GregMN's 1991 W126 350SDL Has A New Home - Page 4 - PeachParts Mercedes-Benz Forum

dude99 · #46 09-28-2018, 11:54 PM

That sounds a lot like a bad or failing turbo. Have you checked your boost level?

Diseasel300 · #47 09-29-2018, 12:23 AM

Sounds like a turbo issue to me too. Does the 350SDL have the overly complicated vacuum wastegate setup, or is it pressure operated like the 300SDL? It won't set any speed or acceleration records, but it should get around pretty good in town. The black smoke is a very good indication that there's a lack of air. Has the manifold ever been off and the coke/sludge cleaned out? If it hasn't, you could be in for a real shock. My SDL's was choked off to the point that the intake runners were only around 2CM in diameter because of the coke/sludge buildup.

Squiggle Dog · #48 09-29-2018, 03:03 PM

The turbo impeller bearings feel smooth and like there isn't a lot of play. I don't know if the wastegate is operating properly. There is some kind of vacuum device under the air cleaner that looks like it might have something to do with the wastegate. I think I'll have to do some research to figure out how that works. I remember it was hard to see down there because it's such tight quarters.

The turbo seems to make sense. The fuel economy has also been gradually getting worse.

The intake manifold has been off and I cleaned it out inside.

dude99 · #49 09-29-2018, 06:15 PM

Maybe before you go too nuts trying to figure it all out, just hook up a boost gauge? Then you know if you even have a problem before you go looking for one.

Squiggle Dog · #50 09-29-2018, 06:26 PM

Quote:

Originally Posted by dude99

Maybe before you go too nuts trying to figure it all out, just hook up a boost gauge? Then you know if you even have a problem before you go looking for one.

I was going to do that a while back, but think I ran into a problem of not finding a place where I could hook up the gauge or something. I'll have to look into it. I get confused as to what I've done and haven't done because there have been so many problems happening with the car that I keep jumping from one thing to another.

Squiggle Dog · #51 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 · #52 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 · #53 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 · #54 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 · #55 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 · #56 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 · #57 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 · #58 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 · #59 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 · #60 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 .