NS DiD: clatter at startup

[erad]

Sorry - I should know but I don't. Is the timing chain tensioner tensioned up by oil pressure from the engine lube system? If it is, this could be your problem - there should be a non-return valve which may be leaking.

[cooperplace]

OK, thanks, I'll ask the mechanic about this when he sees the car on Monday.
A stuck something or other would explain its intermittency.

[Garc]

I found that poor diesel (eg independent servos) made the noise worse. Also using Chemtech diesel additive quietened it down.

[cooperplace]

this is a mechanical clatter, not a detonation type noise.

[basil]

There are only two things to me that it can be.

One is chain slap which can be apparent more so just before the timing chain tensioner adjusts itself to the next notch which the ratchet and paul set up is adjusting automatically.
Tappets will not be loud and then be quiet when they are the solid type of lifter used in diesels.

Injection noise due to a faulty (dirty) injector can sound horrendous at times, due to the injection timing drifting. It can sound like you have dropped a rod bearing. It won't be electrical control of the injector, but rather the delay or extension of the injection cycle. It can usually be fixed with a decent cleaner. (90% of the time)

How long does it take on average to become quiet?

Cheers,

[cooperplace]

There are only two things to me that it can be.

One is chain slap which can be apparent more so just before the timing chain tensioner adjusts itself to the next notch which the ratchet and paul set up is adjusting automatically.
Tappets will not be loud and then be quiet when they are the solid type of lifter used in diesels.

Injection noise due to a faulty (dirty) injector can sound horrendous at times, due to the injection timing drifting. It can sound like you have dropped a rod bearing. It won't be electrical control of the injector, but rather the delay or extension of the injection cycle. It can usually be fixed with a decent cleaner. (90% of the time)

How long does it take on average to become quiet?

Cheers,

that's great to know. I'll have the guys look at the chain tensioner but I'm leaning towards your second suggestion. This is quite a loud sharp clatter, a metallic banging sound. it goes away after 10-15 seconds, but it's intermittent.
I'll try a cleaner.

Thanks

[cooperplace]

this morning on cold start it sounded perfect: no clatter. I haven't put a cleaner through. The other day it sounded horrendous, like a real $$$$ noise.

[cooperplace]

it hasn't done the clatter at cold start for ages, so I'm thinking it must have been an injector noise

[cooperplace]

it's still making the noise, very reliably on cold start. Goes away with warmup. I'd describe at as a combination of a slapping sound and a clatter.



Is the chain tensioner on this operated by oil pressure?

[cooperplace]

my mechanic suggested it could be drive belts. I was sceptical because it sounds metallic. he said "spray some water on the drive belts and see what happens".


It instantly stopped the noise, so I'm getting new drive belts fitted soon. They've done about 90k km.

[Alben]

It seems like you have sorted it out for now, but is your NS a manual or auto?
The dual mass flywheel made a fair bit of noise on startup for us for a few months before it finally let go.

[cooperplace]

it's a manual and you're right about the DMF, which has already introduced itself, and it was replaced a few years ago with a solid f/wheel.