New 300td - Needs Sorting!

[Navy CPO]

Hello to all in W123 land especially Vince (I recieved my window switch covers).

I just came back to the woreld of the W123 chassis by way of a 1982 300TD with 267,000 miles. As you may guess the car has needs. The car must pull duty as my daily driver here on the Mississippi Gulf Coast therefore it is imperitive to keep it out of the shop as much as possible allowing me to do as much of the work myself as possible.

I won't jam this post with all the issues and questions I've got but I'll start with the most significant ones first.

1.) After fixing two problems (leaking A/T cooler lines and fuel tank blockage) the car runs much better. However, the car seems to be still wanting to shift another gear above 55 mph and only shifts twice from a start. Maybe it's just the extra power though. My question is... do these automatics start from second gear in Drive? I've always been told they do. If so, then it is shifting twice meaning it shifts 2-3 then 3-4. I also assume if it isn't shifting out of third gear then it would be hard pressed to go above 45 mph. It will hit 70 but seems to be revving high.
Of course the tach is another needy item. It doesn't work.

2.) Can somone give me a realistic idea of expected miles per gallon? Even after clearing the fuel starvation issue and installing a new in-line filter, it looks like I am stuck below 24 MPG. Real disappointing.

3.) The A/C is not functioning. The compressor is hanging in it's mount and disabled and the belt is off. I've been advised that the system should be overhauled entirely not just the compressor and it could cost 2k!! Any A/C advice? If it costs that much I'll have to learn to love the 95+ degree summer that is
coming soon!

Once again, I really appreciate any help.

R/
MJO

[lkchris]

Mercedes of this era--both gasoline and diesel--are pretty high revving at USA highway speeds.

The trans does start in 2nd.

Here's some opinion/speculation--take with grain of salt if you wish:
Mercedes diesels of this era definitely predate the notion in Germany of diesels as Autobahn runners, diesels seen more as taxicabs and quite more economical in this usage than a gasoline car.

In this era in the USA these cars were diesels for basically two reasons
(1 a number of folks wanting to be different
(2 unavailablity of a Mercedes gasoline engine suitable for the USA.

In this era there were even diesel S-class cars--made ONLY for the USA market and something a European would have considered silly.

25 mpg highway is pretty normal, especially when getting some performance out of it.

Thanks for your service.

[Navy CPO]

Thanks for the reply.

One other issue I left out is a bad leak at the primer pump. I understand a leaky primer pump is not uncommon and a replacement will cure it but the leak is pretty bad and I would like to know if a replacement pump cures it and if there are any installation tips before I source a pump.

Thanks again!
R/
MJO

[johnmci]

Thanks for the reply.

One other issue I left out is a bad leak at the primer pump. I understand a leaky primer pump is not uncommon and a replacement will cure it but the leak is pretty bad and I would like to know if a replacement pump cures it and if there are any installation tips before I source a pump.

Thanks again!
R/
MJO

A vicegrip pliers is fine to remove the old primer pump, mine was all metal. The new primer pump is a bit of a hassle to install because you need a crowsfoot or very small crecent wrench to get at the nut on the flange of the new pump without binding on the entry/exit hoses/pipe on the fuel pump face. You need to ensure the primer is tight (well beware of stripping the threads) otherwise it will leak air. On mine tight was when pushing the primer pump didn't inject small bubbles into the fuel line.

[Maxbumpo]

Chief,

Welcome! Consider joining MBCA - discounts alone at the dealer and/or local independent who supports the local club will more than pay for the $45 fee. Ask who is in the local club where you are, get the skinny on discounts, and weigh your options.

24 mpg highway is a bit low but not out of line. A known mileage killer is clogged fuel filters, sounds like you've already taken care of the primary filter and in-line filter. Lately I've been pondering the possibility that a gunked up tank screen might have the same effect (my '87 300TD is only returning 22-23 mpg in town).

Also, an ALDA that is set too lean reduces power in the lower RPM band, which leads to transmission misbehavior with shift timing, and the two combined can affect mileage. I know that my ALDA needs tweaking, yours may as well. I think that if your 0-100 KPH (0-62 MPH) is more than 13 seconds, and power seems weak below 2500 rpm or so and there is noticable 'turbo kick-in', then ALDA adjustment is in order.

When changing the primer pump, clean clean clean is the order of the day. Be very careful not to contaminate the fuel injection pump with dirt/debris. There are fittings fore and aft of the pump, which when removed will allow good access. A leaking primer pump allowing air into the system causing poor mileage? Not sure, but fixing known problems definitely won't hurt mileage.

DIY AC repair is very rewarding and not too tough. Keep the system R12 if still original - it was designed for R12 and will always work better with that refrigerant. I paid $150 to have a shop provide an R12 charge to a system that I had repaired (and I went w/out AC in SC for about 7 years prior to that!). Get a paper copy of the MB AC manual for your car - it has all the steps to troubleshoot the system so you can fix it yourself.

Keep the questions coming - many here have been-there-done-that and can help you avoid the pitfalls.

[Navy CPO]

Maxbumpo:

Thanks for the reply. I am an MBCA member although I just recently reinstated my membership after an 18 month lapse due to current OPTEMPO. You have responded to me in the past when I owned a 300D euro and was looking at another 300TD which I took a pass on. By your sign off it looks like you are or were Navy!
Currently I belong to the BMWCCA, MBCA and VCOA(Volvo). I am a big believer in supporting a club. It's that core group of members like yourself that make it or break it!

My primer pump is leaking REAL bad this morning so I must source a new one. Does anyone have experience with the new style advertised as a plunger type that does not unscrew to open? Is this superior to the old style?

What is the ALDA?

I'll keep the questions coming for sure. My car has needs!

Thanks.

R/
MJO

[Maxbumpo]

Chief MJO,

Yes, once a squid always a squid. I don't advertise that too much anymore, but I'm still in the Reserves.

New style pump is only option, it works just fine and will fix leaks. I would imagine it is superior, I've never heard of one failing, but I don't know that to be an established fact. It is a less complex design and made of metal vice plastic.

ALDA is German acronym for barometric compensator. It senses the amount of boost from the turbo in the intake manifold, and increases fuel flow from the injection pump to match. More air + more fuel = more power. As the injection pump/ALDA ages, it tends toward the lean side, reducing power (especially in the lower RPM range).

Attached is MB service manaul procedure. What it doesn't say is that you should keep turning the screw left until you can just see wisps of black smoke during WOT acceleration at highway speed. When you get the black smoke, turn the screw to right until it stops, and then lock it down. If while turning left the screw get stiff (getting to end of adjustment range) then you need to remove ALDA from top of injection pump and add shims underneath.

[Alex]

Chief,

1. My 1981 300TD starts in first gear, regardless whether the gear shift lever is in Drive (D), Super (S), or Low (L). The Owner's Manual clearly says so, too. I doubt that M-B changed to a different transmission in 1982, so your wagon should also be starting out in first gear and not second gear.

2. If your wagon is getting nearly 24 miles per gallon it shows that its engine is still in pretty good shape. Don't be disappointed because better than that can't be expected.

3. I can't help much with the air conditioner problems you are having. Can only speak of my experience with mine. The air conditioner in my wagon has not been that great since the car was new. Over the years Freon leaks were fixed, costing little. Since the air conditioner doesn't really cool the car adequately when it's really hot outside and I'm not a fan of air conditioning in general, it hardly gets used. Perhaps M-B improved it in 1982 and yours might be great when fixed. But maybe not. Since your A/C is badly broken and probably won't cool all that great when fixed at great expense, it might be best to forget about A/C in your wagon for now, as you say.

[Navy CPO]

Alex, all:

Thanks for the replies!

Regarding the transmission, I believe it is actually starting in second gear at this time. While in the shop for a transmission cooler line comeback repair, I mentioned it to the mechanic. He drove it and said it starts in 2nd gear alright due to a switch underneath the driver dash that kicks it down to 1st gear but doesn't seem to be kicking in. Does this make sense? Without a functioning tach and considering I have only had the car for 1900 miles, it's hard to tell but it seems to be revving much higher at 55mph+ than it did at first but I can't imagine getting to 60+ mph if it was stuck in 3rd gear.

My main concern right now is the leaky primer pump. Got the part for Saturday. If there is anything else I need to know, please jump in guys. According to Max, it must be CLEAN. Roger that, but I also can't afford any "Uh-oh" moments on Saturday. I guess I should plan to remove the lines adjacent to the pump to get a better grip?

Thanks to all!

R/
MJO

[Navy CPO]

Alex:

I just realized who you are!

THE Alex Rosner. I am VERY familiar with the legendary installations you did in NYC during the 70's! I sure would love to sit down and talk about some of the really "old school" stories you must have. You should write a book!

Regards,

MJO

[Navy CPO]

Alex, Maxbumpo:

Well... I lucked out and got my tach functioning tonite. It was the sensor in need of cleaning and adjustment.

So... I am spinning 2800 rpm at 60 mph. Sound right for 4th gear?

R/
MJO

[Highway Star]

Sounds right, my RPM was at 3200 at 70-75 mph.

[johnathan1]

Where is the tach sensor located? Mine isn't working at the moment. :(

[Navy CPO]

Here's my chance to give back something for all the advice I get here!

The tach sensor is located on the left inner fender in the engine bay. It ismounted on a small pedestal and the round top is tethered (or should be) to the bottom of the sensor and simply unscrews.

You will have to go to Schuman's automotive site for details in the fix. it's REAL easy and worked exactly as described. I picked up the link for the MBCA forums. The address is www.schumanautomotive.com. Lot's of other good stuff there also!

Took about 20-30 minutes and tach works perfect!

R/
MJO

[Maxbumpo]

Alex, Maxbumpo:

Well... I lucked out and got my tach functioning tonite. It was the sensor in need of cleaning and adjustment.

So... I am spinning 2800 rpm at 60 mph. Sound right for 4th gear?

R/
MJO

Yes, would be much higher if stuck in 3rd gear.

Perhaps you can temporarily disconnect the kick-down switch to restore 1st gear?

I don't think a new switch is too expensive.

[VLayton]

Hi gang,

Sorry I'm away so much, another record busy spring season is here and I'm so scrambled I can barely think. Wake, W123, Wonk...(that's me hitting the pillow occasionally)

Just so you know I'm still out here and fighting the fight...I have some two dozen "to-do lists" for clients alone....

I can't even find time for this year's rally, hopefully it will be in the next few weeks. Maybe I'll change it up dramatically for year four. :confused:

Well back to it...

Cheers

[Navy CPO]

Maxbumpo, all:

Max, I'll take your suggestion and keep the questions coming so you might consider this post as "300TD Needs Sorting PT II".

But first my thanks to everyone who has offered me advice.. it is invaluable. To date, I've got my tach functioning again, my very leaky primer pump replaced and confidence that my transmission shifting fine. All due to the advice you guys provided!

The car now runs dependably. Next items to tackle are:

1.) Radiator/ Water Pump: Probably the original set up although I can't be sure. Any general guidelines for a preventative replacement for radiator & pump? Expected service life? There are two existing repairs to coolant overflow tank and radiator top using JB Weld of all things!

2.) Brakes / Wheels: In pretty good shape here except for hard, cracked rear brake hoses and rear brakes that will need replacment sooner or later.
Brake fluid also needs changing so I figure I will do the fronts along with the rears including rotors, pads and hoses while I'm at.
My questions are... should I expect to replace the wheel bearings or just repack? Car has 268,000 on the clock.
Any advice regarding choice of rotors and pads? I usually stick with OEM or the equal and have more recent experience with Volvo and BMW parts sources. Performance Products is my usual source for M-B parts but it's been awhile since I had a W123 and M-B dealer prices are scary compared to Volvo or even BMW!.

3.) Power Antenna/ Rear Wiper & Washer: I admit to being gun shy of everything electrical, but my rear wiper and washer are both non functional and I'd love to get them working. The only hint I have to offer is the rear washer button causes a faint "click" from the rear when I push it but it doesn't pump any fluid. The reservoir has fluid and the fuses are OK. The wiper is really dead. What is the next likely cause? The motor? Switches?
Power antenna is non functioning also and the fuse is good. It is stuck "up" so it's no big deal but.... while I'm at it back there, I may as well fix it. Is the Hirschman unit usually the cause?


Thanks to all again!

R/
MJO

[johnmci]

Maxbumpo, all:
but my rear wiper and washer are both non functional and I'd love to get them working. The only hint I have to offer is the rear washer button causes a faint "click" from the rear when I push it but it doesn't pump any fluid.
R/
MJO

Ok, the pump is just a pump in a plastic housing, water in, water out. If you've a volt meter you should use that to confirm it is getting power, Could be seized, but not sure how to get at impeller, perhaps you can poke at it thru the output hole. I'll note the pump then feeds the water line which goes I believe under the passenger side rear covering up the C pillar, then back to the rear door. Under the rear covering is a one-way check valve. I had mine fail closed so although the pump ran, no water. First confirm the pump does work of course.

As for the wiper motor, I found out (thanks teenagers) that it's possible for the electrical connection to come disconnected via slamming the door shut a bit too agressively. Solution was to electrical tape the connection and place back in clip.

[Maxbumpo]

1.) Radiator/ Water Pump: Probably the original set up although I can't be sure. Any general guidelines for a preventative replacement for radiator & pump? Expected service life? There are two existing repairs to coolant overflow tank and radiator top using JB Weld of all things!

Get a new tank, new cap for tank, new thermostat w/ seal, and coolant. Zerez G-05 coolant meets MB specs and costs about half what the dealer charges. MB coolant is very different chemically, and using anything else WILL cause trouble in the long run. It is PH neutral with lots of buffering, and it has lubricants for the pump seals and other parts in the coolant system. The PH is critical: it keeps the plastic parts from getting brittle and cracking. Some have reported severe erosion problems in the water pump housing and elsewhere due to use of non MB-spec coolant.

If you replace the water pump, only use OE or OEM, as aftermarket pumps may have a stamped impeller vice cast, it is not as good and your car may overheat. Only need to replace the water pump when it starts to leak or make noise.

Coolant is supposed to be changed every 2-3 years, and every other change a new thermostat installed (almost as bad as Navy 3M system, eh!).

2.) Brakes / Wheels: In pretty good shape here except for hard, cracked rear brake hoses and rear brakes that will need replacment sooner or later.
Brake fluid also needs changing so I figure I will do the fronts along with the rears including rotors, pads and hoses while I'm at.
My questions are... should I expect to replace the wheel bearings or just repack? Car has 268,000 on the clock.
Any advice regarding choice of rotors and pads? I usually stick with OEM or the equal and have more recent experience with Volvo and BMW parts sources. Performance Products is my usual source for M-B parts but it's been awhile since I had a W123 and M-B dealer prices are scary compared to Volvo or even BMW!.

I prefer Rusty at www.buymbparts.com, or 800-741-5252. He has a small business (all employees own/drive at least one MB, and they turn their own wrenches) but provides excellent customer service, and his prices are extremely compettitive.

OE or OEM rotors and pads are only way to go. I just put new Balo rotors and Pagid pads at all four corners, replacing some aftermarket crap pads; night and day difference, much much much better braking now.

Wheel bearings can last an extremely long time if properly cared for. If there is no sign of problems now, I'd expect that all you need is clean, inspect and repack. Only use the OE high-temp wheel bearing grease, available at the dealer (use your MBCA membership for discount).

3.) Power Antenna/ Rear Wiper & Washer: I admit to being gun shy of everything electrical, but my rear wiper and washer are both non functional and I'd love to get them working. The only hint I have to offer is the rear washer button causes a faint "click" from the rear when I push it but it doesn't pump any fluid. The reservoir has fluid and the fuses are OK. The wiper is really dead. What is the next likely cause? The motor? Switches?
Power antenna is non functioning also and the fuse is good. It is stuck "up" so it's no big deal but.... while I'm at it back there, I may as well fix it. Is the Hirschman unit usually the cause?

Try replacing all your fuses first; their life is only ten years, and it is cheap to do. Make sure you put in the correct size according to the card under the fuse cover top.

On my '85 wagon, the rear wiper was dead due to failed capacitor (but I completely destroyed it before I figured that out). I got a used unit from salvage yard for $10, but it didn't work. I decided to re-solder all the joints because one or two looked flaky, and that fixed it. On my '87 wagon, the wires were broken in the according joint at the hinge. I spliced three broken wires back together, and restored normal operation to 1)wiper, 2)closing assist motor, 3) third brake light, 4) license plate lights.

[Alex]

Alex:

I just realized who you are!

THE Alex Rosner. I am VERY familiar with the legendary installations you did in NYC during the 70's! I sure would love to sit down and talk about some of the really "old school" stories you must have. You should write a book!

Regards,

MJO
Chief,

Now that you’ve outed me, all I can say in defense is that my 15 minutes is over and it’s a miracle my hearing survived that era.

But not unpunished. God has been making me do penance for my sins by creating a demand for our work in houses of worship, where we have been toiling for years.

Books may be written after retirement. But don’t hold your breath.

In the meantime, please stick to the subject at hand – Mercedes-Benz cars, which is why we’re all here.

[Navy CPO]

Alex:

Come on now...... you're being much too modest!

Look at it this way. You've got a legendary engineering talent and I 'll apply that legendary status to your passion for Mercedes Benz also but reserve the right to bore you with a million questions if I get the chance to have a beer with you.
(Wouldn't happen to know where I could find a Bozak mixer?).

Quite ironic that your current work is in churches, but I can honestly say that my first visit to Paradise Garage WAS a religious experience and Larry Levan was the Bishop ! OK.. enough of that for now.

Seems like my transmission is starting in 2nd gear and shifting twice to fourth. Now that my tach is functioning I am turning 3000 rpm at 65-68 mph. I guess that is just about right. Couldn't be 3rd gear... right?

I do appreciate all the assistance from you guys. My 300TD is sorting out pretty well and I'll keep the questions coming.

R/
MJO

[Maxbumpo]

Seems like my transmission is starting in 2nd gear and shifting twice to fourth. Now that my tach is functioning I am turning 3000 rpm at 65-68 mph. I guess that is just about right. Couldn't be 3rd gear... right?

Sounds correct to me...

What is your time for a 0-62 mph run ? (0-100 kph)

If around 13 seconds or less, everything is working as it should...

[Navy CPO]

Haven't checked the 0-62 mph time yet. I'll get it out tonite and turn that turbo loose!

Thanks for the brake tips, etc. in your previous post. Really helps alot!

R/
MJO

[Navy CPO]

Maxbumpo:

To use the Navy analogy, my 300TD failed the "PRT" last night.

Couldn't hit 60 mph within 13 seconds. Could only muster 50-55 mph from a standing stop to the 13 second mark.

V/R,

MJO

[Maxbumpo]

OK, now you know that you've got some work to do.

Is there a noticable point when the turbo seems to 'kick in'? If so, then your ALDA needs to be adjusted (turbo operation should be seemless). Search the forums, look for posts by Marshall Booth.

I've finally gotten around to tweaking mine. I've only been able to turn the adjustment screw 1/4 to left, which dropped the 0-62 time from 17 seconds to 15 seconds. Idea is to keep going until you start to see black smoke during WOT acceleration in strong sunlight, then turn it back to right just enough to make the smoke dissappear or be very light wisps. If all else is correct, 0-62 time should be around 12-13 seconds or maybe less.