nasty noise on start up

Hi all, when I start up my 300 tdi on an N plate, I get a really horrible rattling sound from the top end until I blip the throttle and then it is back to normal. I'm thinking oil pump as it seems to be dry until I blip it and then oil on the scene and hey presto back to normal. It started only once in a while and is getting more frequent, any ideas, tots.

Could be. When did you last change the oil and filter? Is it low on oil?

hi, thanks for the reply, I'm positively anal about oil and filter changes every 5-6 k miles. Regards Tots

I get the same thing so any suggestions would be appreciated

This sort of noise on starting is associated with hydraulic cam followers, but I don't think you have those. Next is a hydraulic timing chain tensioner, but as you don't have a timing chain or a tensioner for it, we can rule that out too.

All I can think of at the moment is a worn TURBO shaft bearing, that rattles till (a) the oil arrives in force, and (b) the shaft picks up a bit of speed.

Get a stethoscope (for engines) with a metal probe end, and poke it on everything to see if you can pick up the noise.

One more thing - make sure your valve clearances are set accurately.

CharlesY

I had a similar problem, on the oil change we put in a new stuff from america it's called somthing like hydraulic tappet $++)(? somthing also WYNNS do a similar bit of kit it worked!!! it coats everything ive now stuck it in the RS and the boys rover111si and a vast improvement on all has been noticed, the actual stuff is about £15 a pop for about 270 ml wish i could remember name of it, early onset altsheimers me thinks.

Ok, I've no idea what the problem was, but when my cambelt was changed yesterday I ask them to add some molyslip (another ebay special) to top the oil back up. Today there is no noise... so it could be something they touched doing the cambelt or the good ole molyslip stuff.

further to my previous, when you start her up the noise is coming from lower down. If you start it up with the clutch depressed, no noise, start it up with the throttle pressed down, no noise. I'm thinking release bearing...... but my brother in law had the same and did the clutch and release bearing and still has the noise on start up. Any ideas? Tots.

try the vacuum pump - that can make that kind of noise when it's about to go tits up.

tots said:

further to my previous, when you start her up the noise is coming from lower down. If you start it up with the clutch depressed, no noise, start it up with the throttle pressed down, no noise. I'm thinking release bearing...... but my brother in law had the same and did the clutch and release bearing and still has the noise on start up. Any ideas? Tots.

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It's extremely unlikely to be the clutch release bearing as it isn't subjected to high radial loads ~ and they tend to rumble when on their way out.

Depressing the clutch takes a big load of the engine (and starter motor) on start-up ~ your not trying to turn half of the gearbox for a start ~ and if there's no noise then it might suggest big ends or main bearings. Likewise starting with some throttle applied causes the engine to rev straight away on start-up reducing the torsional loads on the bearings and (as a consequence) the noise. I hope I'm wrong, though

Having said all that, Tdi's tend to be rattly on start-up and/or tickover ~ at least in my experience they do ~ but quieter when revving. I've reduced this effect in the past by adjusting the valve clearances which do change as the engine wears. A job I have planned for Joe in the next couple of weeks

HTH

It can't be the turbo shaft as those do not rattle. When worn the compressor can hit the housing but that is more of a scream than a rattle. My 300tdi also makes a bit of a rattly sound when I first start it up, but it is quite high mileage so I ignore it while saving up for a rebuild. What you and I are hearing is possibly piston slap caused by worn bores, pistons and rings. As long as it goes away when the engine warms up you should be ok.

Hi, thanks for all that, I'll wait and see what happens and rebuild or replace if it goes tits up, Tots.