34: Compression Testing the Engine

We compression-tested the engine.

First you rent a compression tester. I didn’t even know this was possible, but then again I didn’t know about compression gauges and/or testing. Live and learn.

The premise of this test is to see what the overall health of the engine is. This helps when making assessments on engines...like doing a rebuild VS purchasing a new one.



Compression Testing

The compression gauge is stuck in the spark plug hole (minus the spark plug) and the starter mashed. Using a handy-dandy clipboard, make a grid chart for all 6 spark plug readings. This is a much better idea than trying to remember which spark plug had what gauge number associated with it. Numbers are recorded and on to the next spark plug hole.

This little gadget by the way is FREE to rent from any O’Reilly Auto Parts store. No kidding. Actually, O’Reilly (a national chain) rents a lot of equipment free for the asking. They figure when you find something wrong on your vehicle (and you probably will) you will come back to them for the parts. Very clever marketing.

After the first round of gauge testing and numbers are recorded down the line, each hole gets tested again but this time with a bit of oil squirted into it beforehand. The comparison tests (with and without oil squirts) tell the mechanic if the issue is a worn piston ring, a blown head gasket, leaking valves or both rings and valves. That last paragraph was for any gear head reading this blog (which is doubtful).

If you’re really curious (again doubtful), detailed discussion found here:

I asked TD what Abbey’s health diagnosis was and he said she was in full blown cardiac arrest.

Afternoon and evening discussions continued well into the next day about an engine rebuild or purchasing a new engine. 

At one time TD said, “You know, when we bought the truck you just expected to pay for it, and then hop in and drive it straight home 3 hours on the highway." 

That’s when I did the laughing. 

I told him back then I didn't know about the Old Car Domino Effect.

I’m learning.