BMC 1.5 Vibration and Rattling

[Dovetail]

I have a situation with my 1.5 BMC and the problem has been getting slightly worse over the past few months.

 

If I have my enging running on just over tick over it’s a smooth as can be but if I increase the revs to what would be a nice cruising speed I get a lot of vibration and rattling from what seems to come from the front of the engine, timing chain area?

 

If I increase the revs further this vibration and rattling smoothes out but I am now travelling at a good rate of knots.

 

So I am hoping and want to just see if anyone also thinks that it can be the timing chain tensioner and it’s the timing chain that is causing the vibration and rattle before I remove the pulleys and timing chain cover or does it sound more serious.

 

I have to say I had the engine reconditioned about 4 years ago by a firm at the time unknown to me about to go out of business retiring and had a couple of issues over the work that had to be put right. So this rattle and vibration does worry me is it something else they forgot to do or tighten? Although a good number of years have passed but….

 

Any advice or suggestions will be appreciated.

[Thewatchmaker]

I have a situation with my 1.5 BMC and the problem has been getting slightly worse over the past few months.

 

If I have my enging running on just over tick over it’s a smooth as can be but if I increase the revs to what would be a nice cruising speed I get a lot of vibration and rattling from what seems to come from the front of the engine, timing chain area?

 

If I increase the revs further this vibration and rattling smoothes out but I am now travelling at a good rate of knots.

 

So I am hoping and want to just see if anyone also thinks that it can be the timing chain tensioner and it’s the timing chain that is causing the vibration and rattle before I remove the pulleys and timing chain cover or does it sound more serious.

 

I have to say I had the engine reconditioned about 4 years ago by a firm at the time unknown to me about to go out of business retiring and had a couple of issues over the work that had to be put right. So this rattle and vibration does worry me is it something else they forgot to do or tighten? Although a good number of years have passed but….

 

Any advice or suggestions will be appreciated.

 

My first thought would be your engine mountings are on the way out.

[Dovetail]

Thanks for the reply watchmaker the mountings although not replaced at the same time of the engine rebuild were replaced a couple of years earlier so only 6 years old.

 

It is a good point as I did have one come loose and needed tightening so I will double check it again.

[Tony Brooks]

Thanks for the reply watchmaker the mountings although not replaced at the same time of the engine rebuild were replaced a couple of years earlier so only 6 years old.

 

It is a good point as I did have one come loose and needed tightening so I will double check it again.

 

 

If that is not it put a stick or long screwdriver between the timing cover and your ear as a kind of stethoscope. If that localises it to the timing cover area I have known the chain tensioners either stick or not be released on rebuild so the noise could be the chain hitting the cover but I would have expected it more at tickover than any other speed.

[Evo]

In terms of vibration at certain speeds I found great benefit in equalising the load on the engine mounts. years ago I noticed my front right engine mount always seemed more compressed than the others even when they were all replaced. They were only replaced because the front right was shot to pieces (the metal stem was poking out the bottom and tapping the bearer).

[Dovetail]

Tony that’s a good idea and may save a bit of time. I have remembered that I have a stethoscope for testing for tappets, although I suspect it is not the timing chain its more of hope as I see that as a simple fix.

 

Evo so you also think engine mounts the thing is they will be a real pig to work on given the position of the engine, it will require a bit of dismantling of engine box to make the job easier and then I will be worried over loosing the alignment of the engine.

 

Perhaps a combination of Tonys stick/stethoscope to the ear with the stick/stethoscope touching the engine mounts may give an indication as to any unusual movement to one or two of the mounts. Assuming that they should all be similar.

[Evo]

Well, without hearing it, I dont know wether you have a serious engine issue or just a loose or badly adjusted engine mount. Its obviously easier to check out the engine mounts and i believe they are a more likely source of vibration than a timing chain.

If the engine is jumping about and making noises because something is internally wrong with it then its a far more serious problem.

[Dovetail]

I hope your right Evo don’t want to be taking the engine out again. I will check the mounts.

 

Cheers

 

Tom

[Tony Brooks]

Well, without hearing it, I dont know wether you have a serious engine issue or just a loose or badly adjusted engine mount. Its obviously easier to check out the engine mounts and i believe they are a more likely source of vibration than a timing chain.

If the engine is jumping about and making noises because something is internally wrong with it then its a far more serious problem.

 

 

Absolutely - I suspect loose bolts holding the mount to the bed and you had already said check the mounts.

[n.b.Goldie]

Do not forget to check the bolts holding the mounting legs to the block. Mine came loose on my previous boat with a BMC 1.5, eventually the leg parted company with the block resulting in the engine hanging on three legs which put so much strain on the coupling that it stripped the bolts out of the (Hurth 100) gearbox and Centaflex coupling. The stern tube was saved by the plummer block bearing.

 

IIRC the initial symptoms were pretty much as you described them but I ignored them for too long

 

Regards

Ditchdabbler

[Dovetail]

Thanks again Tony

 

Ditchdabbler that’s a very good point and easily missed

 

Cheers

 

Tom

[Thewatchmaker]

Thanks again Tony

 

Ditchdabbler that’s a very good point and easily missed

 

Cheers

 

Tom

 

Did you ever find the problem?

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