HELP! How to rebuild clutch slave cyl? '74 240D

[FieroGT42]

Clutch slave cylinder is dead in the '74 240D! I can get rebuild kits for like 1/4 the cost of a complete cylinder... but is the seal pressed in, or what? Do I need any special tools? I believe it's the ATE brand cylinder.

Expedient answers would be much appreciated. Thanks

[MarcusF]

The quality of clutch master or a slave cylinders is entirely dependant on the quality of the core. If the cylinder is out of spec or pitted, the best rebuild in the world will be dead again in no time. Seeing as how the slave is under $30 for a new one, I'd consider the aggravation factor of having the same part fail twice and spring for the $30.

Correction: I’d spring for $75 and replace the slave AND the master. If you do decide to rebuild it you'll probably need a pair of lock ring pliers. I hope this helps.

[carnut1]

These items fail because of not flushing the fluid. Water forms in brake fluid by nature over time, eventually destroying the seals within and/or pitting the bore. If everyone flushed clutch cyl. fluid and brake system fluid every two years, there would be virtually no master cylinders, wheel cylinders and calipers failing. My 81 CD has the original 4 calipers and master cylinder because of flushing. Brake hoses have been replaced based on age and the brake booster eventually tore the diaphram and leaked vacuum requiring replacement. I would NEVER recommend rebuilding any hydrallic brake or clutch components, too much potential for failure!

[KCM]

I have not worked on one quite that new, but if it is like the older models, you simply take off the outer rubber boot and the cup and spring will come out easily with a little air pressure in the hose port. Observe how the pieces fit together, and especially which direction the rubber cup is turned. Back in the old days before cheap Mexico and China parts, brake and clutch cylinders were often rebuilt with new kits.

Check the bore for pitting. If there are any pits, best to get a new cylinder. If it is just surface rust or marks, it can likely be cleaned up. To do this, buy a small cylinder hone at an auto parts store, which can be attached to a hand drill. Using diesel fuel as a lubricant, submerge the cylinder in a small can and run the hone up and down in the cylinder running the drill at a slow to medium speed if you have a variable speed drill. Check it to see if the marking is gone, and if not, repeat the process. You should end up with a cross-hatched pattern on the cylinder wall. When done, wash the cylinder in clean solvent and reassemble with new parts in the reverse order you disassembled.