Let's brainstorm.

[Triple]

I need to remove the old timing belt cog from the nose of my Miata's crankshaft. After much soaking in much penetrating fluid, I have tried:

- Pry bars. The cog doesn't budge; rather, the lip around the inner edge of the cog breaks off.

- A puller. There isn't enough space between the block and the cog to fit the fingers of any puller I've ever seen.

- Drilling. The hardened metal laughed at my feeble Craftsman and broke the drill bit about 1/8" in. Then I discovered there was already a hole beside the one I was drilling. I tried hammering a nail (couldn't find my punch) into the hole, hoping the pressure would split the cog. Instead, I just made the nail impossible to remove.

- Cutting. Destroyed my Dremel trying to cut through the cog with the same wheels that have easily cut through chains in the past. Managed to dig a small trench with my reciprocating saw. I hammered a chisel into the cut in hopes of splitting the cog. No luck.

- Heat. I wanted to avoid this, but I eventually tried heating it with a propane torch. No movement. I let it cool and tried heating just the nail, hoping its expansion would split the cog. No dice.

I'm out of ideas. I can't put the car back together unless I replace this stupid fucking cog.





The healthy, patiently-waiting replacement:

[Amber Lamps]

It may be too late but I always spun hardened bolts in those "holes", they are normally threaded. Which pushes the gear out once the bolt contacts the metal behind the gear...

[Gas Man]

I'm still thinking puller. Most auto zones and such have a nice collection of pullers that you rent.

Or like tig says... but I don't see anything like that from your pics.

[azoomm]

Dry ice?

[pauldun170]

http://www.miata.net/garage/timingbelt.html
* 1990-'91: Remove the 21mm crankshaft bolt. This will be difficult. Put the car in 5th gear and engage the parking brake. Using a long breaker bar, crack the bolt loose.
* Remove the Woodruff key.
* Remove the timing belt pulley.
You may require a wheel puller to get this off.
* Remove the oil seal.
Be extremely careful not to score the crankshaft during the removal. This can cause leaks. The oil seal is a steel ring covered with plastic and rubber. The best way to remove it is to carefully cut the plastic and rubber and pry out the seal with a screwdriver. Be sure to put a piece of cloth between the screwdriver and the metal areas so you don't score anything. This takes a bit of work.
* Install the new seal
Coat the new seal with a bit of oil and press it firmly into place with your hands.
* Seat the seal
You need to drive the seal flush with the oil pump body. A large socket or pipe is good for this. I use a piece of pipe covered with tape to prevent damage to the seal. Drive the pipe against the seal with a hammer until it is seated flush.
* 1990-91: Replace the timing belt pulley.
* 1990-91: Install the Woodruff key.
* 1990-91: Tighten the crankshaft lockbolt to 80-87 foot-pounds.
* 1992 & later: Install the woodruff key and timing belt pulley.
* 1992 & later: You will need to install and remove the crankshaft bolt and pulley a couple of times, so install it, but do not torque it down.

http://forum.miata.net/vb/showthread.php?t=302020
http://forum.miata.net/vb/showthread.php?t=172497
http://forum.specmiata.com/cgi-bin/u...4;t=002926;p=0

[TommyHotWheel]

Puller combined with heat and melt some parafin wax on to the shaft while its hot and then try to pull it off.

[Triple]

There isn't enough space between the cog and the block to fit a puller.

I tried heating the cog with the torch-- for about five minutes straight-- and then hitting it with an upside-down can of air duster, but it still wouldn't break.

[101lifts2]

I cannot really see from the picture, but are there 4 threaded holes in that sprocket? If so, then you use a puller in which all four bolts are threaded into the sprocket and are bolted to a plate some distance away from the sprocket. Then a center threaded bolt, which is threaded into the plate goes into the hole to push on the crankshaft. When this happens, the sprocket is drawn away from the crank. If there are indeed holes, you would have to make a special tool specifically designed to remove this thing.

[askmrjesus]

Originally Posted by Triple

Managed to dig a small trench with my reciprocating saw. I hammered a chisel into the cut in hopes of splitting the cog. No luck.

Dude, step away from the Miata before you hurt yourself.

If you can't fit a puller in there, grind the arms down until they fit.

JC

[Phenix_Rider]

Originally Posted by 101lifts2

I cannot really see from the picture, but are there 4 threaded holes in that sprocket? If so, then you use a puller in which all four bolts are threaded into the sprocket and are bolted to a plate some distance away from the sprocket. Then a center threaded bolt, which is threaded into the plate goes into the hole to push on the crankshaft. When this happens, the sprocket is drawn away from the crank. If there are indeed holes, you would have to make a special tool specifically designed to remove this thing.

Look at the new one- there are no holes.

But I like your idea. Take a 1/4" steel plate, four grade 8 bolts and the original center bolt (or a longer one the same pitch), and a handful of nuts and washers. Drill five holes in one 6" square piece of plate for the outer section of the puller, and make two strips with end holes to go behind the cog. If you can't get behind the cog, get a REAL 3/8" cutting wheel and cut slots in the sucker. Dremels are fine for little stuff, but real work needs full size tools.