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Old 10-15-2002, 01:19 PM
Oliverp's Avatar
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Join Date: Aug 2000
Location: Toronto, Canada
Posts: 436
420SEL High tickover when warm

Just one more question!

When cold, the car idles in park or neutral at about 750-850rpm, and engagement into drive or reverse is smooth.

When the car reaches operating temperature, it idles in park or neutral at 1500rpm, and engagement into drive or reverse creates a big 'clunk', and once drive or reverse is engaged, it drops back down to about 750-850rpm.

I'm getting the valve seals, guides and the head done over the next month or so. Will this solve the problem, or is it an idling problem?

Thanks again everyone
Oliver Plante

---My Previous MBs---
87 300SE (Sold) - Black, Cream Leather
89 300SE (Sold and missed) - Black, Cream Leather
87 420SEL (Died!) - Bronze, Black Leather

---Father's Previous MB's---
2004 S320 CDi - Black, Cream Leather, 18" AMGs
2001 CL500 (Stolen!) - Black, Cream Leather
1999 E55 AMG - Black, Black Leather
1994 500SE - Black, Cream Leather
1990 300SE - Midnight Blue, Cream Leather
1986 420SEL - Diamond Blue, Cream Leather
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Old 10-15-2002, 07:26 PM
Join Date: Dec 2001
Location: Southern California, U.S.A.
Posts: 8,503
When you put your gear selector into drive or reverse and you hear or feel a big clunk, it's probably work out rubber flex discs on your driveshaft, or possible a worn out center support bearing on the driveshaft.

It could also be broken differential mounts, but my money is on worn out flex discs.

You need to get this looked at right away. If it's a worn out flex disc, and it fails when your on the road, you could be looking at some expensive damage.
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
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Old 10-17-2002, 09:31 AM
Posts: n/a
Other than the clunking when tranny put in gear - my 560sel (1988) has just started the same thing. Idle is smooth and about 850RPM when cold and after about 15 minutes it starts to climb to 1500RPM at idle and stays there. However, when I put it in gear, when warm and idling at 1500RPM, it smoothly goes down to 650RPM. When I take it out of gear when warm, it takes about 3-5 seconds and slowly goes back to 1500RPM. Other than that the car runs good. Any one with ideas????
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Old 10-17-2002, 10:13 AM
dpetryk's Avatar
Electrons can do anything
Join Date: Sep 2001
Location: Houston, Texas
Posts: 1,071
Its probably the idle control valve. It has been discussed to death in many threads. Do a search.
I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k
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