Just bought a W126 300SD to drive from NY to CA. Looking for low hanging fruit! - PeachParts Mercedes-Benz Forum

C2CBenz · #1 07-18-2019, 06:57 PM

Like the title says, I bought a 1981 300SD for an event called the C2C Express, a run from the Red Ball garage in New York City to the Portofino Inn in Rendondo Beach, CA. It's a throwback to the days of the Cannonball Run, and as such, only pre-1980 cars are allowed (iexceptions are granted, like my '81).
We are placing a 32gal fuel cell in the trunk, so we will have a total capacity of 52gal or roughly 1,000 miles at ~20mpg. We would like to keep around that number if possible.
We have access to a few local junkyards with plenty of cars available, so taking upgraded parts off other cars to put on this one would be awesome!
I have talked to a fellow W126 owner, and he suggested a few things (EGR delete, cleaning out the plumbing). I was hoping to get a list if items that I can do to free up some power WHILE not drastically decreasing efficiency.
We have only a few weeks to do all of our upgrades, so low hanging fruit is ideal.

83w126 · #2 07-19-2019, 01:56 PM

Swaybar bushings (get new ones from the dealer, they are cheap) would likely make a big improvement. Its usually pretty easy to find Bilstien shocks in the junkyard too. Also, adjust the valves and check the oil cooler lines.

rmasteller · #3 07-19-2019, 02:15 PM

Quote:

Originally Posted by C2CBenz

I was hoping to get a list if items that I can do to free up some power WHILE not drastically decreasing efficiency.
We have only a few weeks to do all of our upgrades, so low hanging fruit is ideal.

Power and economy are generally two opposing forces. You'll probably get more gains in economy than power by fixing/modifying things.

Are you an experienced Mercedes diesel enthusiast/owner? That will let us people here know how detailed to get in their questions and recommendations.

About your car, what can you tell us about it? Did it come accompanied by lots of records of maintenance? Can you tell us about any vibrations, leaks, funny noises, odd running behavior, etc? How many "shake down" miles have you put on it so far to learn what's right and wrong?

I'd recommend safety first. So, tires, brakes and steering would need sorted. Replace rubber brake lines!

Are you concerned about air conditioning? If no, you can rip out the whole system to save some weight and one less component for the engine to drive.

I'll let others convey their infinite wisdom about economy and performance. I'm a noob with diesels.

oldsinner111 · #4 07-19-2019, 02:18 PM

driveshaft,a must

dinman · #5 07-19-2019, 04:25 PM

Jealous! I want to do the same in my 300D one day.

From my many long, long trips in my severely neglected $400 '83 300d, here's all i have to tell you (most being very obvious)

Get the car up to ~100mph or so, track down any/all vibrations.

Check all front suspension components, wheel bearings, etc (slack, condition, etc)

Oil cooler lines! I have been stranded due to this (Thankfully shut the engine down the second i saw the gauge drop). Check for weeping around the rubber and slots cut in them from belts rubbing (bad engine mounts usually)

Check engine vibrations at various RPMs. Try to reduce them if time permits

Replace all braided rubber fuel return lines, and bring some extra just in case (also bring/make an extra end plug for the final injector)

Change fuel filters/bring extras

Check brake system/change rubber lines (they deteriorate from the inside)

Check fan clutch operation

Check belts/replace/bring extras

Check alternator adjusting bracket and mounting bracket (mine broke a while back, and dropped the alternator.

Lube throttle linkages with ATF, and check the condition of the throttle rod rubber chunk on the firewall.

Does the trans shift well? If so i would leave it alone for now.

Check rear axle boots for cracking.

Check flex discs, replace if you see any cracking or separation at all.

Check driveshaft support bearing for the rubber to have rotted away.

Valve adjustment (easy)

Make sure your gauges work properly

I personally would change every single fluid

Most importantly- working radio and working sunroof/windows!

These cars are awesome and can definitely do that trip with ease, but my first 6-9 months of ownership of my neglected example was miserable.

I never got more than 3-500 miles out of it before something else broke, leaving me to limp home. What was my issue?

Car ran "good" but a glow plug had broken off into the prechamber. Destroyed one prechamber, GP, and injector.

I had no clue what it was, until the injector got cracked one day.

Other than that? Um... Key broke off in the tumbler... Ignition switch broke, leaving the car stuck in "on" position, front suspension was so shot i was wearing out tires like crazy. Transmission shifted terribly (vacuum issues). No windows worked. Fuse kept blowing for the blower motor. I can go on and on.

Now? I need to do some minor things but i would not even be remotely scared to drive this thing from Louisiana to Canada, anywhere, you name it. I have put about 20,000 (relatively) trouble free miles on it

my83300cd · #6 07-19-2019, 05:10 PM

Is the fuel cell feeding the tank? How are you accessing the spare?
You might want to consider weight of fuel added, rear suspension. You are taking on an extra 220 or so lbs
Cruise control. Best economy item to have.
Seats. Your back will thank you.
Hydration and result there of. I am guessing you are only stopping to fuel?

pawoSD · #7 07-20-2019, 12:24 AM

As mentioned above adding another 32 gallons of fuel is ~250 lbs + the weight of the tank and anything else you have in the car....its going to be riding LOW.

barry12345 · #8 07-20-2019, 06:29 AM

First a good inspection by a person that really knows these cars. Usually a good independent mechanic. That works or has worked on lots of them and knows them well.

Should locate anything that either needs replaced for the trip or is questionable. You tell him what you intend to do and he will base his opinions on that.

That is not a guarantee that the car can complete the trip with no issues. Just any issue that is obviously present he finds should be addressed to allow the trip. Reducing the probability of issues on the way. I had an owner of a 1986 300 SD drop in the other day. Nice example with 180k probable total real miles on it. Still looked as new inside and out. .

I suggested he consider changing the vacuum pump and told him you might want to keep an eye open for a cheap spare head. I showed him where the head numbers where and what numbers to watch for at auto wreckers. I was very specific in telling him that the car was too good to risk the engine on the original vacuum pump. I suspected his modern Mercedes mechanic might not be familiar enough with these older models. He also asked me if I worked on them. I told him not for others other than if they were traveling through and had an emergency perhaps. I am not a working mechanic.

He did not seem happy either when I mentioned that driving this car in the winter here will create far too much rust far to fast. I could tell by the condition currently it has not been driven in winters in our large rust belt area. Plus you really cannot rustproof these cars. A truly nice example for our area though. I suspect with that car and a good inspection it might have made your trip easily. Although those shop made replacement hard injector lines with compression unions I would suggest changing them. Done neatly but really not a good ideal. Odds are the vacuum pump will not fail in the next 5 thousand miles. If it were to go on your trip .Yet on that car it still would be a good overall preventative change.

His Mercedes mechanic had built a set of replacement injector lines that where not the best approach to one breaking in my opinion but kept it to myself. All too easy to get a good used or new set. They also looked to have less wall thickness but without one off no way to be certain.

JHZR2 · #9 07-20-2019, 03:17 PM

Jealous! I want to come along!!

As evidenced by my 82 CD I just pulled bac out of my garage - sticking calipers are #1.

From there, not sure there’s a lot you can do to increase economy besides slowing down. You might be able to limit turbo boost to limit power and fuel burn but not sure if it will truly help. Lightweighting helps but your fuel additions go against that.

I’d want new anti freeze, oil, psf, brake fluid, diff fluid and belts. ATF is contingent upon color and service history.

Rubber boots on the driveshafts could be a big issue. Other suspension rubber can be problematic, especially ball joints, but if the boots look ok they’re probably alright for this barring any bad play. Shock absorbers should be checked. Rubber lines in the fuel system are all worth replacing.

Don’t forget tires!

97 SL320 · #10 07-20-2019, 07:29 PM

Quote:

Originally Posted by C2CBenz

We are placing a 32gal fuel cell in the trunk, so we will have a total capacity of 52gal or roughly 1,000 miles at ~20mpg. We would like to keep around that number if possible.

What are you doing for a fuel transfer system?

Be sure to test the fuel transfer system at low and full loads to uncover any issues. Running a diesel out of fuel can be a real mess.

Bring a pile of _different_ credit cards / debit cards and be sure to alert the CC company that you are going X country at a rapid rate otherwise you are going to end up with a non functioning card when the fraud algorithm kicks in.

For faster fills, grab the nozzle from the other side of the pump so both both tanks are filling at the same time. Again, use 2 cards from 2 different brands / people so the fraud alert dose not kick in.

my83300cd · #11 07-22-2019, 07:14 PM

Buddy of mine ran a chevy pickup where we had an on board coffee maker, carried cafe bustello, and 5 gallons of water. It helped shave time. Aspen to Brooklyn NY in 32 hrs

vstech · #12 07-23-2019, 11:43 AM

Get an 85 cam and rear diff...
Boost economy into the 30mpg range.
Keep speed below 63mpg, and coast up hills, accelerate down hills... to a point that is.

barry12345 · #13 07-23-2019, 01:43 PM

Quote:

Originally Posted by vstech

Get an 85 cam and rear diff...
Boost economy into the 30mpg range.
Keep speed below 63mpg, and coast up hills, accelerate down hills... to a point that is.

Last time I did the accelerate down hills thing. This police car passed me going the other way. I calculated he would probably get turned around and chase me. After he disappeared over the top of the hill. So I thought as I pulled over right away. I had better make this good. It worked well enough to get off with a verbal warning. He topped the hill a few minutes later with all the lights going. Me sitting there just waiting for him was possibly a surprise.

His first question was why did you pull over with me so far back. I said I suspected it was me you wanted to meet. If not only a few minutes would be lost at most. I was speeding after all.

This car is not mine and seems to like picking up speed downhill. Some law of physics is involved. I am on my way for a biopsy on my face. So it is not my best day either.

I figured with you having to get turned around to pursue me. If I stopped early you would not have to chase me as far. If he were younger perhaps that was not the best ideal. Where he was not and probably did not like the chase them down part particularily. I would have had a fair lead on him.

This got him discussing his job. So I felt I had a chance. Verbal warnings do not go on record unless they are written up and presented. This was a long time ago and I was probably about twenty miles per hour over.

I have no hypnotic skills but the powers of suggestion can be employed. My guess was over the years he may not have had a situation exactly like that one. How do you ticket a guy that is obviously thinking of you and the difficulties of your job. Plus obviously is under some stress over what he is going for. Not my best day was used. Admits guilt at the very first with no questions. Even the excuse does not sound like a manipulation. It instead is just factually offered. He could see an area of my face that was not normal.

Almost nothing will work on a female officer I suspect. The females in our society are far too perceptive. I have never got a driving ticket where I had to pay for it in 6I years of above average yearly milage driving. I have gotten two written warnings for speeding. I have gotten enough parking tickets though. You could not avoid them in Toronto when we lived there.

JHZR2 · #14 07-23-2019, 04:28 PM

Quote:

Originally Posted by my83300cd

Buddy of mine ran a chevy pickup where we had an on board coffee maker, carried cafe bustello, and 5 gallons of water. It helped shave time. Aspen to Brooklyn NY in 32 hrs

Must have had a bladder that was more like a steel pressure vessel!

barry12345 · #15 07-23-2019, 05:21 PM

It takes time to stop and urinate. Technically an offense alongside a road. Rigging a tube and recepticle as fighter planes had and probably still do. Allows urination on the go.

If you get time before going. Check your base oil consumption rate.