Thoughts on 2GM20 noise

[JasperII]

Good evening all,

So I spend the afternoon pottering around my boat, and started up the engine and discovered what I consider to be rather a strange noise.

Now to be honest I can't say whether this noise has been there all along (I've owned the boat around 4 months) but for some reason today my attention was drawn to it.

Before I bought the boat it had been serviced by a Yanmar dealer, so if there was any issues then I imagine it would have been picked up.

I've probably only done a total of 5 hours under motor since owning the boat.

I would describe the noise as a 'buzzing' and this frequency increases with revs.

Also the noise appears to be coming from the oil filter area, see attached video.

Does anyone know whether this is normal, or what the noise may be.

Any help much appreciated!

Greg.

https://www.youtube.com/watch?v=DdvZFY91XwE

 

[RichardS]

I thought you were going to have a metallic ringing which my Yanmars have and which is cause by a sort of loose metal cap on the mixture adjustment screw. At least I think it's the adjustment screw but I've not really investigated other than to put a cable tie on the cap which silences it.

However, mine are YMs rather than GMs and your noise does seem to be connected with the filter or oil pump. It doesn't sound like a problem and might be just oil pump gear noise being transmitted through the oil circulation system and being amplified by the resonance of the oil filter chamber .... which you then deaden with your hand.

Richard

 

[JasperII]

Thanks Richard, appreciate the reassurance!

I'm not an engine mechanic and haven't read up on the oil pumps on these engines, but I did suspect it may have been something like that.

I will bear in mind the adjustment screw noise incase it happens in the future!

Thanks again for your speedy response!

 

[earlybird]

That's a strange noise, the 2GM20 that I owned didn't make that sound, plenty of other noises, but not that!
Oil filters commonly have an internal by-pass valve to mitigate possible blockage, I wonder if that is rattling due to a fault.
I'd try replacing the filter, <£fiver, to see if the noise goes away.
Incidentally, I didn't think that my Yanmar had a mixture adjustment screw! Maybe an idle speed adjustment.

 

[RichardS]

That's a strange noise, the 2GM20 that I owned didn't make that sound, plenty of other noises, but not that!
Oil filters commonly have an internal by-pass valve to mitigate possible blockage, I wonder if that is rattling due to a fault.
I'd try replacing the filter, <£fiver, to see if the noise goes away.
Incidentally, I didn't think that my Yanmar had a mixture adjustment screw! Maybe an idle speed adjustment.

I think it's called the "high idle set bolt" but why it has a jingly jangly metal cap, I've no idea. It's not an idle speed adjustment in the normal sense as that is a lower screw which bears on the throttle arm and directly alters the idle position in the normal way and which I've already adjusted. I think it's something to do with the governor setting but I'm not a diesel engineer and I think the cap might be designed to stop me going anywhere near the screw underneath.

I think if it was the filter by-pass valve it would feel obvious when you touched the filter as the whole thing would be vibrating like a mad thing. However, as you say, it's easy to check by changing the filter.

Richard

 

[Spyro]

Sounds like the noise I used to get when I used a lollipop stick to click on the spokes of a bike wheel to make it sound like a motorbike but that was a long time ago. It sounds more like a noise from the alternator belt but why it goes when you put your hand on the oil filter is very odd. It could be resonance and the filter is amplifying it and by placing your hand on it it is muffling it. Other than the belt it may be the alternator, is the pulley damaged at all?

 

[charles_reed]

Thanks Richard, appreciate the reassurance!

I'm not an engine mechanic and haven't read up on the oil pumps on these engines, but I did suspect it may have been something like that.

I will bear in mind the adjustment screw noise incase it happens in the future!

Thanks again for your speedy response!

Not a gear-type pump but lobed

 

[RichardS]

Not a gear-type pump but lobed

Would that matter? As long as it's a mechanical pump with spinning parts, whether gears or lobes, or even a reciprocating design, it could give rise to vibrations through the oil delivery system which would potentially be most audible at the oil filter.

Richard

 

[Heckler]

g

Would that matter? As long as it's a mechanical pump with spinning parts, whether gears or lobes, or even a reciprocating design, it could give rise to vibrations through the oil delivery system which would potentially be most audible at the oil filter.

Richard

It sounds like a high pressure by pass valve in the oil system?
I would change the filter to be on the safe side.
Stu

 

[JasperII]

Thanks again for all your useful input.

My initial suspicion was the alternator belt being too loose (before I discovered the noise could be changed by touching the filter). I retensioned the belt. The alternator spun with no problem / resistance by hand with the belt removed.

I will be sure to order a new filter and get that fitted ASAP and see whether that resolves the issue.

As a note there didn't seem to be any excessive vibration when touching the filter - only what it sounds like you would feel - if that makes sense!

I will head back to the boat on Sunday and take my mechanics stethoscope and see whether I can narrow it down.

Thanks again for all the input, much appreciated.

 

[nemodreams]

The cap with the wire tag is the fuel rail max stop. Its tagged because of emission reg stuff - and is factory set to suit the engine set up.
When the governor stops spinning - the fuel rail returns to full throttle.
When the govenor spins - it closes the fuel rail.
The throttle lever pulls the other way with a spring - to counter it.
That way - if the engine over-revs fuel is reduced - if it hunts and slows - fuel is increased.
A very clever system based on a couple of springs and a bob weight - probably invented by Stevenson for his rocket and still used !

 

[RichardS]

The cap with the wire tag is the fuel rail max stop. Its tagged because of emission reg stuff - and is factory set to suit the engine set up.
When the governor stops spinning - the fuel rail returns to full throttle.
When the govenor spins - it closes the fuel rail.
The throttle lever pulls the other way with a spring - to counter it.
That way - if the engine over-revs fuel is reduced - if it hunts and slows - fuel is increased.
A very clever system based on a couple of springs and a bob weight - probably invented by Stevenson for his rocket and still used !

But why is the metal anti-tamper cap thing a jingly/rattly metal one? Both my engines were the same from new so it seems to be a deliberate design by Yanmar. I've now silenced them and the engines sound much better but why make them noisy?

I've just looked back through my engine photos (yes, I have detailed photos of both my engines from every possible angle just for reference purposes ... sad or what?). I think this was the starboard engine and the jingly cap is the waisted bobbin-like brass coloured thing in the top centre. This was taken a few years ago before I worked out how to silence the little buggers.

Richard

Richard

 

[Georgio]

Good evening all,

So I spend the afternoon pottering around my boat, and started up the engine and discovered what I consider to be rather a strange noise.

Now to be honest I can't say whether this noise has been there all along (I've owned the boat around 4 months) but for some reason today my attention was drawn to it.

Before I bought the boat it had been serviced by a Yanmar dealer, so if there was any issues then I imagine it would have been picked up.

I've probably only done a total of 5 hours under motor since owning the boat.

I would describe the noise as a 'buzzing' and this frequency increases with revs.

Also the noise appears to be coming from the oil filter area, see attached video.

Does anyone know whether this is normal, or what the noise may be.

Any help much appreciated!

Greg.

https://www.youtube.com/watch?v=DdvZFY91XwE

My 2GM makes exactly the same noise and always has done, I think it's coming from the Alternator when its working a bit harder at startup and seems to go away (i think) after a while.

Either way it's been like it for as long as I can remember and no issues.

By chance I removed the engine today and now have it set up in the garage to run tomorrow but without the alternator so I will see if the noise has gone. With no exhaust system I may not hear it though.... my neighbours love me!

 

[JasperII]

Excellent Georgio that's great to hear.

Your description makes sense as to why I've not noticed the noise. By the time I've started the engine up to leave, prepared everything in deck for departure and gone back down below it has probably gone.

I will run the engine up for longer next time and see whether it disappears.

Agreed - I'll be surprised if you can hear anything for the next week after running it up with no exhaust &#55357;&#56841;

Thanks again.

 

[JasperII]

I can confirm, having been over to the boat this morning, that the noise does indeed disappear after around 5 minutes of running, so looks like Georgio hopefully has the correct diagnosis!

Many thanks again for everyone's input.

Greg.

 

[Georgio]

I can confirm, having been over to the boat this morning, that the noise does indeed disappear after around 5 minutes of running, so looks like Georgio hopefully has the correct diagnosis!

Many thanks again for everyone's input.

Greg.

Ran my engine on it's trailer today with no alternator and the noise you recorded was not evident, I think between us we have proved it. Neighbour was out so no noise complaints!

I ran the cooling system through with some Fernox descaler following advice on this forum and a fair amount of Cr@p seems to have been cleaned out of the system. Great thing this forum for sharing knowledge!

 

[Heckler]

I can confirm, having been over to the boat this morning, that the noise does indeed disappear after around 5 minutes of running, so looks like Georgio hopefully has the correct diagnosis!

Many thanks again for everyone's input.

Greg.

Aha! Cold oil equals high oil pressure which means the pressure relief valve opens making the noise you describe, as the oil heats up the pressure drops and the valve stays shut and no noise from the fluctuating valve. Could be caused by a valve in the oil filter as well, some have a simple bypass valve in them, also, a bit unlikely, but could be caused by too high an oil viscosity rating causing higher than normal oil pressure when it is cold.
Stu

 

[RichardS]

Aha! Cold oil equals high oil pressure which means the pressure relief valve opens making the noise you describe, as the oil heats up the pressure drops and the valve stays shut and no noise from the fluctuating valve. Could be caused by a valve in the oil filter as well, some have a simple bypass valve in them, also, a bit unlikely, but could be caused by too high an oil viscosity rating causing higher than normal oil pressure when it is cold.
Stu

A test for Stu's theory might be to run the engine for 30 minutes until the oil is really up to termperature then stop it. Then turn on all the lights, fridge, whatever for 5 minutes to run the battery down a bit plus just using the starter will add to the drain, then re-start the engine and listen again.

If the noise is still there for a short time it is the alternator. If the noise does not appear then Stu's theory looks good.

Richard

 

[Heckler]

A test for Stu's theory might be to run the engine for 30 minutes until the oil is really up to termperature then stop it. Then turn on all the lights, fridge, whatever for 5 minutes to run the battery down a bit plus just using the starter will add to the drain, then re-start the engine and listen again.

If the noise is still there for a short time it is the alternator. If the noise does not appear then Stu's theory looks good.

Richard

Years ago had a Scimitar with the Ford V6, ran ok but come the winter I started it up, heard a quick bzzz and then noticed the oil pressure had dropped to zero! Switched off quick and had a look under the bonnet, the oil filter was split and most of the oil was on the floor. Cleaned it all up and got a new filter. A few days later it happened again, the same noise just before it blew, a bzzzz! The oil pressure relief valve was relatively easy to get to, turned out that the piston was jammed with crud. The garage (didnt fancy doing it myself, it was winter and the thought of getting cold and oily didnt appeal!) fitted a new one and no more probs!
Stu

 

[Heckler]

A test for Stu's theory might be to run the engine for 30 minutes until the oil is really up to termperature then stop it. Then turn on all the lights, fridge, whatever for 5 minutes to run the battery down a bit plus just using the starter will add to the drain, then re-start the engine and listen again.

If the noise is still there for a short time it is the alternator. If the noise does not appear then Stu's theory looks good.

Richard

Aha, the high pressure relief valve is right there in the oil filter mounting thread, see 20
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