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Old 04-30-2004, 12:01 PM
vintageFan's Avatar
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Join Date: Mar 2004
Location: Colorado
Posts: 2
Question Timing belt

A month ago when I took my '74 450sl (8 cylinder - 4 spd standard shift) in for oil change the mechanic said that he heard the timing belt rattle when he started the car. He estimated it would cost $700 to $800 to fix it now or if I let it break on it's own it would be upwards of $6k as it would involve much damage.

The previous owner (a friend) thinks even if it does break it would not do more harm than needing fixed.

I don't hear any rattle on starting and my s/o agrees the car sounds just like always on starting. The car runs great in my estimation.

Is this mechanic trying to scam me? He did charge me $125 to put an $8 part (took 10 minutes) on my tailpipe previous to this visit.

How does one find an honest mechanic?

Thanks in advance for any advice and thoughts.

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Old 04-30-2004, 12:41 PM
Posts: n/a
To begin with, Mercedes engines do not have timing belts. They have timing chains.

This engine is an interference engine which means that if the timing chains break, it will cause serious damage.

If the timing chains break, the cost to repair the damage will probably be more than the car is worth.

How many miles on the engine? How many miles since the timing chains were replaced. Mercedes used to recommend replacing timing chains if you have more than 100,000 miles on them. I'd say that if you have 150,000 miles since the chains were replaced, you should have it done.

I recommend you take the car to a dealer who has a good reputation and ask that they check it out.

$600 to $800 seems reasonable to me because it used to cost well over $2,000 to change the timing chains on older V8's from a simplex chain to a duplex chain.
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Old 04-30-2004, 01:09 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Changing from the single row to double row is a massive job in comparison to a standard chain replacement. The chain replacment only requires the valve covers to be removed. The conversion required all new gears and the removal of the timing cover. Only the 1981-1983 3.8 liter motors had the single chains.

As I have stated a few hunderd times on this forum, the problem is almost never the chains, the problem is the durable plastic guide rails that petrify into fragile glass like creations and then break when a ruitinely loose chain slaps against it. The pieces then run through and jump the chain. This is what happens 90 some percent of the time.

The rattling will happen occasionally no matter what you do. If the rails are over 100k or 5 years old they are susceptible IF they are plastic. The early v8s had rubber bonded to aluminum and do not have this catastrophic risk problem. A 74 might have aluminum rails and thus have a significantly reduced exposure to the problem.

Proper maintenance will have the valve covers off a 1974 to adjust the valves every 15k and the state of the rails/chain should be evaluated then.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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Old 05-02-2004, 01:19 AM
vintageFan's Avatar
Registered User
Join Date: Mar 2004
Location: Colorado
Posts: 2
Thank You

My 450sl has 150k and I did know it was a chain but well...I did write 'belt'

I just wanted to thank you both for the most useful replies. The previous owner doesn't recall when he had the belt checked/changed. I will do this maintenance when I have the next tune up/servicing.

Thanks again sincerely!
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Old 05-02-2004, 09:00 PM
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Join Date: Aug 2003
Location: Phoenix
Posts: 3,726
What part of Colorado? Al's ******** in Denver is a good honest shop.

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