New to Mercedes, new to diesel, new to biodiesel...need advice

[gzanman]

Hello. It is safe to say I'm a newbie. My wife and I are looking to get rid of both our Toyotas and buy an 80-85 300TD. I was wondering if there is anything I should know specificially about these cars before I get one?

I just saw one I really liked. BUT, when you accelerate from a stop in a diesel/turbo is there always a little lurch/catch? And, when the the key turns the engine off, the engine does not turn right off. Vacum problem? That's what the seller told me. Anyway, it is in beuatiful condition, most all records, everything electric works, no sagging booty, 192,000K, $7500? What do you all think?

Well, I can't wait to get one and get it on biodiesel. The problem is I'm a little green.

Thanks for any help!

Take care,
George

[Walrath]

George,

Biodiesel is B100, 100% from soy oil, etc. Anything less is considered a biodiesel blend. B20 for example is 80% petroleum based, 20% renewable source.

B100 has solvents that are caustic to older cars fuel lines, however the lines can be replaced with newer composition ones that are tolerant of B100. With new diesels today MB recommends nothing more than a B5 blend.

B100 and biodiesel blends are also less viscous at low temperatures. There are ways to overcome some of the temperature problem but they will come with a price or you can use petroleum diesel during the cold months.

The older diesels were not engineered to use biodiesel thus, as with modifications from the original engineering, you usually get mixed results and satisfaction.

Good luck with your plans.

Jim W.

[Maxbumpo]

Latest opinions that I've heard are that the rubber seals inside the injection pump are not resistant to the biodiesel (will soften and begin to leak). Running B20 or lower is probably safe, but higher concentrations may lead to leaks. However, I've never heard from anyone on this forum about the IP starting to leak from BioD. I have heard plenty of cases were the rubber fuel lines began to leak upon using BioD.

Vlayton is probably the biggest fan of 123 diesels you will ever find - great resource of info, but he's an extreme purist (in my opinion ;) ). I happen to think that biodiesel will play a very large role in the future of our country, and that it has superior qualities to dino-diesel, especially with respect to (WRT) superior lubricity. Thus, I whole-heartedly encourage the production and the use of biodiesel in any diesel engine (I think it will extend engine life). Vlayton's comments WRT proper care and feeding of a 123 are spot on. If you want to dabble in biodiesel, that's fine, but if you want to own a 123, be prepared for total immersion!! We've seen a few join this forum, with similar intentions, buy a nice 123 and start to fix it up, fall head-over-heals in love with the car, and totally forget about biodiesel or burning WVO or SVO.

[Howard T]

To answer your question, yes, a turbo will start off slow and at about 15 miles an hour the turbo kicks in and you feel an extra surge of acceleration. In my 116, 300SD, the transmission started in second gear instead of first so acceleration seemed even worse. I could start off in low by shifting down and going through the gears to drive. I don't know what other models started off in second.

When turning off a diesel, vacuum is applied to a servo that shuts off fuel to the engine since there is no electrical ignition to shut off. A vacuum leak or bad diaphragm in the servo will let the engine keep running even with the key off. It could be necessary to raise the hood and push on the lever that is marked "stop". I had a problem where the leak was bad when the A/C was on so the motor would not shut off until I shut the A/C off. That apparently isolated the leak and allowed the vacuum to operate the shut off servo.

You didn't say what year the car you are looking at is. $7500 with 190.000+ miles sounds a little high.

It sounds as if you are going to get rid of 2 cars and end up with just the one then convert it to biodiesel. I would hesitate to do that You would be experimenting with an older car and could be without transportation.

Howard

[Maxbumpo]

Howard, I must disagree about the hesitation on acceleration, waiting for turbo to 'kick in'. Invariably, when an MB turbo diesel of 61x or 60x suffers from what is mis-diagnosed as turbo lag, the problem is really the ALDA/injection pump interaction. As the ALDA/IP age, the function of the ALDA tends to lean out, and not enough fuel is added with increasing air from the turbo.

Adjusting the ALDA, covered ad infinitum (use the search function), will restore acceleration to original spec. There should be no waiting for turbo to kick in or transmission to shift, if all the proper adjustments are made. ALDA adjustment is well with-in reach of medium skilled DIY'r

However, all the rest of your advice is spot on. I also think that price is pretty steep, but if the body and interior are truly exceptional, and there are no other problems than those mentioned, you might be in the ball park. There had better be extensive documentation of all required service and repairs, performed by MB certified technicians (oil/filter changes, transmission oil/filter, brake fluid annually, coolant every 3 years with thermostat every other coolant change, differential fluid checked/changed, power steering fluid/filter changes, and I'm probably forgetting others).

[Gray Poupon]

I agree with Vince. When I bought my car I said, "I do" and entered the first stage of Mercedes matrimony. For better or worse, till death do us part. My four wheeled wife is better than a two legged one because it has an emergency shut off. :D

[Don350SDL]

$7500 for anything other than a near-showroom car is too much.

Biodiesel isn't the bargain you might think, the economics (if you include your effort, mods to the car, equipment in your garage, etc) come out pretty close to regular Diesel, even if the oil is free. Not to scare you away, but to advise you to really research the topic & add up the numbers yourself.

As for the engine not turning off right away: Likely a leaky vacuum actuator, as Howard T explained. Part is under $50, but I had to remove my intake manifold (!) to replace it, and even then it was a full weekend and a whole lotta pain - but I have a completely different model, yours may be different. You might have a vacuum pump problem, $400+ labor (Diesels don't generate manifold vacuum, there's a pump for that). ( I joke to my friends, the problem with a diesel isn't getting it to start, but getting it to stop...)

Bottom line is, it seems like a lot of money, get an expert to check it out for you, there cars can be money pits if you don't watch out. On the other hand, a good '80-'85 123 body is a wonderful vehicle, if maintained it will last almost forever, super reliable.

[gzanman]

Thank you guys for all of the info. the reason I joined this board is that I do love these cars but don't know as much as I should. I have definitely learned a lot just by reading these few posts and I continue to keep checking in here until I get a good handle on all of it.

As for the car in question, $7500 seems a little steep for me too and it is not quite showroom...especially adding in the cost of the vaccum. The seller won't budge so I think we are out of the running.

In terms of biodiesel, I never looked at it as a bargain but rather a way to fuel a beatiful car without depending on oil...that can also carry two dogs. :)

Thanks again and I look forward to learning more about the cars, their care and the pluses and minuses of biodiesel.

Take care,
George

[Marshall Welch]

Regarding lubricity of fuel, according to those in the know on these forums, the MB diesel injection pumps are lubricated by the engine oil, not by the fuel. Some think that running a biodiesel blend MAY prolong engine life.

These are wonderful cars, but they are at least 20 years old now, and will need at least some care. There's always something to do for them, although they are often small projects and fairly easy. I've had my car for a little over 2 years. At the time I acquired it, I didn't realize that I'd grow to love it this much.

I've used biodiesel blend in my car during warmer months of the year, up to B-50, for 2 seasons now. No problems so far, although the fuel hoses are new. The engine does SEEM to run quieter than with 100% petroleum diesel, and it smells nice- like something is cooking. After reading some of the concerns raised on these forums, I'll probably not use a higher biodiesel ratio than B-20 for the forseeable future.

[jer-jay]

you can run 100 percent bio with no problems . the only thing it does is clean your tank and lines i have been using b100 for 2 years and only have to change the fuel filters once in a while. i have 4 mb,s they are all bio diesel operated. and have used svo and wvo. keep your system clean with diesel purge once a year and you will be fine.

[Alex]

Meade,

What is WRT?

[Maxbumpo]

Sorry; WRT = with respect to.