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NJS-1

New Member

• Jun 10, 2010

• #1

Hi all

Ive recently bought a TD4 on an 04 with 46000 on it and ive noticed a tapping noise coming from the engine area when i drive it from cold :-(. It sounds like a diesel knock and it happens when i accelerate fairly hard in each gear for a few seconds, so it only happens when the engine is under load. Once the temp gauge reaches about a 1/4 then it seems to stop. Any ideas what it might be please. Its not a deep down in the bowls knock, its more top end rattle

Regards
Nick

 

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vic.middleton

Active Member

• Jun 10, 2010

• #2

Could be piston slap. This is usual and nothing to worry about. Aluminium i.e. pistons have three times the coefficient of thermal expansion of the iron bore liners, hence have to have a large clearance when cold otherwise they would jamb when then got hot at running temperature. Hence they slap over as the con rod goes over TCD and this creates the noise which goes away when the engine is warm.

 

garfield247

New Member

• Jun 10, 2010

• #3

hi nick
One thing it could be is a blowing exhaust manifold either where it joins the block or where the pipe starts.As the temperature rises any small leak will seal up due to expansion hence the engine gets quieter.Had this on an old rover it used to sound awful when cold but when it was hot it was quiet.All i did to rectify this was tighten a loose manifold bolt.
Hope this might be of some help i might be totally wrong but it might be worth a look

 

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NJS-1

New Member

• Jun 10, 2010

• #4

Thanks for your reply's. You've put my mind at ease as this doesn't sound as serious as i first thought. I only bought the vehicle last saturday and haven't had a chance to look around it but hopefully will this weekend (weather permitting)

 

para1966

New Member

• Jun 11, 2010

• #5

I have always known diesels to do this, I remember the Perkins motors in the FLT`s I used to work on, even a new engine sounded as knocky as anything until it warmed up.