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I just did a head gasket replacement on my 1995 Acura Legend.

Before the replacement, compression was good on all cylinders except #3, which had blown. While the engine was open:

  • I cleaned off the pistons and cylinder walls with WD-40 until they were shiny.
  • Heads were within flatness spec, and the valves were lapped.
  • I didn't do a leakdown check on the valves after lapping them. (though I wish I had now) because I don't have an air compressor, or the right fittings to do a leakdown.
  • The block was also within flatness spec.

After putting it back together, I have not been able to get it started.

  • I had a timing problem at first, where I had lined up the cams with the timing mark, rather than TDC, and so it wouldn't work.
  • I thought it was a fuel problem at first, and probably tried a dozen times to start it with fuel dumping into the engine... oops. Anyway, the engine ended up thoroughly flooded.
  • I've removed the spark plugs to let everything dry and have fixed the timing, but still have super low compression on all cylinders (60 psi) and the engine won't start.

After looking around, I'm pretty sure that I have "washed" my cylinder walls to the point that the oil film is gone, which is causing me to lose compression.

My questions are:

  1. Does my hypothesis sound reasonable? Is there a quick way to confirm?
  2. I have seen some people recommend dropping some oil or ATF into the cylinder to help create that film again. I am curious to know if anyone had any experience doing that and if it matters that I get it up towards the top of the cylinder? With my engine being a "V" I feel like the oil will all fall to the bottom, and I'll only be partially successful at restoring the oil film.
  3. How much oil? A tablespoon? Two tablespoons? Or if I just crank for a while without the fuel injectors or spark plugs present will the oil film come back?

Thanks!

  • Welcome to the site. You have a super level of detail here! What compression numbers should you be seeing on this engine? – Zaid Mar 13 '18 at 6:22
  • I've always had a good time with the oil test regardless of cylinder shape, if you're very concerned you could use some fogging oil- sprayable oil- but I would also suggest changing your engine oil at this point as it's likely contaminated with gas, which will lower its viscosity significantly – Ceshion Mar 13 '18 at 12:00
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A teaspoon of oil is sufficient, but this trick does not work if the pistons are dished... the small amount of oil won’t be a problem, it will fall down / burn away.

  • It started right up! (made a pretty big cloud of smoke for a while) but it's running now! Thanks! – superjax Mar 14 '18 at 0:41
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If you attempted to run the engine with the valve train improperly aligned, you may have caused valve damage to your head, as this is an interference motor. This would definitely affect your ability to produce a lot of compression within the cylinder during testing and could be the reason why it's not running. Unfortunately, about the only way you'd be able to tell for sure is to pull the head and inspect the valves. You may be able to put a bore scope into the cylinders as well, but it would a bit of work to get the view of the valves. You could inspect for damage to the top of the pistons (small semi-circular dents ... damage wouldn't be great and wouldn't affect the running after a head was fixed).

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Does my hypothesis sound reasonable?

What doesn't sit well with me is that the engine has already been cranked a lot (when the cylinders were flooded). Regardless of whether the engine started, shouldn't that be enough to relubricate the walls?

Compression can be lost through:

  1. curvature in the cylinder head
  2. leaky head gasket
  3. leaky valves
  4. gaps between the bore and piston rings

Of these, the first possibility is the only one conclusively ruled out (through the flatness test). There is still a possibility that the other things are causing you grief.

It might be easier to test for valve leaks first.

Consider adding another item that could be a cause for low compression numbers: low intake air pressure. This may be due to a choked or partially-blocked intake.

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