No, that wasn't a used car inspection, that was a basic maintenance check.

For a used car inspection, they should put the vehicle up on a lift and look for signs of collision repair and/or rust damage. The steering components should be evaluated. They should look for leaks.

Dropping the vehicle to the ground, they should examine the body for signs of collision repair, rust repair and damage. All glass should be checked for cracks, chips and delamination. Windows should be operated to verify they all open and close properly. Door locks should be operated to verify proper working order.

The engine should be given a maintenance inspection (as was done) plus a once over to look for leaks. A scanner should be hooked up to see if any error codes are present. The tires should be inspected, doors inspected, all accessories turned on and verified operational and a test drive should be performed. 4 wheel drive systems should be activated to verify that they work.

Seat belts should be inspected. Air bags should be examined to verify presence. Lastly, all light should be operated and verified operational.

 

[QUOTECompression is easily checked by simply taking off the oil fill cap while the engines running. If none or a little white smoke is coming out, its ussually OK. If alot of smoke is coming out, those cylinders are shot. (ring blow by)[/QUOTE]

what about the other 4 cylinders?

 

redford - Thanks for the detailed response. Back to my original question though. Besides hooking up the scanner, don't you think the average person could perform all of the other functions equally well? Years ago I recall that a mechanic's inspection included a compression check of all engine cylinders, pulling brake drums, etc., all items that required some special tools and skills. The stuff you mentioned seems more cursory.

 

The crankcase is wide open, through the head drain holes, so if the other bank is leaking compression, you'll see it at either valve cover.

As for the rest of it, I find that most mechanics don't really care. They aren't responsible if something does crop up, and they are only going to be fixing it for the person anyway.

Of course, if it were me, and my mechanic inspected a vehicle and said it was fine, I'd take the vehicle somewhere else after that, but many MANY people get one mechanic and never EVER go to anyone else. Foolish...

This is why I work on my own vehicles

 

I've bought and sold over 100 vehicles in my life and I can tell you one of the first things I do during a roadtest is floor the gas. If something is wrong with engine/tranny, I will hear it. I've had a few people say don't give it full throttle, and my response is "what are you hiding?" I know some baby their trucks, but full throttle is allowed by the manufacturer otherwise they wouldn't have FULL throttle. Needless to say I did not buy either vehicle. When an engine/tranny is under full load, you will hear if there is a problem. I look for fluid leaks as well and general appearence. I go with my gut feeling. If something doesn't feel right, walk away. Just my .02, no change required.

 

Forgot to mention, compression test are ofter unreliable. To get an acurate measurement, use a cly leakdown tester. This is the most accurate test as it tests both rings and valves.

 

What you are witnessing by taking off the oil cap is crank case pressure. Every engine has crankcase pressure thus the reason for a Positive Crankcase Ventilation (PCV) valve. I agree that blow-by can be a contributor to crankcrase pressure but Im not sure I would strictly rely on this test to determine the status of the piston rings. Unless an engine runs a vacuum pump there is always going to be crankcase pressure and what we all consider excessive is a personal opinion.... unless of course the oil cap shoots through the hood. A clogged PCV valve or blow by tube would increase the pressure giving you a false assumption about the rings.

 

A good "seat of the pants" compression tester is listen to the exhaust at idle, and the intake at wide-open-throttle. If you notice any skipped cylinders, or any type of resonance in the intake, walk away.

There's almost no failure mode where bad compression, or a worn out cylinder(s) won't be obvious.

And Harley, good advice on the go-pedal-to-the-floor.

If they flinch, there's something wrong, or they babied it all the time. I'd rather have an engine that saw some use

 

Depends on your definition of "average person".

An "average person" wouldn't know the difference between milky oil, black oil, or nice honey-brown GOOD oil. Nor the smell of normal ATF vs. burned.

 

I called a couple mechanics when I was going to purchase a 1994 Explorer and was told they would put it on a lift, check for leaks, check the brakes for proper function, and I think they were going to check the compression. There were other basic things, check belts, etc.

One of the reasons the mechanic was going to check all of these things is his feeling was he'd get the "job" if there were things that needed to be replaced. At the time I didn't want to pay for anything that needed to be done and figured I'd do it was time/money allowed. I bought it anyway and just had all the fluids replaced (all of them). After a very short time there was a grinding in the front brakes and a lot of brake dust on the left front wheel. I had to replace the rotor, pads and wheel bearings. The four wheel drive didn't work either, but that was also fixed when I did the front end parts/hub assy.

I would have had to do it had the mechanic found it, but of course, again, the mechanic figured he'd get the job if he already had it in the air. Since I bought it without the mechanic's evaluation I had that $100 he would have charged me to do that diagnostic to put toward the repair I did (which ended up being $200 in parts). Thinking about it though, had the mechanic found and advised me of all the work it needed I probably would have passed on it not knowing exactly how much it would cost (me doing it versus the shop).

I can't imagine for the life of me why a mechanic would do a **** job. I'm willing to bet it'd generate additional work on half the vehicles they get in the air.

But, to answer the OP question, yes you can do it all yourself, probably in less time if you have a floor jack and basic tools.