1975 450 SL - Mercedes-Benz Forum

 
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post #1 of 3 (permalink) Old 01-16-2012, 04:09 PM Thread Starter
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1975 450 SL

Good afternoon.

My uncle recently purchased a 1975 450 SL. He told me about some issues he is having with the car, hoping that I could find some answers online (he is not computer savvy.)

He is a mechanic by hobby, though he rarely works on anything manufactured outside the states (his three babies are a 1971 Cuda convertible, 1969 Cuda fastback and a 1971 Dart swinger.)

A few weeks ago, while driving the 450 SL, he started to hear a "clatter" and then experienced a loss in power, he described it as "running on 4 cylinders." After inspection he noticed the plastic guide for the timing chain had broken. He replaced it, inspected the valve train, noting everything appeared solid, but also noticed clearance between the valves and lifters. He started the motor and again noticed the "clatter", and shut it off. That is where the car now stands.

He mentioned the status of the valve train because he doesn't think valve/cylinder damage occurred.

I know him to be a knowledgeable mechanic, but Mercedes' are a new beast, and he is looking for advice.

I am happy to read, so please share links if they are applicable. Thanks for the help.

- James
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post #2 of 3 (permalink) Old 01-16-2012, 07:39 PM
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Vehicle: 1965 220S, 1999 Volvo V70 (wagon), 2006 Ford Crown Vic Police Interceptor, 72 350SL 4 Speed
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This is a know problem with these engines. Failure to change the oil on a regular basis coupled with a work chain guide on the drivers side causes the end to break off and get between the chain and the sprocket. additionally, chain wear contributes to this as well. Timing skips a tooth or two causing valve damage. Remove the cyl head(s) and replace the bent valves.

Conversely, get another engine and replace the bad one. Replace the chain and the guides in the replacement first.

Near Manassas Va. '65 220S, 2006 Ford Crown Victoria Police Interceptor, '99 Volvo V70, '72 350SL 4 speed

Not part of the in-crowd since 1952. It's BRAKES not breaks. You break a bone, use brakes to stop your car. /rant

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post #3 of 3 (permalink) Old 01-16-2012, 09:18 PM
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Date registered: Jul 2004
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A really quick check would be to pull the fuse to the ECU(so the car won't start) and crank it. if it cranks unevenly it indicates some cylinders have more compression than others= bent valves. Slightly more time comsuming but more conclusive is pulling the cam covers and checking the cam timing and checking compression.

Tony
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