M117 450 Timing chain and valve stem seals

I just got my 450SLC back from having the timing chain, tensioner, camshaft oiler tubes and valve stem seals replaced.   These are all jobs that any owner of a Mercedes V8 of this era will need to undertake at some point.

The primary driver behind this was the need to replace the valve stem seals.   A couple of my sparkplugs, #1 in particular, would regularly foul up.    I didn’t have a lot of visible smoke, but I did see the odd puff of smoke taking off after a period idling.   This is a pretty common problem in these engines.   Age, and lack of use cause the valve stem seals to harden and allows oil to get into the cylinders, in particular at idle.   A number of these engines have been prematurely rebuilt due to this simple issue.

It also seemed sensible to change the timing chain at the same time.    I understood that it had been done a year or so before I bought the car in 2003.    I didn’t have any evidence for this.   Removing the valve covers showed that the chain had been replaced at some point, as had the guides.   However, I wasn’t sure the age of the chain and the guides were now coffee coloured.

I started by ordering the parts I would need.    The part numbers I ordered are listed below.   I don’t guarantee these are correct for any other car.   For a lot of these parts I prefer genuine given their importance to the engine and how expensive this job is.

• Timing chain – 000 997 76 94 – IWIS (In a Febi Box)
• Timing chain tensioner – 117 050 10 11 – Genuine.  This is the tensioner with the port for air injection.   It is quite expensive.   The air injection system on my car has been disabled and it was not clear to me if I could have simply used the normal tensioner.
• Camshaft oiler tube kits x2 – 117 180 00 84 – I wanted genuine, but they are now NLA so purchased Febi.
• Chain guide x2 – 117 052 09 16 – Genuine
• Chain guide x2 – 117 052 08 16 – Genuine
• Tensioner guide – 117 050 04 15 – Genuine
• Guide pin – 116 052 21 74 – got a couple in case they were needed, but they can normally be reused.
• Left valve cover gasket – 116 016 13 21 – Elring
• Right valve cover gasket – 116 016 14 21 – Elring
• Valve cover copper sealing ring x8 – 915035 000016 – Reinz
• Valve stem seal kits x2 – 116 050 01 67 – Genuine

While I was there I also ordered some other parts I needed that will be used later, such as the drier pictured above.    I also grabbed the two pictured air hoses to be replaced at the same time as they were rock hard.

There were no major issues during the job, although my mechanic noted that the valve stem seals are much harder to do in the 107 than the 126.   There is far less room, particularly up near the brake booster.   The oil seals immediately showed why I had an issue with oil getting into the cylinders   A couple had cracked and the rest were so hard they were not sealing properly.

It would appear that Mercedes-Benz revised these seals at some point.   The new ones were rubber, whereas the old ones were a hard plastic type material.     During the timing chain job, a couple of the lifters need replacement.   Unlike during the timing chain job on my 560SEC, none of the guides were broken, but they were all discoloured.   It is not clear how many kilometres were on my chain, but the camshaft sprockets had a reasonable amount of wear on them.

After the job, my mechanic performed a compression test on my engine and he was very happy with the results, even after 313,000km.   The car runs very well now, and seems to even have a little more power.   This was quite an expensive job, but necessary if you are going to own a Mercedes-Benz v8 of this era.

In addition, during the timing chain job, I had the tensioner, guides, and camshaft oiler fittings replaced as per the parts list above.   These should always be done at the same time.