exhast manifold cracking and leaking

[zak]

After their winter hibernation I had 2 glorious weekends here in northern NJ and drove both my 250 sl and 107 280 sl on each day.
Both started right up and drove great in their own way.
I put about 50 miles on each car and many smiles on my face.

But the last Sunday I noticed a bit more then usual  noise and some vibration sounds from the engine compartment as I drove home. The day before I had the oil changed and the mechanic noticed one broken and one cracking rubber donut rings on the mufflers so they were replaced too.

In checking under the hood I could here a leaking exhaust sound and traced it to a visible narrow crack on the cast iron exhaust manifold on the passenger side- maybe one inch long. When I placed my hand near the crack I could feel the hot exhaust leaking out.

Can I assume there is no viable repair scenario and must replace the pair? I see new aftermarket sets selling for between $300 and $500.
Is there a preferred quality brand to buy and brands to stay away from?
I searched the forum and tech manual and found little on the subject.

I did find out that early 230 SLs had sheet metal manifolds. They must make some scavenge sound at high revs.

Anyway any advise is appreciated.
thanks,

jz

[wjsvb]

Rear manifolds are the most likely to crack...they are hard to find and pricey,used and i think not available new; afaik never produced aftermarket.  I have one stashed away just in case!  The front ones are much less rare.  Try eBay or the usual suppliers here!  Manifolds are cast iron.  Apparently they crack from stress carried through the exhaust and tail pipe.

[Benz Dr.]

After their winter hibernation I had 2 glorious weekends here in northern NJ and drove both my 250 sl and 107 280 sl on each day.
Both started right up and drove great in their own way.
I put about 50 miles on each car and many smiles on my face.

But the last Sunday I noticed a bit more then usual  noise and some vibration sounds from the engine compartment as I drove home. The day before I had the oil changed and the mechanic noticed one broken and one cracking rubber donut rings on the mufflers so they were replaced too.

In checking under the hood I could here a leaking exhaust sound and traced it to a visible narrow crack on the cast iron exhaust manifold on the passenger side- maybe one inch long. When I placed my hand near the crack I could feel the hot exhaust leaking out.

Can I assume there is no viable repair scenario and must replace the pair? I see new aftermarket sets selling for between $300 and $500.
Is there a preferred quality brand to buy and brands to stay away from?
I searched the forum and tech manual and found little on the subject.

I did find out that early 230 SLs had sheet metal manifolds. They must make some scavenge sound at high revs.

Anyway any advise is appreciated.
thanks,

jz

Early header pipes make a lot more noise than cast iron manifolds.

[wjsvb]

Forgot to mention: W108 250/280SE are the same as 113's.

[Benz Dr.]

Forgot to mention: W108 250/280SE are the same as 113's.

That's correct when referring only to cast iron exhaust manifolds.

[zak]

2 mechanics told me the same thing, wjsvb . The rear manifold is more likely to crack.
I priced a new pair on manifolds while I was at my MB dealer and their price is $2500. for the pair.
I see used ones on Ebay for around $300 each. ....Should I be leery about using used ones?
There are new aftermarket ones advertised for $400 - $500 per pair. My mechanic is looking around now.

But right now I think I will just replace the rear cracked one and leave the front.
I drove the car on Sunday morning and it drove like a champ ( as usual) with just a slight high pitched hum from under the hood. No exhaust fumes into the cabin either.

Dumb question? The rear exhaust manifold can be replaced without removing the fuel injection pipes above them, correct? 

Thanks gentlemen,

jz

[Cees Klumper]

So long as the used one is not also damaged, it should be as good as a new one, they really don't wear out as far as I know (unless long years of some stress on them finally makes them crack? Come to think of it, why do they crack at all? Can it happen if a large amount of cold, say rain water from the pavement, hits a very hot manifold?)

[zak]

Cees, the rear manifold cracked on the top of the single pipe going down to the muffler connection by the fire wall. It seems like a spot vulnerable to vibration and flexing of the muffler system.
Now that I think of it, at my last 2 oil changes we had to replace 2 separate rubber muffler hanger donuts at each oil change. Why 4 donuts in little more then a year? There must be some flexing and moving the muffler that is stressing the manifold at that point
I will have that movement checked when the manifold is replaced.

BTW, I found what looks like a good used rear manifold- part # 129 142 02 02 - from a Hemmings seller for $ 360 US. I will jump on it as soon as I confirm correctness and condition.   

jz

[mrfatboy]

On the 250/280 there are two sizes of rubber donuts.  I'm not sure about the 230.

Exhaust donut size
-------------------
Large 1134920082 (center muffler)
Small  1074920082

[zak]

I bought the used rear cast iron manifold and it is clean and solid.
Is there an aftermarket source that sells the hardware components ? I believe I need 6 of a certain size and thread and length hex bolt, plus 6 copper coated nuts for the hex bolts.                  Plus  8 additional nuts of a certain size/type for the cylinder head studs. Plus wave washers and 2 round gaskets.

I looked in the Tech Manual and could not find that sizing info, or anything at all about the exhaust manifolds.
What aftermarket vendor would sell this as a package or at least know the correct sizes of everything to buy ?
Appreciate any direction.
thanks,

jz 

[Benz Dr.]

I had my welder fix a manifold for me. You need to preheat the casting and use a special rod to make it work. It helps if you can weld too.

[ja17]

Bad motor mounts or improperly installed exhaust  and missing hangers can contribute to manifold breakage. W108 Mercedes 6 cyl fuel injected sedans of the era used the same exhaust manifolds. Used ones are usually available for less than $200.

[zak]

Joe, it's the old story.
When selling they are 200.
When buying they are 350.
That's what I paid.
Now I wish I could figure out what nuts are bolts I need.

jz