Old engine not losing oil? Count your blessings

  • Article by: PAUL BRAND
  • Updated: July 1, 2011 - 5:56 PM

QI am writing to you about my wife's 1987 Mazda RX-7 with 154,000 miles on it. The engine still runs perfectly, but I am concerned because it does not use any oil whatsoever between 3,000-mile oil changes. I am concerned that the "metering oil pump" is not working properly. This is the pump that lubricates the rotor apex seals.

Do you have any idea how much oil it should use in 3,000 miles? Do you think I'm silly to lose sleep because the car does not use any oil, or do you think I should get the metering pump checked out?

AIf the engine has survived 150,000-plus miles and still runs perfectly, go back to bed.

The rotary engine in the '87 RX-7 featured a mechanical oil metering pump that varies the amount of oil delivered to the rotor and epitrochoid (hourglass-shaped) combustion chamber via a metering rod attached to the throttle linkage. The higher the throttle setting, the more oil is injected to lubricate and cool the apex seals on the rotor.

You can check the function and adjustment of the metering rod and pump, but if you're really concerned and actually losing sleep, you can premix about one ounce of engine oil per gallon of gasoline in the tank to ensure adequate lubrication of the combustion chamber, rotor and seals.

I would guess that you and your wife drive the car so gently -- low throttle settings -- that very little oil is needed to lubricate the rotor and combustion chamber, thus the minimal oil consumption.

By the way, I've waited more than 25 years to describe the shape of the Mazda rotary engine combustion chamber as an "epitrochoid." Thanks for the opportunity!

QBoth the front and rear undercarriage on my '98 Lexus ES300 squeak when I go over humps. The dealership said I need to replace my shocks. But my trusted mechanic insists the shocks are still good and just lubricates all four joints every oil change. The squeak diminishes and the rear even totally goes away for a while. Any thoughts on what may be the real score?

ATired bushings, most likely. Since the squeaking diminishes or stops after lubrication, I agree that the shocks aren't the source. I suspect the rubber bushings on the shock/strut mounts and control arms have dried out and are sticking as the suspension moves up and down. Since the material is rubber, a silicone lubricant is a better choice than a petroleum-based lube.

Besides a visual inspection to identify any dried, cracked or torn bushings, the only way I know to identify a squeaky bushing is to spray individual bushings one at a time with an aerosol silicone, followed by a short, bumpy test drive.

My Alldata database pulled up technical service bulletin SU002-99, dated September 1999, that identifies an updated upper strut rubber bushing to address front suspension noise on bumpy roads.

QI have a 1997 Mazda truck with a 4.0-liter V6 engine and an automatic transmission with 105,000 miles on it. The transmission shifts hard from first to second gear, whether it is shifting up or down. It is very smooth on the other gears. Some mechanics feel it is electronic, some think it is mechanical and others think it is a linkage problem. What do you think?

AI vote electro/mechanical/hydraulic. How's that for covering the bases? First, try a half-can of SeaFoam Trans-Tune added to the transmission fluid before and after a fluid flush and filter change -- called for every 50,000 miles under "severe service" conditions. The problem is probably in the valve body, and the Trans-Tune can help clean and restore sealing function of the valves and accumulators.

A scan tool can identify faults with shift solenoids and other transmission components. If there are no fault codes present, focus on the fluid and valve body.

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