TheSamba.com :: View topic - Trouble removing the fan hub on type 4 engine

Thu Apr 15, 2010 12:00 am

busdaddy wrote: When you do the final assembly JB weld the key into the slot ...

Some years back I had a chipped main pulley key on a Rabbit, and I discovered JB weld was not a successful solution. It lasted on a few days until it was pulverized to dust. Apparently the continuous shocks of combustion was just is too much for it to withstand. I eventually sold it and the new owner replaced the engine. However, a Rabbit crank pulley is driving the cam, so perhaps for an AC engine it may hold.
dan macmillan wrote:
Cut a new keyway 180 deg from that one. Mark your fan timing mark 180 deg from the orig. mark.
I wish I would have thought of this back then. I'd still have the Rabbit (it was a convertible and a blast to drive).

Thu Apr 15, 2010 6:12 am

I would have a quality weld shop TIG in on the nose of that crank where the key tore, dremel it again to fit a new key and run it. Replace the crank when you have it apart.

Thu Apr 15, 2010 6:38 am

Oh yeah1 lapping the taper with some Clover lapping compound is a great idea. I wonder if there's some way you could spin the hub with your drill?

Thu Apr 15, 2010 6:40 am

FlowerPowered wrote:
Some years back I had a chipped main pulley key on a Rabbit, and I discovered JB weld was not a successful solution. It lasted on a few days until it was pulverized to dust. Apparently the continuous shocks of combustion was just is too much for it to withstand. I eventually sold it and the new owner replaced the engine. However, a Rabbit crank pulley is driving the cam, so perhaps for an AC engine it may hold.

Does the rabbit pulley attach to the crank with a taper joint or just a straight shaft and a key? You are correct though in saying that pulley has a bit more going on, but not by much as any engine produces power pulses and that's what chews them up if they get loose. The advantage with a type 4 is the taper, when it's correctly torqued the key almost becomes redundant (other than as an initial locating device).

Thu Apr 15, 2010 6:41 am

GusC2it wrote: Oh yeah1 lapping the taper with some Clover lapping compound is a great idea. I wonder if there's some way you could spin the hub with your drill?
Im thinking if the JB is warm it will squeez out of the taper ok and fill in the lost metal.

Thu Apr 15, 2010 7:20 am

busdaddy wrote: FlowerPowered wrote:
Some years back I had a chipped main pulley key on a Rabbit, and I discovered JB weld was not a successful solution. It lasted on a few days until it was pulverized to dust. Apparently the continuous shocks of combustion was just is too much for it to withstand. I eventually sold it and the new owner replaced the engine. However, a Rabbit crank pulley is driving the cam, so perhaps for an AC engine it may hold.

Does the rabbit pulley attach to the crank with a taper joint or just a straight shaft and a key? You are correct though in saying that pulley has a bit more going on, but not by much as any engine produces power pulses and that's what chews them up if they get loose. The advantage with a type 4 is the taper, when it's correctly torqued the key almost becomes redundant (other than as an initial locating device).

Yep, it was straight. Also as a last resort I had a pro try to weld it, but the darn pulley was like pot metal, that didn't last long either before the weld broke.

Sun Jun 27, 2010 8:41 pm

Billfrog, what did you finally do to fix the chipped keyway slot? I was wondering if whatever you did to fix the problem actually worked. I have the exact same problem and was planning on using JB Weld. I was thinking of JB Welding the chipped piece back into the crank. I would love to get a response from you or anyone else who has faced this issue.

Sun Jun 27, 2010 8:59 pm

ftrdds616 wrote: Billfrog, what did you finally do to fix the chipped keyway slot? I was wondering if whatever you did to fix the problem actually worked. I have the exact same problem and was planning on using JB Weld. I was thinking of JB Welding the chipped piece back into the crank. I would love to get a response from you or anyone else who has faced this issue.

I ended up selling it to my niece, with the understanding it needed the problem fixed. She replaced the engine. However, I wish I had thought of this solution first, cause I loved the car, but that was 15 years ago and I was (more) ignorant:

SGKent wrote: I would have a quality weld shop TIG in on the nose of that crank where the key tore, dremel it again to fit a new key and run it. Replace the crank when you have it apart.

Mon Jun 28, 2010 3:46 am

I was planning to post an update after I'd had a chance to give my solution a good long test; so far it's holding up well but I've only done a hundred miles or so, so it's maybe a bit early to tell. Anyway, the full gory details of what I ended up doing are:

(a) I filled in the chipped-away part of the crankshaft keyway slot with JB Weld, to leave a clean slot for the key. However this was only done in order to keep the key snugly in place during assembly, to locate the hub accurately on the shaft. JB Weld is *not* a replacement for steel, whatever it claims, and I would never rely on it for strength in this situation.
(b) I then lightly lapped the hub onto the crankshaft with coarse valve grinding paste, to get the worst of the shaft surface roughness out. (I rigged up a contraption with a right-angle drill chuck so that I could use a variable-speed electric drill to spin the hub.) This left me with a pretty smooth metal-to-metal contact between the hub and shaft. (Sadly, it also revealed that the hub was sitting so far back on the shaft that the back rim of the hub was contacting the outer surface of the crankshaft bearing. So I had to rig up *another* lathe-like contraption to allow me to spin the hub and evenly Dremel a half-millimeter or so off the rear hub face, after which the hub sat nice and tight on the crankshaft taper.)
(c) I smoothed off the outer face of the hub (where the washer sits) with a file, to get rid of the worst of the weld remnants and provide a good even surface for the washer to bear on.
(d) I then reassembled it all, using Loctite 638 adhesive to secure the hub onto the crankshaft, and tightened the securing bolt as much as I dared. Loctite 638 is specifically designed to secure metal-to-metal taper joints; JB Weld isn't. Because of the of the fact that the hub was sitting further back on the taper than it should have been, I left out the O-ring that is supposed so sit behind the hub, because I wanted nothing there that could reduce the force of the centre crankshaft bolt. All the O-ring does is prevent oil seeping down the keyway, anyway, so I put a thin film of gasket sealant under the washer and head of the crankshaft bolt to stop any leakage.

Since then all has been fine (touch wood!). The new oil seal is doing a great job and I have no major oil leakage any more. In fact, the bus is running better than ever because when the PO welded the hub, I think he didn't get the alignment spot-on and so the timing mark has been about 5 degrees off ever since. Now that the woodruff key is back in place and the fan timing marks are therefore lined up properly, the engine is definitely running more smoothly than before.

This summer we're taking the bus for a week's camping in Amsterdam, so I really hope it all continues to hold together... but I'll post an update if anything exciting happens (!).