1974 280 SE exhaust noise

[carl888]

Thanks S-class, I thought a silencer may have gone where the second "Y" appears under the car.  Appreciate the clarification.

I'm a bit frustrated atm, I'm in Singapore about to head to Melbourne and I am itching to get back into some workshop activities    D.I.Y. is almost non existant here, most people stop at polishing the wheels, or fitting blue parking lamps.......

[carl888]

I threw a tantrum with the 280 SE today, now that I'm driving it more regularly (3,000 kms is two months, yippee) however the exhaust has always annoyed me as it's always leaked slightly.  So until I get around to replacing the "Y" piece with a twin system, I thought I'd give it one last go.

Pulled off the "Y" piece and was surprised to see the leak was not at the crack (Which has been present since purchase) but rather a poor seal between the top of the "Y" and the underside of the manifolds.  It appears that the last time the "Y" was off, parts of an old gasket were not removed from the underside of the manifolds compromising the seal when the "Y" was re-fitted.  You could see the black stain on the section closest to the head where the leak was which is why I never noticed it before removal as it was hidden.

I didn't know the "Y" was actually a pressing, in two sections.  The inner section is a pressing held by the outer section which forms a sort of cage to clamp it all together.  Since I had nothing to lose, I cranked the arc welder up to 140 amps and managed to penetrate the two skins with a bead of weld in one pass and fill the crack at the same time.  It was too dark to take a pic inside the "Y" but I hope you are not too horrified by the snotty looking weld from the outside!  Poor thing took about an hour to cool!

Flashed a little VHT in white over the "Y" to match the manifolds, hopefully have it fitted up by tomorrow. 

Can anyone tell me if there is supposed to be any gaskets in between the top of the "Y" where it meets the manifolds?  Or do I simply use some exhaust sealant on the flanges and tighten?  Thanks for any information.

Some pics.....

[TJ 450]

Looking good Carl,

The poor old "Y" piece really does take a beating over the years. It's good to hear that it was just a gasket issue, there would be a fair amount of lateral movement there through heating/cooling cycles.

I'll probably be getting to know these things intimately. I did see that it was a two-piece pressing, which actually took me by surprise as well.

Tim

[carl888]

Thankfully the saga has ended, at least for now....the project succumbing to the dreaded scope creep!  However it's all back together as of yesterday.

I decided to pull the manifolds off, I could see evidence of exhaust gas creeping past the manifold gaskets and the heads.  Additionally, I discovered two exhaust studs were loose in the heads.  And I managed to get a turn out of a further 4.  You can see evidence of the leaks in the pics below of the gasket.  So after cleaning the mating surface of the heads, tightening the studs, cleaning the manifolds, some Wuerth exhaust paste, a can of white VHT it's all back together.  Not sure if I did the right thing, I used 304 stainless M8 nuts on the manifolds and stainless bolts and copper coated nuts on the upper "Y" piece.  The lower "Y" piece was attached to the exhaust with mild steel 3/8" bolts (This was done by an Authorised dealer!) so I replaced them with M10 stainless and some tooth washers.

The initial leak was from the crack in the "Y" piece along with the area where the "Y" meets the manifolds.  There were no gaskets present when I dismantled it, you can see the replacements in the pics, the small steel "O" rings.

Of course, I couldn't resist starting the engine with no manifolds, see the blue flame in the picture, and it was very loud!

So I think the exhaust issues with the RHD 280 D-Jettronic engine can't really be blamed solely upon the "Y" piece, at least in my case.  The cracked "Y" pieice, some indifferent maintenance, lose manifolds, missing gaskets and the passage of time really suggests you have to go through the whole system.  It has made a tremendous difference to noise of the car.

The next job is to sort the noisy differential.  The substantially quieter exhaust has allowed to the differential to sing louder than it usually does!

Happy days,

Regards,

Carl.

[carl888]

I wonder why in the manual it shows the manifold/Y piece bolts upside down?  I think it looks funny, but that's the way I replaced them.

[s class]

Carl, I've been away from the forum for a few weeks, but I see you answered your own questions - yes there are those crushable metal o-rings between the y-piece and manifolds. 

That crack in the y-piece you welded up looks just like what I used to deal with. 

[oscar]

Love your work Carl, looks fantastic.  There must be heaps of 280s running around with exhaust leaks that people just put up with or get used to and don't realise they're there. I know mine were never perfect nor probs fully resolved.

[mswcpt]

My car - 1975 280S has just developed a slight noise from the manifold side of things - either a hole or crack. Will be embarking on a strip to see what's going on shortly. I love the look of the VHT on the parts.