Knocking noise at startup

[joshhol]

There is a knocking noise coming from the engine in the 220S right after I start it up (from cold) that goes away as soon as the oil pressure comes up.
What could I do, run synthetic? I'm using Delo 15W40, 150,000 on the engine rebuilt in '83. It runs like a champ with respect to everything else.
THanks

[Mark DiSilvestro]

I've owned a number of cars over the years, including 'Miss Daisy'- my 60 finnie, that had this flaw to a greater or lesser degree and still got many miles or years of use.
How's your hot oil pressure? In the case of 'Miss Daisy', She tends to run a bit rich and, combined with the manual choke - especially in cold weather, tends to dilute the oil with gas. That's why I'm running 20W50 and changing at 1000 to 1500 mile intervals. I get about 22 PSI hot oil pressure, with diluted oil, and maybe 5 to 10 PSI better after changing. Either way, it still pegs the oil guage at any speed significantly above idle. I also notice, with fresh oil, it seems to smoke a bit less on startup too. I now only use the minimum manual choke and fast-idle setting to start it. If yours has automatic chokes, you can try cranking the engine for several seconds and giving the oil pressure a chance to build up BEFORE hitting the gas pedal and setting the chokes and fast-idle. I'd start to worry if the rattling continues after oil pressure or the hot oil pressure gets really low and climbs slowly.

Happy Motoring, Mark

[joshhol]

Thanks Mark,
that is reassuring.
My oil pressure barely drops to 30 after a hot run, and I haven't used the choke all summer. Maybe I'll crank longer before gassing it, but sometimes it'll turnover right away cold at the first turn of the key.
I guess I wont worry about it, thanks

[Mark DiSilvestro]

With my manual choke, I pump the gas 2 or 3 times and pull the choke out just enough to keep it idling at startup, without excessive fast idle and rattling.

Happy Motoring, Mark