My 1989 Mercedes 560 SEC

Jupix

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Last week I went to visit my 560 SEC buddy and borrowed his engine idle relay. The high idle speed problem was not fixed but the effort wasn't a complete waste: it appears my idle relay is functioning correctly, or both of ours are broken. Anyway, next in the saga of high idle speed I will be looking at the IAC valve again.

The idle relay is housed in the passenger footwell, next to other electronic equipment such as the OEM alarm system, Webasto control unit and stereo cabling. This space is covered by a plastic "kickplate" that is tightly fastened to the firewall with a plastic nut. The floormats rest atop the kickplate. While we were swapping idle relays, I found that my plate had gone missing at some point in the cars life. I turned to my trusted W126 spare parts guru and he sent me a mint part along with the special plastic nut. Here's some pictures of what a W126 footwell looks like. Note that mine has a lot of non-OEM cabling for the retrofit alarm and stereo.
















I promised pictures of the new stainless steel exhaust tips. Here they are.








One more thing. We looked at the W126 microfilms and it appears the OEM radio for this car was indeed the Becker Mexico Cassette Diversity. The Diversity was a revised model of the Mexico Cassette unit, and was introduced in I think 88 or 89. It was the first radio with a dual tuner and featured, for example, automatic volume adjustment for vehicle speed. The radio reads a signal coming from the speedo. These radios are pretty rare to find as standalone units, usually they have to be sourced from a "spares" car. Refurbished units in retail can go for as much as 500 EUR. On ebay, they cost anywhere from 150 to 300 depending on condition and accessories. I may have a chance of sourcing one with a minor technical issue from a forum buddy for about 140 but this remains to be seen.

 

Jupix

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Same dude sent me a nice original gearlever:



It's made of sturdy leather, and in basically mint condition.

It's a real bitch to install, so it'll have to wait a bit...
 

Jupix

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Changed the bulb in the headlight switch.



Technically this is two bulbs. One is for the foglight caution light, and one for the surround lights. The latter is derived via fibre from a single bulb.
Pull off switch, pull off foglight bulb, undo the large flat nut, pry off switchplate, pull out the rectangular bulb housing from the back. Repeat steps backwards, done. Based on memory I think this goes for at least the W126, W124 and W201 mercs.

It's noteworthy that the OEM bulbs in Mercedes consoles are both low wattage and slightly fogged. These you have to source from a dealership or an OEM part supplier. You can get correct wattage bulbs from spare part retailers but the shade will be slightly off, due to the bulb lacking the fogging.
 

matyas

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It's noteworthy that the OEM bulbs in Mercedes consoles are both low wattage and slightly fogged. These you have to source from a dealership or an OEM part supplier. You can get correct wattage bulbs from spare part retailers but the shade will be slightly off, due to the bulb lacking the fogging.

I have this task also ahead of me. What was the price per dash bulb, out of curiosity?

And a warning to people looking for these bulbs, don't even think about getting a higher wattage one. It might be brighter, slightly, but it might melt the plastic. One of the blower-switch bulbs burnt through the damned switch...another great gift by the previous owner :mad:
 

Jupix

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The bulbs are about EUR 2,50 per. Like I said the headlight switch assembly takes 2 bulbs. On manual A/C, the air controls take 4. Gearshift illumination consists of 1 bulb. Note that this is for my car. If I understand correctly, old W126 models have some differences, like precisely in the headlight switch assembly.
 
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Jupix

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The 560 has now been in my possession for exactly 1 year. During that time, it covered 8300 km. I've bought a total of 1290 litres of 98 octane. That makes average consumption 15,54 l/100km. This is almost exactly in line with what I get on a per-tank basis these days. "Cheap 98 octane" was 1,39 EUR / litre when I bought the thing, now it's 1,59 EUR / l.

The list of stuff I've done to the car is long, and it's all here in this thread, so I shall not repeat.
 

Jupix

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The idle speed was getting steadily worse as time passed. A few weeks ago I put the Merc away for a while because the high idle was becoming intolerable. I would be idling at 1600 rpms while hot and in neutral. Also, while underway, the car would speed up to about 60kph without touching the throttle.

I was able to switch IAC valves with the buddy with another 560 SEC. His part brought the idle speed down a couple hundred rpms. We knew his was probably bad as well, but it was certainly in better condition than mine. His car is the ECE version, with a different fuel injection system, so minute differences in how the engine controls idle probably resulted in a measurable difference in idle speeds despite having the same basic engine and same IAC valve. Mine idled a bit higher than his with the same valve.

Anyway, it was clear that despite getting a clean bill of health from my mechanic last winter, my IAC valve was in dire need of replacement.

It's a relatively expensive part. I didn't even dare ask how much it costs at Finnish retailers. I know from reading forums that it's in the hundreds. So, we organized a group order from Autohaus AZ with a couple 560 SEC owners. They stocked both the VDO (original) valve and related rubber hoses at a fair price ($185 for the valve and about $10 for the hoses).

After about a 3 week pause, I'm driving the Merc again. I have to say I was beginning to miss it pretty bad. For the past weeks I've been driving my dad's 1969 Renault.

First impressions with the old friend 560: damn it's big, damn it's quiet, damn it feels heavy, damn it makes a great soundtrack.


Here's where the IAC valve goes. Removing it is really easy, literally a 5 minute job. You only have to take off the air filter casing. After that, and removing the electric connector, the IAC valve lifts off the metal pipes you're seeing here. Originally there's a rubber fastener around the valve, as seen in the next picture, but mine was broken and didn't really do anything, so I just leave it off. Better take the right side rubber hose off first, while dodging the vacuum connectors on the left. They are fragile and cause problems if they break. After this the IAC valve wiggles off the downward facing pipe.


Here's my old IAC valve. You can feed it 12 volts, polarity does not matter. If I understand correctly the valve should close completely. In the picture it's powered up but has only closed the amount you can see there. I think this was partly responsible for the high idle issue.


Here's the new valve installed. As you can see it's really polished and looks like a quality part, as it should, since it's a VDO. The new rubber hoses were pretty soft and had a really snug fit, totally unlike the old hoses. I was probably sucking in lots of extra air through the rubber hose fitting imperfections with the old parts. That probably contributed to the high idle issue.


All said and done! Once I fired it up it immediately felt more healthy. It did the usual rpm adjustment routine like it should, ran 10 seconds or so at 1000+ rpm, then brought the idle speed down a notch, and again after a while. I'm now idling at about 500-600 rpm while warm and in gear, and about 800-900 rpm while in neutral. No irregularities or anomalies in the idle speed now. This fixes a lot of issues. Now since the idle is so low (meaning normal), engaging a gear doesn't feel as violent as it did before. Also, the car sounds much healthier since it's not constantly "fighting" the high rpms. I'm also now probably using a bit less fuel. Win-win.
 
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Jupix

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It's a model 8 Major with the 1100cc fourbanger and 4 on the floor. Rear-engined of course. In fact it's in every way a polar opposite to the Merc: manual, nimble, light, noisy and buzzy, French, absolutely 100% reliable, and extremely extremely cheap to run. My dad bought it almost new in the 70s and since then it's been in the family almost non-stop apart from one excursion of a couple years. Sadly, this time of year its heater is hopelessly underpowered and the windscreen gets frozen real quick when it's minus degrees outside. And anyway, it hasn't got winter tires.



Also, It has no place on these forums since it's not 100% mine.
 
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Jupix

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I received a new toy today. (finally)



It's a Becker 830, the exact period-correct model that shipped with these cars.

Acquiring it was a journey in itself. We bid on it on eBay, from a German seller. Got really excited when the final bid ended up at a mere 120 EUR more or less. These can go for as much as 200 EUR on eBay. Shipping took foreveeeer. When it arrived the tape deck wouldn't work. This of course has an electric tape deck that sucks in the cassette in a neat way when you just gently press it in. Anyway, the electrics were out. Thankfully the eBay listing had a guarantee clause (for a 20 year old radio!) and the seller had the good sense to uphold it. So we sent the thing back to Germany. Seller received it and said it was fine, and that he was gonna send it back without really doing anything to it. Now we were getting really worried. Couple of weeks later, here it is again and as my buddy tested it, it worked fine.

Overall, it's in great condition. All the lights work, radio works, and all the buttons feel good and similar.

Now I just need to worry about wiring, since it uses the old style proprietary connectors. I'm already trying to source a power connector from eBay.

I'm going to rip out the aftermarket front speakers and try to use the original speakers.
 

Jupix

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If the gearshift lights on your W126 are out, the problem is most likely a blown bulb, as usual with center console illumination. There is one bulb down under the front of the gear selector "box", which is located under the large wood panel. This bulb illuminates the gear symbols, and the fiber that accompanies the shifter, adding a brighter light to the currently selected gear.

First you have to take out the ash tray. It's held in place with two philips screws located under the chrome cup. Unscrew and pull.

After this, the front section of the middle wood paneling lifts off. You have to lift the front end of the panel, after which the whole bit lifts off. This may be either a wood panel like mine, or a storage tray, depending on model/year/options.



Once that piece is off, the large wood panel slides forward and lifts off.



Do not just lift, the plastic clips that hold the panel in place will break.

Completely removing the panel is not necessary to just replace the gearshift bulb.

The bulb is the white piece visible straight below the front tip of the wood panel:



Pull bulb housing downwards, replace bulb, repeat above steps backwards. Enjoy your great new illumination !


Ripped out the aftermarket front speakers that stood out like a sore thumb. Spot the difference:



 

Hartkor

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That gear-knob looks somehow wrong? Is it an aftermarket one? Otherwise I tip my hat to you good sir for preserving such a nice car. And it looks much nicer without the speakers
 

Jupix

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That gear-knob looks somehow wrong? Is it an aftermarket one?

Yes.

While I was in there, I looked at how the gearshift shaft is connected to the box. My plan was to change gearlevers immediately. Unfortunately, it doesn't look like this will get done this time round.

The shaft is screwed on with a locking nut at the far end. The far end is obscured by a rubber sock, hidden inside the shifter box. To get to the nut, I'd have to unscrew two easily accessible screws at the top, and four bolts at the bottom.

The four bolts are proving a problem and basically preventing the whole thing. They are located under air ducts heading to the rear passenger compartment. To remove the air ducts, the side panels of the center console have to come out. To remove the side panels is basically an equal task to just lifting the whole center console out the car.

In addition, it is recommended that the gearlever be separated from the gearshift linkage before it is taken out. This has to be done from the underside of the car.

The knob cannot be simply swapped from the shaft I bought to the one in the car. OEM leather knobs are sewn onto a T-shaped shaft. Separating the knob from the shaft would require cutting the seams and peeling the leather and filler off the shaft in pieces. The aftermarket knob has been installed by a PO by dremeling an OEM knob off the shaft, and attaching the knob to the shaft-stub with a silicone-like paste.

In a nutshell: installing the OEM gearshifter is a real bitch of a job and won't get done now.
 

Jupix

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The center console wood had some pretty bad scratching and swirl marks:



I decided to sand and polish it while I was switching the gearshift bulb.

First, 1500 grit sandpaper





Then 2000 grit sandpaper.

Finally, a rubbing compound with a semi-hard cloth. Result:



Whole piece done, and waxed:



The lacquer on it has cracked in several spots, but that obviously cannot be fixed. The only way is to refinish it. Doing that, you'd have to do the whole vehicle, since the result will most likely be kinda "off".



The radio is not wired yet, but I did put it in place since I'm out of time and have to drive the car to places.



I was able to source all connectors, so all that remains as far as wiring, is identifying all the speaker wires and soldering the main power connector to the wires.
 

Posmo

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For all the hard work you're doing putting the car back into standardish form, I think the BBS wheels would be better suited to a different car. The Pentas however look extremely good on the car, and it's a shame if they're on winter wheel duty.
 

Lastsoul

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There's a golden rule for wheels:

Classic BBS wheels fit everything. :)
 

Jupix

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Actually, lately I prefer the Pentas' look enough that I've been thinking about getting a second set, and selling the BBSes.
 

matyas

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Great to see! Though let's be honest, I really doubt you could have expected anything else. :)
 
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