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280S ALIVE, but help needed.

Started by oscar, 01 December 2006, 09:49 AM

s class

#15
Oscar - as promised some pics of M110 exhaust manifold issues.

First up, the standard arrangement of two 3-1 headers feeding into a Y-piece and into a single downpipe.  I assume this is what you have.  Both my 280S and 280SE had this arrangement. 



The dark grey discolouring is from many applications of exhaust sealant in vain efforts to cure the problems.  The root cause of the problems are that the M110 has a long cylinder head, that lengthens and shortens with heat cylcles.  This causes the two 3-1 headers to shift relative to oneanother ever so slightly.  The result of this is that the copper O-ring gaskets where the headers meet the y-piece stand no chance, and they fail after a very short time, despite meticulous assembly work. 

The second problem is that the Y-piece tends to split.  The pic below shows one of my Y-pieces that I welded up.  They split like this, and perpendicularly along the manufacturing weld lines.  Extremely difficult to fix - requires welding from the inside (!).



To try and fix these reoccuring problems, I elongated the mounting holes on the headers where the studs pass through from the cylinder head to try and get the manifolds to "ride" a bit and reduce the strain on the Y-piece.  It was somewhat successful, but eventually I resorted to adding flat bar "braces" either side of the Y-piece as shown in the top pic to reinforce the arrangement.  This worked for a while, but eventually the mounting faces of the top of the Y-piece distorted out of alignment as indicated in the 2nd pic. 

After stuffing around with this for years, I sought a better solution.  I discovered that the W123 280E used a different arrangment with the Y-piece located much lower down, near the gearbox, and with TWO downpipes from the headers leading down to it.  This would clearly solve the flexing problems. 

The pic below shows this arrangement installed in my 280SE. 



The trick was trying to get two downpipes to fit where there was originally only one. 

Picture below shows the rearmost downpipe, running basically behind the steering box, near the firewall.  It was tricky to get it routed so as not to have any problems with rattling against anything.



In this next picture you can see the front most downpipe roughly following the routing of the original single downpipe. 



I elected to eliminate the Y-piece alltogether and went for a big bore true dual system.

I've had no problems since this modification about 4 years ago.

Ryan



[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

oscar

#16
That's great s class

But now you've got me fantasising about the possibilities of a dual-bore system, custom extractors and twin hotdogs :o
Yes, my setup is the same as your first and something that occured to me was that I haven't checked the engine/hidden side of the "Y" piece that you show was cracked in yours.  It was too hot to shove my hand round there.

So it seems that an improvement was made for the W123. I'll have to keep an eye out for a set of these and get them one day. As for the dual-bore, one day maybe, it may be a necessity if I can't find a suitable "Y" piece.  Thanks again.

Nice clean looking engine BTW. This was the rebuild I'm assuming.
1973 350SE, my first & fave

s class

Oscar,

The Y-piece tends to split on both the visible and hidden side.  I just photographed the hidden side because my welding was neater there  :D

W123 manifolds should be plentiful.  WHen I bought mine from the breakers yard, I took the downpipes and Y that went with it, and used some of the bits in my final installation.

As for true dual, you will of course need a crossover (or balance) pipe at some point, and a little calculation shows that it needs to be not far from where the first silencer is mounted.  Since the silencer I have consists of two perforated tubes inside a can, I figured it amounted to a balance pipe effectively. 

This arrangement changed the sonud of the exhaust quite noticeably.  I would say that it now sounds very obviously '6 cylinder' - a bit like the 1980's BMW325's.

Thanks for the comment about the engine being clean, but sorry that photo was taken yesterday, nearly 200 000km after the rebuild - I try to keep my engines like that always. 

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

Mforcer

Michael
1977 450SE [Brilliant Red]
2006 B200

s class

Mforcer,

yes that is the offending Y-piece.  I replaced mine with a new one at some point at great cost, but it too failed just like the first one eventually.  The ebay pic you show doesn't look quite like the original MB part - it looks a lot more heavy duty.  If Oscar wants to keep the original setup, it may be a preferable option to the genuine MB part.

I posted this information just to share some of the hardships I have had, and help others make a better choice as to whether they want to persevere with the original setup, or consider a modification such as I made. 

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

oscar

Yes it is Mforcer, thanks very much. S-class, I've been typing over the top of you but I've typed too much to edit now ;D

Is it coincidence or am I paranoid?  Every time I say something's broken, the relevant parts pop up on ebay.

MPS, hydraulic suspension pump, 280 motor, 280 trans, and now this to name a few. Twighlight Zone theme. Since MB parts on AUS ebay is a small section, I should be thankful nonetheless and bless the ebay gods for listening. It's now on my watchlist.

At $145, it's tempting.  On close inspection of mine (still attached), I can't see/feel any cracks and it felt very smooth, but it was late at night when I got back from work. I need to start it up and feel for the leak whilst it's cold. Even run a hose over the manifold etc for a few seconds before it warms up. One more thing is there's a few shiny bolts on the Y and front pipe and adjoining the two manifolds.  I'm guessing replacement gaskets which may now be loose or leaking and the Y perhaps replaced with a 2nd hand one. A tightening up after it's warmed up might do the trick if the gaskets are intact.

Then again, I do like the 123 setup, and there's now 123 bits and pieces to look out for which will be easier to obtain.

Interesting s-class re the aftermarket observation.  At first I thought the web between the Y was bigger and the mould different, but looking at yours and mine I concluded that it was just because it is clean and new.  I wondered the accuracy of the "different metallurgy" statement. Mmm, anyway, it still looks a good buy that will probably do for a long time.
1973 350SE, my first & fave

s class

Oscar,

Your Y-piece isn't necessarily cracked - not all of them do, the main problem is with the gaskets.  And yes the bolts from the header to the Y piece tend to work loose.  Certainly I think you first try tightening them.  (thighten evenly front and back).  If this fixes the problem, you are in luck, and I would then suggest adding second locking nuts onto the 4 bolts to keep them where you want. 

Sorry, I didn't mean to make you fear the worst and go rushing off buying spares.  First verify where your leaks are.  My recommendation is simply that if your Y-piece is cracked, you may save yourself a lot of stuggle, frustration and cost by going to the 280E arrangement. 

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

benzlover

Your transmission is a 4 speed auto. and it is supposed to start in 2nd unless you hold the lever down or mash the gas pedal to make it start in 1st.  You can adjust the linkage (it runs over the top of the engine to the carbs and is best left to someone who either can read the maint. handbood or does it professionally).  I adjusted mine on my 78 280SE and it make the transmission shirt much firmer.

Michael
San Diego
1978 280SE
1979 6.9
1972 300SEL 3.5

oscar

Hi Michael and welcome,

Nice choice of cars you've got,

Re the linkage.  I've had a bit of a play according to the manual in the library on this site.  After a bit of mucking around I put it back to how it was since the setup seemed as per the manual.  I've had to concentrate on getting the engine running smoothly.   I've done more to the linkages attached to the holley carb to try and get the idle sorted out.  It's going better except at low revs, there's a misfire and the AC still drags the revs down and it'll stall occasionally.  The carb will get a rebuild after Xmas.  I found a kit for around $80Aus with seals, gaskets, jets etc.  It leaks a little from the float tanks and linkages and has a problem whereby the choke plate occasionally seizes closed whilst the engine warms up.  I think it's partly due to a backfire that occurs if I plant the accelerator. (timing issues)?  The plate is ever so slightly bent and has marks where others have freed it with perhaps a screwdriver. A couple of firm taps with two or three fingers usually frees it.

But like s class said would happen, my biggest improvement in shifting was the engine running correctly.  Once the idle got to where it is now, gear changes are smoother. 

Another possible discovery.  I commented here or earlier in another thread about the rear wheels screeching when the AT was put into R, revs around 1000rpm, and brakes on.  I think the front barkes are new, but whilst they're applied, there's bugger all pressure at the rear, hence the need to "stand" on the brakes to stop the car from reversing at a high idle.  I have to inspect the rear brakes.  All I know so far is there's too much fluid in the reservoir above the master cylinder, ie it's filled up to the cap.  I commented also on how the brakes would squeal, I could be approaching metal-on-metal at the rear.

No word on the exhaust yet, what I do notice is the exhaust side cam sounds noisy.  Much noisier than the intake side.  It'll be interesting to see the condition of the timing chain and how the cams are timed.

It's sidelined till after Xmas, so expect a deluge of questions in the new year ;D
1973 350SE, my first & fave

116.025

Ryan, what model year are your 280's?  Neither or my Euro '77s has the Y arrangement like yours and Oscar's...both of mine are two pipes all the way out.

Oscar, Kudos on the great find.  I know on my M110 (which is about to hit 441,000 kms) that when I did a proper valve adjustment, it was much quieter, it'd be what I'd try first for a noisy cam, but Ryan is more M110 savvy than I, so if he chimes in with a cam suggestion, take his advice  ;)

s class

116.025, good to see you back here again.  My 280SE is a 1980 (they built them up to 1980 here in South Africa), and my 280S was a 1973.  All the other 280S/SE I've seenn here have the same arrangement as Oscar has. 

Oscar, the M110 does not have hydraulic valve adjusters, and tends to exhibit cam-valve 'tap'.  Its fine and normal.  Whilst you're tuning up the engine, I highly recommend that you should check the valve clearances.  Its quite easy to check, I can give you the specs if you need.  Its worth checking, since its supposed to be checked and adjusted every 30 000km or so, which most owners never do.  Sometimes people set the valve clearances too tight, which quietens down the valve tap, but its a bad idea since it compromoses performance and puts you at risk of burning the valves due to insufficient cooling.  And while you have the tappet cover off, check the chain timing.  That's easy to do with TDC markings on the two sprockets. 

If the valve clearances need adjusting, you need a crow's foot wrench - can't remember if its a 17 or a 19.  The ball adjusters really are unbelieveably tight.  They maintain their position only by tightness - there is no other locking mechanism.  I can gove you more help here if required. 

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

oscar

Cheers Chad and Ryan,

I'm looking forward to getting under the rocker cover and diggin round.  I haven't even delved into setting valves on the 350 which was done by mechanic along with my timing chain.  The 280 is going to be a good learning excercise and it looks so much easier to service than a V8.  The project has stalled for the moment.  Understandibly considering the time of year and the heat and a few other things.  But yes, I'd love some advice and more info when I get round to it early next year.

Happy Holidays  8)
Simon
1973 350SE, my first & fave

s class

Well enjoy your break from the projects.  I just had another idea why 116.025's exhaust manifold may be different.  Its possible that the y-piece arrangement may be unique to RHD models, due to space problems caused by the steering box.  On the LHD models it would be easy to route two downpipes. 

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

116.025

Thanks Ryan 8), it's good to be back...work and personal life went crazy for a while...but anyway, I'm glad to be back, I didn't fully realize how much I missed it until I came back.

I'm pretty sure it's a 17mm, when I adjusted my valves, I noticed it seemed to be vital to set the crow's foot just right before attempting to turn the head on the adjuster, otherwise rounding wasn't too difficult, so then I just popped the rocker out and put a deep socket on it to turn it.  Considerably less efficient, since I would have to re-mount the rocker and then check the clearance, but it made it possible to get it done.

Merry Christmas, All!  8)