First things to do on new-to-me 1997 E300D
 

Hi. I'm picking up my 1997 E300D on Thursday. My 5th M-B ever (230SL, 450SL, E420, C230), first diesel.

In another thread, a few recommendations were made regarding what I should do proactively to improve my chances at enjoyable and reliable motoring. I'm starting this thread to focus on the topic.

Do right away
- Change the seal where the wiring harness enters the transmission.
- Check for biodegarded wiring insulation in engine harness, behind headlights, and anywhere else you have access to wires while working on other projects.
- Block ERG connection. (I know recycling gasses can clog up intake, but I would like to hear more about benefits and detriments to this.)
- Remove and clean intake manifold.
- Check for cracks/leaks in the 12 plastic crankcase vent lines going into each intake runner.

Do when you have time, money, or a reason
- Upgrade alternator to something in the 115 to 150 amp range.


Looking forward to all your sage advice!

While you have the intake off - replace all the plastic lines and replace the return lines with the newer gray silicone lines.
I don't know how many miles on your ride but take a look at the rear thrust arm(s) and bushings. These are much neglected and after a 4 wheel alignment give you that tight new handling/ride.

If you can get the maintenance records, the first thing you should do is go over them carefully to determine what has been done. I bought my '98 e300 ten years ago, fully expecting that it would be a car that had been neglected. When I went over them, I learned that the car had been well maintained from day one by the two previous owners and nothing was needed. I drove the car for nine months before it even needed servicing. I may be one of the lucky ones.

Just don't drive a 300DT and you will be fine.

These cars are rock solid reliable and IMO (hate me for it) better than a w124. They don't really ever break, and the 722.6 diesel trans doesn't have the problems the gas models do.

Only thing I'd check on it shocks amd springs.. and obviously rust. I can't see where your from for some reason. At this age, the springs can crack and shocks are worn too.

How's the glow plugs

Spring perches can have hidden rust and can fail.

Congrats Rodd, it is a great reliable car and you will enjoy.
Mine got T-boned with 150,000 miles.
Rust and the EGR were my main issues. The rust was unstoppable. The EGR gets stuck up with greasy tar and performance suffers. Once blocked off and gunk cleaned out the car performs well, but without the turbo you just have to floor it all the time.
As Marshal Booth used to say... drive it like you stole it.
You will enjoy.
best,
jz

TX76513 - The car has 91,000 miles on it. When you say "look at the bushings", do they crack or what? Intake manifold lines sound like a must.
Eschwab - The M-B dealership I bought it from provided about 4 years of records from when the previous owner serviced it there. Lots of oil/fuel leak complaints! I am trying to get service records from original dealership - I found a business card that matched the initial service book stamps.
Jake12tech - I have to check records again to see if glow plugs were replaced. Regarding rust, car was originally from Florida then came to Canton, OH (about 150 miles from me). I had the car put up on a rack and couldn't find any rust on spring perches or, from what I could see, on suspension mount points. No rust under door rubber seals either.
Pimpernell - I had a spring perch fail on my 94 E420, but luckily it failed while sitting in the parking lot at work. I came out for lunch and the car was tilted! I will be watching on this car.
Zakkkk - Yes, I went for the non-turbo for simpler maintenance - one less thing to disconnect over and over. So, is there just no good use for the M-B EGR setup? It never works well for long periods? If you block the passage between valve and intake on a working valve, does it ruin the valve?

Updated list - please supplement:

Do right away
- Maintenance, depending on what the records show.
-- Fluids: oil change, brake fluid change, power steering fluid change, engine coolant change
-- Lubricants: Single arm wiper mechanism
-- Service Items: Check brake pads/rotors, glow plugs, air filter
- Clean around valve cover seal to see if leak is still happening.
- Change the seal where the wiring harness enters the transmission.
- Block ERG connection. (I know recycling gasses can clog up intake, but I would like to hear more about benefits and detriments to this.)
- Remove and clean intake manifold.
- Replace the 12 plastic crankcase vent lines and the return lines on intake runner.

Do when you have time, money, or a reason
- Upgrade alternator to something in the 115 to 150 amp range.
- Check for biodegarded wiring insulation in engine harness, behind headlights, and anywhere else you have access to wires while working on other projects.

Thanks

Blocking off the egr on the 97 is a bit more complicated. You'll need to add a breather filter to the egr valve otherwise you'll get a CEL.
https://i.imgur.com/AcfdvGT_d.jpg?ma...&fidelity=high
Personally the first thing I would do on a 97 is pull the intake manifold and clean it out along with the intake runners to restore full power. While it's out, check/replace any failed vac hoses to the intake flappers that could cause a CEL later on, check replace any bad fuel lines, check engine wiring harness.
https://i.imgur.com/Cf2iaH8_d.jpg?ma...&fidelity=high

https://i.imgur.com/YBsE6xQ_d.jpg?ma...&fidelity=high

While you're in there, check replace the fuel return lines on the injectors, cut the large plastic injectors cover in half so you can remove it without first pulling the large aluminum cross over pipe in the future. Also there are 12 crankcase ventilation holes in the intake runners with broken plastic fittings for each. Plug them up so you don't get any more dirt leaking in.
https://i.imgur.com/llAGgHJ_d.jpg?ma...&fidelity=high

https://i.imgur.com/8a8ZY7h_d.jpg?ma...&fidelity=high

Cabin AC filters ahead of the glove box!!! I don't know how to check the activated charcoal filters. Easy to get to, then what?

How about ATF and filter?

Remove the TCU, second module from the front in the starboard side electronics box, and set it connectors down in a pan overnight. If there's no trace of ATF, keep rocking. Otherwise, open it and spend a can of electrical parts cleaner rinsing off ATF.

Is the turn signal switch fixed or does it move independently of the steering column? There's a clamp ahead of the clock spring that comes loose.

Not vehicle specific but flex joints and diff fluid.

Sixto
98 E320s sedan and wagon

Replace brake hoses and coolant hoses. Yes the fluids are probably overdue for replacement as well, but the hoses that carry these fluids are 20 years old at this point. Rubber hoses don't last forever, and a failure leaves you on the side of the road. The brake and coolant hoses are inexpensive.

- replace the four brake hoses, and fluid.
- replace the coolant hoses, water pump, thermostat, and coolant. serp belt too while you're in there.

I have the same '97 E 300 D, and my advice would be to start by doing only routine maintenance, fluids, filters, etc. You will likely have some diesel fuel leaks that will need to be fixed. The EGR is best fixed by feeding it filtered air and plugging the hole on the exhaust manifold. This will not set a CEL, and will cut down on smoke, and increase pep modestly. The car will tell you what needs to be done. If you listen to all of us about what should be done, you will soon decide that a preventive overhaul is in order. The car works well in flat country, but is less satisfactory in hilly country because of it's modest acceleration.

Awesome, guys! I'll compile the info and compare against scheduled maintenance that is due and go from there. Thanks so much.

Common problems ive encountered on 1997s

K40 relay -- car will die randomly and not start. 150.00 off pelican, one guy almost scrapped his car because the mechanic said ip was bad and would be 2000 or so.

Belt tensioner spring -- these always break on long trips for me. Keep one in glove box. 50.00 on pelican

Tjts1 -- where does that ccv hose go? I like your system. Seems you could put a canister to catch te oil