Enthuza Car

Loctite Fix for the early (1990-1991) Miata Engine

Parts Needed

Name           Cost (Oct, 2000)
Mazda Crank Bolt #630-11-406C      $  8.98
Mazda Key
#B630-11-317A      $  4.11
Mazda Crank Pulley #B366-11-321A      $ 23.46
Loctite 660 Quick Metal        $   4.21
Loctite 243 Thread locker***        $  4.99
 
Valve Cover Gasket (optional)    
Mazda Crankshaft Seal (Optional)    

The Mazda parts came from Trussville Mazda (www.trussvillemazda.com).  The prices and part numbers from October 2000 appear above. They are probably 20% higher in 2007.

Loctite 660 was formulated by Loctite for pulley and keyway repair and is  harder to find. Mine came from an industrial supply house. McMaster-Carr . You can order from their web page - just enter loctite 660 into their search box. .

*** This page originally specificied Loctite 242, which is the standard "blue" loctite available at auto parts and hardware stores. Loctite 243 is 66%, but still allows the pulley to be removed with hand tools later. Available from McMaster-Carr. Also consider buying some loctite primer to improve ashesion.


Overview

Basically, this repair reassembles the front crankshaft assembly using a new gear, key a and bolt. The assembly strength relies both on the glue holding the gear to the cranknose, and the compressive force of the bolt.
Assembled gear and crank bolt. Crankshaft damage. An enlarged keyway..
 
New crankshaft key in worn keyway Heads on view of the assembly showing gap in keyway
   

The Loctite 660 is applied to the enlarged keyway and fills the gap after it cures. Depending on the clearance, either Loctite 660 or Loctite 242/243 is applied between the rest of the contact surface between the gear and crankshaft to bond the three parts (gear - key - crankshaft). Finally, Loctite 22 or 243 is used as a threadlocker on the crankshaft bolt.

Does it work? It appears so. One user has stated that he was able to run the engine 6 months after the Loctite Fix with the crank bolt removed and only the glue holding the gear on the crankshaft nose. See this link.

 

Is it Worth it?

This depends on how much it costs you, Clearly, a do-it-yourselfer has only the cost of parts and his time at risk. If taken to a shop, the labor is equivalent to a timing belt change, i.e, $300-500.Add parts, and you're looking at $700-800? At that point. it might pay to look at the engine replacement alternative..



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