Piston Pin Bushings

Workshop tips: sorting out faulty hydraulic rams

New seals for both old David Silvester, head of Sussex south Hydraulic specialists drives, steps through a recap Andrew Pearce

Rams, as almost all other mechanical things have a habit of giving up the ghost when you use them. Which means a lack of immediate pressure if necessary, and a new predicament, pressure to get the thing fixed.

At this point, the choices are simple: Buy a new ram, have sorted the old or repairing it yourself.

If you like the DIY option, be prepared for the potential of mourning time (or sheer bloody-mindedness of machines) makes some rams reluctant to separate. A word about this from specialist David Silvester: "Rams are held together in a variety of ways, some less obvious than others, it is advantageous to consider very carefully before attempting to take something apart including the internal piston ..

"Then be sure to find the cause of failure. For example, 95% of the rams we repair were damaged piston rod instead of seal degradation with age.If you just fit new seals and re-use of stem damage, sooner or later, the ram is about to expire again. "

Take your time to stripdown he commits. "Sketch or take a picture of the location, order and orientation of each o-ring seal and you'll encounter. Then you can get the new parts back in the right direction and order."

So if you're ready for an unlikely agony, the following photo sequence shows how to do the job. The principles apply to all varieties of ram, so naturally the details - the means for fixing ceilings and piston seal design and number - can vary.

Strip

[1] This Claas combine ram leaking badly. First step for rejuvenation is a deep cleaning externally. Then comes stripdown. Here, the cap (more properly called the bush head) is held by a metal clip, but others are generally screwed. Turn the bush to find the end of the clip. Taken at the end up, then continue turning the clip to feed her throat. While all caps can be awkward, this design is often a guy right to separate, says David Silvester, if the wire is seized or broken.

[2A and 2B] degrease all parts, ideally by steam cleaning. Here the cause of death: Pits chrome piston rod finish (arrows, A), which marked the head gasket bush (B). A new rod, machined on site, was the only long term solution. Also check the piston bore for scoring or other damage - there may be more than one cause of failure.

Piston pin bushings needed - Alfa Romeo Bulletin Board & Forums

Most good race engine shops can rebush the small ends with a correct unworn wrist pin as a sample. If you need the name of a shop that does this work, send me a PM. If you go to the trouble to rebush, it's a good idea to have the rods reconditioned, which involves straightening, checking the big ends for out of round and correcting, shot-peen, balance and so on.

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