...Bosch 11224VSC weak blows.

[Martel]

Hi...

I own a Bosch Bulldog 11224VSR rotary hammer that has very weak blows. I opened it and a quick inspection tells me the the general mechanichal is excellent for a machine that has worked A LOT.

But i also saw that the striker that travels inside the striker piston was quite deep inside the piston (which is in fact a cylinder). I took out the striker and then put it back inside the cylinder so the green O-ring was just passed the side vent hole in the cylinder. I then pushed it hard to check the air tightness and SURPRISE ! I HEARD A FAST AIR LEAK (PFFFT !). I removed the striker and inspected the cylinder's inside to see a circular groove machined in the cylinder. So, if i push the striker far enough to allow the O-ring to access this groove, i lose all my air pressure.

My questions:

1 - Where is the stryker supposed to be in the cylinder ? In front of the
machined groove or behind it ?

2 - If it's behind the groove what does cause my problem ? I inspected both the striker
and the striker pin and i found no signs of wear, no chips, no cracks.

3 - Is my problem with the green O-ring ? And what kind of grease should i use to
get sure i won't have any air leaks in the cylinder ?

Thanks for your attention !

Bosch 11224VSR Parts List and Diagram - (0611224739) : eReplacementparts.com

Edit: I saw that the're service packs for Bosch rotary hammers on eReplacement_parts but couldn't find the one for mine. Can someone help ?

[cmoorejack]

Hey Martel,
1. The striker stays ahead of the groove...
2. The problem is usually caused by a worn o-ring, loss of lubrication..
3. You will need to replace the o-ring..the striker needs to move somewhat back and forth in the chamber to build up a pneumatic force to "strike" against the striker pin..I use a lite air tool oil to lube the o-ring..you really don't want a build up of oil or grease in the chamber and some air has to escape so the striker can move..
as far as the grease required for the gearbox..part # 1-615-430-005 use the whole tube..
parts available at ereplacementparts.com
* not sure if there is a service pack for this model avail..none listed at Bosch website*
Hope this is helpful..
Craig

[Martel]

..the striker needs to move somewhat back and forth in the chamber to build up a pneumatic force to "strike" against the striker pin..I use a lite air tool oil to lube the o-ring....
as far as the grease required for the gearbox..part # 1-615-430-005 use the whole tube..
parts available at ereplacementparts.com
Hope this is helpful..
Craig

Thanks Cmoorejack ! That was helpful ! I went to a hardware shop and bought a bottle of pneumatic tool oil and put a few drops on all of the O-rings, inside the piston's rear portion (this way, the oil will remain inside the piston/cylinder) and also around the piston/inside the sleeve assembly.

I tested the hammer drill with a 7/8 inch carbide bit in hard rock and it works !! Solid deafening blows !

But i won't take chances, i'll order a set of O-rings and a tube of grease.

BTW, anyone, what do you think of synthetic grease (the red stuff that smells awful) ? Also, do i use the same grease for the front slow-revving parts and the rear high RPM input gearbox ?

Thanks !