advanced :))! Anyway, I don't think it is super critical. It probably is designed to reduce possible binding at the forward edges to the pads when rotors turn.

Regarding to the original question of this post :), I was told (by another helpful friend offline) that the extra o-rings are for other calipers such as those for Alfetta. Haha, the box does say Alfetta on it! I have rebuilt Milano rear calipers before so I guess I should have made the connection that those o-rings are used for the parking brake mechanism.
 

Attachments

·
Registered
Joined
·
518 Posts
I had an absolute epic bleeding the brakes after overhauling the calipers, I used a pressure bleeder which helped. In the end though I had to admit defeat before I caused a world shortage of fluid and got my friendly garage to do it with a high volume pressure bleeder, even then it took around 2 hours of flowing through to get them bled.
 

·
Premium Member
Joined
·
85 Posts
I tried bleeding it again this morning by opening up the top two brake line connections at the MC.
I'm thinking I may need to do this because I think the fluid level in the reservoir may have accidentally fallen below the "minimum" level when I was flushing the old fluid. Do I understand correctly that letting the level fall below the minimum mark can introduce air into the system?

When the top two brake line connections at the master cylinder are opened, does the fluid in the reservoir run out, or does just the fluid in the metal part of the master cylinder at the connections run out?

Regarding the fluid in the lines, will the air bubbles in the lines percolate to the top through the fluid, or do the air bubbles in the line push out all the fluid in the line above the air bubbles?
 
1 - 20 of 27 Posts
Top