Wrotten egg smell from exhaust.

[KLP 92]

My friend has bought a 1992 500SL with 90k on the clock. Everytime the car has been driven hard a wrotten egg smell comes from the exhaust. Its that bad you can't stand near the rear of the car when its on! Only happens when the engines hot. Is it normal as mine never smells like this!
Also the car has been regurarly serviced but the car is not as fast as mine although we have the same engine. Any ideas?

 

[jaymanek]

That'll be the Cat...

Used to get it a lot on Fords, not sure what causes it, but its the cat....

P.s havent you sold ure 107??

 

[KLP 92]

That'll be the Cat...

Used to get it a lot on Fords, not sure what causes it, but its the cat....

P.s havent you sold ure 107??

Sort of, a very good friends got it. Still see it quite alot!

 

[Steve_Perry]

Sulphur in the fuel is converted to Hydrogen Sulphide over the catalytic converter and hey presto rotten egg smell and the human nose is extremely sensitive to it. You can smell it at a concentration of only a few PPM (parts per million). My friend who used to have a K reg Ford Escort had exactly the same phenomenon under exactly the same conditions as you describe. I used to hate following him anywhere as the smell would seep straight into my cabin as I followed him.

S.

 

[PJH]

As Steve Perry says, it's the Sulphur level in the fuel. Change to another Brand.
I used to notice that Volvos were bad for this smell when CATs first became standard.

As for the other SL being a bit slow, could it be a worn throttle linkage and isn't opening fully ?

 

[Will]

Not an expert in this field I must admit, but at twelve years old and with 90,000 miles maybe the cat has reached the end of its servicable life?!?

I have heard of knackered cats affecting performance levels quite significantly too (more restrictive).

Does the car get used for many long trips, as I have heard that this can be of benefit by allowing it to warm up nicely and clear some of the deposits?

HTH,

Cheers,

Will

 

[KLP 92]

Does the car get used for many long trips, as I have heard that this can be of benefit by allowing it to warm up nicely and clear some of the deposits?

HTH,

Cheers,

Will

Well i took it to leeds the fist day he bought it. Was doing 3 figure speeds all the way up and back!
It only does it after a bit of abuse, if it was driven normally then no problem. Nut the car does feel restricted in acceleration, almost as if its being held back.

 

[Will]

Leeds to London and back at 3-figure speeds sounds like a good clearout then!

Oh well, was just a thought!

Cheers,

Will

 

[big x]

High sulphur petrol

Can you remember what brand of fuel is in the tank?
High sulphur content in petrol has caused all sorts of
bore wear problems in aluminium heads lined with nikasil
in Jags and BMW's.It also indicates a somewhat cheaper
grade of fuel IMO in that it's cheaper to refine using
high sulphur content and gives more pollution.The Germans of course would not dream of using it!


<<"The “Nikasil issue” is a serious problem that affects all BMW motor cars with engine blocks with “Nikasil” liners in their alloy block when high sulphur fuel has been used. This is 8-cylinder models with the M60 engine made from approximately 1993 to 1996, and 6-cylinder models with the M52 engine made between 1995 and 1998 (note M52 Nikasil engine never went to the USA). The “Nikasil issue” is extremely serious as the final result is a non-functioning engine. The material “Nikasil” is also known as “Galnikal”. "Nikasil" is a very hard dispersion layer of galvanically (electrolytically) applied Nickel applied to the soft alloy bores to prevent wear. If this hard layer is damaged, excessive bore wear occurs rapidly.
TOC

What causes the “Nikasil issue”?
In short, high sulphur fuel. Contrary to popular belief, the “Nikasil issue” does not only affect the USA. It is potentially in existence in all countries, but is a particular problem in the UK and the US. It would appear that Nikasil-lined blocks were not tested with fuels that had a high sulphur content, which was unfortunate because the chemical reaction between the sulphur in the fuel and the nickel lining in the block which damaged the hard nickel lining. Once the lining is damaged, excessive bore wear of the soft underlying alloy occurs very quickly. Some Nikasil engines have failed in as little as 30,000 miles.
Fuel high in sulphur was imported into the UK and (apparently in very small amounts only) into continental Europe. The problems occurred first with cheap (supermarket) fuel in the north west of the UK, although in time the whole of the UK was affected - and it was no longer just supermarket petrol that was causing problems. Having said which a vehicle run only on good quality fuel which was low in sulphur would not have problems, but there was no way the consumer could know which fuel to buy. There do appear to be quite a few Nikasil-engined vehicles which, either through luck in the fuel used or some other mysterious reason, appear to be absolutely fine even after very large mileages.
Continental Europe (through essentially not getting high sulphur fuel) appears to be largely unaffected by the Nikasil problem: it would appear that they did not suffer from imports of high sulphur fuel. I have not heard of any problems with Nikasil cars on the Continent, nor have I found any reference to any difficulties.
TOC ">>>>

adam

 

[Ralph]

I had a car once that suffered from this problem. I found an air filter change / clean rectified it. The restricted air flow was the problem.

 

[Dieselman]

Also the car has been regurarly serviced but the car is not as fast as mine although we have the same engine. Any ideas?

This will be due to engines with Cats have to run over-rich to waste fuel down the exhaust. This fuel is used to ignite the Cat.

I am prepared to bet that the upstream mixture on your friends car is richer than yours.