GregMN's 1991 W126 350SDL Has A New Home - Page 3 - PeachParts Mercedes-Benz Forum

Squiggle Dog · #1 09-29-2018, 06:47 PM

The left front subframe attaching area on the body had rusted out, but fortunately it was repaired with a steel plate before we got the car. One of the round retainer plates fell off later on, though, so we got one and a bolt from a forum member.

The left rear plate was cracked, so a replacement was found at a wrecking yard.

The front suspension creaks loudly and shakes above 70 MPH, and it pulls hard to the right. I took the car to an alignment shop and they said that every component of the front suspension will need to be replaced before they will do any work. So, a front end suspension rebuild is in the future.

Squiggle Dog · #2 09-29-2018, 06:57 PM

I had been noticing an oil leak that was coming from the bottom of the oil filter tower. It suddenly worsened. I expected to find a leaking crush washer, but it turned out the oil pressure sending unit was cracked and about ready to blow.

While waiting for a new one to arrive, I plugged the hole with a bolt and a spacer with an aluminum crush washer on each side.

We got a VDO brand sending unit.

Squiggle Dog · #3 09-29-2018, 07:36 PM

The air conditioning stopped working, so that was an emergency fix. After checking several points in the system, it turned out there was a secret blower motor fuse which had a hairline crack in it. This is a special-order fuse that the auto parts stores don't carry, so in the meantime I installed an inline fuse.

The transmission started acting up and was shifting poorly. Fortunately, this was corrected by a new, updated shift modulator.

Due to the high-powered sound system, the taillights keep blowing bulbs. But the reverse lights were no longer working even with new bulbs, so I replaced the neutral safety switch. The part of it that controls the reverse lights went bad. It would have been an easy job, but there's hardly any room around it and it's nearly impossible to get at the upper bolt.

Squiggle Dog · #4 09-29-2018, 07:38 PM

The 350SDL had been getting hard to start, and the other day my roommate called me from work because the engine wouldn't crank over at all. It turned out the four-and-a-half year old Bosch battery was bad (it would hold voltage, but not much amperage), so he got a new pro-rated one from Pep-Boys.

The battery tray was rusty, so I replaced it with one that he had powder coated. I also installed a new washer fluid reservoir and pumps. An interesting feature of this car is that the washer fluid and windshield glass are heated by coolant.

It received a new Bosch battery under proratia. Apparently four-and-a-half years is beyond life expectancy of a battery in this climate. Pep Boys was saying they get a lot of batteries returned after only 6 months.

I also replaced the combination switch on the steering column (which wasn't easy) in hopes it would solve the high beam indicator light being stuck on, no high beams, and the windshield washer not working when the headlights are off. (which it didn't). So I still have a bunch of electrical problems to chase down.

Look at all the damage that has to happen in order to replace the combination switch.

At least we found a new genuine Mercedes combination switch on eBay for only $80. That was a score as they are normally over $300. Otherwise it would have been using a ÜRO brand or used one. I still ended up having to add two contacts from the old switch and it was odd how the cruise control stalk slides and clips in.

After replacing the battery, the alternator tested bad, so I replaced the voltage regulator on the alternator with a new Bosch one (made in Taiwan). It fixed the problem. Look how worn the brushes are on the old one (right) compared to the new one (left).

dude99 · #5 09-29-2018, 08:47 PM

The window washer lights on thing sounds a heck of a lot like a bad\dirty ground to me

vwnate1 · #6 09-30-2018, 12:08 AM

This is good, you endlessly hurting down those niggly little things that can make owning an old car frustrating .

Back to your loss of power & fuel economy : your OM 603 (?) engine might be slightly different from the old 6 cylinder OM617's I fool with so I don't want to give useless advice so post up some clear, well lit pictures of the turbo and any hoses, pipes, banjo fittings and so on connected to it or the entire intake manifold, this will tell the collective here where to make the next search .

I just recently discovered a bad waste gate diaphragm (overlooked by everyone else who's looked at or touched my battered Coupe) and in teaching my self how to diagnose and repair it, I discovered the valve proper can get so coked up it remains stuck partially open, this too will reduce the boost in RPM application and total boost amount, once I figured out what to test and how, I made rapid progress, looking at your thread here I'm quite certain you'll learn and get this car running strongly again too .
'

Squiggle Dog · #7 09-30-2018, 03:13 AM

Quote:

Originally Posted by dude99

The window washer lights on thing sounds a heck of a lot like a bad\dirty ground to me

I'll be cleaning all grounds soon, and maybe the plugs for the washer motors are reversed.

Quote:

Originally Posted by vwnate1

This is good, you endlessly hurting down those niggly little things that can make owning an old car frustrating .

Back to your loss of power & fuel economy : your OM 603 (?) engine might be slightly different from the old 6 cylinder OM617's I fool with so I don't want to give useless advice so post up some clear, well lit pictures of the turbo and any hoses, pipes, banjo fittings and so on connected to it or the entire intake manifold, this will tell the collective here where to make the next search .

I just recently discovered a bad waste gate diaphragm (overlooked by everyone else who's looked at or touched my battered Coupe) and in teaching my self how to diagnose and repair it, I discovered the valve proper can get so coked up it remains stuck partially open, this too will reduce the boost in RPM application and total boost amount, once I figured out what to test and how, I made rapid progress, looking at your thread here I'm quite certain you'll learn and get this car running strongly again too .
'

I'll try to investigate the turbo wastegate more and get pictures. I noticed there was a vacuum valve of some kind on the turbo with no hose attached to it.

Squiggle Dog · #8 09-30-2018, 03:21 AM

The left rear door lock wasn't functioning, and the power window in the same door got stuck a while ago. So, I replaced the vacuum lock actuator that was leaking and replaced the broken slider on the regulator.

The left rear window regulator slider broke again. I dislike power windows because they always seem to break. Unlike on my W116 which uses a clip, in order to replace the slider on a W126 you either have to buy a new regulator or grind it off.

What's left of the slider has been punched out, with a socket on the other side to support the regulator arm.

Here is the new slider that needs to be beaten and mushroomed into place.

The new part mushroomed onto the regulator arm. I recommend having at least two of these on hand in case you break one during the process. I took this one apart to reduce the chance of breakage.

The window regulator is put back into place. The window glass was difficult to move in the tracks, so I cleaned the felts, lubricated them with silicone, and adjusted them so the glass would slide easier. Hopefully the repair lasts longer this time.

Mike D · #9 09-30-2018, 07:07 AM

It's too late now but for future repairs take a look at Diseasel300's replacement sliders. He had some made up but he might be sold out now. He was talking about making some more.

The "Diseasel" - '86 300SDL

Another way to go which eases replacement. Thanks, Warren!

W126 rear window won't go up

Both of these repairs have the added advantage of not having to remove the regulator assembly if future replacement is required.

vwnate1 · #10 09-30-2018, 12:07 PM

? Is this a replacement part from where and what P/N please ? .

I'm amazed that Dorman, Champ items Et. Al. don't make a simple kit for this, they used to specialize in this sort of thing .

Squiggle Dog · #11 09-30-2018, 12:12 PM

Quote:

Originally Posted by Mike D

It's too late now but for future repairs take a look at Diseasel300's replacement sliders. He had some made up but he might be sold out now. He was talking about making some more.

The "Diseasel" - '86 300SDL

Another way to go which eases replacement. Thanks, Warren!

W126 rear window won't go up

Both of these repairs have the added advantage of not having to remove the regulator assembly if future replacement is required.

I saw those replacement sliders. They look clever. The clevis pin idea is smart, too. My roommate bought a pack of four of the stock sliders a while back, so I guess I have to use those ones up.

But, if this same left rear window slider breaks again, then it warrants heavier duty sliders. I can see why it broke the last two times, because the window was very hard to slide due to the tracks being too close together, but if it happens again, then obviously the stock sliders are just not up to the task. It seems that the newer the car, the more ridiculous it is in design.

Diseasel300 · #12 09-30-2018, 08:20 PM

That "thing" on the turbo looks like an air recirculation valve. Is your turbo a Garrett or a KKK? I don't see the boost actuator is why I ask. The 126FSM shows the ARV for 1987+ vehicles but doesn't show a vacuum wastegate. Mine's an '86 Federal with the Garrett turbo, so no emissions equipment and not a good comparison.

Squiggle Dog · #13 09-30-2018, 09:26 PM

Quote:

Originally Posted by Diseasel300

That "thing" on the turbo looks like an air recirculation valve. Is your turbo a Garrett or a KKK? I don't see the boost actuator is why I ask. The 126FSM shows the ARV for 1987+ vehicles but doesn't show a vacuum wastegate. Mine's an '86 Federal with the Garrett turbo, so no emissions equipment and not a good comparison.

I don't know. I can't even see the turbo much at all, but it looks different than the Garrett T3 that's on my car.

vwnate1 · #14 10-01-2018, 09:43 AM

I can't see the wastegate either so crowded in there but I'm betting that's your power problem .

You alls keep saying "vacuum" when talking about the wastegate, it works off _PRESSURE_, completely different .

? Have you yet tried a small, cheapo boost gauge to see what the actual boost levels and RPM's are ? .

I bought a 1" 'Mr Gasket' (cheapo Chinese brand) $20 fuel pressure gauge for boost testing my my grey market 300TD, it only goes to 15# so it's very sensitive, easy to connect using simple vacuum hose and a plastic 'T' , it would let you know what's going on in your engine boost wise right away ....

I'm trying to remember what FLAPS I bought the gauge at, prolly an O'Rielly as they're my go to place for cheaper filters and basics .

Diseasel300 · #15 10-01-2018, 09:50 AM

Quote:

Originally Posted by vwnate1

You alls keep saying "vacuum" when talking about the wastegate, it works off _PRESSURE_, completely different .

In a normal world, yes. In the 90s German car world, no. At some point in the early 90s, they migrated to a VACUUM operated wastegate actuator that's controlled by the ECU instead of the pressure operated wastegate that is passively operated off the intake manifold pressure. The 124's got it for sure, the 140's had it, but not sure if it was ever fitted to the 126 (hopefully not).

The ARV should be disabled when vacuum is not applied to it, but it could possibly be stuck partially open. If so, boost is bleeding off back into the atmospheric side of the compressor housing, more or less defeating the purpose of the turbo. Checking boost pressure will tell you a lot real fast. Put a T on the ALDA sense line and tie in a pressure gauge and go for a ride.