Oil Pressure & Clicking Noise (Typical professorial tome, skip unless you are a glutton for punishment!)

["Dick Benjamin" <dickb@xxxxxxxxx>]

There is a type of exhaust gas leak that sounds a lot like a ticking valve
lifter, but you can separate the causes by noting that the valve doesn't
care what the engine is doing, it always sounds the same.  The exhaust gas
leak will intensify when you place a load on the engine or goose the
throttle.  There is also a mechanical cause of a sharp rap that intensifies
under load, namely a poorly fitted piston pin, but this is very rare in a
modern V8.

Valves that tick all the time are not a sign of anything serious.  (If the
car has hydraulic lifters, one or more has collapsed, and needs to be
cleaned or replaced, but no other damage is occurring, and if you can stand
the noise, you can drive it that way forever.  If the car does not have
hydraulic lifters, they are supposed to tick!)

Valves that tick for a short while after startup of a cold engine are not a
sign of anything serious.   (Hydraulic lifters will slowly collapse if the
engine is stopped with its particular valve open - some lifters take a week
to do this, some take a few minutes, and some seem to take it for a long,
long time.   If it shuts up shortly after the engine is started, no harm is
done and there is no need to take action).

Valves that tick only under the specific conditions that Dan described are a
sure sign of very low oil pressure, and his flickering oil warning light
merely confirms that situation.

Very low oil pressure is a very serious problem, and will lunch the engine
quickly if not taken care of.

To review the serious type situation, Dan has valve ticking after thoroughly
warming up the engine, and letting the engine idle or run slowly.  This
indicates that as the oil thins out from the increased temperature, the oil
pressure is dropping below the minimum required to operate the valve
lifters.  This pressure is only about 4 PSI, so the oil pressure to the rest
of the engine is probably also very low, low enough to wipe out cam, main
and rod bearings very quickly, and low enough to starve the higher parts in
the engine of adequate lubrication (things like rocker shafts, push rods,
timing chain and gears) and low enough to stop the spray on the cylinder
walls which keeps the pistons from galling the bores, and cools the cylinder
walls.   An engine in this condition is about 1/2 mile from seizing up!

Possible causes of this problem are many, and usually compound.  To list a
few, in probably order of importance:

1. Bearing clearances above specified limits.
2. Failing oil pump or blocked pump inlet screen, or stuck pressure relief
valve.
3. Oil too thin for the condition of the engine - worn engines require
thicker oil to keep the engine in service.

Dan was running quite thin oil, and his engine is probably nearing rebuild
time - thus the advice to use heavier oil, especially one which stands up to
high temperatures better.

Dick Benjamin
----- Original Message -----
From: "Mark McDonald" <tomswift@xxxxxxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Sunday, April 27, 2003 10:03 PM
Subject: IML: Oil Pressure & Clicking Noise


> Reading the recent posts about oil pressure problems and a clicking
> noise got me to wondering . . . how do you know when it's a valve
> clicking, and not something else?
>
> I have had small exhaust leaks on almost all my Chryslers.  And to me,
> they sound like "clicking" or "ticking."  Most recently, I had an
> exhaust leak on my '70 New Yorker that some folks SWORE was a bad
> valve.  My uncle, who has many more years experience than I working on
> cars, told me I was flat wrong when I said it was an exhaust leak.
>
> Fortunately, I have heard enough small exhaust leaks to recognize the
> sound, and I was right on that one (wish I'd bet him some money).  But
> I'm not sure if I've ever heard a bad valve.  How can you tell the
> difference?  Someone told me you could listen at the tailpipe, not at
> the engine, and if you could hear the ticking back there it was a
> valve.  Hmm.  Or was that the other way around?
>
> Anyway, just how do you know what that clicking is you're hearing??
>
> MM