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URGENT HELP! Knocking sound in engine

BlueStringPudding
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BlueStringPudding Veteran II

BlueStringPudding

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Hello. Since yesterday our engine has developed a knocking sound. :rolleyes: We're rather concerned about it, as having ignored one knocking sound in the summer, our air filter box jumped off the engine (fixing bolt had sheared off entirely); and a second rattling sound turned out to be one of the alternators not being fixed to the engine properly (didn't ignore that one, learned our lesson by then!)

 

We're obviously very worried about this one. :rolleyes: I've checked all the nuts and bolts and I can find and nothing appears loose. I found one small nut just sitting in a crevice of the engine, but can't find where it's supposed to go as all bolts seem to have nuts on now (it could have been from the old alternator problem some weeks ago)

 

Whereas the past two experiences were rattley sounds this is a deeper pitched noise. The engine starts with no problem and sounds completely normal, except every 3-4 seconds there's a "knock knock" sound. (And I don't think it's trying to tell us a joke!) :D

 

When standing to the left of the engine, the noise sounds like it's coming from the right; and vice versa. So we've come to the conclusion that the noise is either coming from deep inside the actual engine or just beneath it.

 

I've run my hand along the underside of the engine to every bit I can reach and can't find anything loose or wobbly.

 

Any ideas anyone? Batteries are at 12.4V and we're going easy on the electrics (about to have a shower in the RSC dressing rooms!) in case running the engine to charge them up again makes the problem worse or damages something in the engine.

 

I'll be at my laptop only for the next couple of hours - any suggestions of what the problem might be or if it's something I can fix myself, (or whether it'd be safe to run the engine) would be very much appreciated!!!

 

Thanks all.

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Smudge Community Regular

Smudge

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Hello. Since yesterday our engine has developed a knocking sound. :rolleyes: We're rather concerned about it, as having ignored one knocking sound in the summer, our air filter box jumped off the engine (fixing bolt had sheared off entirely); and a second rattling sound turned out to be one of the alternators not being fixed to the engine properly (didn't ignore that one, learned our lesson by then!)

 

We're obviously very worried about this one. :rolleyes: I've checked all the nuts and bolts and I can find and nothing appears loose. I found one small nut just sitting in a crevice of the engine, but can't find where it's supposed to go as all bolts seem to have nuts on now (it could have been from the old alternator problem some weeks ago)

 

Whereas the past two experiences were rattley sounds this is a deeper pitched noise. The engine starts with no problem and sounds completely normal, except every 3-4 seconds there's a "knock knock" sound. (And I don't think it's trying to tell us a joke!) :D

 

When standing to the left of the engine, the noise sounds like it's coming from the right; and vice versa. So we've come to the conclusion that the noise is either coming from deep inside the actual engine or just beneath it.

 

I've run my hand along the underside of the engine to every bit I can reach and can't find anything loose or wobbly.

 

Any ideas anyone? Batteries are at 12.4V and we're going easy on the electrics (about to have a shower in the RSC dressing rooms!) in case running the engine to charge them up again makes the problem worse or damages something in the engine.

 

I'll be at my laptop only for the next couple of hours - any suggestions of what the problem might be or if it's something I can fix myself, (or whether it'd be safe to run the engine) would be very much appreciated!!!

 

Thanks all.

Imposible to say mate you need to get someone to look at it might cost a bit but might save loads

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onthecut Proficient

onthecut

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Hi BSP.

 

Have you an oil pressure gauge fitted and, if so, is it reading the normal pressure when hot and at tickover ? If so, then hopefully you've not got the death rattle of deceased crank bearings. If it is reading low, then don't run the unit any more, or you will compound any damage and repair costs. What is the engine ? I'm a bit curious about the every 3 or 4 seconds. You have checked your oil level is OK, both engine and gearbox ? Just wondering if the pump is hoovering up what oil there is, running out (hence the knock) then sending a bit more around as some returns to the sump ?

 

Mike.

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BlueStringPudding Veteran II

BlueStringPudding

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Hi BSP. Have you an oil pressure gauge fitted and, if so, is it reading the normal pressure when hot and at tickover ? If so, then hopefully you've not got the death rattle of deceased crank bearings. If it is reading low, then don't run the unit any more, or you will compound any damage and repair costs. What is the engine ? I'm a bit curious about the every 3 or 4 seconds. You have checked your oil level is OK, both engine and gearbox ? Just wondering if the pump is hoovering up what oil there is, running out (hence the knock) then sending a bit more around as some returns to the sump ?Mike.
Hi Mike,No there's no oil guage. We checked the oil level of the engine a fortnight ago and it was fine. As for the oil level of the gearbox, I'm too ignorant to know where to find that! :D The engine is a Kubota 3 cylinder.Just spoken to an RCR engineer who thinks it's something to do with the engine mounts (apparently the 3 secind delay is a common symptom of the engine moutns needing a tweak. I'm about to go back to the boat the check it out when the engine's revved. If the knocking goes away when revved, then engine mounts it is and it's safe to run the engine. If it still knocks when revved, I have to turn it off and call him back!here I go...
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dor Veteran II

dor

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Could be as simple as the drive plate.

 

You really need to get someone who can diagnose these things to listen to it. It could be a myriad of things from very cheap to new engine and all possibilities in between.

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BlueStringPudding Veteran II

BlueStringPudding

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RCR are on their way out to us... feels like a regular occurance. First time they came out to us, I gave the feller a bottle of wine. Second time they came out to us I made him coffee and cake (same feller)... when he gets here this afternoon, I'll probably have cook him a three course supper, and provide cabaret entertainment. :D:clapping: I hope the engine noise isn't too serious... :):rolleyes:

Could be as simple as the drive plate.You really need to get someone who can diagnose these things to listen to it. It could be a myriad of things from very cheap to new engine and all possibilities in between.
Zoiks! I don't even want to think about that. No money = no new engine = no home! :rolleyes:
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Christine Proficient

Christine

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and provide cabaret entertainment. :D

 

A girl has to do what a girl has to has to do, like. :rolleyes:

But very best wishes BSP I get distraught if I get a sock in the washing machine pump so - my thoughts are with you at this stomach churning time.

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BlueStringPudding Veteran II

BlueStringPudding

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A girl has to do what a girl has to has to do, like. :rolleyes:

But very best wishes BSP I get distraught if I get a sock in the washing machine pump so - my thoughts are with you at this stomach churning time.

 

Thanks Christine. On the plus side, I had a really extravagant scorching hot shower in one of the RSC theatre dressing rooms this afternoon, (as the water on the boat's cold with no engine on!) Lovely! :rolleyes: I felt like Ian McKellen... :D except fatter...

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Yamanx Rising Star

Yamanx

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Hi Mike,No there's no oil guage. We checked the oil level of the engine a fortnight ago and it was fine.........................................

 

I dont know how often you run your engine. But you should check your oil every day that you do.

 

I hope its nothing serious, could just be a noisey tappet? :cheers:

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BlueStringPudding Veteran II

BlueStringPudding

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Hello all - back at w*rk so back on here, as per usual. Here's an update.Lovely engineer man came out to us on Saturday afternoon, tested every millimetre of the engine and was completely flummoxed by the knock-knock noise. He says it's out of synch with the engine itself. Sometimes the noise gets worse as you rev the engine, sometimes it disappears for a while. He suspects it's something to do with the alternator/fan belt system (he'd done some work on that a few weeks ago himself so he was a bit concerned) but he couldn't locate exactly where. He made sure it would be safe to continue running the engine (his initial concerns were that it was a serious engine problem but he ruled that out eventually) and advised us to keep going as normal until something goes Clang! or Pop!... by which time it'll be obvious what's wrong and he'll be able to fix it! :lol: Something which we've noticed since last night (and which backs up what he suspected about one of the alternators) is that the battery monitor is showing that the batteries are charging very differently to usual. Normally, if we put the engine on for an hour, the batteries charge up to 100% capacity and to over 12.7V (dropping down to 12.7V after a while). What's happening now is that the voltage builds up to 12.7V as the usual speed, but the percentage is taking a very long time to build up (about 1% every 60-90 minutes) Most unusual. :cheers:

 

I dont know how often you run your engine. But you should check your oil every day that you do.I hope its nothing serious, could just be a noisey tappet? :cheers:

 

Oil's fine.

Edited by BlueStringPudding
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dor Veteran II

dor

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A friend that used to work for ERF told me they had a procedure for unidentified noises called LID. This highly sophisticated diagnostic device was "Let It Develop". Seems like that is what your engineer is suggesting.

 

I once took my boat into a boatyard to get the engineer to listen to a nasty rattle that I couldn't pin down. He listened for a bit, then moved a bit of steel ballast that was in the engine 'ole. Noise disappeared - how embarrasing!

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John Orentas Veteran II

John Orentas

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Hi Bluey.

 

One of the reasons that this sort of thing is very difficult to diagnose is that there is very little on an engine that you can isolate.

 

However if the alternators are suspected (but I must say your description does not sound like alternators), it is relatively easy to isolate them or confirm them as the problem.. One at a time remove one 'V' belt then the other, if your problem goes away or remains the culprit if there is one will be hopefully be obvious.

 

Take care though one of the belts will doubtless also drive the water pump, but it will run OK for long enough to do the test, just keep an eye on the temp gauge or warning light.

 

You must be aware that the variation in charging you have observed may simply be a result of not running the engine so much since your knock.

Edited by John Orentas
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Hairy-Neil Veteran

Hairy-Neil

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A friend that used to work for ERF told me they had a procedure for unidentified noises called LID. This highly sophisticated diagnostic device was "Let It Develop".

 

An 80K Peugeot 205 diesel I bought about 5 years ago had a noise from the front end on bumpy roads. I could find nothing obvious and it passed the MOT ok so I thought, LID....... 5 years, 6 MOT's and 190k on the clock now and it still knocks when you go over bumps....... :cheers:

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