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#1 LukeW10

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Posted 12 January 2018 - 04:47 PM

So my 1988 1275 engine was running absolutely perfectly until a couple of days ago when, whilst out for a drive and stopped at traffic lights it developed a knocking noise. I returned home and had a look/listen. I thought it was coming from my alternator so after a bit of research on here I found someone had a similar problem where it was the bearings. I sprayed a bit of WD40 into the pulleys and the noise seemed to quieten for a few seconds and then it would return. This made me think it was the alternator and it looked a bit rough around the edges anyway so I bought a new one and have fitted it this afternoon.

Started her up and she is still knocking. The noise is 100% coming from that area (bottom right as you look at the engine bay). I have had a plastic screw driver down there for a listen and still can’t pin point where the knock is coming from.

The knock doesn't get loader with revs or whilst accelerating it is just a steady knock.

 

Does anyone have any suggestions or has anyone had this problem before? any help would be appreciated.

 

Also...is anyone around the North Yorkshire area? I haven't seen many mini's on my travels...

 

 



#2 hhhh

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Posted 12 January 2018 - 05:08 PM

Water pump maybe? Grab the fan blade and feel for play, but you'd expect it to be leaking if it were knocking. Slacken the alternator to disengage the fan belt so nothing turns and listen again.



#3 Northernpower

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Posted 12 January 2018 - 05:12 PM

Water pump maybe? Grab the fan blade and feel for play, but you'd expect it to be leaking if it were knocking. Slacken the alternator to disengage the fan belt so nothing turns and listen again.

I find its always a wise thing not to have the engine running when you grab the fan blade :D  :D



#4 Northernpower

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Posted 12 January 2018 - 05:16 PM

 

Also...is anyone around the North Yorkshire area? I haven't seen many mini's on my travels...

 

 

Its the wrong time of the year to see them out of hibernation. I'm only 20 minutes down the road from you but I don't mind admitting I don't use it when there's been a lot of salt on the roads



#5 Retroman

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Posted 12 January 2018 - 06:20 PM

I have had a badly knocking S in which had had the EN40B crank swapped out for a metro...Centre main thrust bearings built up with solder....knocked like crazy, crank was banging the block at each end...frightening.

Also a '61 Mini Minor knocking slightly and rumbling, it was the water pump.

If its really bad you can feel it in the fan as movement.

You can take alternator and or fan belt off to see if that quietens it.

Pump bearings, and wheel bearings can make a hell of a rumble.

It could also be something in the timing chain cover I have seen a few with broken tensioners usually more of an intermittent rattle.

Not sure what bottom pulley you have but they can come undone, modern lock tabs are rubbish.

Pressed steel ones can also start to part as they are riveted together...all sorts of rattly knocky type noises.

Northernpowers advise is good too...DONT mess with it when its running, fingers are precious.



#6 cal844

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Posted 12 January 2018 - 11:09 PM

Use the long screwdriver technique, on the a+ the water pump mounts the alternator but if you listen to the water pump casting you should hear it well. A doctor's stethoscope with a piece of petrol pipe works well too

#7 LukeW10

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Posted 13 January 2018 - 04:16 PM

Slackened the alternator this morning and ran the engine for a moment without the fan belt. Couldn’t really make out if the knocking had gotten quieter or stayed the same.

I’ve also miss placed the plastic screw driver so couldn’t have a listen to the water pump. :/ I did cup my hand to my ear and place it on the radiator housing and that seemed to exaggerate the knock. But that may mean nothing. I didn’t want to get my head or hands any closer to the moving bits!!

The noise is hard to explain. It’s not a banging knock but nor is it a tapping knock. Not loud enough to hear it when accelerating but on idle it stands out over the engine noise.



#8 LukeW10

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Posted 13 January 2018 - 04:18 PM

 

 

Also...is anyone around the North Yorkshire area? I haven't seen many mini's on my travels...

 

 

Its the wrong time of the year to see them out of hibernation. I'm only 20 minutes down the road from you but I don't mind admitting I don't use it when there's been a lot of salt on the roads

 

I wish I could lock it away over the winter but since the mrs has knicked the daily driver I have to enjoy her all year round. :D



#9 hhhh

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Posted 13 January 2018 - 04:24 PM

At risk of pointing out the obvious, the point of slackening the fan belt was to stop the pump. It could still knock while not turning of course, but it would certainly be a different knock and not as regular. If in fact the pump was not turning and the same knock was still there, you can rule out the water pump. For the little effort involved, I'd check the valve clearances.



#10 dyshipfakta

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Posted 13 January 2018 - 04:53 PM

If it doesnt change with revs I cant see it being anything that has been mentioned. It is most likely something hitting something else in my opinion. Shake components with the engine off to see if you can replicate the noise.

#11 hhhh

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Posted 13 January 2018 - 05:34 PM

I don't think he said it doesn't change frequency with revs, just that it doesn't get louder. It could be the balancer disintegrating.



#12 dyshipfakta

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Posted 13 January 2018 - 11:25 PM

I don't think he said it doesn't change frequency with revs, just that it doesn't get louder. It could be the balancer disintegrating.


Maybe I misunderstood as op said steady knocking i took it as not changing if you catch my drift

#13 Cooperman

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Posted 13 January 2018 - 11:39 PM

A very strange reason for a knocking noise on one of my Minis turned out to be a fracture of the engine front plate where the alternator fits onto it.
I have ever only seen this the one time and it was hard to diagnose. I only found it after I started stripping it down to check the bearings/crankshaft.

#14 wile e coyote

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Posted 14 January 2018 - 11:01 AM

Although an absolute swine to diagnose - remotely far worse, any chance of posting up a decent video OP? (illustrating the condition of components with engine off, on start up, warmed up,revving and from inside the car on the move - may lead to some slightly better guesses........and guesses is all it can be without being with the thing....

 

Given how ancient and tightly packed the A series is knocks and rattles can easily be from a good distance away from where you may think.....a good check over of the valve clearances first is a good plan though as is checking the engine mounts , exhaust and dizzy clamp  are good & firm, pull the dipstick any metal flecks in there?....

 

Recently had a mini "visit" ( for anticipated "free" labour ....hmm) with a badly knocking engine... diagnosis 10 seconds... oil starved engine..(sump threads gone and "any old bolt" bodged in with bathroom sealant)  knackered - pure idiocy as loads spent on the "shinies" just not the mechanicals......consequently I now own the car tucked up in the barn as a future project and my spare freshly rebuilt lump & box  lurks in the corner of the garage :-)



#15 Retroman

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Posted 14 January 2018 - 06:34 PM

I don't think he said it doesn't change frequency with revs, just that it doesn't get louder. It could be the balancer disintegrating.

I had the same thought, never had one do it, but guess it will be an intermittent noise that may come in at different revs?






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