New W123 owner, a few questions to start. - PeachParts Mercedes-Benz Forum

i_amnt · #1 10-06-2014, 11:04 PM

I just purchased a 1985 300TD Turbo Diesel, Manilla Beige (or maybe ivory, I still have to check the color code) with palamino interior. 236k miles and seemingly in rather good mechanical condition.

My first line of business is to fix the vacuum system. It seems overall it's just leaky, nothing is failing but everything is just slow or with it's quirks. For example when cruising around 60 a whistling will start quiet and grow louder until you give it more pedal and then abruptly goes away. The auto trans shifting is understandably a little rough, but nothing that is too out of control. Also, you have to be sure to turn the key slow when turning off the car. The first time I shut it off it kept running with the key out. When I went to open the hood to turn the engine off manually, it shut itself off.
The previous owner told me that the first thing he would do is buy just about every vacuum fitting, elbow, 3-way or 5-way or whichever that I can find off the EPC and replace them as I work my way through various repairs on different parts of the car over the next year or however long it takes.

Is this generally a good way to revamp the vacuum system? I also would plan on replacing the plastic distribution valve piece I think I read on ************** or DieselGiant. The right name for the part escapes me right now.

The other issue I need to address is the Self-Leveling Suspension. It's rather springy back there and makes for a bit of a jarring and bouncy ride down the expressway. That seems to be it's only symptom. No leaks to be found and it has a new hose going from the accumulator running the length of the car back to wherever it connects. It was also flushed with new fluid until it came clean. He said he wasn't really sure on how to bleed them properly. I'm trying to do some research but I feel I need a good rundown on how the system works. I was considering buying the ***************SLS system operations and diagnosis and troubleshooting guide.

Other than that, it seems in great shape, maybe I'll get out the good camera tomorrow and get some pictures.

uberwasser · #2 10-06-2014, 11:16 PM

It's not a BAD thing to go through the vacuum system and replace the rubber connectors, 3-way and 4-way's. But you can also gain a lot by being more methodical and testing the various systems. Check out this door lock diagnosis guide I wrote. It was done on an earlier W123, a 1979, but the concepts are very similar for your door lock system and for other vacuum systems on your car.

https://www.ifixit.com/Guide/Mercedes+W123+Vacuum+Lock+System+Diagnosis+Technique/20201

Someone else would need to chime in on the SLS. Best of luck and congrats on the new car!

vstech · #3 10-06-2014, 11:42 PM

This forum is PLENTY for diagnosing and repairing the SLS system on this wagon!

First, you are going to need new accumulators. They are steel spheres near the back wheels. They control the fluid dampening, that controls the bouncy ride.

Those "guides" are nothing more than reprints of the Mercedes FSM and it's free.

uberwasser · #4 10-06-2014, 11:50 PM

What guides are you referring to? The one I linked to and the ones like it? I put a lot of work in to the 60+ guides I've photographed and written descriptions for. I document the jobs as I do them, they are not just reprints. In some cases they go beyond the FSM in many ways, with better pictures, more user friendly descriptions, details about "gotchas" I came across doing these jobs that relate to working on these cars that are 30-35 years old, etc. And for some topics, like vacuum system diagnosis and repair, I have never seen a usable FSM section for so I wrote a detailed guide.

And they are all also completely free.

i_amnt · #5 10-13-2014, 08:18 PM

I believe he was talking about the guides on a certain website that rhymes with kercedes kource. I will definitely be picking up a FSM instead. It looks like they are the original accumulators, so I may just go ahead and change them out. I see conflicting views about whether rebuilding the SLS valve is worth it, or if it will just go ahead and leak out. But, I think I'll start with the accumulators.

I am waiting to purchase the FSM in a week or two, but does anyone have any clue why my vent blowers would only work when the engine is off. Going to replace the seals and recharge with R12 and see what happens. If not, I may attempt to rebuild with a sanden compressor.

uberwasser · #6 10-13-2014, 10:07 PM

The FSM is available for free at startekinfo.com under MB Workshop Resources, Service Manual Library.

If your blower is only working with the engine off you might have a faulty ignition switch. Or perhaps faulty cold engine lockout. Just a few ideas.

dieselbenz1 · #7 10-13-2014, 11:39 PM

Listen to Vstech I agree you need new accumulators.

mike-81-240d · #8 10-14-2014, 09:13 PM

New accumulators.

i_amnt · #9 10-17-2014, 09:34 AM

Alright, ordering some accumulators and will be picking up a windshield seal and MB hydro fluid for the SLS from a nearby dealer. I thought my only issue with the HVAC was no a/c. The ignition was keeping the blowers from working while engine on. A jiggling of the key got the blowers to work this morning, but they seem to blow only cool air, not hot, not cold. So, I thought I'd have all winter to get the A/C working. But, with no effective defog, that could get dangerous. If that temp sensor mounted between the center vents goes bad, could it cause an issue like this?

Also, the engine seems to run very cold sometimes, like on a cool evening going 60mph, it will get down to 60*c. Once or twice on a hot afternoon, the aux fan kicked on and brought it back down to 80 from around 100*c, which seems normal.

leathermang · #10 10-17-2014, 02:49 PM

No defog is very bad....
check your thermostat for the low temperature of the engine.. IF you are sure your temperature sending and receiving units are reading correctly...