Just bought a new 86' 300SDL and have questions
 

I've been searching for a long time and I finally found it--a 1986 300 SDL with 140K that "seems" to be in excellent condition bodywise and mechanically (but no service records). Sunroof does not work, and driver seat springs are sagging, but everything else seems good to go. I paid $4,500. Here are my "issues":

1. I want to properly maintain this car, and I'm thinking I should bring it to a dealer or another mechanic to check it out and perform any overdue maintenance (with 4 kids I don't have much time myself). Problem is I live in a small city and their are only 2 independents that claim to work on MBs and one MB dealer who is close. What questions should I ask to see if these shops are comptent to work on older MB diesels? Should they have certificates confirming training or anything like that? I don't know of anyone else around hear that owns an MB.

2. I'm going to immediately change the engine oil, air filter, transmission fluid, rear differential fluid and coolant. Should I use special MB parts/fluids? If so, wheres the best (read cheap) place to get them--I'm assuming it isn't at the dealer.

3. Should I do any other maintenance right away?

Thanks for the help.
Robby

First welcome and nice car, I am a big SDL fan.

Here is a quick and dirty run down of some fluids to use:

Oil, any good diesel oil, Delo 400 is good and cheap to. Do a search :D

Any regular atf will work. Dexron 3

Mobil 1 75w-90 is the best for the rear end, but any 85w-90 gear oil will work fine.

Use only MB coolent, I'm sure you know about the 603's head issues.

As for filters, Fastlane can get you oe quality filters at great prices.

Also change the brake fluid, and power steering fluid+filter.

Other then that enjoy, their nice cars. I have done tons of work to mine, they are simple to fix.

It's not possible for us to properly teach you everything you would need to know to challenge a "competent" mechanic and determine if he is a fraud or not. In fact, most of us, with experience in these machines, would have to go head to head with them and they are a stubborn lot.

My advice to you regarding this vehicle is to bring it to one of the "indys" as we call them and ask them to evaluate the vehicle for you. It will cost about $100. but it is money well spent. I did this myself with the SDL and I am reasonably knowledgeable regarding the vehicle.

They typically do not provide a written report, however, pay careful attention to every detail that the indy states to you and write it all down.

Now you have a "record" or a baseline for which you can make some useful decisions on what work to do and how much work to do. It has been said that you can bring one of these machines to a dealer and he can find $7,000. worth of work to do, if he really wants to. Whether it truly needs all this work is questionable. It certainly does not need all this work immediately.

With your "record" in hand, you can now use this forum to your advantage and educate yourself as to what is required and when it is required. Certain things such as brakes and steering need to be attended to in fairly short order. Other things can wait until you have the money or the time.
I currently need to do the exhaust and the front brake rotors and calipers on the SDL. Nothing urgent. I'll get the parts and try to get it all done before the cold sets in.

Good luck and welcome to the forum.

If you are real wealthy you could just drop it off at Benz and tell the service writer you want it brought up to snuff :eek:

If I were in your shoes I would take a close look at both independents and take it to the one that has the most 123/126 diesels being worked on.

I know someone who does this all of the time to their 1986 SDL :eek: :D It must be nice to be able to do that.

Brian; brakes I thought you never used those? :confused: :D

BTW Brain try the ATE power discs, I like the set I have on mine.

rkinz do a search to, any problem you have I have probably already delt with, or someone else. These SDL's all seem to have the same problems.

Sounds like the start of a coolant thread. :D

The manufacturer of the coolant the MB sells also sells to the general public. Zerex G-05 is sold at Autozone and other auto parts stores for much less than the dealer.

1) Ask them about the weak points of these cars; not generic W126 weak points, specific 300SDL weak points. If they don't mention the cylinder head, bait them by asking how long head gaskets last and how frequently they replace head gaskets and do valve jobs on these engines. Ask them why another SDL you looked at has a big fat pipe above the exhaust manifold (trap oxidizer). Don't be obnoxious about it :rolleyes:

2) Zerex G-05 coolant is okay to use. How does the brake fluid look? Pointless to do all that other work and ignore the brake fluid.

3) Look at the vacuum pump at the front of the engine. If the front cover of the vacuum pump has no screw heads, replace it ASAP. If it has 4 screw heads, it's probably okay. Also look at the idler of the sepentine belt. It's a few inches towards the center of the engine from the vacuum pump. The idler should be perfectly parallel with the belt. If the idler is skewed, typically the driver side end sticks forward more, plan for a new tensioner soon or a new fan and radiator later.

Sixto
95 S420
87 300SDL

Why do you say this Sixto? I took mine off a few months ago to inspect it and it looked fine. I don't remember 4 screws on the cover? It is probably original, but it looked real clean and not much wear for 236k miles at the time. Aren't they $300?

Just beating Dave/gsxr to the punch. Supposedly the old design bearings can escape the race and get into the timing chain. The new design has more of a casing around the bearing races. I have a perfectly good original if anyone wants it.

Sixto
95 S420
87 300SDL

So your saying if it fails it could dump bearing's into the tc? Well hopefully mine won't fail anytime soon. Maybe I will replace it sometime next year. It has been fine for 230+ miles I don't think 10k more will bother it.

I recall the recommended mileage at which to replace the vp to be 150k mi.

Thanks for all the ideas--its all a bit overwhelming right now, but I'll work thru it.
By the way, the seller stated the engine has a "version 17" set of heads, and that the radiator hose to the engine was "soft and pliable", and this supposedly means the head has no cracks or gasket leaks, and is in top shape. What's he talking about? What preventative maintenance should I do to make sure I don't have cylinder head problems down the road?

Robby

1986 300SDL

The version 17 head is one of the newer heads. The original head was number 14. Its first replacement, and the original head on mine, is number 15. Then came number 17. Each head is an "improved" version of its predecessor. The number 14 heads are the most prone to cracking and the latest version, the number 22 head has never cracked, as far as Dave knows (GSXR, one of the most knowledgeable people on this forum with regard to the 603 engine).

After running the engine and letting it sit overnight, squeeze the upper radiator hose. If it is soft and pliable, it is a good sign that there are no leaks from the combustion chambers to the cooling system (read cracked head or blown head gasket). If it is hard as a rock, open the cap to the expansion tank. If the upper hose is now soft and pliable, you have a problem (read cracked head or blown head gasket).

Nobody had determined, with any data, that any specific driving style, or maintenance habit, has prevented cracking of the head. The only thing we are in agreement on is that the engine can NEVER be overheated for any reason, even one time. If it does overheat, consider yourself on borrowed time.