924Board.org

[Beartooth]

Well, I'm still plodding away, hopefully getting close to being roadworthy. I've got a set of tires to mount when I get around to it, got one caliper rebuilt and painted, got a bunch of parts to refresh and reseal the transaxle and wheel hubs. I cleaned out the front hubs and repacked the wheel bearings. I wrecked one of the outer wheel bearings trying to use it to pull the seal out (I've found that's the only way to get the inner bearing out on my Mercedes, sometimes you can reuse the seal if you get a straight pull). The cage pulled off and just the inner race popped out. And then I find that the seals pop out easily by prying on the lip... So I put one new bearing and race in, but not a case of "probably needed it anyway;" the other bearings all looked great.

The disks are in rough shape - a little shy of minimum thickness - but they should work until I decide what's next. I got the ignition switch and turn signal switch replaced. The turn signal switch is an aftermarket replacement from RockAuto - one of the off-brands, but the part itself was made in Germany and had "Meyle" etched on it - it doesn't fit perfectly, the plastic through-holes are a little off, but I got it in and it seems to work. The genuine replacement is NLA, and I'm not sure if the KMM brand that's listed but out of stock is any different. Hopefully it holds up; it doesn't look like there's a better option out there.

Most of the work I've been doing recently has been on the turbo, and the gory details of that are covered in my thread in the 931 Tech section. That's all mounted up and should just need some finishing touches to be road worthy. Most recently, I decided to take the vacuum hoses and components apart and replace all the hoses. I'm still getting a big bog just past idle, and it takes some playing on the throttle to get it to rev past it. I haven't found anything that looks like a definite leak point, but I did find that the vacuum lines at the distributor were reversed. The port on the throttle body (pretty sure that's a "timed" port, closed until the throttle is opened part way) ran to the underside of the vacuum pot and T'd off to the vapor canister servo valve, while the line going to the constant vacuum side was connected to the top side. If I'm reading the sticker under the hood right, the timed port goes to the top of the vacuum servo on the distributor, and the underside port should be connected to manifold vacuum.

One other thing that I don't think would have anything to do with the bogging is that I have the port to the charcoal canister (or maybe it's that servo) on the air flow sensing assembly, just under the air flow plate, plugged off. I think that allows the slight negative pressure in the air flow sensing assembly to pull fuel vapors from the charcoal canister and draw fresh air into the canister from the air filter, and I'm not sure how blocking that would cause the bogging issue, but thought I'd mention it. I just started it up and adjusted the timing (took a little fiddling with my ancient timing light, but it still works!), then started running out of gas. I drained the first batch of gas I put in it (was just a gallon or so left) and put 3-4 gallons of fresh in recently, so I'm not sure how it ran through that so quickly. Could be it's struggling when it's low because of the filter I put between the tank and pump; I'll put more in to alleviate that before I start it again. I figure once I get it going, I'll run it mostly full while I have that filter in, then switch to the 944 strainer once I've run it around enough to clear the gunk out of the gas tank. If it were a straight drop-out, I'd have just pulled and cleaned the tank, but it looks like a big hassle to drop, and I don't think it actually got that bad, judging by what I'm seeing in the (clear) filter I put between the pump and tank.

Anyway, I've finally got the garage cleared out, so I figure I'll have it in and out to tackle the brakes, finish the clean-up items on the turbo reinstall, go through the halfshafts and repack and reseal the rear hubs, and replace the transaxle seals. I might add some transmission fluid to the transaxle once I get it driving to clean and flush that out a little. Not sure on that one; could do more harm than good if it's hard to get all the oil out. But if that's the case, it might almost make sense to drain and refill with the cheapest GL-5 I can get my hands, then drive it a bit and drain and refill with the Red Line oil I've got. Before that, of course, I've got to figure out why it's so boggy. Well, one thing at a time, I suppose.
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1980 931 diamond in the rough

[Beartooth]

Oh, one thing I forgot to mention: I got plates for it a week or two ago. I also inquired about personalized plates, but got some bad news on that. Montana won't allow just a number, and while nothing explicitly says they won't accept it, the person I talked to said they didn't think they'd accept an alpha-numeric with on letter and three numbers. What I was planning on doing was simply "931." That's definitely out. My next thought was "P931," but that's out too. I guess I could do something like PRSH931, but that's not nearly as "worth it" as simply 931. Incidentally, my Mercedes, before I bought it, had CA personalized plates with "W126" on it, so apparently I couldn't do that either. I was pretty gung-ho on "931" - it's simple, and only Porchofiles would get it - but I probably won't bother unless I come up with another idea I like just as much.
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1980 931 diamond in the rough

[Beartooth]

I've got her back inside (really good thing since it's below 0, and getting colder this week). I can start her up without much trouble, but it's hard to get it to do much more than idle. So, once I got it back in, I checked the control pressure, and it's way too high again. Kind of frustrating; it was spot on after I cleaned out the screen in the warm-up regulator. I took that out and cleaned it again, but it didn't seem to make a difference. Must be somewhere else this time. I think that explains the way it's running: if you adjust the set screw so it idles best, you can hardly get it to do anything more; adjust it rich, and it'll barely idle, but you can get some revs out of it. So I've got more work to do there. I'm still hoping to have her on the road before long; I'd better not hit the year mark without putting in a few miles! At the moment though, with these frigid temperatures, a bunch of seals in need of replacing (hatch seal is pretty much gone; sunroof seal isn't much better), and an iffy heater, it's probably a good time to have her inside and keep ticking off fix-it items.
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1980 931 diamond in the rough

[Mclaren924]

Let me know how you tackle the sunroof seal, been looking for a good one but no luck so far. Found a perfect donor hatch tho
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1980 931 "Salt" Bucket wannabe racer (not started)
1979 924 "Pepper" Restoration (almost done)
1980 924 "Donnie" (Parts car)-DEAD
1977 924 Slicktop "Pennie" Bucket turned Silver Spoon

[Beartooth]

Well, it'll probably be a while before I get to that, but I'll keep it in mind. I'm going to put a few miles on it before I commit to buying anything that's not needed to make it go and do so safely. That said, I've seen a few different options available. One is almost certainly garbage (URO brand), another is unbranded but from an "OE supplier" (supposedly made by the same supplier Porsche uses), and the OE replacement also seems to be available. I've seen reviews of the unbranded OEM seal that report a poor fit - have you tried that one? Given what I've read, I'd probably spend a little more for the Porsche part, but I have to wonder if that might have the same issue.
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1980 931 diamond in the rough

[Mclaren924]

[Beartooth]

Well, I'm finally making progress again. I had some other things get in the way, figuratively - I'm working on building a shop, had to pull the transmission on my truck, and going snowmobiling when I could - and literally, in the form of a huge drift that likes to form in front of my garage, so I couldn't have got it out even if it was ready to go. But the weather is turning nice, and I'm working on some of the "need" items to make her roadworthy.

Like I mentioned, I didn't have much trouble getting it running last fall, but it wouldn't rev much - it would just stumble and not pull much past 2000 RPM. The control pressures are way off (again), so it looks like I'll have to flush out the lines and WUR (again). I did some testing on the FD and injectors by putting each injector in a jar, and ran some gas through and measured the amount. I did it twice, and saw a maximum of 7% variation between the four. So the FD is probably fine. The injectors are still tending to dribble a bit. If you get a little flow going and back off, they all spray properly, if in irregular patterns. Injectors are on the list of things to replace if I can't get it to run right, but I've got some hope that they'll clean up with enough fuel run through them. I think I need to ditch the in-line filter I put between the tank and pump sooner rather than later. I notice the fuel pressure drops if you push the plate much past a third, and I think it's because that. Hopefully I don't need a bigger fuel pump; the one I got wasn't a direct replacement for the 924, but is spec'd for other CIS applications. I'll have to see if the fuel pressure holds steady once I swap to a proper fuel strainer.

Anyway, what I'm working on now is going through the rear brakes, bearings, CV joints, and replacing all the seals I can get at back there. The transmission has been leaking pretty badly, but at least the output flange seals are pretty easy to get to. Hopefully the front seal isn't too bad. One win, it seems I do have a limited slip. I got CV boot kits to replace all those. Surprisingly, the boots appear to be original, and still in good shape. I would have been tempted to clean them up and reuse them, but it would have been such a pain to get the caked-on grime cleaned off, and then who knows if they'd last. Frustratingly, while the boot itself that comes in the kit seems to fit perfectly, the clamp that comes with is too small, and the spring washer is too big and slides right over the stop under the splines. I probably needed to take the CV joints apart: the grease was pretty waxy, and I think the grease had been separating and a some of the oil seeped out over the years. I flushed them out and got them squeaky clean. They do seem pretty tight, so hopefully they'll be good to go for a good long while.

The brake drums and shoes all look decent, so I'll just throw it back together and make sure it's all in adjustment. I had one leaking wheel cylinder, so I bought new ones; the ones that I took off may be repairable, but both have some rust inside. One thing I'm wondering, what do you guys do as far as packing the hubs with grease? They were packed nearly full, and what was in there looked like it could have just been put in, but there was no circulation. I cleaned out the bearings, and they seem to be in great shape, but the grease in them was pitch black. I've always wondered if there's any point to packing extra grease in the hub; it seems like it always just sits there (especially on a stationary hub). I've never been able to find any solid guidance saying how much grease should be packed on either a stationary hub or rotating hub on spindle. Haynes is no help. The closest guidance I can find is from Mercedes service manuals, which uses a pretty similar hub, and says to pack 50g of grease in there. It's just one of those questions that's always kind of perplexed me: I've never seen how packing the cavity full does any good (and I have read it can't circulate at all without enough air space), but how much is beneficial is the question, or if it's actually needed. I have read of just packing the bearing, then smearing more around the bearing itself, but I can't imagine why they'd come from the factory with a bunch of grease in the hub if there wasn't a reason.
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1980 931 diamond in the rough

[Beartooth]

Well, I found an answer to the hub packing question, turns out Haynes does give an amount: 80g. I'd started with 50, so I added another 20g or so. I think if I do it again, I'll measure out 80g, draw from that to pack the bearings, then put the rest in the hub. It still seems like a lot: there's still some air space, but 80g is enough that it takes a little care to pack in. if I were to dream up my own amount, I'd probably go with enough to half-fill the hub, minus the area the spacer and shaft take up. I still wish I could find a good explanation on how much is ideal and why. I do know packing it completely is counterproductive and maybe even undesirable (It's a different situation with hubs like you find on trailers, but those are designed to let you pump grease in and through the bearings), and that just a thin coat around the hub isn't going to do much. I'm probably overthinking it. It's just $5 worth of grease anyway, so even if it just sits there for twenty years and gets thrown out, it's not the end of the world.
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1980 931 diamond in the rough

[Mclaren924]

I had to use two packs of doorman CV boot grease, think you could probably survive without all 80 but every axle I have ever pulled that wasn't trash was backed to the brim with it. Glad to hear things are going good on your build
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1980 931 "Salt" Bucket wannabe racer (not started)
1979 924 "Pepper" Restoration (almost done)
1980 924 "Donnie" (Parts car)-DEAD
1977 924 Slicktop "Pennie" Bucket turned Silver Spoon

[Beartooth]

Well, the axles are back together. I weighed out 60g of grease for each, which between the four kits left me with one leftover pack. I doubt it would have hurt to put the full 80g that came with each boot kit though. I'm waiting on a few new bolts to finish that up, plus I misplaced a couple of the washer plates or whatever you call them that I'm hoping will turn up...

Anyway, I've got the hydraulics all fixed up, as best I can tell (hard to test the clutch and brakes out while it's on jackstands, but both pedals feel like they should, and the clutch doesn't suck itself halfway down anymore). I'd rebuilt one caliper last fall, and finally got around to the second one. Unfortunately, the piston on the second one had a small gouge in it. I can only guess somebody tried to pry it out with a screwdriver at some point. I smoothed it out with a polishing stone, then filled it in with JB Weld and smoothed that back down. Not sure it'll do any good though; I'll just have to watch it and hope for the best.





I took one of the rear shocks off, and it's an original Koni. I have no reason to believe the front struts are any newer. I think I'll go with Bilsteins all around, but will hold off until I'm able to put a few miles on just to make sure I don't have any show-stoppers before I spend the money. I did paint the drums, as well as the axles, and will paint the exposed CV "pucks" too.

More recently, I decided to tackle the cooling system. Like almost everything on the car, I don't know that anybody ever touched anything on that. Every hose appears to be original. I've got the radiator hoses, and I think I can fit some generic hoses together for some of them (like the radiator to expansion tank hose). I did buy the water pump to heater pipe hose, and I'm tempted to buy the convoluted hoses going to the heater hose, but of course one's $50, and the other I can't even find listed anywhere. I found and started digging through the Gates hose catalog; there might be a couple that I could make work. It's quite a conundrum though, between spending money on the OE hoses, trying to make something else fit, or just reusing the original hoses (that look surprisingly good). I hate to just put them back in though: I had a hose spring a leak on my Mercedes last summer, and it's ten years younger. Add to that, I'd hate to have to dig back in as deep as I am right now just for a hose.

Finally, I've got a new thermostat to go in, and it looks like a good choice on that. The one that was in it is a 160 degree and I don't recognize the name at all (Bertshaw Controls). What's more, as you can see in the picture, it doesn't open as much, and the opening is smaller too. I doubt it'd cause it to overheat, but it seems the $25 or so was well spent here. The new thermostat is a Wahler (well-known German brand for thermostats) sold as a Borg-Warner.



So, progress. A little slow, but hopefully I'm closing in. I've got some bits and pieces for the hatch and such coming, along with a fuel distributor kit. Hopefully with that, plus cleaning out the frequency valve (I think it may have been plugged, which would explain some things) will get it running better. I'm also going to strip and paint the wheels before I mount the new tires. Finally, I have to tackle the shifter bushings. I'm not settled on it yet, but I'm leaning toward cutting an access for that; I'm just too impatient to go through the trouble of dropping the transaxle for now, plus it'll probably come in handy at some point.
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1980 931 diamond in the rough

[Mclaren924]

[Beartooth]

I'm planning on cutting the hatch now - I was leaning that way anyway, and it's the sort of thing only a very picky purist would ever care about (the kind who pays people to do this stuff). Right now I've got the steering rack stripped down. It's in rough shape, but fortunately, nothing broken. One boot was just sitting loose on the tie rod, and I think it'd been driven like that and/or never been re-greased. The rack has some pretty significant scoring where it rides against the adjuster. I took some fine sandpaper to smooth it out, just folding it over like a taco and pulled down on the ends, working it back and forth. I've got new boots, naturally, and other than the grease, it looks like that's all I'll be replacing. It seems anything like a rebuild kit doesn't exist, but for the 931 in particular, the worm gear and shaft have been out of production since I was a kid. We'll see how what I've got works for now; hopefully it'll still be pretty tight despite the wear and tear.

Anyway, I do have a couple questions. First is whether I need to worry about getting the pinion in alignment with the rack as it originally was. I know if I moved it over a tooth or two, the steering wheel wouldn't line up, but I'd think I could just re-clock that. I notice the pinion gear has a shiny spot that I assume corresponds to straight-ahead, and I'd think it'd be a little tighter if I turn it a couple teeth away from that, but maybe there's a reason to keep it where it was? Also, I'm wondering what the factory used for grease, and if anyone has any idea how much to put in. At my disposal I've got Mobil multipurpose synthetic grease, Valvoline moly synthetic grease (my go-to for packing bearings), a tube of Mobilith 1500 (a lighter synthetic industrial-grade grease), a tube of Lucas Red and Tacky, and a few packs of CV joint grease. I'm also reading of gear oil as the lubricant of choice for older racks, but I'm pretty sure that wasn't what they used, and I doubt the rack would be sealed well enough to hold it in. I'm guessing it's the kind of thing where anything will do a decent job if you keep enough in it, but I always have to wonder what the best choice is.
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1980 931 diamond in the rough

[Beartooth]

I just got back in town on 10-day trip that became a 12-day (thanks, United), but before I left I was tinkering with the Lambda controller, and thought it must be dead. I couldn't get a signal at the control valve connector, but it turns out I was missing some things. It wasn't really an issue for me, but the first thing I've found is that all you apparently have to do to power up the system is to jump the fuel pressure relay. You don't need the key on or anything else. Next minor item is that the frequency valve works by the controller cycling the ground, not voltage to it. The big thing I missed is that either the controller or something needed to activate it is grounded to the engine, so if you're troubleshooting with the engine wiring undone, it won't work. I finally figured that out when I connected the frequency valve with the system powered up and noticed it started buzzing momentarily when I was moving it around - I was momentarily grounding one of the ground straps on the engine wiring. Once I grounded that, it started buzzing away. Then I thought I could check the duty cycle directly at the frequency valve connector. I was able to get something, but my meter showed 22%, dropping to 10% when I grounded the full throttle contact. It may have been reading it backward; it may have actually been 78 and 90%, but I'm pretty sure those numbers are meaningless because it didn't seem to work properly until I checked it using the test connector WITH the frequency valve hooked up and buzzing away. Then I was able to get readings of 48% and 62% with the full throttle contact jumped. Those numbers don't seem quite right by what I'm reading, but at least they're in the ballpark, and should be good enough to make it run ok once I get it all back together.

I noticed one or two of the injector lines seemed to be pumping noticeably more fuel than the others when I checked it over a month or so ago, so I decided to get a "real" rebuild kit. I used a Salvox kit when I rebuild the FD in my 560, but I found a seller by the name of missingparts on ebay, based in Germany, that sells a more comprehensive kit and that may be better quality (hard to be sure). It did take almost two weeks to get here, but that's the only downside so far. Incidentally, you can buy all the o-rings you'd need - Viton and not just nitrile - for a few bucks, except that you're stuck either ordering online and getting quite a few more than you need because of minimum quantities, or buying just the number you need at a big mark-up. I've got half a thought to buy enough for a dozen FDs and resell them; we'll see. Anyway, the o-rings you'd need are:
Two 13x2mm for the top and bottom of the barrel.
Four 7x2mm for where the slits in the barrel port to the chambers.
One 17x3mm that goes in the base of the FD where the barrel seats.
Four 2x2mm o-rings for the trim screws adjacent to the injector lines.
One 4.5x2mm for the fuel pressure regulator plunger.
One 7x2mm for the outer end of the FPR.
Those sizes are all ID and o-ring cross-section. To get the OD, you'd need to double the cross-section and add it to the ID. I'm not totally confident on the sizes for the 17x3 or 2x2, but I think I've got the others. Some fudging will probably work, for what it's worth; I was able to make it work by putting in the closest o-ring I had sitting around. Nitrile o-rings should work, but won't last as long, especially if they're subjected to solvents or moisture (which is pretty much the case if you have to live with ethanol). Anyway, those o-rings and a new diaphragm should be all you need to rejuvenate a FD, provided it's not rusted out or mechanically damaged. As always, your mileage may vary, I'm not responsible for any damaged caused by following these instructions, this is a technical job that should only be left to professionals, yada, yada, yada.

Anyway, while I was thinking my Lambda controller was bad, I had an idea to use a PWM controller to control the frequency valve directly, and I think it's got some merit. You can pick up a 12v PWM fan/motor controller for around $10, but it seems most of those won't work. The issue is that they're pretty high-frequency. 25 kHz is common. At that frequency, and even lower frequencies I'm seeing (like 1200 Hz), I doubt very much it would work correctly. Most likely, it'd be too little to open the valve until you hit a certain point, and then you'd just have a very narrow range where it affected flow before it just held open. I checked the frequency the Lambda controller uses and it measured at 68Hz. It seems the two options would be to build a PWM from scratch with around the same frequency, and controlled by a rheostat (ideally), or to use a micro-controller like an Arduino. The latter might give you the possibility of incorporating a more sophisticated warm-up mode, and maybe even full lambda control, but I don't know enough about it. It's another thing I want to experiment with some day, but it's a huge can of worms I don't have time to get into for now. Obviously, you can incorporate a Microsquirt, but that's over $400 (even assuming you get most of the sensors and such that you need for free). It's such a rudimentary system, you could build and map a much more capable controller (giving you better warm-up and even the ability to compensate and adjust enrichment by RPM and such), and at a pretty minuscule build cost (like $50). Obviously, there are plenty of reasons to just go with a Microsquirt, but it's overkill for most cars, and too complicated if you're just looking to replace a faulty controller. I've done enough tinkering with electronics - minor circuitry fixes, I built a headphone amp, that kind of thing - and I think I could figure out how to build such a thing. The programming scares me most, really, but I should really bite the bullet. Of course, this is all a rabbit trail for now, but hopefully some day... If anybody else here wants to brainstorm, feel free to start a thread.
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1980 931 diamond in the rough

[Beartooth]

I've been making some progress, partly working on a top to bottom refresh of the cooling system. I've got just about everything torn apart on that, and have collected most of the hoses I'll need. I think I have found some alternatives for some of the NLA and crazy expensive hoses. Unfortunately, there are a few of those that I don't think there's any alternative to; it's a little painful because those 2-3 hoses cost as much as the whole box of Gates hoses I bought that I'm pretty sure will cover the rest of the system.

Anyway, the big thing I finally got done is painting the rims. I figured what better time to take care of that than just before I put the new tires on - nothing to worry about masking and no need for multiple trips to the tire shop. I'm not sure what you call the type of rims the 931s came with, maybe basket-weave or snowflake - but whatever you call them, they're an absolute pain to strip, prep, and paint. Maybe the best approach would be to dismount the tires and valve stem, then acid dip them or something, then powdercoat them. That would have been less labor, but probably just as much time running around town if I couldn't find a place that could do it all, and definitely more money. I used Summit Racing's urethane paint and clear coat (a silver metallic base coat, which could be used a single-stage, but I clear-coated so it hopefully lasts longer), and the total cost for the paint was less than $150 - and that's enough to do another two sets of rims! I might have to do one of my sets of Mercedes rims.

For stripping them, I first pressure washed them, then sprayed them down with paint stripper and pressure washed them again. That didn't take off as much as I'd hoped; it definitely didn't get down to bare aluminum. I won't necessarily recommend this, but next I took a brush and coated them with old brake fluid, and I think that did more than the paint stripper... Anyway, I wasn't able to get all the old coating (whatever they used) off, so I pressed forward and spent a couple hours with scotch-brite pads, painstakingly working into every recess. I still wasn't able to get down to bright shiny metal, but after spending a couple days working on it on and off, I decided to primer over it all and hope for the best. Short of a complete paint failure, anything would outshine how the rest of the car looks.



I decided to build a stand that I could set each rim on and spin it freely, and I would highly recommend that; you'll destroy your back and/or have a much harder time if you try to do it with the rim laying flat or on a fixed stand. I used a basic (Rustolium, I think) automotive etching primer. I made sure it mentioned aluminum; I'm not sure how much difference it makes, but I'm pretty sure using a bare metal primer can only help. That about wore my hand out! If you're going to rattle-can a set of rims like this, I'd suggest only doing one or two a day, or at least getting one of those pistol-grip attachments: it takes more force than you realize pushing down on the nozzle, and you're painting in hundreds of bursts. I used a cheap detail paint gun, and I wouldn't want to attempt it with anything bigger. That also helped because all I have for air right now is a pancake compressor. It kept up just fine, but I might have been pushing it's maximum duty cycle. I just did it outside on the apron in front of my garage - I didn't want the fumes getting into the house, and didn't have a respirator handy. PSA: I'm guessing most of us aren't as disciplined on that as we should be - kids, you might get away with it, but this stuff can hurt and even kill you, especially with repeated exposure. Moving on, I was fairly impressed with how the paint went on (we'll see how it holds up): it wasn't too hard to get it to lay on, and on a less difficult application I don't think I would have had any trouble getting it to lay down without sagging or running. On these rims, it was basically impossible to avoid a few spots where you built too much on the outside of the spoke while trying to work it into all the recesses and crevices. Fortunately, I can only find a handful of spots on each wheel where you can really see it, and I don't think it'll even be noticeable from a typical viewing distance. I also didn't take the time to clean up and fill the numerous nicks and dings - again one of those things that would have been nice but added more time to something that already took too long. Ultimately, I'm very happy with the results! You'd never confuse it for a top-dollar restoration, but I'd venture precious few to-fors would be let down by these slippers.






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1980 931 diamond in the rough

[Mclaren924]

Those rims came out looking really good mate, will have to steal some details for when I do some here soon.
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1980 931 "Salt" Bucket wannabe racer (not started)
1979 924 "Pepper" Restoration (almost done)
1980 924 "Donnie" (Parts car)-DEAD
1977 924 Slicktop "Pennie" Bucket turned Silver Spoon