Disco 2 ticking/tapping noise on acceleration

as the title suggests, i have the above- quite loud ticking/tapping noise on hard(ish) acceleration. the obvious culprit would be the manifold gasket. however upon inspection, all the studs/nuts are still in place. i can't replicate it by revving at standstill so its only happening under load. i realise the studs may have stretched rather than snapped so it could still be the manifold, if not, where else should i look? i considered removing the belt and driving up the road for a few minutes to eliminate belt slap or anything pulley related but not sure if its safe to do so. (its just had a brand new crankshaft damper pulley fitted so i know its not that)

I would refrain from driving with no belt but does it sound like diesel knock? My manifold gasket wAs leaking and it made the engine sound clattery and a little rough too

Discodevon said:

I would refrain from driving with no belt but does it sound like diesel knock? My manifold gasket wAs leaking and it made the engine sound clattery and a little rough too

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to be honest i wouldnt know what diesel knock sounds like but its more of a fluctuating tapping under load, a bit like a playing card in bicycle spokes. it sounds a bit like the exhaust/manifold leak i had on my V8 which was actually the y-pipe but all the studs are there so i'm not so sure thats the issue, though it could just need a new gasket.

I had a gasket blow on my D1 between the manifold and tar Y pipe flange, the studs and nuts were still there, why shouldn't they be?, but a small part of the gasket wasn't. That sounded like a machine gun under load.

discool said:

I had a gasket blow on my D1 between the manifold and tar Y pipe flange, the studs and nuts were still there, why shouldn't they be?, but a small part of the gasket wasn't. That sounded like a machine gun under load.

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apparently, D2's have a habit of snapping studs when the manifold warps. funnily enough, my old D2 snapped a stud on the front cylinder but never made a noise or caused any issue. i only happened to notice when i was doing the water pump but i wouldn't have known otherwise.

The studs may look fine but until you get a spanner on them you wont know for sure, number 5 was alwasy the favourite on mine and you can get your hand down under the manifold with a spanner to check/tighten the nuts, it will seem better but in reality the studs are actually pulling out of the head.
The reason you cant repicate it when revving it at a standstill s becasue you need to be making boost pressure.

lynall said:

The studs may look fine but until you get a spanner on them you wont know for sure, number 5 was alwasy the favourite on mine and you can get your hand down under the manifold with a spanner to check/tighten the nuts, it will seem better but in reality the studs are actually pulling out of the head.
The reason you cant repicate it when revving it at a standstill s becasue you need to be making boost pressure.

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which is exactly what i thought. however... if i try to remove the studs to replace them, what are the chances they will shear....?

My 200tdi was doing that exact same thing. Twas injector seat copper washer on mine.

Flossie said:

My 200tdi was doing that exact same thing. Twas injector seat copper washer on mine.

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how could i tell if its an injector issue? would a nanocom throw up a code?

I don't have or need or even know what a nanocom is really.
I was chatting to a mechanic at my local indy about it(the ticking) and he said try replacing the injector seat washers so I did and it worked.

Flossie said:

I don't have or need or even know what a nanocom is really.
I was chatting to a mechanic at my local indy about it(the ticking) and he said try replacing the injector seat washers so I did and it worked.

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a nanocom is an expensive magic box which tells you whats wrong with your td5. as td5's are run by wizardry, trolls, nanobots and gremlins, we need them to defeat said mythical beings. 200tdi's run on coal, with wooden cogs and pit-ponies, therefore dont need such electrickery sorcery.

Bobdog said:

which is exactly what i thought. however... if i try to remove the studs to replace them, what are the chances they will shear....?

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You have to remove the manifold to remove the studs and as they are most likely already pulling out they wont take much effort to get them out, then its helicoil time and get the manifold machined flat, all much easier than it actually sounds

Get the manifold skimmed Bob it’s not too expensive

well... problem apparently solved... replaced my crankshaft pulley about 3 weeks ago, in the absence of a torque wrench, i was advised (by a mechanic) to leave the air-gun on it for a couple of minutes and that should do it up tight enough. i've seen the same said on here as well. anyway, all seemed well... whilst looking for this tapping sound, i had a quick check of the crankshaft bolt - i could undo it with my fingers! .
so, breaker bar out and looking for something to lock the pulley, i came across my viscous fan spanner. because its cranked, it hooked under one of the damper bolts and laid across the socket, i was able to get some really good force on the bolt. now its tight as a nuns chuff and my tapping has gone. what i will do though, is undo it again and put some threadlock on it. (probably should have done that in the first place)
i would assume, the tapping was in fact belt slap, as the pulley slipped on the bolt under acceleration.

More concerning to me would be the oil pump and cam chain drive, which Im assuming is keyed? I would have a good look at that and see if theres any slap/play between the key and the gear as you may have had variable valve timing hence the tap noise.

You must have the weakest air gun in known history?

lynall said:

More concerning to me would be the oil pump and cam chain drive, which Im assuming is keyed? I would have a good look at that and see if theres any slap/play between the key and the gear as you may have had variable valve timing hence the tap noise.

You must have the weakest air gun in known history?

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nothing to do with the chain. the pulley drives all the ancilliaries and is not keyed. not sure why you think it would affect the oil pump?

Bobdog said:

nothing to do with the chain. the pulley drives all the ancilliaries and is not keyed. not sure why you think it would affect the oil pump?

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Because the pump drive cog IS keyed and is held tight on the crank by the crank pulley bolt crushing the lot together, so loose bolt means the gear can fret on the key and potentially damage the key meaning inaccurate valve and injection timing.

So what i am saying is remove the aux pulley and shine a torch down the crank nose and give the crank a little wiggle back and forth and see if theres any play in the key, no play sweet loctite and gun job done, plys set the timing up properly then loctite and gun job done

lynall said:

Because the pump drive cog IS keyed and is held tight on the crank by the crank pulley bolt crushing the lot together, so loose bolt means the gear can fret on the key and potentially damage the key meaning inaccurate valve and injection timing.

So what i am saying is remove the aux pulley and shine a torch down the crank nose and give the crank a little wiggle back and forth and see if theres any play in the key, no play sweet loctite and gun job done, plys set the timing up properly then loctite and gun job done

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i dont think it is. the end of the crankshaft sticks out proud of the engine and the pulley bolts onto the end of it. is doesn't crush anything together. you cant see the keyway due to the crankshaft oil seal. are you sure you're talking about a td5?

Right correct me if Im wrong here,
The crank has a plain shank at the nose end, ie pulley end, there is a jeyway, the keyway locates the timing/oil pump chain pulley/cog, the keyway only locates the cog it does not actually hold it as its not strong enough, then you fit the crank pulley and tighten the crank bolt, this effectively crushes the pulley and the cog tight against the step in the crank so the whole lot is locked together.

At one time crank pulley bolts coming loose was a 200tdi thing and the keyway used to rattle about so much it damaged the crank itself, casuing variable valve/injector timing.
They work exactly the same except they use a belt instead of a chain but the principle is the same.

If you think like a suspicious mechanic a loose crank bolt on its own will not cause an injector noise UNLESS it also had some means of effecting the valve/injector timing.

Pic with seal removed you can clearly see the gear/cog