S211 E220 Diesel leak, overflow valve?

dan1w

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I have a pretty serious diesel leak. I've taken as much off as I can around the high pressure fuel pump and I can't be certain but it appears to be coming from the overflow valve which is at the back on the bottom left.

Can anyone tell me why this valve would be letting by? Is it indicative of the pressure being too high and if so what could cause that?

Any help much appreciated as I'm desperate to get this back on the road.

Dan
 

mersum1es

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no such thing as overflow valve... and deffo no 'indicative leak' outside, that alone will pin point you have found a faulty component... pls post a pic which valve you mean?
 

Westheath

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Bottom left is the fuel quantity valve Y94 held on with 3 torx screws, if its leaking check the seal is ok.
 
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dan1w

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Scrap that. It's not coming from the valve.
 
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dan1w

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no such thing as overflow valve... and deffo no 'indicative leak' outside, that alone will pin point you have found a faulty component... pls post a pic which valve you mean?

It's listed as an overflow valve on the exploded diagram and has a ball bearing at the end. Doesn't matter though as don't think it's that now.

I'm going to replace the seals. I have had a nightmare trying to find out what repair kit I need. According to Bosch they don't actually relate to the specific pump and the best you can do is buy a kit with most of the o-rings you require.

Why do these things always happen at the weekend?
 

lasa

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Why do these things always happen at the weekend?

So you have the weekend to suss out how to fix it :p.

Sorry, but there ain't no good time o_O
 

Westheath

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It's listed as an overflow valve on the exploded diagram and has a ball bearing at the end. Doesn't matter though as don't think it's that now.

I'm going to replace the seals. I have had a nightmare trying to find out what repair kit I need. According to Bosch they don't actually relate to the specific pump and the best you can do is buy a kit with most of the o-rings you require.

Why do these things always happen at the weekend?

What's the part number on the pump ?
 
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dan1w

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So you have the weekend to suss out how to fix it :p.

Sorry, but there ain't no good time o_O

I work shifts so weekends aren't any better for me. However they mean I can't get any obscure parts delivered until the Monday.
 
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dan1w

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What's the part number on the pump ?

0445010078.

I've ordered F00N201973. According to Bosch, F00N201979 would have more seals that fit my pump, but still not all of them and I can't get hold of that one before Tuesday. I've also ordered the shaft seals from MB. Hopefully that will be enough to sort it.
 

Westheath

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Regarding the overflow valve (300), I have never replaced one of those, but have every other thing bolted to those pumps :)
 
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dan1w

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Regarding the overflow valve (300), I have never replaced one of those, but have every other thing bolted to those pumps :)

Thanks, an injection specialist said the same which led me to investigate further.

Could you tell me how you remove the low pressure fuel lines on the S211 E220? Hopefully the parts are coming tomorrow so I thought I'd make sure no bolts are stuck by loosening and tightening them again (car being used to shuttle caravan a few meters forward and back as I work on my driveway, so couldn't remove it). There's a hex on the connector for the fuel lines so I tried to turn that but that would only twist the pipe so not sure how they come out.
 
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dan1w

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What a pain. After waiting days for the seals - with the car off the road, trip to mercedes and lots of reading and looking at exploded diagrams - parts arrived, removed the pump and two bolts fall out.

Tightened them up and back in business. For anyone with a leaky pump, check those bolts first!
 

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