Engine rattle at high revs - any suggestions as to culprit?

[Amh300]

Hello fellow boaters,

So, I've completed a ten day trip from the Midlands to London. My nb engine is a Thornycroft BMC 1.5-litre, four-cylinder, water-cooled, diesel engine. It was thoroughly serviced prior to the trip - new injectors and injection pump, new lift pump, and an expansion tank fitted. After about day 4 of gentle cruising, I noticed a vibration that became more pronounced over time. As you can hear from the video linked below, at low revs the rattle is inaudible but then gets louder as the engine is revved. I couldn't ID any obvious loose nuts/bolts. It became really annoying!

 

Link to video: 

 

I'm certain that this is an impossible ask, but does anyone have any bright suggestions as to a culprit? In the audio, you may also be able to detect a second, feinter sound too.

 

Thanks in advance!

[Mike Tee]

Have you checked any cupboards in the engine area for loose stuff? I had a second chimney that was stood on the back cabin stove and it took me a while to find out my engine was not self-destructing.

[Peugeot 106]

2 minutes ago, Mike Tee said:

Have you checked any cupboards in the engine area for loose stuff? I had a second chimney that was stood on the back cabin stove and it took me a while to find out my engine was not self-destructing.

My gas locker lid can sound a bit like that if it’s not on properly. Suggest you go round pressing on things and see if it stops to start with

[Amh300]

Other suggestions so far have been: Tappets; prop shaft coupling bolts; engine mounts. 

1 hour ago, Mike Tee said:

Have you checked any cupboards in the engine area for loose stuff? I had a second chimney that was stood on the back cabin stove and it took me a while to find out my engine was not self-destructing.

My engine area is cupboard free - but it's a good suggestion. And I would be delighted to discover that my engine is not self-destructing!

[matty40s]

I see no engine....

 

Take the top cover off and check if oil is making it up to the rockers or not??

Found the same on a RN this week.

[MtB]

Have to say, it doesn't sound like an engine rattle to me. More like something around or near it clattering. 

[Rob-M]

I had a horrendous noise when one of my floor supports dropped on to the top of the engine, I thought the engine was about to blow up.

[Tony Brooks]

45 minutes ago, matty40s said:

I see no engine....

 

Take the top cover off and check if oil is making it up to the rockers or not??

Found the same on a RN this week.

 

It certainly sounds as if it could the early onset of a lack of rocker lubrication, but who knows. Several of the suggestions are plausible. I think it is time for a listening stick.

[Amh300]

14 hours ago, matty40s said:

I see no engine....

 

Take the top cover off and check if oil is making it up to the rockers or not??

Found the same on a RN this week.

Thanks Matty- photo of engine FYI 

13 hours ago, Tony Brooks said:

 

It certainly sounds as if it could the early onset of a lack of rocker lubrication, but who knows. Several of the suggestions are plausible. I think it is time for a listening stick.

Thanks for the suggestions - what's a listening stick? 

[Tony Brooks]

1 hour ago, Amh300 said:

Thanks for the suggestions - what's a listening stick? 

 

A length of wood, a long screwdriver, or a mechanic’s stethoscope, which is a bit like a medical one but terminating in a length of metal rod. One on goes to an ear and the other is touched at various points (usually on the engine or gearbox) and when you get close to the source of the sound it becomes much clearer/louder.

 

Edited to add - don't on any account touch the listening stick to any moving parts, especially if the other end is against your ear.

Edited July 6 by Tony Brooks

[PeterF]

1 hour ago, Tony Brooks said:

 

A length of wood, a long screwdriver, or a mechanic’s stethoscope, which is a bit like a medical one but terminating in a length of metal rod. One on goes to an ear and the other is touched at various points (usually on the engine or gearbox) and when you get close to the source of the sound it becomes much clearer/louder.

 

Edited to add - don't on any account touch the listening stick to any moving parts, especially if the other end is against your ear.

And if using a long screwdriver but the blade against the engine and the handle against your ear, not the other way round.

[MtB]

Thanks for the photo.

 

Does it still do it now you've lifted the floor panel over the engine?

 

 

[Amh300]

20 minutes ago, MtB said:

Thanks for the photo.

 

Does it still do it now you've lifted the floor panel over the engine?

 

 

When I lift the floor panel, I can't hear the vibration over the sound of the engine. So, I'm assuming the vibration is continuing.

1 hour ago, Tony Brooks said:

 

A length of wood, a long screwdriver, or a mechanic’s stethoscope, which is a bit like a medical one but terminating in a length of metal rod. One on goes to an ear and the other is touched at various points (usually on the engine or gearbox) and when you get close to the source of the sound it becomes much clearer/louder.

 

Edited to add - don't on any account touch the listening stick to any moving parts, especially if the other end is against your ear.

No way! I thought you were joking. Ok, well that sounds like a systematic way to go about it. Thanks 

[Tony Brooks]

25 minutes ago, Amh300 said:

When I lift the floor panel, I can't hear the vibration over the sound of the engine. So, I'm assuming the vibration is continuing.

 

No way! I thought you were joking. Ok, well that sounds like a systematic way to go about it. Thanks 

 

1. That suggest to me that it might very well be a rattling floor plate. I glued rubber U channel around the lip the floor plate sits on to stop that and help seal the sound into the engine bay.

 

2. I very rarely joke about technical matters and having ad years of experience in dealing with FE motor mechanic students know just how silly some can be, hence my edit, and thanks to PeterF for his timely comment

[nb Innisfree]

2 hours ago, Tony Brooks said:

 

Edited to add - don't on any account touch the listening stick to any moving parts, especially if the other end is against your ear.

I wonder why? 🤣🤣🤣

1 hour ago, PeterF said:

And if using a long screwdriver but the blade against the engine and the handle against your ear, not the other way round.

🤣🤣🤣

[Amh300]

1 hour ago, Tony Brooks said:

 

1. That suggest to me that it might very well be a rattling floor plate. I glued rubber U channel around the lip the floor plate sits on to stop that and help seal the sound into the engine bay.

 

2. I very rarely joke about technical matters and having ad years of experience in dealing with FE motor mechanic students know just how silly some can be, hence my edit, and thanks to PeterF for his timely comment

Thanks Tony! Appreciate you taking the time reply

[Slim]

If you can hear it with the cockpit boards down but not with them up I can't see how it could be the engine. Must be 'external'. I see you have an aluminium checkerplate board(so did I). Check that it hasn't distorted slightly. Mine used to over a period of time and needed 'adjustment'.

[tosher]

My engine is an Isuzu 42 and the air filter casing sits just above the rocker box. With normal engine vibrations It has a habit over time of working it's way down till it touches the rocker box and causes a rattle just like you have. Cheers .

[PeterF]

4 hours ago, Slim said:

If you can hear it with the cockpit boards down but not with them up I can't see how it could be the engine. Must be 'external'. I see you have an aluminium checkerplate board(so did I). Check that it hasn't distorted slightly. Mine used to over a period of time and needed 'adjustment'.

I had aluminium checker plate on a previous boat and I had rattles so I put a strip of expanded neoprene self adhesive tape under the aluminium plate where it sat on the metal gutters. Similar idea to Tony's but on the plate not the gutter. No more rattling.

[Tony Brooks]

28 minutes ago, PeterF said:

I had aluminium checker plate on a previous boat and I had rattles so I put a strip of expanded neoprene self adhesive tape under the aluminium plate where it sat on the metal gutters. Similar idea to Tony's but on the plate not the gutter. No more rattling.

 

I also tried that, but on Buffalo board and I found that after prolonged exposure to rain & condensation it came unstuck, so I went to the U section glued on with impact adhesive. The section went on while the glue was still wet, not in the usual impact adhesive manner.

[Slim]

4 hours ago, PeterF said:

I had aluminium checker plate on a previous boat and I had rattles so I put a strip of expanded neoprene self adhesive tape under the aluminium plate where it sat on the metal gutters. Similar idea to Tony's but on the plate not the gutter. No more rattling.

As did I, however, over a period of the the tape compressed , shifted as the adhesive deteriorated etc. This combined with the slight bowing of the plate resulted in rattles And yes, the underside was strengthened with ribs but since it was tack welded on bowing still occurred. 

[Amh300]

Thanks to everyone for your replies - what an amazing response! I will post here on how I get on 👍