1991 300d basket case - PeachParts Mercedes-Benz Forum

bfrinkus1 · #1 06-19-2012, 06:12 PM

I got a cheap 91 300d 2.5 turbo this weekend. When I got it home, I realized I got exactly what I paid for

. Pretty much every system on the car has problems of some sort. I'll just jump in and appreciate any help I get!

-ABS light on. I checked the OVP relay, the 10 amp fuse on top had continuity, but I put a new one in just for kicks. Can anyone advise proper diagnostics on ABS light?
-There is a small strip fuse holder located over front driver's wheelwell in engine compartment. Some idiot just put some wire in there. I ran the car for a few minutes and monitored temp of wire with non-contact thermometer. No heat buildup, so it shouldn't burn, but I still want it right. What is the correct amperage for this strip fuse and what does it control?
-Neither turn signal nor hazards work, however windshield wiper works fine (I mention this because I understand they share a combo relay?). Can anyone advise if this is indicative of failed relay? Also, can anyone advise location of this relay? I don't know if this is relevant, but the hazard switch on the dash feels fishy...
-When key switched on, the glowplug light does not illuminate. Starting is difficult and light comes on once car is running. I assume I have one or more failed glowplugs. I also assume the intake has to come off to service them. I see this car takes different plugs than my 190d OM601...should my glowplug reamer for the OM601 work on this engine?
-Generally speaking, vacuum system appears to be in poor condition. It looks like many check valves, hoses, etc have been "repaired" with some sort of epoxy. Car is slow to shut off after keyswitch turned off, it could just be a fuel shutoff valve on the IP, but I'm suspicious that the car just can't hold vacuum due to multiple leaks in system. Can anyone point me to a good vac system overhaul guide for this car and/or common weak points in the vac system? I'll be getting my MityVac out and checking what I know to check soon.

The car shows 225k on the odometer, physical condition of the car is consistent with shown mileage. However, car does not seem to have been well cared for. Are there any preventative maintenance issues that I need to be on the lookout for? I would love to fix this thing up and get another 225k out of her.

Thank you all!
Brad

shadetree77 · #2 06-19-2012, 08:23 PM

ABS-check sensor wires on each wheel (i think it's 4 wheel abs). being a 91 there's probably a way to pull codes too.
replace the hazard switch- if it doesn't work or isn't plugged in the turn signals won't work either (they run through the switch)
glowplugs-check em, if they turn out good it's prolly gonna be the relay

shertex · #3 06-19-2012, 08:57 PM

How much did you pay for it?

These are great cars....I've got two of them. I hope you're able to bring it back.

The combo relay for turn signal and hazard light is in the compartment behind the fuse box.

One thing you'll want to do is start using the EPC. EPC-net Online Sometimes it can be little confusing to find what you want to find, but it's a great help in identifying parts.

jbach36 · #4 06-19-2012, 10:18 PM

If you can't do the repairs yourself and want to save money, hire a mobile mechanic who is familiar with these, or if you don't mind spending more, take it to a MB mechanic.

If you can do some of the work yourself, get the parts, read up, get the tools you need, and knock it out. The glow plugs are probably the hardest, and just FYI, when you put them back in, there's some wire on the one the furthest to the left as you're working on them, that if it's touching something metal, it will short out the glow plug system, and the car won't start. I forget what the wire's from.

The other thing with the car not shutting off, is probably your Shut Off Valve, or it could be a vac leak in your hoses.

Do yourself a favor. Spend the money on good parts, get everything fixed that needs fixing, and be done with it. Don't do patchwork. Spend the money. Get it fixed. Clean the engine. Clean the injectors. Change all of your fluids.

Codifex Maximus · #5 06-20-2012, 04:31 AM

A MB reality check:
There is NO SUCH THING as a cheap used Mercedes.

You either pay $1000USD for a car and spend $4000 making it a $3000 dollar car OR you pay $4000 and get a car that has already been restored.

Having said that, you get your foot in the door with the $1000 purchase and learn a whole lot about these cars while restoring. It is a rewarding hobby in itself - working on em.

There are helpful folks on this board that are pretty much experts at taking a car and fixing all the little details in one fell swoop. They end up with a really nice car after going thru the checklist. (and no car payments)

I'm not particularly well endowed with cash and I've got three cars that need lots of attention. So, I'm getting there but it takes time. Next Mercedes I buy will be the $4000 dollar already fixed up car.

pwogaman · #6 06-20-2012, 08:09 AM

I also have two of these, and a spare engine for rebuild and rotation into the other cars. There is plenty of support for these cars, but even better is when you can meet up with someone who knows them and go over them together for the price of a beer and some pizza. Put your location in your profile and you may get lucky.

Jetmugg · #7 06-20-2012, 08:48 AM

Based on your description, the strip fuse is for the glow plug relay. I believe it should be an 80 amp rating.

This may be a major contributor to the reason that the GP's don't work and the GP indicator light coming on after the car is running.

If the car is rust free, those other problems sound pretty minor in the big picture.

SteveM.

Jetmugg · #8 06-20-2012, 08:49 AM

Replace the hazard switch. That will most likely restore full function to the turn signals and the hazard lights.

Steve

brakeengr · #9 06-20-2012, 08:51 AM

Quote:

Originally Posted by bfrinkus1

-There is a small strip fuse holder located over front driver's wheelwell in engine compartment. Some idiot just put some wire in there. I ran the car for a few minutes and monitored temp of wire with non-contact thermometer. No heat buildup, so it shouldn't burn, but I still want it right. What is the correct amperage for this strip fuse and what does it control?

30A; blower motor fuse.
I have a '92; just absolutely love it. Everything works, zero rust, very clean.

bfrinkus1 · #10 06-20-2012, 04:27 PM

Jetmugg, I'm still daily driving the 190d I bought from you. Getting ready to turn 435k. Rust is taking it's toll, maybe the 5-spd in it will one day reside in my recently purchased 300d...

Maximus, you are RIGHT! No such thing a cheap MB. Like you, I've got one that needs work that I don't mind putting into it. In the end, I'll have spent just as much as if I'd bought a nice one up front.

Shertex, thanks for the lead on EPC-net, it looks like an excellent resource.

Thanks for all the tips, 1 more question...

Electric engine fan runs all the time the ignition is switched on. Assuming it has not been straightwired by a previous owner, is there a common switch/relay that fails and produces this symptom?

It's going to be slow moving, but I'll update this forum as progress is made.

Thanks!
Brad

bfrinkus1 · #11 07-01-2012, 02:46 PM

A few weeks has gone by and I'm making progress on the new member of the family!

-I purchased (and mostly read!) the W124 Owners Bible, it's a great resource
-Rigged fuse WAS a 30amp for blower motor, has been replaced and has not blown or shown any signs of overheating!
-Inoperable turn signals and hazards WERE due to a failed hazard switch. I found a BRAND NEW one for only $5, installed it in 5 minutes and all signal lights now work great.
-My car wouldn't shut off and I thought vacuum system was leaky all over. Turns out it wasn't as bad as I thought. I replaced a handful of rubber vacuum line connectors and installed a new brake booster vacuum line (the one that runs from the vac pump to the brake booster with the integrated valve) and car now shuts down quickly!
-I haven't fixed glow plugs yet because I got sidetracked on the belt drive system (getting ready to start a new thread about this...), but think that glow plug diagnostic and repair will be fairly straightforward once the intake is off and I can get to things.

I'm getting ready to move on to the next round of repairs and wanted to close out this thread with a thank you to the vets who helped and to provide a reference for the rookies that follow me.

Thank you all!
Brad

Bio300TDTdriver · #12 07-01-2012, 03:21 PM

Location?!?

bfrinkus1 · #13 07-02-2012, 04:19 PM

Watkinsville, GA. I finally updated my profile to show this!

ZRatedDog · #14 07-02-2012, 04:27 PM

Quote:

Originally Posted by Codifex Maximus

A MB reality check:
There is NO SUCH THING as a cheap used Mercedes.

You either pay $1000USD for a car and spend $4000 making it a $3000 dollar car OR you pay $4000 and get a car that has already been restored.

well said

Jeremy5848 · #15 07-02-2012, 04:53 PM

You can check the glow plugs by removing the cover of the pre-glow relay and unplugging the connector that leads to the glow plugs. Use an Ohmmeter to check each pin of that plug to ground, should be 1 Ohm or less. Any that measure more than a few Ohms are probably bad. One or two of the glow plugs may be removable with the intake manifold in place (I don't remember exactly how the 602 Turbo engine is laid out). Once you have 5 good plugs the pre-glow light should return to normal.

The ABS problem may be dirty front wheel sensors. Jack up each front wheel in turn, remove the wheel, then find the sensor. It should be attached with one or two Allen screws, probably very tight. Remove the screws and the sensor will come out, danging on its pigtail lead. A dirty sensor will be obvious. You also need to inspect and clean the toothed wheel that makes the sensor send pulses to the ABS electronics. A small brush, air gun, and vacuum cleaner adapted to small hose will allow you to clean the sensor and the toothed wheel. That may be the cause and is certainly the first thing to try as it's no-cost.

I think the OM602 engine came with the later-model vacuum pump (has 4 screws on the face). The early model (came on the 603 engine) has a plain face and inside has an open ball bearing cam follower that can disintegrate and dump scrap metal into the timing chain cavity. Others will know whether your vacuum pump is OK or not.

The serpentine belt tensioner on these engines will fail every hundred thousand miles or two; this allows the idler pulley to sit cock-eyed and causes excess belt wear and can damage other components. Repair is not a major job and a knowledgeable mechanic or DIYer can help you see what's going on.

The front two engine mounts are hydraulic and also last 100,000 miles or so. If they are bad the engine will sit too low and there will be excess vibration in the engine and transmitted to the chassis. Again call upon someone experienced to diagnose this problem. Replacement is DIY, parts about $60-100 each depending on the source. The rear mount is solid rubber/metal and rarely fails.

Other than that, most of the jobs are the ones you do on any engine -- fresh oil/filter, clean cooling system, etc. The suspension systems are rather sophisticated and can be expensive but much of it is DIY-able. Unless you're getting terrible clunking noises or atrocious tire wear you may be able to ignore that for awhile.

Good luck, keep us informed, pictures please.

Jeremy