08-22-2003, 10:12 PM
I just recently purchased my first MB. I bought an '86 300 SDL. I am so in love with this car!!! I have heard from a few people that the 603 engine was not very reliable and that was why they didn't put it in production for very long. Since I'm a newbie, I'm not sure whether this was bogus info. I am hoping this is the case. What can you tell me? I am also planning on doing a vegetable oil(SVO/WVO) conversion on the engine provided that I can find someone to trust to do the work! I am not an experienced mechanic and I would prefer to have a little more experience with diesel engines before I try to tackle something of this magnitude.
08-23-2003, 10:26 AM
Welcome to the board, VLB, and congrats on your purchase!
The 603 was a very good engine, but not without its problems (like any engine). The only real problems were the earlier cylinder heads were prone to cracking (as I have fallen victim to myself) and the fix was to use the 350 cylinder head. To see if you have an earlier cylinder head, look at the part numbers on it ( I believe the driver's side). The 3rd and 4th TO LAST numbers are the ones to be concerned with. The problematic parts had the numbers 16 or 17. Later than that and you are okay. Even if you do have the "problem prone" part numbers you can still have a healthy engine for life, but this is just something to be aware of. The cracking that happens is typically between the valve seats and said to be due to running the engine hard and then shutting it off right away, without a chance to cool down properly.
I am not sure if the 350 was considered a 603 as well, but that was the real problem child. It was known to throw rods and wear the cylinders out of round. Some later models of the 350 have had all the updates and perform well, but I believe that is an engine to be avoided (ironic considering the previous mentioned cylinder head fix).
I believe the real reason the 603 engine was "short lived" (wasn't IMPORTED for long is all...) was due to emissions. When the diesels returned later, they had smaller engines with emiisions failsafes that were electonically governed and difficult to bypass. The 603 engine can run with the EGR and other devices disabled. If you try the same on the newer 602, it will shut off the turbo! Also not to be forgotten with the 603 engine was the fatal "trap oxidizer". This would appear as a huge canister next to the valve cover, between the exhaust manifold and the turbo. If you have this, get rid of it! Internal parts woud break off and ruin the turbo. This was a recall item that I am told Mercedes dealers will still honor. The fix was to replace it with something more akin to a pipe with foil wrapped around it. I understand this to have a catalytic surface in it, but I am not certain af that information.
Barring those flaws, the 603 is an outstanding engine, and is actually preferred to the 602 by those of us who know. I am sorry, but I know nothing of the veggie oil conversions, and cannot help you there.
(BTW, I have heard that disabling the emissions parts (vacuum controlled) on the passenger side of the engine, performance can be gained)
08-23-2003, 05:01 PM
Thank you very much for the return post! I truly like the "(sometimes you just gotta go)"! I have lucked out on the trap oxidizer, this MB came in through an East Coast port and did not have emissions control on it :D .I will check on the valve cover to see if that has the potential to become a problem. I feel alot better knowing that this engine in this application will probably not be a problem. Thanks!