This weekend when I started my car (cold) it made a ticking noise from the passenger side (420 series V8). Once it quit after driving about 70 feet and the second time it did it I immediately shut off the engine and waited a few seconds and restarted it. It did not do it.
The history of this engine - 150,000 miles - this summer had valve stem seals, timing chain and tensioner replaced. Also replaced timing guides and all oilers for heads. Mechanic said there was no sense in doing a valve job - valves seated well and guides do not appear to have much wear. I use Mobil 1 10w-30. This only has happened when it is cold -first start up of the day. However it did not do this this morning. Any ideas???

Which 420?

I'd put money on a bit of dirt in one of your hydraulic compensators ('lifters'). These have tiny oil holes that can plug up temporarily, which prevents them from pumping up fully until the oil is warmer (more viscous) or the blockage flushes itself out. Try a bottle of your favorite oil additive/cleaner to start, that may do the trick. If not, use a mechanic's stethescope (or the old screwdriver-on-valvecover) to locate the ticking rocker and replace the lifter. There's lots of info here on how to do this job...hope this helps.

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1986 560SL
2002 Toyota Camry
1993 Lexus

Thanks. I wondered about this. It is a 420sel. I have been changing the Mobil 1 every 3,000 miles but have decided to up it to 4,500 - 5,000 because of the expense and lack of equipment I have on hand (I change oil and filter at a friend's that has a "working" garage - he goes to school in Illinois and is not home very often).
If this does not do the trick I will investigate and change out the "offending compensator".

nasty old "oil tube", check out MENU #18 on my page. The normal giveaway is a loss in oil pressure when warm; typically around 1 bar.

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Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

Both oil tubes and all oilers replaced when doing the valve stem seals. No loss of oil pressure whatsoever. I would bet that donbryce is correct in his assumption that there is some sort of debris in there (at least I hope this is the case).

My exprience with my car that had the same issue is two bad hydraulic lifters. My 560 SEL did the same thing and I changed the lifter and the noise is gone.

Thanks