Is it a known issue for the fan hub bolt to loosen?

Backstory: car started running like hell last Spring on my Microsquirt conversion. Wouldn't rev, #3 CHT going vertical, very hot exhaust. WTF, over? I checked some basic stuff, nothing found.

Drove it again a week later and it seemed to be getting worse. Checked the ECU logs and all seemed normal, TPS, MPS, all working as expected. I even went back to a tune that worked great in November (only difference was cold startup stuff, which I can test/adjust in the Spring when it's colder), but still even worse. Checked timing with an adjustable light at full advance, spot on for what the ignition map was calling for.

I parked the car. Life was busy this year and I just didn't have time to deal with it. But I trotted it out again in September, and it was just as bad. Since I had problems with the IGN4VW coil a year or so ago (mounted in a hot place and was cutting out), I replaced the coil with one from NAPA.

Suddenly the car would not start at all. And when I looked at the ECU logs during cranking, I was seeing 0 RPMs. Bad crank position sensor?

Today I put the car on the lift and visually inspected the crank position sensor (as well as I could, anyway; the toothed gear replaces the A/C spacer) and the spacing of the CPS tip to the teeth was clearly too large; whereas it should be about 50-thou, it was actually around 1/8"-3/16". I pried on the sensor bracket with a screwdriver, and it was solidly mounted, no looseness.

I know I spent a LOT of time getting that sensor set just right during the install (you can't get it it with the engine installed). So I knew something was up. The sensor was solidly mounted, the toothed wheel was not loose, so there was only one thing to check...

..and yup, the hub bolt was loose, allowing the hub to walk outward. Sigh...

I tightened it down - best spec I can find in the interwebs is 23ft-lbs - and of course the car fired right up and drives fine. I hope this didn't cause any other damage...

Is this common? I've never seen it before. The engine was built in California and I truly don't recall who installed the hub, them or me. It's torqued down right now and I'm going to check it on a regular basis (I thought about pulling the bolt and putting Blue Loc-Tite on it, but if I lost that bolt in there then I'd be toast and would have to pull the engine to get it back. Arthritis in the thumbs and tennis elbow so NFW I'm tempting that Fate...)

Oh, and then I broke the door cam actuator when I was putting it back in the garage..it just never ends, does it...? - GA

It does not end

Having the fan/pulley loose on the crank is generally not good. Need to get things apart to get a good look at what's going on. There was thread recently with this issue.

IIRC, the hardened steel crank is no match for the aluminum hub

Good luck

Would the trigger wheel material have something with it? It is probably different than the stock spacer washer.

Edit: Sorry, just realized you aren’t talking about the fan, but rather the hub.

I can't seem to get the idle down below 1350 RPM, no matter how far I retard the advance (that's how I'm manging the RPM).

I just rechecked the ignition timing with an adjustable timing light and it's spot-the-freak-on between the pulley timing mark and the ignition map. Which makes sense, since the toothed gear is sandwiched between the fan and its hub and the CPS is fixed.

But then I pushed the rear tin back and compared the pulley mark to the nice big "V" notch in the top of the flywheel that I painted and highlighted when I installed the engine...and the pulley mark is about three fan blades retadrded versus the flywheel mark...or about 15-20 degrees off:

http://www.914world.com/bbs2/index.php?showtopic=339759

Using the diagram in that photo ^^^ my fan pulley is right about even with blade #3 when the flywheel "V" is centered in the crankcase split line.*

Sadly, I can only conclude that the hub keyway is either destroyed or missing and the fan pulley has moved. DAMMIT.

I sincerely hope I have not damaged the crankshaft...any reasonable hopes for that?

DAMMIT.

Looks like I have a weekend project...which I hope won't turn into a winter project.

DAMMIT.

GA

*Doesn't explain why I can't reduce my idle, as that's more a symptom of too MUCH advance...but it clearly does''t match the flywheel.

Was the flywheel mark marching the fan mark when you assembled it? I remember reading that there can be discrepancies and the flywheel was a better reference (if I recall…). Hopefully the experts will chime in.

I'd love to hear otherwise, but I seem to recall that when I was installing the engine I intentionally marked the TDC on both forward and rear flanges of the fan pulley as well as the flywheel. Yellow junkyard paint marker base with a black highlight...

I'm not going to feel comfortable driving it until I pull it all apart again.

Probably safe to take it down for inspection, if the fan/pulley is loose maybe it's not too bad. I would suspect the crank is not damaged, maybe the fan/pulley. Are you sure the tapered connection has come loose? The taper does all the work here, keyway is for indexing only.

No confirmation. All I did was reach in and snug the hub bolt - it had not come out entirely - down to 23 lb-ft, which seems to have seated the hub back on the taper and pulled the toothed gear back toward the CPS.

Here's the CPS design: https://thedubshop.com/type-4-crank-trigger/

But here's the question: if the hub moved rotationally on the crankshaft, then where's the keyway? I'm pretty sure the hub is fully seated back on the taper, as it's staying in place, I can visually inspect the backside behind the fan housing and the CPS is back to around 50-thou or so from the gear. I can't imagine the keyway would escape with only 1/8-3/16" walk of the hub? Wouldn't the face of the fan stop it from walking outward?

Or, did whomever put the hub on (could have been me, no idea to know for sure) totally forget to put a keyway on? I mean I suppose I could loosen the fan hub bolt and see if it spins freely...

So which is right: my fan pulley or my flywheel? Only way I can confirm TDC with any accuracy is a depth gauge in the #1 hole, and/or confirming that the fan pulley is keyed properly onto the crankshaft. To do either requires engine removal...

This is why smart people buy new cars. - GA

@GregAmy
Had the same problem last spring. Woodruff key sheared. You would be the third instance that I am aware of this year.

"Woodruff key". That's the search term I needed.

And I don't like what I found.

http://www.914world.com/bbs2/index.php?showtopic=365861
http://www.914world.com/bbs2/index.php?showtopic=363970

That last one is a damned good bit of info. And if this is becoming a bit of a problem with our engines...maybe this is a problem with our rebuilds.

I'm aware that taper fits are very reliable; hell, the '00 Audi B5 S4 I used to have had every pulley on its whole V6 timing belt system secured by taper-fit pulleys and no woodruff keys! (yes that made me nervous when I was doing the t-belt job). You'd jig it all up, move things into proper place, then tighten it all down (and, I thought to myself, "and pray"...it worked).

But to be reliable, the tapers have to fit snugly; if there's any imperfections then the friction is lost...and the bolt loosens and stuff moves.

I had my 914's engine rebuilt a couple winters ago. I sent the rebuilder a core engine I bought off here, along with all my accessories, probably including the fan hub. Now, let's be clear: I don't know who assembled the fan hub on this engine. But I wonder if either of us had even considered the "sympatico" of the taper fit of the hub to the crankshaft? I know I didn't.

We're a small community. The failure of three for this whole year really makes me wonder if using valve lapping compound on these things shouldn't be a standard part of our rebuild procedures...?

I'm likely to pull the engine onto my toolbox Edd China style and lap (likely a new) hub onto my crankshaft over the winter. It's annoying, but I suspect it could be worse.

Then we can talk about that 968 I convinced myself to buy (no, not letting go of the 914s...) - GA

P.S. Dammit.

The front crankshaft seal rides on the fan hub. If it sustained any damage, you will have a front seal leak.
When you go in, it's probably best to ditch the old hub and install a fresh one.
Lapping the tapered face shouldn't be necessary.

I mispoke earlier, crankshaft is hardened steel, hub IS NOT aluminum, but also steel

No front seal leaks, Chris. It only came out about 1/8" or so, so the seal was still sealin'...I agree you shouldn't need to lap it in, but I'll feel better if I do (and use Blue Loctite on the bolt).

I was thinking overnight how in the hell was the car was still running with 20 or more degrees retarded timing, let alone idling too high. Then it hit me: I'm actually off enough to where the car is running ~70 degrees or so advanced for the subsequent cylinders. And that makes sense, since I noticed it started hard the first time I tried (acted kinda like the spark plug wires were not installed correctly, which I subsequently checked) and I now do recall hearing some "tinkling" during my brief (2 miles) test drive after tightening the hub.

So it all comes down to "the hub spun on the crankshaft". I'll get a replacement hub and maybe pull the drivetrain onto my toolbox in a weekend or two (I'm fortunate to have a lift and a 44" toolbox...and beer).

Fingers crossed it just need some light filing/emery cloth and some lapping in...news to follow. - GA

I had the bolt come loose on mine a year ago. It all started with replacing the alternator. I adjusted the belt, went for a test drive, made it maybe a mile heard a bunch of noise as the fan became loose. I bought the car with a 2270 motor. Pulled the engine and found not much left of the key and the crank key way on one side looked pretty bad. Now I have a stroker crank that doesn’t look good. I went for it and did the shade tree mechanic repair. I figured that it will turn out to be a total rebuild if it didn’t work anyway.
I got anther hub and new key, then lapped them. The threads in the crank were worn because the fan moved with the loose bolt. I tapped to the crank to the next size. Used jb weld to set the key into the crank. The crank had one good side of the key way. Put the hub on and lock tited the bolt. The one thing I didn’t do and should have was confirm the timing mark on the fan in relation to the engine. Just a little bit off at the hub gets bigger at the mark on the fan. It’s close as I didn’t touch the distributor before and check the timing after and it looks right.
It’s been running for a year now with about 4000 miles. No problems.
Dave

Major victory "tapped the crank" I wasn't sure this was possible with it being hardened. Must be at the journals only

My gut would have said there is little chance for lasting repair when there is damage.

You can come see me for one of those hubs. I might have a good halfmoon key too.

Seems like there have been Woodruff key issues recently from what is being said…
Is this a situation of poor quality non OEM spec keys?

Good luck with your repair.

How many,what size are you looking for?

https://www.mcmaster.com/products/keys/

When fitting the hub, it should be mandatory to test with Prussian Blue

Bolt torque 23 ft/lbs

And...update. Here's several thousand words in photos.

Click to view attachment Click to view attachment Click to view attachment Click to view attachment Click to view attachment Click to view attachment Click to view attachment Click to view attachment

And a nice surprise:

Click to view attachment

Ouch

Any idea how long this had been loose?

Think this item will go on my list of winter projects, check and double check the taper fit

Just a wild-assed guess, but "not long at all". My fuel logs indicate I've driven it only about 400 miles since October 2021 (not a typo)...

The engine was rebuilt in November 2020 by a company out west, and I installed it over that winter. Fuel logs indicate that was roughly 2,000 miles ago. Most of the miles I put on it since were in 2021.

I seem to recall hearing a light banging noise from the front of the engine earlier this year or maybe late last year, but it went away off idle. Since I had installed a crank position sensor toothed gear behind the fan pulley when I installed the rebuilt engine I thought ok maybe I didn't tighten the fan? So I actually stuck a socket in there to check those bolts but they were fine...but I didn't think to check the hub bolt since I had not removed it since the engine rebuild; there was no reason to.

How long was the bolt loose? Anyone's guess. But with two o-rings stuck in there, maybe it wasn't even tight when I got the engine (or maybe the crushed o-rings affected the torque). I don't recall if I ever checked it.

I'd suggest it was a major failure of imagination on my part for continuing to drive the car once I heard that light knocking happening, and I should have parked the car right then and there to investigate it. That's my fault.

I'd also have to offer that, absent the cranked tooth gear getting massively off time causing the engine to basically stop running, it's quite possible I'd still be driving it anyway.

What a mess. We'll see if we can repair it. Otherwise I think the car will have to get stored somewhere long-term, as I recently got laid off and I have no desire, money, or patience to pay for a replacement crankshaft and new engine rebuild.

We'll see what happens. Fingers crossed. - GA

This happened to me.
The guy who put the engine back together got distracted and didn't tighten the crank bolt properly. It was just finger tight when the whole engine went back in the car.
It worked loose and sheared the woodruff key just like the previous pictures.
I noticed it at the emissions testing station. I was watching as the engine was running but the fan was not turning. It got hot enough to deform the rubber grommets around the spark plug wires.

The next time I saw the guy, I told him he was an idiot and tried to kick his @$$.











My wife is not happy about the broken mirror.

You owe my a keyboard.

Pretty good chance you can repair it with careful file work, emery cloth, lapping and Prussian Blue.

Patience

I’ve repaired worse looking Morse tapers to useable condition with just those basic items.


Don’t lose hope. Sorry to hear about the layoff - that hurts. Why do those companies always pull this around the holidays. them!

I'm a bit more worried about the damaged keygroove. Considering how to reshape the groove after doing some weld buildup on the edge... or possibly using bronze to secure the key on the crank. I'm pondering if I can do it on the assembled longblock. Tough spot to work in. First step will be to practice on another crank, without all the challenges.

This is not an easy repair. It's possible you can pull it off, but .....

From what I know the key/keyway do little work other than indexing the hub. At least 90% of the work is done with a well fitting tight tapered connection.

Woodruff key only determines timing mark location relative to crank.

If the key is a little loose side to side it will only affect timing as seen with a timing light. Example 27 degrees may now be 25. A little trial and error will figure out the offset.

The key has no significant effect upon securing the fan to the crank once the taper is engaged properly. This is borne out by how easily the key shears once the taper comes loose and can no longer handle the torque.

The taper does 100% of the work.

Machine tools like Jacob’s tapers, and Morse tapers, ER collets; all can take a lot of torque and none of them have a key way or positive engagement feature to resist torque. R8 taper has a key way, but that is only to prevent the collet from rotating while the draw bar is tightened, pulling the collet tight into the R8 taper.

I was recently reminded that early Miatas had a problem with the valve drive gear bolt coming loose; we used to lose Miata crankshafts often in racing, and checking the crankshaft bolt became a regular pre-weekend prep item. The design was fixed after '91 with a longer nose and bigger bolt.

The Miata design is different, in that it's a straight fit and the keyway drives the pulley. But a buddy reminded me of the DIY trick for "repairing" the situation if you're on a budget.

https://www.miata.net/garage/hsue/Loctite%2...%20Part%201.htm

And a video from Loctite: https://www.youtube.com/watch?v=LLSLtr0ECbc...%AENorthAmerica

I'm leaning toward small files to knock down the high bits on the backside of the key damage and then valve-lapping-compound the taper all the way around with a replacement hub (and bolt and key). Chris is leaning toward having me schlep the assembly to his shop for bronze TIG, but I'm wondering, given a good taper, if something as simple as Loctite 660 to stabilize the key would be fine. Loctite lists the shear strength of 660 as approaching 3000 psi, which is more than adequate. What I can't tell if the keyway would removable; I'm guessing not.

Let's check those bolts, team. It's not hard at all to do and I fear there may be more of us out there...23 ft-lbs and use Loctite 243 on the bolt. - GA

Loctite site says 500F heat to remove the key.

I have no experience with that product but sure looks interesting and appropriate for the application. I would imagine you’ll still get minor variation in timing depending on how perpendicular the key is to the crank.

I remember the Miata fiasco vividly - had a friend with a 90’. Mine was a 91’ specifically to avoid that issue. Pretty rare for the Japanese to screw up the engineering that badly but it happened - probably in the rush to get it to market. Put 220k miles on my 91 and never had an issue after they fixed it. Completely different design than a taper though!

https://www.youtube.com/watch?v=6-m2IT4Xojo

What grit lapping compound do we suggest?

Amazon cart has:
- Loctite 660 "quick metal"
- Loctite 22355 cleaner/degreaser
- Loctite 7649 primer
- Loctite 243 Blue threadlocker
- Small set of needle diamond jeweler's files

Add in some lapping compound and I can probably get this done for less than $120 and an hour or so of patient work (plus reinstall)...we'll see. - GA

P.S., I'm not worried about small timing variations. I can set my baseline timing off the mark I put on the flywheel, visible by moving the rear sheet metal back. I can even adjust it in the Microsquirt so that the pulley matches. The important part is ensuring the hub is secure and never to move again...

Start coarse and work down - use Prussian blue to monitor progress until you have uniform contact around - across the entire taper . With lapping compound it’s not like you’ll ever take too much material off.

Pits below the surface are of zero concern but you don’t want any high spots.

Budget three hours

Anytime I tell my wife it will only take an hour in the garage - it’s three or four.

Per other thread, Clay’s suggestion to pack the seal pocket with grease and/or magnet to catch shavings should be a good one.

Knock down the high spots, the low spots will be 0 contact, but will not hurt you

The high spots create point loads and will in a short time start to rock. You are looking for as close to 100% contact as you can get. The Prussian Blue will tell that story

Is this a build blog now...? Hey, maybe it'll help someone else in the future.

More conversation-via-photos, as follows:

- Reminder of the original discovery
- First pass at finding the high spots (using the sharpie method)
-




Click to view attachment

Is this a build blog now...? Hey, maybe it'll help someone else in the future.

More conversation-via-photos, as follows:

- Reminder of the original discovery
- First pass at finding the high spots (using the sharpie method)
- Surprisingly little rework with small jeweler's files and then a couple passes with 150 grit lapping compound
- Couple more 150 grit passes and the nose came in
- Couple passes with 280 grit lapping compound. Not much difference so I'm going with this
- Nighty-nite for the Loctite 660 to cure overnight

Wake up this AM expecting it to all be good...and the Loctite 660 hasn't set. I was listed as anerobic and for spaces up to 20-thou (my gap is about 1.5mm) so maybe I shouldn't be so disappointed. I sent a note to Loctite for guidance.

Maybe steel-infused JBWeld is the answer...? <shudder>

More soon. - GA

Click to view attachment Click to view attachment Click to view attachment Click to view attachment Click to view attachment Click to view attachmentClick to view attachment

That looks pretty good Greg

Tedious work, no doubt.

I know lots of folks swear by JB Weld but has anyone tried Marine Tex? It’s pretty tough stuff that’s also workable, on the package it says can be used to repair manifolds, etc...

Surprisingly, easier than expected. Really, only an hour or so worth of work (with another hour tossed in for being careful).

I'm all ears for any alternative materials; Loctite's response was, "It could be likely that your product is counterfeit as we do not support Industrial products sold though Amazon. Or you could not be using the product correctly, a primer is needed if the product is used on a passive metal."

GA

Looks like you are getting a decent amount of contact. What did you use as an abrasive?

Definitely looking better and promising.

Would love to see that lapped down to 400 or finer.

The smoother the surface finish, the higher the torque that can be applied to the taper.

I wonder if the loctite would have cured more readily with clamp force applied to the key to ensure that no oxygen was able to get in under the key or on the sides to get the cure started? Assume you did use primer too? Their response to the question is highly annoying as if Amazon is the only place that could end up with counterfeit product and that seems unlikely to begin with. Who’s getting rich counterfitting such a specialized product?

Not like your average auto parts store or Walmart carries their more specialized Loctite products!

You might want to make sure that the hub doesn’t bottom on the crank face before the taper is fully engaged. Could the crank have been to long and kept the first hub from fully engaging? Other people have had issues with counterfeit products from amazon sealing 911 cases.

This same thing happened to Betty's car 35 years ago in a little town called Copperas Cove, Texas. We were in town for an AX, and on her last, best run, the engine spit the fan into the shroud. She always said it was because of the lightened load on the engine gave her more HP to the wheels!

Turns out the bolt holding the hub onto the crank broke. So, with the help of a local auto parts shop owner, I got a wodruff key and a new washer and bolt, plus some locktite. I then took the hub off the fan, and put it back together. No crank polishing, no checking it, nothing. We had to drive home that day to be at work the next day. So It was a "field expedient" repair. One of the "repair" techniques I did was to use a brass hammer to drive the hub onto the crank before installing the bolt. That way I wasn't pulling against the bolt to install the hub.

The damn thing stayed on the engine for another 5 years before I had to remove it to replace the seal. And it was a bitch to get back off when I did.


Good luck in your fix!

Still ongoing. Using a dental pick I realized the very bottom part was solid (it's anaerobic, after all) and the key was supported so I put in the o-ring and crank seal for final install. Then as I was taking it out one last time for inspection (Shroedinger's o-ring) the key came out with it, along with some of the upper part of the 660.

Visual inspection showed that the bottom part of the 660 was still there and when I put the key back in it was well-supported, no movement. I slipped the hub on and there was no more side-to-side movement. So I packed the top of the space with "JBWeld Steel" and I'm going with that. It'll be reassembled today.

New spark plugs, fresh valve adjustment (love me them zero-lash chromoly pushrods) and I'll get the whole thing leisurely installed this week/end.


Loctive Clover 150 grit lapping compound, then a follow up with 280 grit lapping compound. Got plenty left if you need some...


Thought about going higher than 280 but honestly I think this will be fine. I guess we'll see.

Did not use the primer as I couldn't get it within a reasonable timeframe.


It's not; you can see how far up the lapping compound was grinding on the taper and there's a lot of space left. And when I test-fit the hub with the bolt torqued down the or-ring wasn't over-compressed.

I do kinda wish that I had measured the distance from the end of the hub to the nose of the crankshaft; I'm curious how much farther in all this cleanup and grinding allowed...

Will be watching.

I think it’s all going to work out just fine.

maybe put a bit of clay to get a measure from the back of the hub to the face of the crank? It's hard to imagine you took off too much material, but a double check might not be a bad idea.

NOTE: not an attack on anyone - no ill intent. I understand why folks would be concerned.

The distance the taper moves inward will be a fraction of few thousandths of an inch.

The distance moved inward is a function of how much material was removed (lets call that A) and the angle of the taper (lets call that angle Z).

The depth moved inward will be A x sine(Z).

Lets assume some numbers. Let's say .001" of material was removed off the surface of the taper by lapping. This would be quite a lot.

Let's assume the taper angle is 15 degrees (I honestly don't know what it is but it could be measured).

So removing .001" of material off the face of a 15 degree taper moves it inward .001" x sine(15) = .00026". You couldn't conceivably measure that with out CNC measuring devices.


Sleep easy tonight.

It's done, no more checks/changes. Hub, toothed gear, fan, and housing are on and torqued, valves getting adjusted tomorrow and back into the car it goes.

I'm sincerely hoping that I never have to post in this thread for as long as I own this car.

Go check your fan hub torque. - GA

Ok, really really last post here, I'm hoping: drivetrain installed, engine is running nice. Took it for a spin tonight and I'm pleased.

Interesting data point, the difference between the notch on the flywheel and the zero mark on the front pulley are 5 degrees apart, per my adjustable timing light; I don't know if it was like that before, as I always used the pully. I'll use the flywheel mark as my core reference. - GA

Ok, seems I can't quit you...

I was cleaning up the garage yesterday from the mess I made with this project. Came across the old pulley hub (with its slice of key still in the groove) and decided to add it to my "wall of shame" of failed parts I have (when you get into racing you tend to collect stuff like this).

On the shelf, I picked up the broken crankshaft from 2019(?) and was going to slide the hub on there but the crank still had a key in it; I tapped the key out and noted that the key was damaged, offset like the old offset keys we used to use on VW overhead cams for timing. And there were scuff marks on the downstream side of the crank nose where its pulley was chattering.

So that engine's pulley was loose, too. I don't know if that was related to the crankshaft failure, but this certainly caught my attention.

I put the race car on the lift and checked its crank bolt - that engine uses a Bus fan and shroud - and that bolt, too, was slightly loose, about 1/16 of a turn to get it to 23 ft-lbs. So I removed the bolt, loctite blue'd it, and reinstalled to 30 ft-lbs. And I know who built that engine and I know he would not have missed something like this.

One time is random; twice is coincidental; three times is a trend. I think we have a trend going on here. I certainly seem to...

Does anyone know the class of bolt that's being used here? The markings on it are not standard. If it's equivalent to a 10.9 then most charts are showing in the 40 ft-lbs range. The underside of the bolt has locks similar to a Schnorr washer, and I'm sure the engineer didn't want that taper to get hammered in too tight (it would be a bitch to get loose).

However, I noticed all three crank washers have a circular groove where those locks have dug in; if that groove is too deep then the locks may be making less grip contact. Are these supposed to be single-use bolts and washers?

Maybe I'm overthinking this thing, but I've now experienced three potential failures, just in my own garage. So I'm'a thinking that proper torque, Loctite Blue, and maybe new bolts and washers is in order here. And maybe a higher torque value.

Has anyone else checked theirs? What have you found? - GA