general questions for a new (of an old) 300SD driver - PeachParts Mercedes-Benz Forum

bigblue · #1 05-20-2008, 12:48 AM

I've had my car for almost a year (acquired it cheap with lots of small issues) and recently just started really driving it. 1985 300SD with 256,xxx miles and needs a bit of attention.

So far I've recently put on about 500 miles. Took the radio out for the extra zen level of sensitivity. All I hear is the engine clattering.

Now that I've gotten to know the way it rides as well as how to take some of it apart, I've already answered a few of my own questions by searching previous posts (like my recenly discovered leaking oil cooler hose) and I know not to bother asking about issues I really must figure out myself (like where my AC refrigerant likey leaked out from)

Since I don't have another local car for comparison, I have no form of reference and wanted to ask some general quesions

How can I determine if my timing chain is original or stretched?
How can I tell if the injector pump timing needs to be adjusted?
Is a little bit of constant blue smoke form the tailpipe acceptable?
is 21mpg way too low?
What kind of oil should be used?
With it's gearing, should an old diesel be revving at 3200 rpm at 70mph?
Turbo oil drain line is weeping going into engine- is that an easy fix?
Does my engine make low/normal/high output for it's age/mileage?
My front shock absorbers are riveted to the lower control arms. Are they still the original shocks?
Rear sway bar end links are worn and causing a lot of clanks over bumps. -is there a trick to replacing them?

sixto · #2 05-20-2008, 01:11 AM

Next time, number the list

1) Pull the valve cover, align the cam and cam tower marks, check how far off ATDC the crank pulley TDC mark is from the pointer.

2) Unless you're an expert, you can only tell indirectly through poor performance, poor fuel economy, etc. Otherwise you can only know it needed to be adjusted if you change any settings while attempting to adjust it.

3) Not to me. The most I'll put up with is a wisp I can see as a shadow in sunlight or in the headlights of the car behind me.

4) It is if you've addressed the basics - valves, chain, filters, etc. You might just have a heavy foot.

5) For the engine, I believe CF or higher rated -40 or -50 oil. Don't quote me on the rating.

6) Yes.

7) Going into the engine??? It's a bit of a puzzle to get new seals in place. I'd keep an eye on weeping and wait for the leak to get worse. Maybe there'll be a reason to pull the turbo in the future.

8) Uhh... yes

9) The front shocks have a stud that extends through the fender up top and the common hoop-with-a-rubber-bushing below. It'd take some monster rivets to hold a shock in place.

10) As tricky as calling Phil for a set of new ones. Try the Buy Parts link at the top of this page.

Sixto
87 300D

6)

toomany MBZ · #3 05-20-2008, 06:10 AM

Quote:

Originally Posted by bigblue

Is a little bit of constant blue smoke form the tailpipe acceptable? Yes.
is 21mpg way too low? Yes.
What kind of oil should be used? I use Shell Rotella T.
With it's gearing, should an old diesel be revving at 3200 rpm at 70mph? I don't drive that fast, but seems right.
Turbo oil drain line is weeping going into engine- is that an easy fix? Haven't done it, I understand it's a tedious task.
Does my engine make low/normal/high output for it's age/mileage? What's the dyno reading?
My front shock absorbers are riveted to the lower control arms. Are they still the original shocks? I hope not.
Rear sway bar end links are worn and causing a lot of clanks over bumps. -is there a trick to replacing them? No trick, very easy. Most difficult part is removing the rear wheels.

Hope this helps.

Cervan · #4 05-20-2008, 09:48 AM

Quote:

Originally Posted by bigblue

I've had my car for almost a year (acquired it cheap with lots of small issues) and recently just started really driving it. 1985 300SD with 256,xxx miles and needs a bit of attention.

So far I've recently put on about 500 miles. Took the radio out for the extra zen level of sensitivity. All I hear is the engine clattering.

Now that I've gotten to know the way it rides as well as how to take some of it apart, I've already answered a few of my own questions by searching previous posts (like my recenly discovered leaking oil cooler hose) and I know not to bother asking about issues I really must figure out myself (like where my AC refrigerant likey leaked out from)

Since I don't have another local car for comparison, I have no form of reference and wanted to ask some general quesions

How can I determine if my timing chain is original or stretched?buy the CD, or search for the instructions to check for chain stretch.
How can I tell if the injector pump timing needs to be adjusted? Knocking, obnoxiously loud, or white/black smoke. (advanced and retarded)
Is a little bit of constant blue smoke form the tailpipe acceptable?Depends, blue smoke means your burning oil, check your blow by and oil usage and determine that for yourself. (FSM says that 1quart every 1000 miles means its due for an overhaul)
is 21mpg way too low?I get about 19-23 because i drive at 85 on the freeway and frequently hit the rev limiter.
What kind of oil should be used?Any oil that is mercedes 223.3 rated. (delvac,rotella,amsoil 15w-30 or 40 is good for year round)
With it's gearing, should an old diesel be revving at 3200 rpm at 70mph? Im guessing you have an automatic, that is right on the money. these engines are made for high rpm's let them roar.
Turbo oil drain line is weeping going into engine- is that an easy fix? Yes, but wash off the engine and look for more leaks before you pull the turbo so you can collaborate your parts.
Does my engine make low/normal/high output for it's age/mileage? it depends what you call output, its a very reliable engine with alot of torque.. (not much horsepower lol) For its age, it was gold 30 years ago still gold today.
My front shock absorbers are riveted to the lower control arms. Are they still the original shocks? Probibally.
Rear sway bar end links are worn and causing a lot of clanks over bumps. -is there a trick to replacing them? They arent very hard to replace at all, wich is the niche these cars have except for a few things such as the wonderfull evaporator replacement procedure..

Ooh me me i wana go too!

tyl604 · #5 05-20-2008, 09:53 AM

My 81 300SD has gotten about 20MPG since I purchased it in 1984. Combo of city/expressway driving but heavily weighted to city driving. Seems like I get about 25, maybe 26 on the expressway. Do not drive above 70-75 MPH.

bigblue · #6 05-20-2008, 10:20 AM

Thanks guys.
As for the front shock absorbers being riveted on, I just took a peek at them for the first time when I had the front wheels off to rebalance them (1 was off and made a huge difference at 60mph! - Went from "thought I was gonna die" to smooth sailing)

I'm pretty sure those are some type of rivet or permanent fastener holding the bottom end of the shock absorber in place. Instead of a screw it looks like a 10mm steel tube with roll formed edges going through the common hoop/bushing (to be drilled out for the first replacement?) If the car were 10 years old or newer this wouldn't seem odd to me at all, but after a quarter million miles and 23 years I'm doubting myself.

In regards to the engine power question, I suppose I was a bit too open ended with my original posting. I don't intend on renting dyno time for this beast. I guess I was hoping somebody might be able to give me a cheap point of reference as a tolerance like "zero to sixty between 2-3 minutes" or some simple test to run.

Yes my oil return line- oil pan seal is leaking. Doesn't look fun

. I understand leaking oil cooler line should be replaced first though.

And most likely my evaporator is leaking too

vstech · #7 05-20-2008, 10:49 AM

you gotta get that wheel back off, and take some pictures of this "rivet" I do not believe even MB used rivets from the factory for user replaceable items like shocks.
3200RPM sounds high for an 85, lemme check...

nope, it should be approx 2700RPM... minus TC slip of 5%... 2800 tops... if you are turning 3200, you are either slipping WAAAY bunches in the TC or you have very small tires, OR, most likely, your speedometer/odometer is incorrect.
also of note to check it the tach itself.

bigblue · #8 05-20-2008, 10:59 AM

Quote:

Originally Posted by vstech

you gotta get that wheel back off, and take some pictures of this "rivet" I do not believe even MB used rivets from the factory for user replaceable items like shocks.

Willdo. Hopefully I'll get a chance to do it this weekend.

Quote:

3200RPM sounds high for an 85, lemme check...

nope, it should be approx 2700RPM... minus TC slip of 5%... 2800 tops... if you are turning 3200, you are either slipping WAAAY bunches in the TC or you have very small tires, OR, most likely, your speedometer/odometer is incorrect.
also of note to check it the tach itself.

Yes I double checked this morning I was a little off there. At an indicated 74mph (actual GPS measured speed on flat road of 70mph) I was at exactly 3000rpm.

205-60-14 tires

vstech · #9 05-20-2008, 11:23 AM

that is still too high... but closer... it is possible that you have had your rear differential replaced from an older MB... that would throw off your speedo and force your tach to be reading 3K at 70...
300CD Can anyone give me a few tach vs. speedo references??

with this formula, a 3.07 rear (what the older MB's would have) at 70MPH with a 25" diameter tire equals 2,987.5398 RPM after adding in 5% for TC slippage...

bigblue · #10 05-20-2008, 11:39 AM

thanks vstech. So the speedo/tach are dead on for the most part. I'm glad to hear that my TC/auto trans aren't as loose as I had feared since it's the softest shifting one I have ever driven (partially why I bought it)

vstech · #11 05-20-2008, 11:52 AM

so, your mileage figuring is off due to the rear change... and your efficiency is off as well. I would source out a replacement diff from an 85 MB or get a gasser rear for it's 2.47 rear... then you will REALLY like your car... providing you get the speedo to match...

bigblue · #12 05-20-2008, 12:27 PM

Quote:

Originally Posted by vstech

so, your mileage figuring is off due to the rear change... and your efficiency is off as well. I would source out a replacement diff from an 85 MB or get a gasser rear for it's 2.47 rear... then you will REALLY like your car... providing you get the speedo to match...

I was underneath the rear of it yesterday and am pretty certain it has not been replaced. And at (GPS) 70mph, an indicated 73.5 mph is pretty accurate in my opinion. Definitely meets factory speedometer precision tolerance.

I couldn't imagine swapping a 2.47 in place of the 3.07. Sure it would lower the highway revs but this thing needs all the windup it can get off the line.

My mileage figure was not a very accurate one as well since I didn't have enough cash to fill the tank exactly (at $4.64/gal being the best I could find.) I'll have a more accurate mpg figure next time I fill up.

sixto · #13 05-20-2008, 01:25 PM

I made a mistake on the front shocks. The bottom attachment includes a plate through the tubular bushing. The plate is bolted to the lower control arm. I've owned 3 W126s. None had riveted shocks. Bilsteins come with new bolts.

Sixto
87 300D

bigblue · #14 05-28-2008, 09:49 PM

Quote:

Originally Posted by vstech

you gotta get that wheel back off, and take some pictures of this "rivet" I do not believe even MB used rivets from the factory for user replaceable items like shocks.

Sixto is right. When I first glanced at it, I didn't notice that plate is removable from the lower control arm and immediately focused on that "tubular bushing" which was what I considered a rivet where a bolt is usually seen. When I replaced the oil cooler hoses the other day I payed more attention to it and here's the promised pic...

Still looks like a really old shock absorber. I already have a new set of bilstiens ready to go in.
disregard the oily tie rod. Doing that job is a mess!!!

Brian Carlton · #15 05-28-2008, 10:09 PM

Quote:

Originally Posted by vstech

so, your mileage figuring is off due to the rear change... and your efficiency is off as well. I would source out a replacement diff from an 85 MB or get a gasser rear for it's 2.47 rear... then you will REALLY like your car... providing you get the speedo to match...

He already owns a 2.88 diff.........OE on the '85.