Squeaky O-320 H2D Engine

Squeaky O-320 H2D Engine

I've recently performed a pre-buy on a '79 172N and when we did the compression check we found a strange noise???  It sounds like an old rocking chair when the prop is rolled through the cylinders.  The noise appears to travel through all the cylinders as the prop is rotated.  It is not a belt...but something in the engine that seems tight.  The engine has recently had some TOH work and cleaning done to the cylinders but no notes in the logs on rings.  Any ideas?

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Re: Squeaky O-320 H2D Engine

O-320 H2AD 160HP ENGINE...Sorry.

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Re: Squeaky O-320 H2D Engine

Not sure what's causing your strange noise. I can tell you I had a rocking chair sound when the prop was turned back and forth a bit. Turns out we believe it was some of the rings scraping the cylinder walls. Noise disappeared after major overhaul.

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Re: Squeaky O-320 H2D Engine

My first thought  - the vacuum pump vanes. They like to make strange noises.

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Re: Squeaky O-320 H2D Engine

R.V.  I fly a piper aircraft that has lycoming O-360 series engines, and they both make the same noise you describe, engines have 500 hours SMOH .  Engines run great and have no mechanical irregularities to report.

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Re: Squeaky O-320 H2D Engine

I've been on the phone with Lycoming and Penn Yan tech departments and they feel the cause may be the Rockers or Guides.  At least, that's a starting point and can be further reviewed without too much time and effort.  I'll let everyone know what we find out.  Thanks.

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Re: Squeaky O-320 H2D Engine

My O-320 does the exact same thing. very faint, almost unnoticeable. I always suspected the vac pump.

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Re: Squeaky O-320 H2D Engine

Bryan,

That was one of the ideas that we had early on but it is "not faint" and it seems to move with the cylinders within the engine top itself. 

In this case, it doesn't appear to be a steady noise in the vac pump area.  They're going to take a valve cover or two off and look at the rockers.

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Re: Squeaky O-320 H2D Engine

Has anyone tried using a mechanic's stethescope?
Sometimes it's amazing how you can pinpoint a particular sound.

I hope whatever it is...is ever so minor!!
Michael

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Re: Squeaky O-320 H2D Engine

07100R.V. Wrote:
-------------------------------------------------------
> I've recently performed a pre-buy on a '79 172N
> and when we did the compression check we found awe
> strange noise???  It sounds like an old rocking
> chair when the prop is rolled through the
> cylinders.  The noise appears to travel through
> all the cylinders as the prop is rotated.  It is
> not a belt...but something in the engine that
> seems tight.  The engine has recently had some TOH
> work and cleaning done to the cylinders but no
> notes in the logs on rings.  Any ideas?

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Re: Squeaky O-320 H2D Engine

HI! I'm adem çakýr from Antalya/TURKIYE

We have a C172 and we havn't got the RPM over 2200. For that reason we need some recommendation for our aircraft.We have the propeller type of Mc Cauley 1c160DTM-7557.We need your halp immadeatly.Thank's your answer from now.

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Re: Squeaky O-320 H2D Engine

Hello Adem;

Has this been a problem since the engine was last overhauled?  if so, you may have a camshaft to crankshaft timing problem.(Please see my post from 6/25/2006). According to the POH and the Type Certificate Data Sheet for the 172N, the Static RPM should be between 2280 and 2400, with maximum cruise RPM of 2700 (Red Line). The Type Certificate Data Sheet is available on the FAA web site. The symptoms you described are what I experienced, which turned out to be the camshaft to crankshaft timing problem. The camshaft to crankshaft timing problem can be determined using the following procedure from the Sacramento Sky Ranch web site:

Crankshaft to camshaft timing off. Note: It is easy to assemble the Lycoming O-320H2AD with the internal engine timing 1 tooth off.

This condition may be checked by first disconnecting starter. Remove top spark plugs and rocker box cover on #2 cylinder. Turn engine to TDC on compression stroke #1 cylinder. Engine timing is checked by first observing the number two cylinder valve rocker arms. Both valves should be closed or nearly closed. Move the propeller slightly in one direction. Rocker arm motion should be seen as one valve starts to open. STOP. Now rotate the engine back to the original position with the #1 at TDC.. Now move the propeller slightly in the direction opposite from the first movement. Rocker arm motion should again be seen as the other valve starts to open. If the two valves started to open as described with only a small amount of engine movement in each direction, the engine timing is correct. If movement in either direction exceeds twenty degrees of engine rotation before motion of the rocker arm occurs, the crankshaft to camshaft timing is not correct and the engine was assembled incorrectly.

Check this before you attempt any repairs, as I spent a lot of money on a propeller overhaul, carburetor overhaul, magneto timing check, compression check, new tachometer, and other "fixes" that didn't solve the problem.

Hope this information is helpful.

Jon

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Re: Squeaky O-320 H2D Engine

H2AD, I'd stay away. That series had had ongoing issues with cams and lifters spalling. Also, instead of two seperate mags, it had two mags married together and driven by a single gear. It is a one off design....can you say expensive?

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Re: Squeaky O-320 H2D Engine

The "H2AD" engine is just as dependable as anything that Lycoming makes """Providing"""" that the Serial Number is suffix "T". Without the suffix this design is sure to make for tiny pieces of metal in the filter or screen. The original design used a modified version of the Ford 302cid lifter which did not last. The "T" mod as they call it, increases the lifer diameter about two fold, which also requires a new or refurbed case. It is getting harder and harder to find an H2AD without the "T" mod. As far as the magneto goes, it is a bit more expensive to overhaul, but if properly maintained it is a pretty dependable piece. One thing about this magneto that is very often overlooked, is when overhauling this mag, it is prudent that the condensers be removed from the cap/harness and sent to be checked for condition. Most of the dual mag overhauls that I have seen were simply a bad condenser eating points.

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Re: Squeaky O-320 H2D Engine

Regarding the squeaky h2ad-this is not an answer but my experience- My brother in law owned a 1980 172n that in 2001 at 1100 hrs had the same thing noticed at annual. The a&p condemmned the engine, causing a partial teardown to be done with no problems found in the engine. It was returned to service and he later sold the plane. Fast forward to 2008. I purchaced the same plane from an interim owner who had it from 2002 to 2008 and ran it to 1600 hrs. I am flying it now and I habitually level the prop when I tie down and secure the plane-you guessed it-it is slightly tighter to turn and is squeaky. I too suspect vac pump vanes. See if you notice it with a cold engine, i bet it is absent or much reduced. Bottom line, Im flying it to TBO and not worrying too much.

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Re: Squeaky O-320 H2D Engine

Tom Wrote:
-------------------------------------------------------
> The "H2AD" engine is just as dependable as
> anything that Lycoming makes """Providing"""" that
> the Serial Number is suffix "T". Without the
> suffix this design is sure to make for tiny pieces
> of metal in the filter or screen. The original
> design used a modified version of the Ford 302cid
> lifter which did not last. The "T" mod as they
> call it, increases the lifer diameter about two
> fold, which also requires a new or refurbed case.
> It is getting harder and harder to find an H2AD
> without the "T" mod. As far as the magneto goes,
> it is a bit more expensive to overhaul, but if
> properly maintained it is a pretty dependable
> piece. One thing about this magneto that is very
> often overlooked, is when overhauling this mag, it
> is prudent that the condensers be removed from the
> cap/harness and sent to be checked for condition.
> Most of the dual mag overhauls that I have seen
> were simply a bad condenser eating points.

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