Boost pipe/EGR removal CLS250

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molgrips

Active Member
Joined
Jul 26, 2021
Messages
112
Location
Cardiff
Car
CLS 250
My car is a 2013 CLS 250 CDI and there appears to be a crack in the hard plastic pipe going into the throttle body. A common problem according to the dealer which is why they had the part in stock.

Anyway I think I have to remove the whole EGR valve assembly to access the bolts to remove the pipe, I don't think removing the actual gas cooler itself from the valve body is going to be enough.

From what I can tell the coolant runs from the block into the valve body via a second hole in the casting next to the EGR hole, and this means having to drain the coolant.

Am I correct? How does one drain coolant on these cars? Just pop the hose off and hope you catch it all, or is there a neat drain plug so I can partially drain? Does it need special MB coolant to refil? Any gotchas?
 
Have a look here https://www.youtube.com/c/davesterl/search?query=mercedes

Sure this guy has a video on egr removal etc on the OM651 engine, he has done some good work on these.

I am pretty sure the coolant will need to be drained, refilling and bleeding is the hard part though as the water pump is on demand and the thermostat is mapped so not a straight open close type. When I had my water pump replaced, the garage used a vacuum pump to suck the air out of the system and use the created vacuum to refill it. Even so, after 30 or so miles of driving I got the top up coolant message, even though it was full when I collected the car. For the next few days I was topping it up until it finally settled.
 
From what I can tell the coolant runs from the block into the valve body via a second hole in the casting next to the EGR hole, and this means having to drain the coolant.

Am I correct? How does one drain coolant on these cars? Just pop the hose off and hope you catch it all, or is there a neat drain plug so I can partially drain? Does it need special MB coolant to refil? Any gotchas?
I don't know the specifics of your car but if the orifice that will leak is relatively high, you only need drain down to that point and that may be possible by drawing the fluid from above with a suction or syphon device.

Draining from below via drain plug or hose is invariably messy.
 
I don't know the specifics of your car but if the orifice that will leak is relatively high, you only need drain down to that point and that may be possible by drawing the fluid from above with a suction or syphon device.

Ah yes, good point. It is high up on the engine. I had planned to pop the hose off the top and open the drain plug to let the fluid drain down. But I think the point where the coolant comes out of the engine is the lowest part, I wouldn't be sure when I'd drained enough to avoid a messy surprise. It may just be easier to take out say half of it and deal with the inevitable bleeding issues. Unless it's a special procedure?

I remember removing a ground floor radiator in my house and simply undoing the connector, to my amazement no water came out which is what I'd read would happen. So it's possible if I leave the coolant cap on nothing will come out? Bit of a gamble mind!

Even so, after 30 or so miles of driving I got the top up coolant message, even though it was full when I collected the car. For the next few days I was topping it up until it finally settled.
That happened when I drained and refilled the coolant on my last car even though it was basic! Took ages to settle.
 
I remember removing a ground floor radiator in my house and simply undoing the connector, to my amazement no water came out which is what I'd read would happen. So it's possible if I leave the coolant cap on nothing will come out? Bit of a gamble mind!


That happened when I drained and refilled the coolant on my last car even though it was basic! Took ages to settle.
Loving the optimism but suspect it is misplaced!
Inevitably air will enter and fluid escape. If there's space there to get a bowl or something to catch it in though...
You can probably check you have removed enough by removing just enough the part to see if coolant is still emerging. If it is, promptly shove it back in and remove some more.
Fully removable drain plugs are cleanish but the tap type (where the bung remains) make a real mess - just not quite as bad as removing the bottom hose.
I regretted draining mine (drain plugs on the block) for changing inlet manifold gaskets as the quantity that had to be removed was negligible but I wanted my Pela for the oil and didn't have another method to remove from above. My bigger mistake was trying to refit a drain plug mid-flow. - don't!
 
So how on Earth do you remove enough coolant from above? You'd have to poke a tube right down into the EGR valve and hope there weren't any bends.

Or maybe if you could take enough out of the header tank, then disconnect the EGR and it'd flow backwards into the header tank ..? But how much to take out?
 
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So how on Earth do you remove enough coolant from above? You'd have to poke a tube right down into the EGR valve and hope there weren't any bends.
From the radiator - or thermostat. If you can get a hose down some depth of the radiator (should be easy enough on a horizontally flowing radiator) then with fluid removed the level in the block will drop in synch.
 
From the radiator - or thermostat. If you can get a hose down some depth of the radiator (should be easy enough on a horizontally flowing radiator) then with fluid removed the level in the block will drop in synch.
Is there a hole in the top of my rad?
 
Is there a hole in the top of my rad?
Maybe not if the cap is on the reservoir. Just remove a hose for access - you wont lose much fluid at the top end of the rad.
Have you figured a method to draw the fluid? In the absence of a suction device you could try syphoning by the two hose method.
 
I think I'd siphon using a long thin tube and a large syringe.
 
I think I'd siphon using a long thin tube and a large syringe.
That's pumping - which will work.
Syphoning is establishing a flow and then leaving gravity to do the work. If you have an appropriately sized syringe though, you have it covered.

And will be a lot less messy that draining.
 

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