I have a 2000 clk 430 and the car has been running rough. I took it to the shop and the mechanic told me the intake plenum was leaking, causing the car to run slightly rough. The mechanic informed me a used unit was $500 and a new one is $1,300. My questions is get a new one or a used one? Also, was told the unit bolts together, is there any way to use gasket seal to seal the leak? Mechanic has never tried to replace a gasket and said there is not a gasket made for the intake plenum. Can one be fabricated or is the unit glued with sealant and can't be broken?
I also have a mysterious AC leak. Dye was put into the system last spring, but there is no evidence of leaking from the high pressure hose, but the compressor was completely empty.

Thanks

 

I just went through a similar situation, you might want to read this write up that I did, it includes some detailed pics of the manifold.

https://mbworld.org/forums/clk-class...etc-fixed.html

It completely depends on where it's leaking from. I suggest you take the time to inspect all the vacuum lines before you go replacing the intake. These are a more likely source of vacuum leak. Specifically the lines on the front of the engine. These provide manifold vacuum to control the "Variable Intake". Look at the lines very carefully, the cracks in mine were not apparent until I looked at the backside of them and flexed them a little. Also, be very careful with the line that runs down underneath the manifold. Mine sheared off as soon as I touched it, and it can be difficult to replace. Read this before you mess with it:

http://www.benzworld.org/forums/w208...rate-no-2.html

There are also a couple vacuum lines on the EGR valve on the rear, passenger side of the motor, check them also. The manifold is not designed to be "opened", or the two halves split. I did split my old one because I had to replace it, and I wanted to post pics for people like you. The two halves are only sealed by what looks like some sort of silicone sealant. I didn't see any reason why you couldn't reseal it and bolt it back together. But when they assemble the manifold, there are two pins that protrude from the top half, and press into the lower half. If you open the manifold, the pins break (or at least that was my experience). I don't think they serve any purpose other than to indicate to the dealer that it has been tampered with. I was able to bolt it back together without any apparent problems.

I purchased a used manifold on eBay, and installed it on the car. From what I saw, there is not much that can go wrong inside the manifold (under normal use), so if you end up replacing it, I would suggest a used one, as long as the seller offers a guarantee. I also took time to thoroughly flush the manifold with solvents before installing it, to make sure it was as clean as possible.

When I was deciding what to do, I came across new manifolds online for less than what your mechanic quoted:

http://www.europartsdirect.com/epc-items.asp

http://www.carpartsdiscount.com/auto...ml?3593=267946

You can also double check the torque of the bolts, the manifold-to-cylinder head bolt is 20nm, not sure what it is for the other bolts that hold the manifold together, since it's not designed to be serviced, I don't think they provide a spec for it. Hope this helps.

 

Oddly, the metal on the intake plenum is rotting. It is pitted in various places and leaking air. Apparently yet is an issue as other mechanics have reported similar problems