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  #1  
Old 08-03-2008, 11:40 PM
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Broken Manifolds on 117 & 116 engines

I have owned my 350SL 4.5L since 1989. It had a new passenger side manifold in 1988, againin 1995 and again in 2001, Current one is still OK, but with others having only lasted about 7 years and say 7000 miles each, I am getting worried that I may soon have another failure

Anyone else have experience with these manifolds failing?

On current one, we drilled the holes out slightly oversize so as to allow some room for expansion. Brackets were installed at the lower end of teh exhaust downpipes, but these were recently removed when teh Tranny cam out for a reseal. I am asking myself whetehr I should re-install them or perhaps have bellows installed in the down pipes.




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Old 08-04-2008, 09:48 AM
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Is there room for headers? ;-)

That manifold design seems to leave something to be desired.
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Old 08-04-2008, 10:11 AM
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Quote:
Originally Posted by todds View Post
Is there room for headers? ;-)

That manifold design seems to leave something to be desired.
I agree it does and MB changed it several times it seems. Originals seemed to be solid, then two bellows added and on 116 even a third added. So, there must have been problems.

I am interested to find others with same problem and see what they have done to correct it.

I am interested in headers, but where do I find someone who has designed them for this car?
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Old 08-04-2008, 12:12 PM
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Quote:
where do I find someone who has designed them for this car
Well I doubt anywhere unfortunately, if someone knows about it - they'd probably be on this list.

I was thinking you could have them made for you if you brought them your manifolds. I think many custom exhaust shops have experience fabbing headers. This wouldn't be cheap, but it might be a bargain if you have to source and install new manifolds every so many years.

One thing I wouldn't recommend is to go whole-hog and put on a noisy performance exhaust system which would be totally out of character for the car. You could emphasize noise control over wide open throttle performance for instance.
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Old 08-04-2008, 12:50 PM
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Are your engine mounts ok? Maybe there is more then normal stress being put on them.
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Old 08-04-2008, 05:27 PM
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it's the USA emmisons control devices and the heat generated to work the Cat cons that causes that. The Manifold is so hot it's expanding at a different rate to the head. Heat soak on engine shut down is another problem causing loose head bolts.
The third bellows connection is the only way to solve this plus a flex connection on the down pipe. This really common on todays cars because of this very problem .
This is an example.
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Old 08-04-2008, 08:29 PM
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Originally Posted by alabbasi View Post
Are your engine mounts ok? Maybe there is more then normal stress being put on them.
Good Question. Last time I replaced manifold, I had a good mechanic do it. I asked him about mounts and he said they were OK, but I think it's hard to tell. How do you check the mounts? I think the engine shock was changed.

What we did do, was check the stud spacing vs the hole spacing in the manifold. It was not exactly same, so we drilled out the manifold holes slightly and made sure the manifold flanges were smooth. Idea being some movement could now be tolerated.

We also added supports at bottom of downpipes - just 1" wide rubber webbing between clamp on downpipe and bolt (on torque converter, I think). But these are no longer there - removed during a transmission reseal.
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Old 08-04-2008, 08:33 PM
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Originally Posted by mercmad6.3 View Post
it's the USA emmisons control devices and the heat generated to work the Cat cons that causes that. The Manifold is so hot it's expanding at a different rate to the head. Heat soak on engine shut down is another problem causing loose head bolts.
The third bellows connection is the only way to solve this plus a flex connection on the down pipe. This really common on todays cars because of this very problem .
This is an example.
There are no cats on this 1972 car.

But, I have thought about adding those flex units in the downpipes. Adding a bellows to the manifold is more difficult - cast iron and not much to work with. The MB ones with 3 bellows on 116 engines had a strut to support the downpipe. They did not offer these on 117s. Maybe no room or perhaps 117s did not have as much of a problem?
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Old 08-04-2008, 08:54 PM
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hi,there is a lot of heat in there ,but there should be support brackets on the rear of the trans, it is normal MB practice to have a cross bar bolted to the trans crossmember and a rubber bushed support each side. The mounts,if they are originals will long overdue for replacement. Normally they look shot when they are very bad but can look ok to the untrained eye.
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Old 08-05-2008, 04:19 AM
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The latewr engines (5.0 M117) havew reinforcing ribs on them. will one of these fit your car?
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Old 08-05-2008, 09:50 AM
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Originally Posted by mercmad6.3 View Post
The latewr engines (5.0 M117) havew reinforcing ribs on them. will one of these fit your car?
Wow - yet another design change on this manifold! I don't know if that would fit or not - it looks like it might but in pictures below, looks like downpipe is offset a bit?

If that is off a 5L 107, would that be a Euro version 500SL? If so, might have trouble finding a used manifold here in NA? Tom Hanson at Mercedes Classics suggested a double pipe unit might work - one from 77-79 with catalyst chamber.


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Old 08-05-2008, 04:44 PM
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Hi,yes it's a right drive 5.0 liter manifold but it would fit if the down pipes were modified to suit. The ports are twice the size though ,I sat this one next to a 3.5-4.5 manifold last night and the difference is rather stark . also the down pipe is designed to head the pipe really close to the trans bell housing . Almost over the top of the trans in fact. Perhaps later W107 manifolds are what you need because this design makes it obvious that the engineers realised a design fault and rectified it ....later.
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Old 08-05-2008, 08:13 PM
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My wife killed her 280se 4.5 ages back by hitting something with the exhaust. The rather sudden thrust up on the system snapped the manifolds. -CTH
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  #14  
Old 08-05-2008, 08:22 PM
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Quote:
Originally Posted by cth350 View Post
My wife killed her 280se 4.5 ages back by hitting something with the exhaust. The rather sudden thrust up on the system snapped the manifolds. -CTH

I had the same thing happen on my 107. I had to make an emergency manuver (get hit head on or get up on curb) and mine broke right at the bend going to the downpipe. The g-d-a-m-n thing sounded like a domestic pickup truck with flowmasters. . .I wouldnt suggest driving with a manifold like this, the hot exhaust blows right against the back of the footwell, the possibility for the foam or your carpet to catch fire does exist.
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Old 08-05-2008, 08:45 PM
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Quote:
Originally Posted by mercmad6.3 View Post
Hi,yes it's a right drive 5.0 liter manifold but it would fit if the down pipes were modified to suit. The ports are twice the size though ,I sat this one next to a 3.5-4.5 manifold last night and the difference is rather stark . also the down pipe is designed to head the pipe really close to the trans bell housing . Almost over the top of the trans in fact. Perhaps later W107 manifolds are what you need because this design makes it obvious that the engineers realised a design fault and rectified it ....later.
Thanks - It was interesting to see how MB had modified the manifolds by the time they got to the 5.0L engine. I would like to find out if there an improved design that will fit my car.

The early cars had manifolds like mine. Then the US cars had catalysts in the engine compartment. Later these moved under the car. Don't know how the post catalyst manifolds compare with the early ones, but would be interested if they were improved.

Question - I don't recall any fixed clamp on the exhaust pipes under my car. I may be wrong, but I think all supports are hung with rubber o-rings. Is this true for my car and other SL models?

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