Pulsating Oil Pressure

The author is experiencing an engine oil pressure issue never seen before. The engine is a 231 cubic inch V-6 from a 1979 Chevrolet Monza Spyder. This engine currently has over 205,000 miles on it and is currently powering a 1984 Buick Regal that has over a quarter million miles on it. The engine powered the Monza Spyder for 95,000 miles and the Regal for 110,000 miles. All engine gaskets were replaced before installing the engine in the Regal. The engine has been well maintained over the years, uses approximately one quart of oil every 1,700 miles, and acquires about 22 Miles Per Gallon (MPG) on the highway in the Regal.

While the engine is running, the oil pressure gauge needle pulsates (i.e. wobbles, quivers, vibrates, etc.) at a frequency approximately equal to the engine crank shaft Revolutions Per Minute (RPM) and as much as 5 Pounds per Square Inch (PSI) above and below the oil pressure produced at a given engine RPM. This issue was first noticed at about 203,000 miles. Below is a list of videos that show the oil pressure gauge pulsating at various oil pressures. The videos were produced using a digital camera and are rather blurry and the movement of the needle is somewhat jittery compared to the acutal pulsating movement.

10 PSI

20 PSI

30 PSI

40 PSI

50 PSI

One theory was that the pulsating oil pressure may be due to a broken oil pump gear. The oil pump cover was removed and the gears inspected but no broken or worn out parts were discovered. For those interested, visit the Internet Web Page Oil Pressure Puzzler in regard to distributor gear breakage when installing oil pump covers.

It is currently believed that a part may be broken or missing that causes the pressure to be relieved for a few degrees of crank shaft rotation thus causing the oil pressure to pulsate. For example, suppose a portion of a lifter bore is broken out and as the pressurized section of the lifter moves past the missing portion of the lifter bore, the pressure would drop during that moment of time.

When the engine finally wears out (consumes excessive oil, pollutes the air, or acquires poor fuel mileage) or destroys itself due to a loss of oil pressure related to this issue, the engine will be disassembled and inspected for clues for what would cause the pulsating oil pressure (assuming any evidence remains if it does destroy itself). Any such evidence will then be included on this Internet Web Page.

In the meantime, let's see if Tom and Ray Magliozzi (i.e. "Click and Clack, the Tappet Brothers") at Car Talk can solve this dilemma as well as the Oil Pressure Puzzler.

The following email was sent to the Tappet Brothers at http://www.cartalk.com/email/email.html:

Hello Thomas and Raymond:

I have an oil pressure dilemma that I have never seen before. It is described and shown on the following Internet Web Page:

If you have any idea what would cause oil pressure to pulsate as that described, please feel free to contact me at: Tim026300@aol.com.

If you like, you may also investigate the "Oil Pressure Puzzler" at: http://SpareTimeActivities.net/OilPuzzler.htm.

Thank you for your time and efforts in this matter,

P.S. If you happen to know of anyone who may be interested in this matter, please do not hesitate to distribute this email message and the web page addresses referred to.

In case you ever wondered where their name, "Click and Clack, the Tappet Brothers", came from, it's because "in the old days of car repair, out-of-adjustment engine valves would click and clack and make quite an annoying racket-so the connection is obvious".