Thursday, May 15, 2014

An Oil Removal Apparatus For Lawnmower Engines Without Drain Plugs

Our newish lawnmower has no oil drain plug in its engine. That appears to be becoming standard practice on rotary mower engines -- you drain the oil through the filler tube by tipping the entire machine over.

That's not exactly my notion of progress. One hopes that the automakers don't take up the idea -- then we'd see the price of oil changes go up more than a bit.

Anyway, the practice of draining oil through the filler tube struck me as needlessly inviting a huge mess, especially with my Briggs & Stratton engine. The configuration of mower-handle/engine/filler-tube just doesn't lend itself to a graceful procedure.

It dawned on me that I have a vacuum pump and a brake bleeding vessel, so I thought, "Why not apply them to oil removal?" I rigged up this.

And that worked fine. The only shortcoming was the small size of the vessel -- I had to stop and empty it a few times to get all the oil out.

The solution, obviously, was to adapt a bigger vessel, like a sauerkraut jar. A couple of 1/8" pipe fittings, some 7/32" diameter brass tubing and a few minutes at the lathe got me this.

Functionally, it's the same as before, but with a big enough jar to empty a crankcase at one go. Here's a view of the apparatus on the job on a Tecumseh engine.

It works. That beats wrestling with the entire mower to pour out its oil.

- - -


Following are some notes, in no particular order, on construction and use of the apparatus:

  • The jar lid's gasket must be in good condition. A jar lid that leaks vacuum won't work.
  • Brass tubing is available at hobby shops.
  • Use the apparatus on a warm engine, so the oil will be free flowing.
  • Oil capacity in rotary lawnmower engines is typically about one pint -- roughly 500ml. A 750ml jar serves with plenty of margin.
  • Just about any source of suction will work. If it has a check valve, it should also have a purge valve, so that suction can be easily terminated when desired.
  • One could use one's mouth as a suction source, but that would probably be ill-advised.
  • The only downside to the large jar is that it takes a fair bit of pumping at first to establish a vacuum. Other than that, the apparatus works nicely.

# # #

# # #