My ôpawn shopö Bosch Roto Hammer 11248 EVS slowly lost hammering strength until it stopped hammering altogether.
A troubleshooting guide recommended checking for proper lubrication.
The gears were virtually devoid of any sign of lubrication.
I couldnÆt find any specifications or recommendations as to the proper
... Read moreamount or type of lubricant, so I used some standard tool gear grease and a little 90w differential oil.
(After purchasing a proper ôoil reservoir and sealö kit as well as some tool grease, I realized that, no grease shouldÆve been in the gears, and only 50 mL of the specified oil. The grease is only for use on the bits.)
The tool ran fine for an hour or two but then stopped hammering all together.
On opening the oil reservoir I discovered that the plastic hammering pistonÆs rod had snapped and a small triangle of metal had snapped off the back of the hammering cylinder.
My son suggested that perhaps I had over-lubricated, causing too much pressure on the piston rod.
Since a new piston rod and oil reservoir kit was not nearly as expensive as a tool rental I decided to try replacing the parts to see if I could restore the tool without replacing the hammering cylinder.
After flushing the improper grease and the damage debris from the reservoir and installing the new oil, the tool works fine.
The only trick to putting it back together is making sure that the ô clutch sleeveö is in the proper position to engage with the hammer/rotor hammer selector. (If you have to disassemble the oil reservoir again, the reservoir seal may stretch and not go back into place properly which will require a new seal. Perhaps if when installing the replacement seal, you bed it in high temp (red) silicone it may resist stretching if you have to disassemble it again.)
I also managed to damage the little shuttle which keeps the trigger from locking in ô turboö the Roto Hammer setting.
Now when the trigger is activated the tool is always in the ôturboö (locked) setting.
(This doesnÆt seem to be available as a repair part.)
In retrospect, it would have been better to have some sort of directions for flushing the reservoir, aligning clutch sleeve and a specification for the oil fill.
(Perhaps the volume of the oil reservoir kit should have been a clue.)
On the other hand, maybe only ôcertified repair techsö get this level of information (or, they are the only ones who know it, because they have had to learn it by experience.
Took off top. Rotated the piston drive shaft off of rotating pin. then pulled piston out of cylinder .
New part went in in reverse order.
Rotary hammer worked after new part installation.
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