Re: Vacuum Pump tick theory...was Re: 4000sq tick tick tick tick !!!

["Smith, Kirby A" <kirby.a.smith@lmco.com>]

Michael Williams <daserde@ucla.edu> wrote:

>>>>>>
Carey Lyn decided to speak these words:

>Sounds like the famous valve lifter problem that most 4kq and coupes 
>have. I have never met a 4kq or coupe that didn't tick.  I've heard
>it is a result of using the wrong grade oil and non-factory filters.
>Maybe a different grade oil or a special oil treatment would help.  I
>tried one oil that helped some but not totally.  The car would tick at
>first and then stop after it got warmed up.

Well, always make sure to check that it is not hte vacuum pump, that is
a 
simple procedure.  Anyway, no one seems to know why the vacuum pump 
ticks, except i now have a theory.

It seems as though the spring which activates the pump gets slightly
worn 
and there is a slight amount of clearance between the spring and the 
pushrod when it is fully inside of the engine...So, when it gets pushed 
back out against the spring, it ticks...that may be why it sounds so
much 
like lifter noise, it is a similar thing.  
>>>>

When I measured mine on my 90q, there was plenty of overlap, i.e., no
clearance; the pushrod was always under compression by the spring, at
least statically.  This does not preclude, of course, that a gap can
occur dynamically, if the spring-loaded pump shaft does not "follow" the
pushrod.  I have found that the ticking is ameliorated by opening the
vacuum pump cover and cleaning out the excess oil that builds up inside.
This approach was first suggested by another lister.  Information on
this is in the QFOM.

         ....  Kirby  (kirby.a.smith@lmco.com)
                   New Hampshire, USA
                      2 X 1988 90q