sort of knocking noise

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bmwz32.8
Joined: Sun 08 Sep, 2013 22:00
Posts: 10

  Z3 roadster 2.8

sort of knocking noise

Post by bmwz32.8 » Wed 23 Sep, 2015 17:26

HI My Z3 2.8 1998 has a sort of nockin noise not really metallic but seems to be cylinder related as it goes dunk dunk dunk regular it only happened yesterday and only heard it when up to normal temp now it does from when cold any ideas please

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colb
Joined: Sat 05 May, 2012 23:46
Posts: 567

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: sort of knocking noise

Post by colb » Wed 23 Sep, 2015 19:20

If you think it is coming from the cylinders when was the last time you changed the oil, it could be a sticking valve lifter, might be worth putting some engine cleaner in the oil, running it then changing the oil to remove any build up of varnish or gunk from the lifters. Try that to see if the noise then goes.

Colb
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

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Southernboy
Joined: Thu 07 Oct, 2010 13:39
Posts: 6312

  Z3 roadster 3.0i
Location: Johannesburg

Re: sort of knocking noise

Post by Southernboy » Thu 24 Sep, 2015 09:24

Small plastic cup / tumbler and a short length of hose fitted into the tumbler base makes a really good stethoscope for listening and isolating the origins of noises... You may want to do that and try to locate the source of the knock. Once you have the source narrowed down, you can tackle the possible causes which would affect that region of the motor. It may be the water pump bearing,the fan bearing or the vanos... These motors very seldom run main or piston bearings, in fact they're pretty much bullet proof.
...stick the hose in your ear and the tumbler end to receive the sounds... :wink:
"Normal is overrated"
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bmwz32.8
Joined: Sun 08 Sep, 2013 22:00
Posts: 10

  Z3 roadster 2.8

Re: sort of knocking noise

Post by bmwz32.8 » Thu 24 Sep, 2015 14:47

Thank you for your help and info I thought it was going to be an expensive exercise i took it to a garage (Back street) as i am in Manchester working and not at home they did not know what to make of the noise but said they could strip the engine down to find the problem I left quickly my mate at work said why don't you call the AA so I did this old boy listened took the top cover off the one covering the spark plugs got a long screw driver put one end (handle) on his ear and went along each plug its this one he said sounds like you got a loose spark plug 5 mins later my baby is running sweet again one for the book

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colb
Joined: Sat 05 May, 2012 23:46
Posts: 567

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: sort of knocking noise

Post by colb » Thu 24 Sep, 2015 15:15

Good result, if you had tried Sothernboys suggestion of using a stethoscope you might have found it yourself, I have used the old screwdriver in the ear method to listen to injectors its a useful method of pinpointing noises.

Did you check the rest of the plugs for tightness?

Colb
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

Hairyscreech
Joined: Thu 16 Apr, 2015 13:08
Posts: 69

  Z3 roadster 2.8

Re: sort of knocking noise

Post by Hairyscreech » Thu 24 Sep, 2015 19:20

Good catch, I have seen a loose plug "pop" when the car was started on an old cavalier 8v, it took the threads out of the head and a chunk out of the wall 20' away, much to the horror of the guy standing 2' from the open bonnet!

Might be a good excuse to do a full plug change.

bmwz32.8
Joined: Sun 08 Sep, 2013 22:00
Posts: 10

  Z3 roadster 2.8

Re: sort of knocking noise

Post by bmwz32.8 » Thu 24 Sep, 2015 20:42

did not check the others just over the moon it had not damaged the threads but I think I will take your advice and do a plug change when I get home its just had a service oil ect. also new discs and pads did not get the plugs changed it has the ones that have four spark thingys suppose to last but I still have two left from last time come in fours so had to buy eight so I will get four more and change them do you have to torque the plugs in, the garage did it last time (not very well it seems ) I just bought them but to be fair they have looked after her changed all the bushes to poly ones new shocks all round and this last service and mot discs and pads.To change the subject I am getting pressure from the other half to sell her I drive about 500 miles a week now that I work in Manchester and live in Grimsby it seems a shame to put so many miles on her about 80,000 at the moment but rising about 2,000 a month its a 1998 S reg wide body silver 2.8 electric roof seats ect full service history all the tools in boot even the first aid kit ect.black leather chrome gills ect nice condition don't know what price to ask any one any ideas I have not seen any wide body ones for sale recently

Dino D
Joined: Fri 10 Feb, 2012 16:59
Posts: 376

  Z3 roadster 2.8

Re: sort of knocking noise

Post by Dino D » Sat 26 Sep, 2015 23:24

I had a Bosch plug do this, was a worrying sound!
I read on a US forum that Bosch plugs tend to do this so went with Ngk.

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