In a message dated 97-05-05 14:16:04 EDT, prische(at)mshare.cupertino.k12.ca.us
(Paul Rische) writes:
>
>When starting up my Series V after sitting for a week or two, I often will
>hear a loud tap,tap, tap noise coming from under the hood. It would go a
>way after a driving a couple blocks or after restarting several times. I
>have been worrying about it and the last time it occured I also noticed the
>oil pressure was zero. After the tapping went away the oil pressure
>returned to 40 which is where it always is on my car when it is running.
>Any ideas of what is going on? I suspect the oil pump but any suggestions
>would be appreciated.
>thanks
Hate to ask it this way, but just how often do you look at your oil pressure
guage? From what you've written, it sounds like maybe you've been starting
up the car without noticing the lack of immediate oil pressure. Yikes!
Even a relatively fresh engine makes a "tap-tap" sound if it is started and
run without pressure long enough. If the "tap-tap" hasn't become a
"knock-knock," you might have lucked out and not need new rod bearings yet.
(I'm assuming the "tap-tap" is not just an abnormally noisy valve train
waiting for oil to make its way up top, which ALWAYS seems to take forever).
40psi at speed (hot) isn't great, but its not all that bad, either.
A bad pressure relief valve could cause this, but on the ones I've had
problems with, the pressure didn't drop until the engine had warmed up.
(keep an eye on the oil pressure when hot - if it noticeably fluctuates at
steady RPM's, its probably the valve) The oil pump is always a possible
culprit, as well as plain-old low-oil level. Any chance the dipstick isn't
original, or....? Another reason for lack of pressure at startup is under
the timing chain cover. That little pipe which drips oil onto the timing
chain has a spring loaded ball at the fitting. When the engine is turned
off, the ball seals the oil gallery so oil doesn't drain off, giving faster
pressure upon startup. Unfortunately, the spring gives with age, so that
eventually the ball ends up inside the spring. Even with a bad spring,
though, you should have some pressure within about 5-10 seconds.
Dick Sanders
Seattle
B395005413
B395009510
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