Stethoscopic engine testing

[REBrueckner]

My YF and 8V71TI engines were just surveyed and I wondered what engine experts think of the following survey statement and results:

"...stethoscopic testing of the engines in the course of operation indicated no looseness in the journals, main bearings,upper end components.water pump impellers or bearings...these are not new engines, but port engine ran younger..."

The engines were run under load about 15 minutes or so at about 1600 RPM and then again at WOT....

Can all this be ascertained from stethoscopic testing?? and what's the testing device utilized??? (I was stuck at the helm and so did not know what the surveyor was doing.) I had told the buyer the port engine had new liners, pistons and rings about 1,100 hours ago, so I wonder if the surveyor simply reflected that input or could actually "hear" a difference.

 

[mobilemn1]

I've actually seen my Dad take a long screw driver and put the handle to his ear to listen to internal engine parts for any unusal noises. Guess a real stethoscope would be better. I have used the screwdriver method myself to determine which cylinder was making the noise that I was trouble shooting for damage. I had one cylinder knocking a little in a cummins. I determined that the wrist pin was bad as the knock was only at the top end of the stroke. Sure enough the pin was shot.

 

[SportFishCruising]

I'm an independant manufacturer's sales agent; one product I represent and am Certified in is Acoustic Ultrasound which I sell for Predictive Maintenance purposes. The Ultrasound Unit allows you to listen and measure Db for turbulence, friction and metal on metal impacts. It is very similiar to having a calibrated screwdriver/stethoscopic to inspect for air/gas leaks, underlubriction and faults in bearings & gearboxes and listen to the operation cycles of steamtraps. We have detailed info and example sound files of bearing, etc. at www.sdtnorthamerica.com.
If I were listening to your motors, I imagine I would be able to detect which motor had been recently rebuilt compared to the other and able to pickup any grinding or metal impacts which could indicate 'looseness' or misalighnments and if something was just not lubricated properly.
I listen to the motor in my truck and boat for faults on occassion but haven't found anything. The advantage on your boat is that one can compare like motors under similiar load that should be performing uniformly.

 

[Trojan]

My experience with a stethoscope has only been used to isolate a given noise that you can hear but not locate. I would think that if you had a sound track of a previous engine you could compare. But to place it on an unknown engine. I would be hesitant to make any positive decision one way or the other as the condition of the engine. Outside of making general comments like it sounds like there no obvious strange noise. The engines are SOUND. Mind the pun. I think there are better ways to check the engines condition and adding the sound check would help backup the other. I would not make any decisions on the sound check alone.


BILL

 

[SportFishCruising]

I would not make any decisions on the sound check alone. BILL

I absolutely agree with Bill, one cannot do complete diagnostics by sound alone. In Predictive Maintenance, Ultrasound is a complimentary technology to temperature, vibration, oil analysis amongst others. Temperature has min/max standards, vibration spectra analysis signatures denote specific faults, sound is rather objective because it's variable amongst people and we lose hearing frequency range while aging. Acoustic Ultrasound measures Db which can be trended and set standards for alarms but other technologies are better for diagnostics.
I wouldn't want heart surgergy just because my Dr. thought he heard something with his stethoscopic.

 

[Finalee]

When in the car repair business we got pretty darn good with diagnosing wristpin noise, bearing rap, piston slap etc. with stethascopes. But that was on gas motors. Think it would take an extremely trained ear to do this on diesels.

 

[REBrueckner]

Has anyone had diesels surveyed by Detroit Diesel certified mechanics that used stethoscopic testing?

 

[yachtsmanbill]

Was that survey done by DR.DETROIT ??? That old boy should've done a colonoscopy down the blower to go with it... "Yup... the piston tops are black all right.. better get a rebuild..."
I thought you knew better REB...LOL. ;-)) ws
http://www.imdb.com/title/tt0085450/

 

[Will]

Although stethoscopic testing can provide valuable information, there are other commonly used techniques which in the hands of experienced diesel technicians, offer pretty reliable evaluations of engine condition. The key is your technicians experience, particularly with your specific model engine.

For example, I've seen 6-71s without con-rod bearing caps running at various maritime academies to impress students with 2-cycle engine design. What might stethoscopic testing tell you about the condition of those bearings.
Will

 

[MikeP]

"stethoscope" evaluation has been around for at least 100 years so it's not like anyone has invented anything new (except for a way to take someone's money).

It's another tool like any other..useful but, like oil samples or compression testing, should not be considered any sort of absolute. It's an indicator and should be treated as such.

 

[(Nobody You Know)]

You don't need a screw driver. Unscrew the wooden handle from the mop (you do have a mop don't you - and where it is?) and touch it to selected metal components of your engines (heads, pumps, gear, etc.) and place your ear at the other end. Get familiar with the natural sounds of these systems.

FWIW, invest in a laser beam (gun) thermometer. Make a record of what each system's normal operating temperature is at cruising speeds.