My 420SEL Timing Chain disaster...Help... - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 09-09-2008, 03:32 PM Thread Starter
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Date registered: Aug 2008
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Angry My 420SEL Timing Chain disaster...Help...

One owner car, at 68K, started after 5 hours of evening parking (not cold wather), started, idled for 5 minutes, then gave sudden trhottle, moved about 20 meters and stopped as if running out of gas...

Suspected fuel filter, pump failure and tried to start with starter fluid. There was no other noise at all, before or after this. The engine sounds like about to start. Towed home, and next morning tried to start, no odd or bad noise, almost started for a second and behaved as if 'NO GAS SUPPLY.

Opened the hood and noticed that there was split open crack on driver side VALVE COVER at the timing end (1 mm gap, 2inch x 1 inch opening). Sadly realized that the timing chain had jumped.

Took to local MB agent and they tried to rip me saying that the valve could be bent. Waht is this could be?
If any of the valve is bent, will the engine torc like nothing is wrong. The previous owner, auto engineer friend, said with all the descriptions, the valves are intact. And advised only to replaced the upper rails (guides), if necessary the chain, not needed to replace tensioner.

Is there a quick way to test for bent valves?
I also am trying to get a used driver side VALVE COVER.

This car was 54 point inspected by CrowEuroCar in dublin, OH just a day before this mishap was certified in excellent condition, with no repair suggestions. It is the same agents quoted 30 hrs of labor and 1500 parts.

Any advise will be help ful. Please share your knowledge and experience.

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post #2 of 2 (permalink) Old 09-09-2008, 04:42 PM
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Date registered: Jun 2003
Vehicle: 1991 300 SE
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Although rare for a relatively low miles engine to have the plastic chain guides fail, that seems to be the case with your car. Were the oil and filter changed at a proper interval?

The M116/117 engines are an interference design: if the timing chain goes the valves are left hanging to be smacked by the piston crown.

If any of the valve is bent, will the engine torc like nothing is wrong.
The valves won’t do anything with the timing chain off – you’re just spinning the crankshaft with the starter. A compression test may confirm the condition of the valves.

As an aside – and of little help to you – this is one of many reasons why I’ll never own another M116/117 powered MB. Good luck.
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