Welcome to the forum Neil...

I'm with Strife on the chain & guides issue. Its the guides that wreak the havoc by breaking apart (plastic + heat + age = brittle). My 500 had no noticeable symptom(s). One day folowing a 3 week lapse in running it around, I heard the dreaded chain slap because the tensioner had leaked down. At 97K + 20 years, I decided to go ahead with chain, guides, oiler tubes and not just the tensioner. When it was opened up, we (my mechanic) found one of the upper guides cracked into two pieces - just waiting to chunk apart.

My recently acquired '90 560SEL (145K) is at the doctor's today having it done - no symptoms at all but no record of a previous replacement either. Waaayy cheaper than fixing the damage if it goes.

Lots of help and DIY info is available here and over at sl107(.com). Its DIY unless you're mechanically challenged like myself.

Kevin

__________________
"Dangerous with a wrench...and not smart enough to know it"

Stable (in order of acqusition):
'84 500SL, 280SEL (Euros)
'77 280SE. '90 560SEL
'79 450SEL 6.9,
'95 C280 (totalled by daughter 8/07)
'81 280SL (rescued) '88 300CE
'86 560SEC '95 C36
'01 CL55

DD's: '04 S500 4Matic (SWMBO)
'04 F150 Crew