Knocking noise

[craigiow]

Hi

having probs with my 300tdi,

there is a knocking noise that increases speed with the engine, and sat at tickover is quite loud. car drives perfectly with no loss of power etc, no idea where to start, was told it could be the cat making the noise but convinced its from the engine . any ideas what i can do to find the problem

Craig

[Frankie-Boy]

Hi Craig,

Its very difficult to diagnose noises from descriptions, but if you give an idea of your location someone is bound to be fairly close to you who might be able to help you.

We're quite helpful like that you know.  :)

[Skibum346]

I'm guessing he's on the Isle of Wight... Craigiow!!!

 :lol: :lol: :lol:

Skibum

[craigiow]

yeah on Isle of Wight

[Skibum346]

yeah on Isle of Wight

Woohooo!!!!    :dance: :dance: :dance:

[Frankie-Boy]

Frank,

Some people are too clever for their own good,  :lol: :lol: :lol:

In my defense, I wasn't wearing my bins and read the name as CraigLow, my mistake.  :oops:

[craigiow]

Bit of an update, been out trying to track it down, and the noise is much louder under car or stood by driver door than under bonnet looking down on engine, so either bottom end of engine bay or cat, if i suspect cat is it worth decatting it or trying to clear out existing cat/replace cat ?

may be silly questions but not very mechanical, expect that will change the longer i own the disco  :lol:

[Guardian.]

NOT The crank flapping about is it.?

[craigiow]

how would i check that as not to mechanical ?

[Skibum346]

how would i check that as not to mechanical ?

Sump off... look up!

But if it's "flapping about" as gaurdian so elequently put it.... it's a fairly serious rebuild!

I'd go with the cats to start...

Make sure all the exhaust mounts and joints are done up correctly, and make sure any diff gaurds etc are well bolted down. I spent months trying to figure out why my exhaust was rattling against the cross member.... only to realise after a while my bikini style diff gaurd wasn't bolted onto the back!  :oops: :oops:

Skibum

[craigiow]

ok cheers ,  will check the exhaust out first,

might be a stupid question but could i remove the exhaust and start it up to see if the rattle is then gone ?

[muddydisco]

Tappets loose or possible lift pump arm

[craigiow]

just had the tappets adjusted,

is lift pump easy to replace ?

[SteveGoodz]

just had the tappets adjusted,

is lift pump easy to replace ?

You'll get a good idea if it's the tappets (or not) by removing the oil filler ... if the noise gets really louder then it's likely to be a top end rattle.

If you can hang on until the last week in July I'll be in Sandown on holiday and can take a look for you 

[Range Rover Blues]

As said it's not easy to diagnose a knock via the internet, but a couple fo interesting things that have cropped unb in the forums recently include a valve stem cap going AWOL and causing a heavy tappet noise, more of a knock than a tap.

The of course there's broken valve springs and the snapped rocker shaft which caused a bit of noise.

If the knocking is heavy and low down then crank shaft or big ends, it's not unheard of for a bearing liner to go AWOL too :-o

[Evilgoat]

200TDI I/m planning to strip and rebuild has lost a bearing liner :) Previous owner found it when taking the sump off.

A Stethoscope can be handy, falingin that you can improvive using a large screwdriver or rod with a flat plate on the end. Press the chosen item against areas of the engine, you will eventually find the place where it is loudest.

As mentioned though it sounds like its going to be a big end bearing or crank bearing. Does the knocking change under load?

[craigiow]

yeah speeds up with the engine, almost seems quieter under load.

will try the stethoscope idea at weekend

[Evilgoat]

One of the crank bearings :(

Running under load, there are no forces acting to oppose the throw of the cranck and it 'flaps about' as Guardian said, the knocks will co-inside with BDC on the pisteons closest to the missing/bust/dead/worn bearing.

Under load eventually the engine will be workign against enough tourque to force it to comply with the shape of the bad bearing and it'll ease up.

It will get worse, probobly quite quickly :( Sure someone else will be here in a sec to tell you how to do the bearings. It is worth visually confirming it though, you should also be able to check for endfloat on the front pully too, which may give a clue.
 

[thebfg2003]

Had a similar loud knocking noise on my 300tdi. Was expecting a major problem. :shock: Took it to garage mate....turned out to be a bent pushrod and snapped adjuster. £120 all in. :D   Runs and sounds great now.  Well chuffed

Kev

[craigiow]

got it booked in to a garage later today to try and diagnose it ,fingers crossed nothing to major

[mike142sl]

If you're not mechanically minded this sounds like a trip to your local independant garage. Unless this is where you want to start learning, but you will need the proper tools and space to do it - and be prepared to be without it for a few days whilst the vehicle is in bits and you're waiting for new parts to arrive etc.

[Guardian.]

good luck mate, hope its a relatively simple and cheap fix. fingers x

[Evilgoat]

Been there too. It really sounds like crankshaft but I had this on the audi, heavy knocking on acceleration too. After convincing myself it was time to look at paying £3k on a new engine it turned out to be the vacuum assist pump.

Crankshaft will be a very heavy knocking, almost like someone striking the block with a hammer.

[clover]

Hi

If its the cat then your exhaust will be red hot... literally... it will be glowing red! You also will get small bits that look like sparks out the end of the exhaust that are actually red hot bits of your exhaust innerds!

Cheers

John

[Ricky]

Remove the auxil drive belt. that will rule out alternator, aircon compressor and all the other belt driven components.
i had a bad knock on my old 300 removed the belt and it went, turned out to be the alternator bearings.

[craigiow]

forgot to add its had a new head on it just before i bought it if that makes any difference

well had it n ramp and not the exhaust , will try to take aux belt of at weekend, but dont have air con pump so only alternator,


must admit im tempted to drive it till the engine lets go as does not affect driving at all, and either hunt around for second hand engine or rebuild the one thats in there, as rest of the disco is  solid and just went through mot with no real probs


either that or there is a nice 200tdi down the road for a good price, depends what i would get for mine with the knock

[Evilgoat]

Discopinky - Deisels dont have cats, well not of this age :)

Well looking a doing a 0 mile rebild on one here and most of the bits like bearing shells etc are quite cheap. Disco crankshaft bearing seems to be a few quid as opposed to £9 a throw on the audi. Its an arse to do bottom end on any car but it may be worth doing it. If it is the carnkshaft bearings or a big end bearing you may knacker the crank and/or the big end and that WILL cost.

Thought here though, if it was serious I would have expected to see an oil pressure drop, not seen your oil light of recent have you? (assuming its not like the suzukis and doesnt work)

[craigiow]

Had a mechanic friend look at it last night , he reckons it sounds like tappets and as i have just had them all adjusted reckons its a worn cam, hopefully he knows what he is on about as he just rebuilt his 300tdi 110,

[Guardian.]

top end taps and clatters more than knock though.

[Range Rover Blues]

But a tappet on a 200TDi can sound like a big end on a 1100 eurobox, all things are relative.

Evilgoat makes a good point, if the crank bearnig were badly worn there would be a drop in oil pressure, whereas if it's had the head done there is the distinct possibilty that something has gone awry in there, or that the cam is goosed.  If it's cam wear, live with it, but it's not too intrusive to take the rocker cover off and have a look-see inside.

It could just be the tappets were set badly, or the locknuts not done up [-o<