Continuing on the great intensive
overhaul of Mikuvan’s steering and braking systems, I took the opportunity while the front end was off the ground to address another mountain-induced problem. The power steering pump, which as far as I can tell is original, had been making “interesting” sounds for the prior year or so, mostly at the far end of steering travel.
After one of my fall North Carolina adventures, the same one which began seriously seizing a brake caliper, it got, shall we say, more drastic.
Not only was it making funny noises all the time, but the steering pressure had begun pulsating and it would puke fluid overnight to the magnitude illustrated. It seemed like it was pushing fluid not only out of the pump seals, but out the end of the rack as well. Something was just overpressuring all over the place, like a relief valve or overflow valve.
Yeah, with Mikuvan emitting substances on multiple fronts, it was time to just go over everything. You know what’s coming: With parts availability in the U.S. almost nonexistent, it was time for a mystery Chinese steering pump to join my mystery Chinese fully dressed cylinder head assembly.
I’ll point out that said cylinder head has been absolutely flawless in spite of my flogging these past few months. As I mentioned in that post, the entire premise of my part exploration is that Chinese people also probably like having cars that work.
Before I made any orders, though, I wanted to dismount the pump and make sure any replacement I get is dimensionally correct. While I was at it, I was going to take it apart for mechanical curiosity’s sake.
The power steering pump is the most prominent component in the entire engine cave. It’s just right there when you pop the hatch! One banjo fitting and two screws (and a catch pan) later, I had the pump on my workbench.
Yup, this thing is definitely old and beaten. I figured it was a vane or internal gear pump, and only the silver section in the middle did anything – the rest being bearings, manifolds, valves, and the like. The pulley appears to be pressed on, so my only choice was to deconstruct it from the backside.
Hey, there we go. Honestly, the pump mechanism itself looked way better than I was expecting. It was very clean inside, albeit full of slightly ｂｒｏｗｎed fluid indicative of overheating.
I plucked the pump housing ring and noted that it still had its original honing pattern even, so the pump section itself was probably not the issue at all.
The only other juicy thing in this assembly was the output valve, which is pretty complicated. My understanding is that the spool valve portion on the left which is spring loaded closed is the overpressure relief valve. If this portion is seized or sticky, then the pump will slowly destroy itself and everything it feeds with abnormally high pressure. Given it was peeing out the shaft seal (which otherwise seems undamaged) and was also possibly causing the steering rack seals to leak, I’m going to guess you’re the culprit here.
However, my mission for now isn’t to rebuild this pump, it’s to find the modern analog.
So back together it goes. I’ll keep this thing in a baggie in case I do need to blow the valve out and put it back into service, I suppose, or someone else is able to find a use for it.
My first stop, as usual, was RockAuto.
There wasn’t any in stock, but they had a rebuild service available. I was a bit doubtful of the rebuilding house being able to get all the parts too, but it’s good to know about and after all the dust settles, I might elect to try it out anyway.
The next stop was eBay, using the OEM Mitsubishi part number…
Alright, that was a mistake.
Interesting that these things come from overseas and are supposedly new and OEM – meaning probably new-old stock at this point. I’d expect the Middle East to still be crawling with 3rd-gen Delicas, so while it isn’t too surprising….
Alright, time to get a bit more creative. Instead of going by part number, I started searching for some variation of Delica or L300.
Now we’re getting somewhere. Not only am I getting parts that look the same, but I also have a list of presumably new and current part numbers. The MB501281 part seems to be the direct descendant of the OEM. Invoking my personal Law of Chinese Product Packaging Inertia, if multiple places are selling the same looking thing from China, you can probably hit up Jack Ma himself directly for better selection and pricing. My next stop was AliExpress:
This is just a selection of parts that cross reference to that exact number. If I just drop “Mitsubishi L300 steering pump” or similar in the search bar, I get a whole lot of newer models as well. Now, since I need the V-belt (not the serpentine belt) pulley and also the fittings to be in vaguely the right shape, the way to go is just using the MB501281 part number.
One of the traps prevalent both on eBay and AliExpress (and other Chinesium hawkers) is the shipping price is often deceptively high to mask the price of the object itself. So you have to compare things holistically – there might be a $100 part with $50 shipping that is more worth getting over the $100 part with $40 shipping, because the $50 shipping option actually is DHL instead of the Evergiven; the “cheaper” vendor in this case is trying to turn more profit by making the shipping artificially expensive.
So with a little prodding at different listings, I was able to find one which advertised a courier service instead of China Post, and received the part about a week and a half later.
Well, it’s definitely the right shape. Look, given the state of the world, that this object was able to be transformed from a pile of rocks and some cups of oil to even remotely the right shape, and was in my hands in a week and some flat from the other side of the planet… We truly live in a society.
Comparison time? Comparison time. The new pump has a larger pulley by eye, but I believe it’s actually the same pitch diameter because it’s designed for a wider section (1/2″ or 13mm) belt than the OEM. The pulley has a retaining nut, which implies removability. The fittings are practically identical. The new pump has a M10 tensioner screw hole (this will become important later) instead of M8, and the lower mount is a pressed-in stud instead of another threaded hole.
On the backside, virtually identical. The new pump body is cast aluminum instead of cast iron. I’m hoping there’s still a steel pump rotor and housing inside…
To fit the new pump, I had to convert the stud on the lower mount to a clearance hole for an 8mm bolt shoulder, as Mikuvan’s power steering bracket has a welded nut to accept the pivot bolt. The rear hole had to be enlarged to 10mm to pivot on the wider shoulder on that end.
A fairly easy operation with everything set up on the drill press. The pulley came off relatively easily after the nut was removed; it’s on a spline and is a gentle press fit. I didn’t have a 8 or 10mm “slip fit” drill, so I used the Next Best Thing in crazy inch land – a size Y (10.25mm) and size P (8.2mm).
With the pivot bolt sliding in freely, it’s time for a quick test fit.
I wanted to make sure the pulley was in the same plane as the other pulleys. Else, I’d need to machine the pulley slightly and add spacers to shift it around on the shaft. While a little bit of non-planarity with a V belt mate is “alright” at the distances involved, it’s to be avoided if you want long belt life and minimizing the risk of it jumping.
The next mild modification is the tensioner screw, which on the new pump is M10 x 1.25 pitch. The old pump, however, used a M8 bolt in the same spot, and the slider slot does not pass a 10mm screw.
This is where I decided to get a little cancerous. Coincidentally, the M8 coarse thread standard is 1.25mm pitch, while the 10mm fine thread standard is…. 1.25mm. You might see where I’m going with this.
By just driving a M10 x 1.25 Helicoil thread repair insert into the hole, I’ve turned it into a M(8 and a bit) x 1.25 hole. I call this “Reductionist Helicoiling”.
I used some thread locking compound on the insert and let it cure before installing the pump. That way, the insert itself is pretty permanent.
Sure, it’s a liiiiiittle bit wobbly, but drive a long enough screw in and…
Nothing matters. All the hosiery has been reinstalled now, with new copper gasket washers for the pressure hose. I trimmed the return hose some because the original section which went over the return fitting had become fairly mummified. I probably should replace this whole section eventually, but not right now.
And we’re under power. Nothing leaks, nothing made horrifying sounds. As I pointed out, the new pump pulley is for a wider section V-belt, so the original belt size looks funny in it. I filled up the reservoir (a few times) and cranked the steering wheel a couple of times to let everything fully purge.
That’s all for this episode. We’ll now zap forward a few months into this past spring, when one of the rear axle wheel seals began leaking, rendering one side’s rear drum brake rather ineffective and covering everything in grunge. That was an interesting dive!