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My First w123

2K views 11 replies 5 participants last post by  Stretch 
#1 ·
Hey guys! So after posting a few times for various problems I've encountered with my car, I figure I would try and gauge whether Im a fool for buying this car or I'm close to making it a daily driver.

I would pass the '81 300D everyday on my way to work, and was in the market for a car so I figured I'd look into it and see what I could do. The car was recently re-painted ($3000 paint job) and had about 6k worth of service done to in in the past 4 years. The problem was the engine threw a rod and blew a giant hole through the bottom. After sitting in that state for a year it still turned over and ran with 4 cylinders. :grin The price was 1800 firm, and I was in love, so i pulled the trigger.

Not having any mechanical experience in the past, my manager agreed to help me swap the engine out with one that was in working condition and teach me the ropes. We got the car towed over to his place and proceeded to pull the engine.

When I decided I wanted to take the chance with this car, I figured it would be a more reliable investment. While changing out the engine I would replace as much as possible and address all problem areas while I was at it. Heres a short list of things Ive replaced off the top of my head;

Glow Plugs
Fuses
Motor mounts
Injectors
All rubber hoses attached to or around the engine
Water Pump
Thermostat
Trans cooler hoses
Belts
Transmission filter and Pan gasket
Intake/exhaust gasket
I did a valve adjustment on the engine before I even put it in the car
All filters obviously
Exhaust hangers
Various bolts
Battery
Positive/negative cables
Rebuilt Starter

I also took this opportunity to clean the engine bay and just various things around the car so as to make future work a bit easier in terms of cleanliness.

The moment of truth arrived after two months of tinkering and learning yesterday, we got the car to fire up and let me tell you, it purrs. After a few short trips around the block I made a short list of things that will need to be done soon:

Brake fluid flush
flex disc replacement
Tie rods
One of my rear axles is missing an entire boot, so that will need to be replaced

After getting a little over zealous and excited that I finally had a car and that I did the work myself, I drove it about 40 miles. It was very reserved driving, but the car accelerated without hesitation and idles just fine. Heres where I'm at now though; It has leaked about 2 quarts of oil slowly over a two day period. They are coming from around the alternator and the bottom of the engine. Monday I'm changing the oil pan gasket to see if that may be a possible source of the leak. I know there are two other leaks but I haven't been able to pinpoint them. I should have replaced the front main seal while the engine was out but decided to take the risk, hopefully it isn't leaking.

Secondly, I was trying to get home and the temp went up to about 100 degrees, and if I came to a stop would inch up a tiny bit until I got up to speed again. Opened the hood and there is a steady drizzle of coolant coming from where the thermostat mates to the block. Ill take it off and see why this could be, as of now the car has leaked all of its coolant while sitting in the driveway.

Thirdly, the transmission is insanely erratic. Sometimes it will shift early and soft, other times the engine will rev up and stay there until it finally "catches" and shifts into 3rd gear. It slipped once or twice. Im thinking the last engine threw the rod because somebody might have gunned it and the tranny didn't catch and it over revved itself. I can't afford for this new engine to blow because of something like that. I intend to investigate a bit more and replace the red vacuum modulator and have it adjusted. Living in Central Texas I can't seem to find a single mechanic around me that will work on my car, much less one I'd feel confident leaving it with. I don't have the know how or patience to deal with the transmission, so I'm desperately searching for someone who can get it sorted. The P/O had it rebuilt about 10k miles ago, I'm unsure if the people who rebuilt it didn't do a great job, or if its just a vacuum issue.

So after all this, the car is parked out front. Im so excited to finally have a vehicle again, and I've spent a ton of money and time trying to get it in daily driving shape. I realize I could have purchased a running w123 for a fraction of the price and repaired as things went wrong, but I went with the blitzkrieg approach.

Anything I should do next? How hard can you push a newly installed engine?
 

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#2 ·
WOW bought a car with a thrown rod for 1800....that is crazy...then doing all that work...as you said you could have got a good runner for 2500$...

This is one of those cars, you'll be up the creek with out a paddle...

Not sure what to tell you, or where to tell you where to go....you more or less need a local member to come by and look it over and tell you what you have done right, wrong and what needs to be done....hopeful someone else will chime in..
 
#3 ·
#4 ·
Same car, that was my managers thread when we first started the project. He knows way more about how cars work and is pretty technical. The project is slowly coming to an end and he'll be on to his next project soon so I figured I'd take over from there.

I'm hoping I'm not up a stream without a paddle, all my cards are on the table with this car so to speak. I figured starting fresh with a decent engine would be preferable to inheriting a potential lemon from somebody else. There aren't that many 300D's for sale in the immediate area that were in any sort of shape to drive. I test drove two down in Austin before I pulled the trigger on mine and they were in abysmal condition. One that stood out had hood pins drilled in, was missing the gas pedal and the engine was about to go.

I am ultimately wanting a classic car that is reliable, straight forward to work on, and has a wealth of information I can tap into in times of need which is what these forums are. My current thought is that the car runs fairly well for the amount of work we've done to it. Im not sure what the protocol is when you replace a cars engine but some immediate oil leaks are normal, at least until you fine tune the system and work out the small kinks from what I'm told.

Does anybody else encounter mechanics who work primarily on Mercedes not wanting to touch one thats so old? Its a little worrisome to me
 
#5 ·
Same car, that was my managers thread when we first started the project. He knows way more about how cars work and is pretty technical. The project is slowly coming to an end and he'll be on to his next project soon so I figured I'd take over from there.
...
OK - Fair enough - I was confused.

...

Does anybody else encounter mechanics who work primarily on Mercedes not wanting to touch one thats so old? Its a little worrisome to me
I think that is quite a common problem for cars of all ages - most mechanics find a niche and stick with it. Many don't like moving out of their comfort zones. You either need to find someone who likes your car or someone who is willing to like your car!

...
After getting a little over zealous and excited that I finally had a car and that I did the work myself, I drove it about 40 miles. It was very reserved driving, but the car accelerated without hesitation and idles just fine. Heres where I'm at now though; It has leaked about 2 quarts of oil slowly over a two day period. They are coming from around the alternator and the bottom of the engine. Monday I'm changing the oil pan gasket to see if that may be a possible source of the leak. I know there are two other leaks but I haven't been able to pinpoint them. I should have replaced the front main seal while the engine was out but decided to take the risk, hopefully it isn't leaking.

...
In the other thread it was stated that the front crankshaft seal was leaking

...

Secondly, I was trying to get home and the temp went up to about 100 degrees, and if I came to a stop would inch up a tiny bit until I got up to speed again. Opened the hood and there is a steady drizzle of coolant coming from where the thermostat mates to the block. Ill take it off and see why this could be, as of now the car has leaked all of its coolant while sitting in the driveway.

...
There is a gasket between the two parts that should probably be replaced. Make sure you use MB spec coolant - aluminium radiators - aluminium coolant pipe etc etc etc

...
Thirdly, the transmission is insanely erratic. Sometimes it will shift early and soft, other times the engine will rev up and stay there until it finally "catches" and shifts into 3rd gear. It slipped once or twice. Im thinking the last engine threw the rod because somebody might have gunned it and the tranny didn't catch and it over revved itself. I can't afford for this new engine to blow because of something like that. I intend to investigate a bit more and replace the red vacuum modulator and have it adjusted. Living in Central Texas I can't seem to find a single mechanic around me that will work on my car, much less one I'd feel confident leaving it with. I don't have the know how or patience to deal with the transmission, so I'm desperately searching for someone who can get it sorted. The P/O had it rebuilt about 10k miles ago, I'm unsure if the people who rebuilt it didn't do a great job, or if its just a vacuum issue.

...
http://www.benzworld.org/forums/w12...3-transmission-diagnose-adjustment-722-a.html

...
So after all this, the car is parked out front. Im so excited to finally have a vehicle again, and I've spent a ton of money and time trying to get it in daily driving shape. I realize I could have purchased a running w123 for a fraction of the price and repaired as things went wrong, but I went with the blitzkrieg approach.

Anything I should do next? How hard can you push a newly installed engine?
Fix what is wrong first.

Do not push the engine hard with a dodgy coolant system and transmission problems. When a car groans and complains it is saying "fix me"!
 
#6 ·
81 was a transition year as far as a few controls go.

Your transmission may or may not use vacuum, but you state it has a modulator.

What year engine is in it now?

What transmission is it? Stretch told you how to find out.

As Stretch also mentioned, there is a gasket between the block and t'stat housing. If you need to get to that, be sure ans replace that short 40mm hose. Maybe that's where the leak is anyway.

As far as the oil leak goes, once you have replaced the oil pan gasket, clean the front of the engine as best you can, start it up and observe.

Not in the area, so can't recommend an MB mechanic. There's a good one close by me tho. I use when I don't have time or feel comfortable wrenching on something.

I had missed the other thread, but went over it a bit just now.

You may want to look into the epc as well;

EPC-net Online

Good luck and keep us posted.
 

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#7 ·
Thank you for all the information guys! The donor engine was from a 1979 300 wagon. I still have the sls pump and I'm trying to decide if getting a block off plate for that is aesthetic or necessary. The transmission is the original from 1981, there is no Bowden cable but there is for sure a vacuum modulator, We accidentally broke the little nipple the vacuum line attaches to, and had to glue it back together.
 
#8 ·
FrankenBenz, ah.

The controls will probably be the same, with no Bowden cable. A series of push rods will determine the shift points.

I would use a block off plate and ditch the SLS pump, but that's me.
 
#9 ·
WOW put in a 79 engine, you've lost some horsepower and gained some issues from that year.

The linkages between the two engines are totally different, the 79 may have had only a bowden rod/control pressure rod control for the transmission, so no vacuum equipped meaning you would have to switch the injection pump over....may even need to have used that transmission...

Then you also have a different thermostat housing setup, different glow plugs, heater hose connections possible..
 
#10 · (Edited)
It sounds like you're totally lost and have no gameplan whatsoever, or at least one that could feasibly work.

First things first, these engines generally don't just "throw a rod". I'm not saying it can't happen, but 99% of the time it is because the car was run with no oil. The first important thing to do while you had the old engine still in it and it was running would be to find out why it is running low on oil. Is it a coincidence that your new engine is loosing so much oil? Could be, but we won't know at this point.

Next, you are adding a bunch of unknowns together or taking a stab in the dark. If I were you, I would stop doing more things like changing the oil pan until you exercise the grey matter to figure out what the problem *really* is. You could actually induce more leaking by changing the oil pan. Working on old Mercedes cars can be rather tricky -- some of these jobs have to be redone even by experienced mechanics. This is not the way you fix things. I'm sure there's some way to isolate the problem. Why don't you tie a plastic bag around the oil pan and see if you get oil leaking into the bag or if it keeps leaking on your driveway? Another obvious question if the oil pan stayed on the engine through the swap is whether it was leaking on the donor vehicle.

You don't know the status of the new engine -- i.e. whether it is in good shape. You don't know the condition of the transmission since you couldn't drive it very much. You have no idea what condition the rest of the drivetrain is in, but instead you just assume to spend a bunch of money on a bunch of parts that may or may not have needed to be replaced. I'm not sure how you think this is a good investment since these cars cost a phenomenal amount of money to build, they are much needier in terms of maintenance/repair than an Asian econobox, and you have no idea how long it will take to get this to be a reliable car.

One painful lesson that all W123 owners learn eventually is that preventative parts replacement even with OEM ones doesn't necessarily mean the new parts will be any better or more reliable than the old ones.

Next, it sounds like you didn't research the compatibility between various systems in exchanging various parts between models. It's one thing to swap one part with another like one -- there are many howtos on this site and others, but it's another to try to adapt systems from one car to another -- that requires more expert knowledge, and even with that in many cases it's not a good idea to begin with.

When you find yourself in a hole, the first thing to do is stop digging.

The best thing IMO would be to find a sympathetic indy in your area who can start with some diagnoses. Unfortunately, finding one who is capable and willing to help may be a bit difficult. I don't think anyone can provide you with much help over the internet because there are so many details on your swap that could have gone wrong. It's much different than having a working car (or even a complete non-working car) and diagnosing problems. Your problems may turn out to be on an engineering level.

Do you know anything about the history of the donor engine -- i.e. where it came from, how many miles, when it was last driven, whether it was leaking excessively, etc? Also I would make sure you didn't install the thermostat backwards and installed the seal properly. Two quarts over a 40 mile period is a lot of oil. You should be able to just let it idle in your driveway and watch it spill out and see where it is coming from. Most of the oil leaks on these cars are a few drips here and there that go from top to draining on various components and can be a bit harder to trace.

Mercedessource has a good diagnostic PDF I would recommend you buy called Why does my W123 diesel leak.

Dkr.
 
#11 ·
You're correct in your view of the situation, it has been my first foray in to mechanical restoration. It has cost me a substantial sum, and it is still taking me time; I'm intensely happy with the results though. This is a very handsome car, it fits my driving style perfectly and in the end its one more 300D that would have been lost forever saved. My friend helped me tremendously, we stripped the engine down to just the block, and added everything back on to it. If a part wasn't new, it was reconditioned, and the problem of system compatibility was taken into account.

Many lessons were learned, a few drops of blood shed. Ultimately I am happy with my project. Next is to replace the entire suspension, get new tires, and reupholster the headliner. I'm thinking of doing it in a tartan pattern but haven't decided yet.

On a side note, we are also considering a chevy 350 into a 81' 3 series BMW, just for fun. Who knows.
 
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