Header pipe

[RBurg]

Looked the BBB cd and was unable to see if there should be a lock washer on the three bolts from the manfold to the down pipes? Can anyone be of help?  Mine came loose and wondering if the mech missed putting lock washer on.

Will have up date by Monday on last weekends of German car show  and concourse, soory for the delay

Ron - Minnesota
71 280SL Tobacco "O GIGI"
97 E420 Silver Mist

[69280sl]

The picture parts book for the 250-280sl, shows only a nut and bolt, no washer.

Gus
280sl

[Cees Klumper]

Those bolts and nuts working themselves loose can be the result of the manifold/downpipe not being a tension-fit. The flange is supposed to force the down pipe into the manifold and the joint should be under tension at all times; this prevents the bolts/nuts from coming loose.
I had this problem for a couple of years, when, no matter what I tried (lock washers, new bolts, new nuts), the nuts would always work themselves loose. Then I replaced my downpipes and the problem went away.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[jeffc280sl]

There is a compression washer that fits over the pipe prior to inserting it into the exhaust manifold.  I think this is part of what Cees is talking about when he describes tension on the bolts.  The nuts are different than any I've seen before.  They are similar to a lock nut with nylon.  Instead of the nylon, which would not hold up well to the heat, there is a ring on the top of the nut which helps keep it in place through friction on the threads of the bolt.  The bolt and nut are specific to the header and are hardened for this purpose.

Jeff C.
1970 280SL 4-speed

[ja17]

Hello Ron,

You must have the correct all metal lock nuts to be successful. Most likely these are designed to be used only once for best results. Yes the metal crush seal on the pipe helps make a tight seal.
Snug all three bolts evenly before tightening each all the way. If you do not tighten things up evenly, you can break the expensive cast iron exhaust manifold. I like to lube the pipe connection with 100% silicone sealer before assembly. It helps everything slide together nicely, then it helps form the seal.

The expansion and contraction of the bolts during hot and cold engine cycles causes any incorrect hardware to become loose. If you must use standard hardware your only chance would be to double nut each bolt, this should prevent loosening.

Joe Alexander
Blacklick, Ohio

[Cees Klumper]

In my case the metal compression washer (it is very thin) did not do the trick - in fact, even three new ones stacked together did not either. One should be more than sufficient. The fit of my old downpipes was just wrong - there is a ring welded on the ends that, positioned incorrectly, prevents the tension fit into the manifold.
The nuts have a slit cut through them, then the top of the nut is bent downward to add some tension to the way it 'grabs' the bolt.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[glcg123]

Having installed a complete new exhaust system from MB there should be:
- Seal ring that fits over each pipe. This is for the seal between the exhaust manifold and the pipes. Only 1 is required for each pipe. MB P/N 915035-000023 $4.46 each - Cdn $ 2004

- Three bolts with copper nuts to attach the pipe to the manifold. The bolts are steel. The nuts are made of copper and are a locking type. They are designed to handle the heat and be more easily removed at a later date. They were purchased from the MB dealer. He had them all in stock, bolt P/N 304017-008043 - $1.29 each. Nut P/N 000-990-32-50 $2.90 each.

It is not worth it to go non-stock in this area because once it leaks you will have to start over. I have done a few exhaust systems for trucks and equipment when I lived on our farm. When we used common bolts and nuts, even with lockwashers, we usually had problems.

George
1965 230SL - 4 spd