Rebuilding a pressure washer

[zcacogp]

Chaps,

Just wondering whether there is anyone here with experience of rebuilding pressure washers? More specifically, I have an old Stihl RE102K machine, which has lost a lot of ooomph and is popping seals. I have it apart, and some new rubber O-rings would help immensely. Getting these won't be that hard, but finding out the torque settings required for the bolts holding the aluminium casings together would be appreciated.

I'll see if I can find an eMail address for the Stihl technical department, but PH may be able to help as well ...

Thanks, in advance, if anyone can help.


Oli.

P.S. Failing some Ft/Lb numbers, is there any way of calculating maximum torque for a given tread diameter, pitch and depth? There must be a formula for this sort of thing, and given the way the seals have popped I want to do it up as tight as I can, without stripping things. Anyone have any idea?

[spikeyhead]

zcacogp said:

P.S. Failing some Ft/Lb numbers, is there any way of calculating maximum torque for a given tread diameter, pitch and depth? There must be a formula for this sort of thing, and given the way the seals have popped I want to do it up as tight as I can, without stripping things. Anyone have any idea?

There is, but its very dependent on the quality and cleanliness of the threads. You'll get better results aiming for a snug and then an angle of tightening.

[Trevelyan]

If you're feeling mathematically minded

http://www.roymech.co.uk/Useful_Tables/Screws/Prel...

If you don't want a headache then there are some summary tables here:

http://www.dansmc.com/torque_chart.htm

I'm not sure what the implications of bolting into an aluminium casting are though. I'd guess the tables were created for steel bolts into steel threads. Failing all else, my strategy of doing things up until they scream for mercy normally stands me in good stead

[svm]

I'd nip the bolts up just past finger tight, then power it up. If it leaks, tighten a bit more.

Whenever I ask for torque settings, I just seem to get told to go with the manufacturers recommended settings most of the time. Bloody helpful that.

[jeff m]

I'm not aware of your particular model but....
Assuming it is multi piston....
If it is just a bit low or is pulsing then you could get away with new check valves.
If it is totally xxxxxx then you will have to re pack it. (and still put new check valves)
Re-building kits for most (good) models are available.

As with rebuilding any peice of equipment copious amounts of oil are used.
USE THE CORRECT OIL.

[zcacogp]

Chaps,

Lots of answers. Thanks.

The torque issue ... problemmatic bit is the final stage set of valves, which are are in an enclosure between two castings which are bolted together. There is an O-ring around each valve, and one of these (the end one) keeps popping out of the gap between the castings. The question is how hard ot tighten the casting bolts. They go into aluminium, and I don't want to strip it. However, I have done them up pretty tight and the O-rings still pop, out of an impossibly small gap. I am seriously thinking of getting some gasket card and cutting a proper gasket for the gap.

The torque calculation - thanks Trevelyan. First link is beyond my ability, second one is better but how do I know what grade I am on? Is this the grade of the bolts? What about going into a thread in an alumimium casting?

Jeff M - it sounds like you have tried this sort of thing before, thanks for chipping in. The snag is that I can find very little about the model in question on the internet (I think it is quite old). It is by a reasonable manufacturer (Stihl). It is essentially a large motor, with a pump on the end. The pump comprises three pistons which move in cylinders, with a valve in and a valve out of each cylinder. Each piston is around 1.2cm diameter, and the travel of each cylinder is about the same (1.2cm). They are arranged in a circle, and seem to move in and out in turn.

I am guessing that the check valves you speak of are the valves into and out of each cylinder. These are small plastic affairs, which seem to be in decent nick. However, it has started 'pulsing' recently and seems to be significantly down on ooomph in the last year or so. The popping of the seal is what has finally led me to dismantle it ...

You speak of using the right grade of oil ... I haven't come across any kind of oil reservoir at all. Have I missed something?


Oli.

[jeff m]

They very often sell pressure washers by the name of the motor that drives it.
Hence Honda Power washer, Briggs & Stratton etc.
Somebodyelse makes the pump. Of course I don't know that for sure with your model.
Does it have a info plate on it with perhaps a number starting with TSxxxx
Assuming it has three big nuts top and three big corrosponding nuts front, these contain the check valves, an O ring and an O ring on the bolt. These look like baby pyramids with a small spring inside. Pull 'em out with needle nose pliers get the old o ring out with a dental pic.

Oil is pump oil (mineral oil), you cannot use reg oil it will destroy rubber.

Re packing is the car equivalent of new piston rings, it is putting new peices of alternating rubber and brass rings on the "con rods" . The bottom end or big ends and main (car equivalent) are not usually needed to be changed as a pump does not undergo combustion. If they were worn it would be beyond economic repair. Approx pricing for pump that lists at $800; discount price 550, check valves 40 (for six) packing 70 (for 3), repacked by shop $180/220.

I erred on the side of caution giving out torque for an unknown pump, but remember to reduce by 15% for oiled bolts.
If you do not get a figure then 30 ftlbs would be my guess.

Oli, I just re read your post the check valves may look good (to you), but if its pulsing it is worth changing them as they are cheap and may give you a workable machine for little cost.

Edited by jeff m on Tuesday 13th January 15:50