Miata Mailing List: February 1993, Message #9
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   From: (none)
Subject: Another valve adjuster question
   Date: (none)

The question was raised as to engine valve noise after hard runs. 
According to the 1990 Miata Workshop Manual (Page B-7) tappet
noise may occur on starting the car (1) right after oil replacement,
(2) when the engine is started after sitting more than 1 day, (3)
after cranking more than three seconds, (4) after HLA replacement.  I
think that HLA refers to hydraulic lash adjusters. The noise is 
claimed to be normal if it dissapates within a few seconds after 
starting to ten minutes.  If it continues more then 10
minutes the manual claims that it is due to low oil pressure or a
defective HLA.  On the same table, tappet noise after high-speed 
driving only indicates low oil level or degenerated oil.  On page B-3,
however, engine noise related to valves or timing-related parts lists
possible problems in the HLA, a broken valve spring or excessive valve
guide clearance.

Herb Samuels