Now that I'm looking around I'm thinking that the 1/2 hour leak test might be for other systems such as the cooling system ... that certainly makes sense.

For cylinder tests, one of the URLs above mentions a 1/2 psi loss in 5 minutes ... but that is starting out at only 10 psi, not 100.

 

Leak down tester measures pressure drop across an small (0.040-inch) orifice w/ a continuous air flow and upstream pressure (regulator) from pump. The percentage leak is ratio of measured pressure drop divided by upstream pressure. So a pressure of 20 psi drop across orifice over 100 psi upstream is 20% loss.

good luck

 

Okay, I understand how the leak test works now ... a simple compression test doesn't test with much pressure since the gases aren't igniting. With ignition in the cylinder chamber the momentary pressure in the cylinder chamber must be a whole lot more than the spec of 178psi ... I would guess an order of magnitude greater. You're going to get a lot more blow-by out of the cylinder in those conditions than a static compression test.

So the leak test will check for slow leakage which is likely to allow noticable blowby during ignition. Even a good static compression test result won't eliminate that as a possiblity.

Fyi I pulled the cat out yesterday to see if it was blocked -- it looked clean.

I then ran the engine with open exhaust (sounded like a Harley, not nearly as bad as I was fearing) to see if the air coming out of the valve cover oil filler hole would reduce or disappear -- it didn't. And the exhaust came puffing out of the header pipe reasonably strong ... so it doesn't seem like the exhaust is blocked in any significant way.

So that is now pointing back to rings and valves. Next up ... leak test ...

 

Rings only, leaking valves will in no way cause excess crankcase pressure (if anything, leaking valves will reduce crankcase pressure).

 

Youre right ... I was thinking leaky valve guides, but after thinking about it you're right, no way you would get blowby through the valve guides when the valves are closed

So if it's rings, then I may be out of luck. The car isn't worth the cost of an engine rebuild. So the question is -- is there anything cheaper I can do as a "fix" to relieve the crankcase pressure and alleviate the oil drips? I'm not concerned about top engine performance -- it still runs pretty strong -- I'm concerned about the oil mess the car leaves in the street over time.

Two things come to mind:

1) miracle ring repair products (ha!) ... I've heard about these, no idea if they really work. Again the engine isn't going to get a rebuild, and at this point I either dump the car or keep it around a a student vehicle, so something as questionable as a ring job additive I would go for at this point.

2) venting the oil filler cap or PCV valve so that it will let all of the air escape quickly. Probably illegal though, unless there is a way to get more air through the PCV (a high flow PCV valve alternative?) and back through the air intake.

Thanks. John

 

You can probably find a serviceable motor in a bone yard for under $500; if nothing else that will increase the resale value of the car if you decide to dump it.

 

It's still not worth it. The car needs some body work as well (was hit in the right rear quarter panel) which I am not planning to spend the money on at this time.

I checked around, and it looks like the first thing I could try is to up the viscosity of the oil. I'm using Penzoil dino 5w-30, but in the SF Bay Area our temps range from 50-90F and rarely ever get below freezing in the winter. Based on the attached chart found in the service manual, I should be able to go up to 20w-50 if I want.

I will start with 10w-40 on the next oil change and see how it goes.

 

Even if you change to 15W-60 grade oil it will not help the blow-by.

 

well, maybe it will at least help suppress the oil drips a bit more.

Currently the dripping issue is relatively minimal. Occasionally -- but not every time -- when I park the car I will get a drip wet spot maybe 2" in diameter. I can't tell when this happens because when I drive the car to work (8 minute commute, including one freeway exit) I don't seem to get an oil spot. So I'm trying to figure out when the oil seeps out. When it's cold only? When it's hot? freeway driving vs local driving?

Anyway, if by thickening up the oil a bit will allow it to withstand the crankcase pressure better and not seep out around seals, then I've pretty much solved my short-term problem.

The car otherwise runs fine. No error codes whatsoever, the crankcase and cylinders all appear to be clean. And a reasonable amount of power out of the engine.

 

Using a heavier grade of oil will NOT reduce crankcase pressure or oil leakage; folks have been trying that trick for literally decades now and I've yet to see even a single success story.

As I see it, your two options are to deal with the car as it is or swap out the engine.