Known Issue for the '76 450sl?

[ncgirl05]

Hi All,

When I was researching the differences throughout the years for the 107sl I recall reading that there was something particular about the '76 model year that made it a bad year to buy...... I just can't remember what it was. It had something to with with a part being right by the engine and it caused problems. It was the only year this part was by the engine and they moved it in the '77 models.

Does anyone know what part I'm talking about? We are looking at a '76 currently and I am trying to remember why I always disregarded that year.

Thanks!!
Leigh Anne

[rowdie]

The US 1975 and 1976 models had the catalytic converters attached to the exhaust manifolds in the engine bay.

[ChiefRider]

...and that raised underhood temperatures considerably, contributing to greater/earlier wear and tear.

[halman2228]

IIRC.

Kevin

[ncgirl05]

Thanks all!!

[meltedpanda]

yes , all issues related to heat and the CATs upstream, many were moved after several reported under hood fires

[Gilly]

I want to also chime in that I think the 1976 would be in range for the front subframe recall, there were reinforcement gussets that had to be welded in. or if cracks were already present, the front subframe actually got replaced, I worked on MBs long enough ago that I remember replacing subframes, one car came in with 1/2 of a control arm already broken off. A dealer could do a VMI check to see if this recall was done, or someone who knows what they are looking at should be able to tell you if the subframe is gussetted.

[Gilly]

Here is a link to a thread at benzworld which discusses it. In this thread they make it sound like this is not actually a recall, I would dispute that, I'm relatively sure this was a recall:
C/R107 Front Sub-Frame Recall Information - Mercedes-Benz Forum

Note pic in thread of an SL coming off a flatbed with breaks in the frame, we had one DRIVEN in like this, totally unbelieveable what people will do to save money. "Humans have the uncanny ability of overlooking obvious hazards"

[ChiefRider]

The subframe issue should NOT be a mystery to anyone owning or contemplating a 107 SL. Here is what you should know.

EVERY pre-1986 R/C 107, no matter what engine, should have its front subframe reinforced. There are documented failures for every engine/trans/year combination. The 1986 redesign included a new subframe that did not suffer from these failures.

The ONLY cars included in M-B's willingness to repair are North American, 1980 and earlier 450SL/SLC or the US 350SL with 4.5 engine.

[nobby]

Originally Posted by Gilly

Here is a link to a thread at benzworld which discusses it. In this thread they make it sound like this is not actually a recall, I would dispute that, I'm relatively sure this was a recall:

No...it was not a "recall". A recall would be MB contacting all owners of the affected cars and bringing them in forthwith to be inspected / modified / replaced.

If that was the case....we would not be warning owners of suspect subframes because they would have been dealt with 25 years ago.

'MBUSA Service Information Letter 33/001, Sub-frame Modification dated 11/1/85' was at the dealer's and MB's discretion and not a publicized document.

If the owner mentioned it....it would be dealt with. If your dealer liked you and was looking for work he'd tell you. If it was, in fact cracked....no questions asked.

[Idle]

Concerning the underhood convertor.

I owned one of these at one time. The real problem was that this was not a cat converter but a thermal reactor. Porsche used the same system that year and they had the same problems.

The inside of the reactor is made of a ceramic material which allows the internal temps to reach levels necessary to burn up all the stuff that a cat was designed to deal with. OK, so far so good. But with age the ceramic will crack and allow hot gasses to escape into the stainless shell that covers the ceramic.

The effects of this depend on where the cracks open up, but with all the heat in one spot and no way to escape the paint on the hood burns off in short order. Not the entire hood; just the spot over the reactors.

Vibration is another problem. As in any engine vibration at all will cause the flanges to crack off the ends of the reactors. They can be welded back if you can find someone to do so, but since this is an emission item a lot of shops will not work on them for fear of the EPA kicking down their door.

New reactors were once available for about $1,600 each.

The good news is that these were only installed on California emissions cars, or so I have been told. To Mercedes California meant the western zone, so these cars were sold as far east as New Mexico.

If your state allows it these can be ditched and replaced with 49 state exhaust manifolds and pipes. There is nothing to but to bolt them on. The exhaust manifolds of the California cars is different so they can accept the reactors.

The 1976 230, the one with the four cylinder gas and sidedraft carb, also had these as well as some 1975 230's, but only if they were sold in the western zone.

[ChiefRider]

To my knowledge, all US 1975 and 1976 450Sl/SLC's had the underhood convertors/reactors.

[Frank Reiner]

I'm with Chief on this one; the requirement for catalytic convertors from model year 1975 onwards was a federal requirement. 75/76 107s had the cats integrated with the exhaust manifolds (as did W114s and W116s with the M110 engine). Non-catalytic thermal reactors were a 1974 California-only device. Outside California the 74 systems were the same as 73, i.e., Federal.

[Idle]

Originally Posted by Frank Reiner

I'm with Chief on this one; the requirement for catalytic convertors from model year 1975 onwards was a federal requirement. 75/76 107s had the cats integrated with the exhaust manifolds (as did W114s and W116s with the M110 engine). Non-catalytic thermal reactors were a 1974 California-only device. Outside California the 74 systems were the same as 73, i.e., Federal.

Thanks for the correction. I am relying on a memory of 25 years ago and it is possible the car I had was a 1974.

And while I might not remember the exact year I do remember dealing with the situation. Thermal reactors allowed an owner to burn leaded gasoline which was cheaper than unleaded and this was considered a selling point at the time.

There was also a fear of not being able to find unleaded gasoline as not every station in rural areas carried it.

[ctaylor738]

And you can still buy the reactors from MB, only $2800 the pair.