Rebuilding a power steering rack

Does your Mitsubishi L300 make a strange noise? Need wheel alignment specs?
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Rebuilding a power steering rack

Post by Growlerbearnz » Mon Sep 24, 2018 11:01 pm

My steering has developed a mysterious clunk and a touch of vagueness (EDIT: see next post for a postmortem on my original steering rack). More importantly though, someone pointed out that the steering rack on my van was probably the only part I hadn't modified, rebuilt or replaced!* We can't have that. Here we go...

Rebuilding a power steering rack. According to the workshop manual it's not rocket surgery, as long as you have all the special tools. I don't have the special tools, but I reckon I can figure something out.

You will need:
MN103497 rebuild kit (contains 2 of the 3 bearings, all oil seals and O-rings, teflon seals, tie rod lock washers, gaiter retaining bands, new locking nut, Molybdenum rack grease)
One bearing size 37mmOD x 20mmID x9mm thick, without seals (not included in the rebuild it, for some reason).
MR455426 tie rods x2
MB527650 tie rod ends x2
MB501711 gaiters/bellows x2
A steering rack suitable for rebuilding- no rust pitting on the rack, rack teeth shiny and un-worn.
Workshop manual ( (530.44 KiB) Viewed 749 times
2.KitContents.JPG (498.84 KiB) Viewed 749 times
3.workshopmanual.JPG (208.62 KiB) Viewed 749 times
I bought a steering rack from a 2WD L300 to rebuild, so the van wouldn't be out of action while I waited for parts etc. The 2WD rack is the same as the 4WD rack, except for the tie rods; 4WD tie rods are longer. The MN103497 seal kit is only suitable for L300 steering racks, which suggests that no other vehicles use the same rack.

Remove and strip the steering rack as per the workshop manual. Clean everything thoroughly, except the pinion and valve assembly- just blow any fluid out with compressed air. You don't want solvent or dust getting in there. Check everything for wear, especially the rack where it passes through the seals- it should be clean and undamaged.
4.RackDisassembled.JPG (294.08 KiB) Viewed 749 times
Remove the bearing from the pinion and valve assembly using a bearing puller.

Following the reassembly steps in the workshop manual:
35: back up washer and oil seal. Use the rack as an installation tool. On the short (non-toothed) end of the rack place one of the old rack seals (we're using it as a spacer), the new rack seal (lubricate it with ATF and slide it onto the rack carefully, with the lip first) and the backup washer. Insert the rack into the housing, and press the seal into place. Before you remove the rack, give the housing a shake- if the backup washer rattles, you haven't pressed the seal in far enough.
5.OilSeal.JPG (252.94 KiB) Viewed 749 times
34: needle roller bearing. This one needs to be pressed in, not hammered in (hammering can bend the bearing race and pinch the rollers), it needs to go in dead straight, and you don't want to damage the bore the pinion and valve assembly goes into later. I used an old bearing sleeve as a guide, with a close-fitting socket to press on the bearing, and a G-clamp to do the actual pressing. You could also wrap a socket in tape until it was a snug fit in the bore.
6.spacers.JPG (64.06 KiB) Viewed 749 times
7.Spacer.RollerInBore.JPG (62.8 KiB) Viewed 749 times
8.socket.JPG (63.46 KiB) Viewed 749 times (95.56 KiB) Viewed 749 times
Check that the needle rollers are installed all the way.
10.RollersHome.JPG (52.07 KiB) Viewed 749 times

33: oil seal. The rack support is the perfect size to press the seal in, if you wrap it with tape to keep it centred and to stop it damaging the bore. The manual says "be sure the seal faces the correct direction”- the lip goes upwards, towards the pinion and valve assembly/away from the needle rollers.
11.SealInstall.JPG (58.75 KiB) Viewed 749 times
12.rackSupportWrapped.jpg (60.96 KiB) Viewed 749 times

32: ball bearing. Get it started by hand, then install the cover plug to press it home.
13.bearinginstall.JPG (85.77 KiB) Viewed 749 times
-The rebuild kit comes with two O-rings that are nearly the same diameter. The thinner O-ring goes on the rack piston, the thicker one is for the end bushing/seal.
-Before installing the new piston O-ring and seal, polish the rack to help the end seals do their job.
14.PistonSeal.JPG (77.8 KiB) Viewed 749 times
25: installing rack in housing. Cover the teeth with a piece of PVC/electrical tape, leaving a flap of tape on the end (this will protect the new rack seal from being shredded by the teeth).
15.RackTape.JPG (257.43 KiB) Viewed 749 times
Lubricate the rack with ATF and install, threading the flap of tape through the inner seal. Catch the tape as it goes past the rack support hole, and peel it off as you install the rack.
16.PeelTape.JPG (76.63 KiB) Viewed 749 times
21: pinion and valve seals. Lubricate the new seals with ATF and slide them onto the valve from the splined end, so they end up in the recesses between your existing seals. (Keeping the old seals in place while you do this helps protect the new seals). Try not to stretch or twist the new rings- some stretching and twisting is inevitable, but try and keep it to a minimum.
18.ValveSeals.JPG (72.69 KiB) Viewed 749 times
Carefully cut the old seals, taking care not to scratch or damage the seal body or the new seals, and slip the new seals into place.
19.CutOldSeals.JPG (63.25 KiB) Viewed 749 times
20.StretchedSeals.JPG (72.52 KiB) Viewed 749 times
The new seals will have stretched, so to shrink them a little wrap the valve body very tightly in electrical tape, about 5-10 turns, stretching the tape as you go to build up the pressure.
21.TapeWrap.JPG (80.57 KiB) Viewed 749 times
Install the bearing while the tape is doing its work.
22.bearing.JPG (73.76 KiB) Viewed 749 times
Remove the tape and apply grease to the pinion, wiping it deep into the teeth so it won't get all over the seals or bore when you install the valve later. Grease the rack teeth.
23Grease.JPG (280.57 KiB) Viewed 749 times
Lubricate the valve assembly seals with ATF, then install the pinion/valve assembly. You will feel the assembly stop when it reaches each of the new seals- just push harder, and it will pop in. Watch your fingers!

Loosely install the tie rods, then install the retaining nut a the end of the pinion. (The tie rods stop the rack from moving too far so you can tighten the pinion nut).

Adjustment of pinion torque: you might have to get creative.
24.Cover.JPG (95.26 KiB) Viewed 749 times
Here's my amazing torque-o-meter.
25.torque.JPG (88.5 KiB) Viewed 749 times
You want to end up with the rack support cover *not quite* touching the rack support- the spring should be doing all the work. If the rack cover is touching the support, you'll be able to feel binding when you turn the pinion. The easiest way to get there is to wind the cover down until it stops, then back it up about a quarter turn.

For the rest, just follow the manual. It's fairly straightforward.
26.FinishedRack.JPG (344.36 KiB) Viewed 749 times
installed.JPG (326.17 KiB) Viewed 636 times
One last tip. Once everything is back together, wheels pointing straight ahead and steering wheel centred, but *before* you have it aligned, remove the bevel gear box (the thing behind the bumper that turns the steering shaft 90 degrees), rotate its input 180 degrees, and reinstall. The bevel gears mostly wear in the straight ahead position- by turning the gearbox 180 degrees you're now using the un-worn part of the gears for straight ahead. It just removes a little bit more play from the system.

*They're wrong: I've not touched the wiper motor and linkages, power window motors, or fuel filter bracket.
Nothing says "poor workmanship" more than wrinkles in the duct tape.

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Rebuilding a power steering rack

Post by Growlerbearnz » Wed Sep 26, 2018 12:35 am

...and here's why you might want to rebuild your rack as a precaution, rather than when it starts to get clunky. This is my van's original rack, 27 years and 275000km old, which I've stripped down after swapping it out for the rebuilt rack.

Here's the first sign that something's not right- rusty sludge on the cover plugs and rack support bush, it looks like a mixture of grease and ATF.
PLugs.jpg (327.83 KiB) Viewed 665 times
Yup, the grease is no longer a lubricant, it's more like a grinding paste with all the rust particles in it.
wet2.JPG (332.19 KiB) Viewed 665 times
wet.JPG (309.9 KiB) Viewed 665 times
This rack is ruined. Rust pitting on the areas that go through the seals:
Rusty.JPG (275.58 KiB) Viewed 665 times
rust2.JPG (255.1 KiB) Viewed 665 times
The rack teeth should be polished and shiny, not rough and rusty:
rack.JPG (70.86 KiB) Viewed 665 times
Even the far end has got marks where rust has etched the surface, and then been polished off by the seal:
SealGrooves.JPG (217.79 KiB) Viewed 665 times
This rack is ruined. Maybe a professional could polish the rust pits out of the rack (but they seem pretty deep), but the gear teeth are still wrecked. In the recycling it goes!
Nothing says "poor workmanship" more than wrinkles in the duct tape.

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Rebuilding a power steering rack

Post by thelazygreenfox » Sat Oct 06, 2018 8:05 pm

Good write up guys. Just went through a year of rack problems till I had mine rebuilt by Randy at Steering Solutions 9785 192 st Langley 1 877 513 9813

A month after the rebuild with lots of backroad driving it's still holding up well. FYI Randy is not a steering rack fan. If he blows you off wait a week and phone him back or just drive there and hand it to him like I did. He's a one man shop and does get busy.
. $525.00
MD :-D
I've been a lazy brown, green and white fox. :M Moby Dick isn't lazy anymore but what's a "Dick?" :-D

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Rebuilding a power steering rack

Post by Growlerbearnz » Sun Oct 07, 2018 1:41 am

Wow, that's a great price! I spent about CD$300 on parts alone (though shipping costs to NZ doesn't help).
Nothing says "poor workmanship" more than wrinkles in the duct tape.

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