[DBCoooper]

I need to replace my catalytic converters. I'm looking for the exhaust manifold to down pipe "donut" gasket. The one right at the end of the exhaust manifold. All diagrams I see from MB don't show anything. Is there a gasket here and if so does anyone have a part number?

 

[BoatWaco]

It looks to me like item #3 is the gasket for the manifolds - and 8 required. So if they’re showing that but not one for the down pipe, maybe it doesn’t use one there. Have you tried calling local MB parts department or a local muffler shop to confirm this?

 

[DBCoooper]

Thanks for the reply

Yes, I think we're reading the schematic the same, and I have to assume at this point there isn't a "donut" gasket there. I'll see if the local MB parts counter can help. I've never seen a manifold to down pipe connection without one, but that doesn't mean much.

 

[BoatWaco]

Let me see if I can open EPC / WIS and check on the parts for this - it may show more details. I'll get back with you here soon.

 

[BoatWaco]

EPC only shows what you've already shown. They do call out sealing rings 6 and 7 as in your diagram, but nothing for the flange connecting to the manifolds. Except bolt with flange A1299900410 - which appears to be the bolt to connect the pipes to the manifolds.

 

[DBCoooper]

Thanks for looking. As soon as I have time I'll call an MB parts department. So far it looks like the connection between the exhaust manifold and the down pipe is made without a gasket.
Really appreciate you looking this up!

 

[e-420]

If it's like my E420 MB (a) doesn't use steel bolts but brass or some other material so they come out easy peasy, no problems with heat seizing them and (b) the mating joints are somewhat of a "ball and socket" arrangement with just a small gasket making assembly easy. Couldn't believe how easy it was to unbolt the Cat from the header pipe and exhaust, drop it down and replace.

 

[DBCoooper]

Thanks for the input. Does that mean there is a gasket at that location( manifold to down pipe)? That's what I'm really looking for.

 

[DBCoooper]

To close this out, I have verified there are no gaskets between the manifolds and the down pipe. MB uses (at least on the 99 SL500) two bolts into captured nuts on the manifold themselves. There is a convex radius on the manifold and a concave radius on the down pipe with a flange that pulls them together. Nice setup.

By the way, I got a set of cats (4) with pipes from Rock Auto for about $1.1K. They are Davico brand. They bolted up well, but are not in the same league quality wise compared to the MB parts.
I had to chase the o2 bungs with a tap as there was slag on the threads which wiped out a good o2 sensor. I didn't see it, and before I could feel there was an issue (installing by hand) it had grabbed the o2. I couldn't get it to back out without a wrench, which of course took out the threads, costing me a downstream sensor. The welds are poor compared to the MB parts. They do seem to work fine, and stopped the gravel sound I was getting with the factory cats.

If you can find them, I'd go with a MB set of pipes. Magnaflow makes them, but they make the MB parts look downright cheep.

Dan

 

[BoatWaco]

Thanks for closing the loop here - this is very helpful information to have!