Tappety TDI

[muddyboots]

When I start my Passat the first time each day, it makes a tappety noise for a few seconds until the oil pressure is up, then it goes quiet.

If I stop and start up again later in the day, it's fine - only makes the noise when it's been stopped for a long time (ie overnight).

I know it's covered 100k now and isn't meant to sound like new, but is there anything I can do to help ?

It's service time now, I was wondering if using some flushing oil would help, perhaps the oilways to the tappets are a bit clogged

Any suggestions ?

 

[sssstew]

it will be the tappets, (not sure if they are hydraulic on the PDs)

 

[EdButler]

Muddy, mine has done exactly the same when it went into the the dealers (twice) - Its the only time it doesnt get driven for 12+ hours and made a tappety noise which soon disappeared - never heard it since.

Mike_OBD has an 05 with about 22k and his does it occasionally. It could be just a sticky tappit. I dont think its anything serious at all, ill ask Mike to see what the JBS chaps thought of it...

 

[micky 32]

Its normal. my fathers passat does it too since new

 

[basstard]

excuse my ignorance guys, but what are tappets?

 

[sssstew]

http://en.wikipedia.org/wiki/Tappet

 

[cheshire cat]

it's a hangover from pushrod-rocker and valve stem days. I guess now, it's the part which allows for a clearance between cam and the end of the valve whatever is inbetween the two. Muddy, does your filter have the oil dam inside, if not try a genuine part

 

[basstard]

thx to both stew and nic

 

[muddyboots]

it's a hangover from pushrod-rocker and valve stem days. I guess now, it's the part which allows for a clearance between cam and the end of the valve whatever is inbetween the two. Muddy, does your filter have the oil dam inside, if not try a genuine part

Hadn't thought of that, but I would hope so as it's only ever been serviced at VW until now.

I will be buying a genuine VW filter though, plus a can of Millers.

Might get some flushing oil too, guess it can't hurt after 100k miles, bound to be a bit of gunk in there !

OK another question:

How do hydraulic tappets work, I presume the oil must get pumped in somehow ?

 

[craig-pd130]

Yeah, they've got little inlets and outlets, the idea being to maintain a certain pressure in the tappet (but not so much that they "pump up" at higher rpm). Over time the oil inlets / outlets wear a bit and let more oil drain when the engine's stopped than normal. Hence the tapping when you start from cold, while the tappet fills up again.

 

[Muttley]

cheshire cat wrote

it's a hangover from pushrod-rocker and valve stem days. I guess now, it's the part which allows for a clearance between cam and the end of the valve whatever is inbetween the two.

The tappet is present in most engines as a cam follower, and is often the location for valve clearance adjustments to be made. Some overhead cam engines, though, have the cam acting directly on a rocker arm - the VAG 24-valve VR6's work like this. In these cases a bucket tappet can be located over the valve stem.

http://www.autozine.org/technical_school/engine/tech_engine_packaging.htm

For a long time, valve clearances were adjusted by hand at service intervals, either by a screw-and-locknut on the rocker arm or tappet, or by shimming the tappet to the correct clearance.

Nowadays most engines use hydraulic tappets which are self-adjusting.

http://www.tpub.com/content/construction/14264/css/14264_91.htm

Engine oil pressure is what forces the hydraulic tappet to take up the clearance, which is why you sometimes hear a brief clatter on startup. The tappet includes a calibrated bleed so that the expansion of valve stems and other engine parts can be adjusted for - the tappet is able to slowly change its length while still acting as a solid connection for the duration of the valve opening event.

 

[basstard]

excellent links muttley!! thanx!