940 power steering question

[Aidan]

No, not yet Nick, been trawling thru the internet trying to find the info but just getting bogged down in endless lists of companies supplying recon racks. Found plenty of sites offering free repair manuals but when you click the link all you get is a load of advertising crap. I'll keep trying and if I get anything I'll stick it here. If anyone has the info I would really appreciate it, thanks.

[nick]

I found two brief articles that I will probably try to implement soon (with pictures):

Saginaw Style Pump Mod

Article by Jim Weed (No Pictures)

If I find the setup is similar to the "Saginaw" article, then I will try to shim the spring similar to the "Jim Weed" article.

[Aidan]

Thats the type of article I'm looking for Nick, I'm not sure about cars sold in the states but from what I've been reading, apparently there are 4 different racks that were fitted to the 940's sold in Europe so I need to identify what one I have and then see what I can turn up. If I find anything usefull I'll let you know.

[Aidan]

Nick, I just found this article, sounds like what we're both looking for,,,

http://www.swedishbricks.net/700900F...Identification

scroll down to "stiff power steering" near the bottom of the page

[Aidan]

Got it Nick, this is what we want,,,,

http://westtexasoffroad.homestead.co...rsteering.html

I'm going to try this at the week end on my old 740 first and see what the results are, if it works out ok then I'll do the same to the 940. I'll let you know how it turns out.

[nick]

Great! I'm excited to hear how it turns out for you. That looks like the same article I posted above (Post #12).

I don't think I have time to try it in my 760 this weekend, I'll probably have to wait until next week. I don't think I'm going to to drill anything, instead I'll just shim the spring to increase to the bypass pressure.

[Aidan]

Right, my 740 has a totally different pump so that blew that idea out, anyway, I decided to go ahead on the 940 and see what happens. I'll give a full run through of the procedure for anyone else wanting to try this. Before attempting this, make sure your pump and rack seals are good, if there is any sign of leaks it would be a good idea to get them done now as increasing the pump pressure could very well blow the seals out.

Ok, first place a clean container under the pump, clean the pump and run a wire brush around the fittings to remove any crap and muck. The fittings are very tight so use a spanner (or wrench as you yanks like to call them) to hold the high pressure fitting as you undo the feed line fitting otherwise the whole lot will turn and you wont be able to remove the feed line from the fitting
[ATTACH=CONFIG]212[/ATTACH]

Once the feed pipe is removed, remove the high pressure fitting then use a magnet to draw out the pressure piston and then a pair of long nose pliers to remove the piston spring. This is what you'll have
[ATTACH=CONFIG]213[/ATTACH]

and this is the part that you'll be working on, the pressure relief piston
[ATTACH=CONFIG]214[/ATTACH]

the article that I gave a link to says to hold the piston in a vice,,, DONT, you'll fuck it up, instead use a pair of vice grips to hold it like this so that you dont damage the machined surfaces
[ATTACH=CONFIG]215[/ATTACH]

also be aware that in the end of the retaining cap there is a very fine gauze filter so dont go poking around at it
[ATTACH=CONFIG]216[/ATTACH]

remove the retaining cap, be very carefull as the cap is VERY tight so make sure you've got a good grip of everything. When the cap is loose undo it with your fingers and be prepared for it to fly off as there is quite a bit of spring pressure behind it.

[Aidan]

This is what you have inside the pressure piston. I had to borrow this pic as my camera decided to play silly buggers at this stage
[ATTACH=CONFIG]217[/ATTACH]

Some pumps will have 1 or 2 shims as shown, other's wont, my one didn't. If you do have shims then remove one at a time and refit the whole lot to the pump and see how it is, if it gives you what you want, great, if not then you need to shim the spring that controls the pump pressure. basically what you do is get a couple of shims or washers and put them into the piston body then refit the spring, stud, ball bearing and cap. I used a couple of 6mm spring washers as they were a smaller diameter than the piston body, so that I could remove them easily if need be and also they wont restrict the fluid flow.
[ATTACH=CONFIG]218[/ATTACH]

I used 2 pair of pliers to remove the "spring" from the washers so that they sit flat, the height of the 2 washers was just under 3mm.
[ATTACH=CONFIG]219[/ATTACH]

The linked article says to grind off part of the stud to prevent it blocking fluid flow but I found that even with the spring fully compressed, the stud is still shorter than the spring so there is no way it can block off the fluid flow so I left the stud as it was.
[ATTACH=CONFIG]220[/ATTACH]

Now fit everything back together, be carefull as there is now a lot more spring pressure on the retaining cap and it can be a bit of a pig to get it back in.
Refit everything to the pump, top up the fluid, start the engine and let it run to bleed any air out and to make sure you have no leaks.
Ok, time for a test run. Well, there was a slight increase in power assist but nowhere near as much as I was expecting, or hoping for,,, however, what I did find was the steering was a lot smoother, and no longer suffers from "kick back" when driving round a bend on a rough surface so it was much nicer to drive and the self centering action was a lot better than before so definately some improvement, but I still wanted it lighter so I thouyght I'd have a go at stretching the main spring that the piston rests against in the pump, although I didn't hold out much hope for any improvement to be honest. The spring in my pump was just under 2 inches long so I stretched it to 2 and a half inches, fitted it back in the pump and went for a drive,,,
[ATTACH=CONFIG]221[/ATTACH]

Whoa, thats more like it now, a noticable improvement in the lightness of the steering, I can one finger it now quite comfortably under normal driving, and, there's no loss of road feel at all. So all in all, not too bad a result for 30 minutes work.

[nick]

Wow! Thanks for the write up Aidan. Now I'm even more excited about trying this on my 760!

[nick]

I just found this video for a Saginaw type pump like my 760: Here. Skip to about 1:30 for the good info. At 2:00 the guy pulls out the pressure regulator.