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

Squiggle Dog · #1 03-01-2014, 09:10 PM

A couple of weeks ago, GregMN sent me an email letting me know that he would be visiting Phoenix in the near future to pick up an ML320 CDI. He would be driving his 1991 350SDL down from Minnesota and returning in his new purchase. He offered to give me the 350SDL for free if I wanted it. All he asked was that I let him keep the wheels and battery.

Naturally, I was interested, but my roommate Jamie had been wanting a W126 for a long time and had been browsing through craigslist for them, hoping to purchase one when he had the money. He didn't want a gas-guzzler with a V8 engine, and he wanted the long-wheelbase version, but didn't want a "rod-bender" OM603 engine. His favorite car color is white, so I knew this would be a perfect fit for him. The 350SDL also has working air conditioning, and none of our cars here do. With over 100 days over 100 degrees, and summers as hot as 120 degrees, air conditioning really is a necessity. A few months ago, Jamie saw a W126 in the wrecking yard with nice Bosch Euro headlights, so he bought them in hopes that some day he would have a W126.

So, I decided to give the car to my roommate. Greg made it down and gave him the car like he said he would. I drove the car the 30 miles home from where Greg bought his new car, with him following behind. The car drove very nicely on the freeway. We pulled off the wheels and battery, chatted a bit, and he signed over the title.

It was a very thoughtful and generous thing for Greg to give away his extra car. It will be in good hands, as I am Jamie's personal mechanic. The body is in good condition. It just needs a little rust removal, touch-up, and buffing. The interior is in great condition. In fact, short of the driver side seat skin, it's nearly perfect.

The engine will be detailed, and fortunately, it is not the original OM603 "rod-bender", but from a newer W124 300D, and it's a great fit. The car has done well over 50,000 miles on waste vegetable oil, and has a complete, very well done two-tank system. I run nothing but B99 biodiesel in my daily driver 300SD, so it will be interesting to learn about waste vegetable oil.

Now we are on the hunt for a set of 15" or bigger wheels that will fit the W126, preferably with good tires on them. The transmission does not go into reverse, but I think that replacing the B3 valve will solve the problem. Greg has offered one from a spare transmission. We are hoping to have the SDL in daily use in the near future, as Jamie's current daily driver is having transmission problems, and he doesn't want to keep putting miles on his backup car (1965 Ford station wagon).

Below is Greg (left) and Jamie (right):

I will update this thread as progress is made on the vehicle.

suginami · #2 03-02-2014, 11:57 AM

What a great story.

GregMN was very generous in offering his car to you for free, and you passed it along by giving it to your roommate.

65aircooled · #3 03-02-2014, 02:32 PM

Very nice indeed, congrats to both of you!

Squiggle Dog · #4 03-06-2014, 12:47 AM

We were out at the wrecking yard looking for wheels, and all of the ones we could find looked bad or had the wrong offset. Then we saw a W126 that had 16" CLK wheels on it. Jamie got them, and we scrounged up a few wheel bolts as well.

They cleaned up nicely and at least now the car is off of jack stands. The tires are holding air. As I fit the wheels, the center caps popped off of the fronts. The grease caps were sticking out too far. Ugh! Then I realized why the W126 we removed them from was missing the grease caps. The CLK wheels clear everything, but not by much. I believe that spacers are needed.

The original wheels had an offset of 21.5mm, and the CLK wheels have an offset of 37mm. If we use 15mm spacers, this will bring the offset to 22mm, which is almost exactly the original specifications. Then again, those would be pretty thick spacers and we don't want the wheels sticking out too far. 5mm is all we need for the center caps to fit and to give additional clearance, but I wonder if it would be better to try to get as close to the original offset as possible. We could compromise and go with 10mm spacers. I am not sure what to do, and spacers seem expensive.

I've noticed that the light grey color lower plastic body pieces are difficult to find. Jamie wants to find a new front bumper and a jack hole cover. He's on the lookout for a pair of front fenders and a driver side door in the matching color so he won't have to repaint. We'll probably clean up the rust around the rear fender flares and will install chromed fender trim. I found a set of chrome door edge guards at a yard the other day.

Greg had a receiver hitch built for the car a few years ago, and they did a great job at it, as it does not impede the function of the bumper shock absorbers and looks strong.

Squiggle Dog · #5 03-06-2014, 12:58 AM

The interior of the car is nearly perfect. There are no cracks on the dashboard, the seats are in great condition, the original cassette deck still works, the locking center console box is still there, and it seems that everything works, even the air conditioning, cruise control, sunroof, windows, locks, and seats.

I wonder how difficult it would be to install a reclining rear seat.

The original 3.5 liter "rod-bender" 603 engine was replaced with a 3 liter engine from a 1990s W124 300D. It looks like the original engine and is a perfect fit. We will shine it up and make it pretty.

Greg installed a waste vegetable oil system and has run well over 50,000 miles on it. It looks very well-done.

moon161 · #6 03-06-2014, 02:45 AM

I like the back to back fuel tanks. The FPHE is usually a final heater and much closer to the injector pump than the trunk. Maybe there's a second one up front-doesn't look like he cut the tank to put a heated pickup in like is common in two tank systems. Don't hit this one w/ lard or PHO.

gatorblue92 · #7 03-06-2014, 07:20 AM

That is a pretty impressive hitch on there.

Squiggle Dog · #8 05-04-2014, 04:05 PM

I tried to install the set of Bosch Euro headlights in the 350SDL, but the existing headlight wiring would not plug into the Euro lights. I read a post that said to use the taillight plugs. I got some taillight plugs from a W126 and they did not fit because the pin holes were spaced too far apart. So then I removed the taillight plugs from a W123, and they fit. So, that was taken care of.

I put the headlights in place on the body and screwed in the two top screws. Then I looked under the car and saw that the brackets for the headlight wipers weren't even close to fitting. The USA and Euro headlight wipers are different. I thought the wipers would work with the new Euro headlights if I could figure out a way of securing the motors so they weren't flopping around underneath the lights.

I thought these things would be plug-and-play like the W111 and W116, but they were being really difficult to install. I was thinking of taking some steel and cutting out adapter brackets, but the dang wiper motors fit directly in the way of the mounting holes on each light, which discouraged that idea.

Euro wiper motors and brackets aren't easy to find or cheap. And then the holes in the valance panels are different between the USA and Euro wiper motors.

So, I thought about it for a while and decided to make adapter brackets. The motors mount to the body in one place, and also mount to the bottom of the headlight in two places. The engine oil cooler also had to come out to access the area underneath the left headlight.

There is a lot of difference between the bottom of the USA headlights, and the bottom of the Euro headlights.

Squiggle Dog · #9 05-04-2014, 04:08 PM

I started making some adapter brackets out of a length of 1" steel, available at hardware stores. Each bracket received a couple 11/64" holes, with one hole having an 11/32" hole partially drilled in order to fit a countersunk screw. After drilling the holes, I cut each piece out with a rotary tool.

I bought flathead countersunk 3/4" long #10 screws to use on the holes that attach the adapter brackets to the headlights. Even though they are SAE screws, the thread pitch was almost identical. This allowed the screw heads to not be in the way.

One of the clips will need to be flattened as it will be placed in between the adapter bracket and the bracket for the motor, and the lip that curls up would be in the way.

The 3/4" screws were a little too long, so I had to cut the point off of the ends so they wouldn't poke into the headlight body.

Squiggle Dog · #10 05-04-2014, 04:09 PM

Here is how the brackets looked after cutting, filing, and painting:

This is how they fit on the Euro headlights, with the new screws fitting in the original clips and the heads not protruding out the top (I used some of the clips from the USA lights on the adapter brackets):

I installed the filler panels from the USA lights onto the Euro lights.

Squiggle Dog · #11 05-04-2014, 04:09 PM

And here are the headlights in place with the adapter brackets:

Fitting the Euro headlights is tricky. It helps to have the panels under the headlights loose, as well as having the motors loose at the body so that the parts can be fit together.

The wiring harness needs to be altered to work on the Euro headlights. The USA headlights use a 4-hole plug:

And the Euro headlights use a 6-hole plug (which is the same as the rear taillight plug used in the W123 NOT W126--there are 2 versions, both will work):

Squiggle Dog · #12 05-04-2014, 04:10 PM

The wires need to be transferred from the 4-hole plug to the 6-hole plug like so (left):

Right:

If you are unsure of the wiring, you can look inside the headlight and follow the wires, which are the same color.

Before:

After:

Squiggle Dog · #13 09-24-2018, 09:14 PM

It's been over four years since I've posted an update, but a lot of work has been done on the car since then, and it is currently at daily driver status for my roommate. I will attempt to fill in what's happened.

I replaced the B3 valve on the transmission in an effort to restore the reverse gear. It did not, which left having to rebuild the reverse clutch pack. He didn't want to drive the car without reverse.

He bought a set of wheel spacers, but they didn't fit, despite being advertised as fitting the second generation W126. So, I cut off the lip that sticks out and ground away the stepped down portions on all four. It took all day to do, but now they fit and so do the CLK wheels.

Drawing trying to figure out how to make the spacers work.

Spacer on right is before cut, spacer on left is after cut.

Wheel spacers and bolts installed so center caps would fit.

Squiggle Dog · #14 09-24-2018, 09:48 PM

The engine was running roughly and I couldn't get it to idle or rev up. After much cranking, I couldn't get it to start, so I replaced the main fuel filter and loosened the lines at the injectors to bleed out the air. After this, the engine would idle. However, the throttle response was poor. When I put my foot down, the car crawled along, and then finally started to pick up speed after a few seconds.

I added some biodiesel to the main fuel tank, and the SDL passed emissions. I started the car the next day, and it was smoking lots of white smoke out of the exhaust, but the exhaust smelled like unburned fuel.

It seemed that the engine might possibly be low on compression since it had trouble starting when cold and the throttle response wasn't good at first. My roommate wanted a compression test done on the engine so he'd know if it was worth putting more money into the car.

Before I did the compression test, I ran the engine until it was up to operating temperature. Then right after I shut it off, I started removing the injectors. The test came back as follows: #1 405, #2 395, #3 375, #4 375, #5 405, #6 375.

The factory service manual states healthy compression as between 377-464 PSI. So, 3 of the cylinders were a hair below those specs, but should still perform well enough. The minimum acceptable compression is listed as 261 PSI, which is well below the numbers seen. The cylinders also shouldn't have more than 44 PSI difference. There is only a 30 PSI difference at most.

So, the engine passed. I figured the next most likely problem was bad injectors. I also looked through the injector holes to see if the glow plugs were functioning--only the number 1, 4, and 6 plugs were glowing!

I then did a "wet" compression test; I squirted automatic transmission fluid into each of the cylinders and rechecked. The compression went from #1 405 to 420, #2 395 to 410, #3 375 to 405, #4 375 to 415, #5 405 to 415, and #6 375 to 395. So, the rings were the cause of most of the lost compression, as opposed to valves or head gasket, but it's still acceptable.

Squiggle Dog · #15 09-24-2018, 09:56 PM

After the painful task of removing the intake manifold (yes, it must be removed on the OM603 slant 6 engines) I had easier access to removing the glow plugs, but once the plugs were fully unthreaded from the block, they would not pull out. Well, except for one which was the only Bosch plug in the engine. The rest were Autolites. Autolites do not have the tapered tips that the Bosch plugs have, so if they swell even a little bit, they will get stuck in the head.

I tried gripping the plugs with pliers and besides the Bosch plug, I was only able to remove one other plug by pulling very hard. I then tried a few other techniques such as using cheap wire strippers to grab the ferrule on the ends and even tried using a hammer. I also sprayed penetrating oil in through the injector holes. I then tried something different. I found a nut which fit on the body threads of a glow plug (which surprisingly seemed to be SAE threads).

I used a rotary tool and cut the nut into two pieces.

I then placed each nut half on the threads of the glow plugs since the plugs were no longer threaded into the holes, just stuck at the tips. If you run out of threads, you can place a shim of some sort (like a washer) between the nut and head.

I put a 19mm (3/4") wrench on the nut and then used a ratcheting 12mm box wrench on the glow plugs. As I turned the glow plugs, the nut would move closer to the head and then it started to push out each plug.

And out come your Autolite plugs that you thought were such a good deal. It works very well! I had them all out in about 5 minutes. So now I know an easy way to remove stuck glow plugs.