hi all, just seeing if someone can shed any light on a puzzling noise on start up. my car is a 51 plate octavia elegance 1.9 tdi with 107000 miles. when starting from cold the engine seems lumpier and noisier when cold and the aux belt tensioner seems to vibrate a lot the after approx 3 minutes there is a click sound then everything is smooth and the tensioner has no vibration at all, no idea what it is, all i know is it sounds a lot worse driving it until after this 3 minute period is up. does it have some kind of knock sensor that kicks in after 3 minutes ? the difference after 3 minutes is amazing, its like a different engine, any ideas anyone ? ?

the only other niggle is the abs cuts in at very low speed and only when cornering, ie, pulling into a parking space.

any response would be much appreciated. cheers Mike.

secondary air pump

Diesels don't have a secondary air pump, that is a feature reserved for causing trouble with the petrols

The aux tensioner wobbling about excessively is generally caused by either a failing tensioner (damper is too weak), or the freewheel pulley on the alternator being seized). My pulley failed last year at about 160k and snapped off the alternator after starting to make an evil groaning noise about 60 miles before hand.

I wonder if there is some larger electrical current demand for the first 3 minutes, but I wasn't aware of anything on my 110 TDI (2001). Although that said for the first couple of minutes of driving (with a cold engine) there is a relay click from under the steering column when I pass over 2.25k (approx) revs, and again when the revs drop back below that value. Mine has done this for many years - some people says their car does this, and others say it does not happen.

ABS cutting in early - maybe a dodgy sensor/cable, any fault codes?

The aux tensioner wobbling about excessively is generally caused by either a failing tensioner (damper is too weak), or the freewheel pulley on the alternator being seized). My pulley failed last year at about 160k and snapped off the alternator after starting to make an evil groaning noise about 60 miles before hand.

I wonder if there is some larger electrical current demand for the first 3 minutes, but I wasn't aware of anything on my 110 TDI (2001). Although that said for the first couple of minutes of driving (with a cold engine) there is a relay click from under the steering column when I pass over 2.25k (approx) revs, and again when the revs drop back below that value. Mine has done this for many years - some people says their car does this, and others say it does not happen.

I have always thought that the click (yes, mine does it too) is the glow-plug supply relay clicking on and off. If it the works the same way as on my previous car, then the glow-plugs are energised when the revs are below 2.5k and the temperature or timer demands it. That would explain the point about alternator pulley or tensioner as the glow-plugs take around 80A ( translated that means more than 1¼ horsepower through the belt).

First check I would say should be on the alternator tensioner and freewheel.

Mike

I have always thought that the click (yes, mine does it too) is the glow-plug supply relay clicking on and off. If it the works the same way as on my previous car, then the glow-plugs are energised when the revs are below 2.5k and the temperature or timer demands it. That would explain the point about alternator pulley or tensioner as the glow-plugs take around 80A ( translated that means more than 1¼ horsepower through the belt).

First check I would say should be on the alternator tensioner and freewheel.

Mike

hi again, i recently removed the aux drive belt as it looked like the original one and replaced it with a new one. while it was off i checked the tensioner and various pulleys and everything seems fine although i dont know how i would check the tensioner damper. i even kept all the covers off and started it up the next morning to observe what was going on and the tensioner just seems to vibrate about for the 3 minutes then as soon as the click noise happens it all just settles down perfectly, even the engine note changes, its quite wierd to watch but thats what happens. because nothing else is worn or about to drop off i'm just going to accept it for what it is and just let it idle for the 3 minutes before i set off in the morning as the engine seems to sound a lot louder if i set off straight away until the 3 mins are up. i havent checked for fault codes but did have it serviced recently which flagged up a coolant temp sensor which i replaced with a genuine new one. do i now have to get the fault code erased i wonder ? anyway, apart from that i'm just putting up with the odd abs fault i have, although i have had an identical abs pump offered to me which came off a 64000 mile vrs - a lot less than my 107000 miles - but will it cure it ? i dont know. by the way, i just cleaned my turbo out the other week along with the inlet manifold and the egr valve and it runs a lot cleaner now. has anyone changed a cambelt before on these engines - asv - as it needs doing along with the water pump but it looks a bit fiddley to do.

thanks for the reply's, mike.