I have just bought a 1988 MB 300E from a friend for $1500, and I just wanted to find out about a few of the small issues it has. For the most part it runs really well, but it does have a few things:

1)Running hot...it hasnt overheated(according to my friend, it never has), but it does run hot in traffic, and when I start it after turning it off for anywhere from 5 to30 minutes. It starts to run really rough if it is idling or not driving much.

I am not so concerned about the heat problem as I am about the rough idle. I know that it is related somehow(directly or indirectly) because the car runs really well on the freeway when it gets a lot of airflow, and even for a good while after exiting the freeway, but if I have to wait a while at a few stop lights, it will start back up again.

Now I am not sure the heat is 100% of the problem...because my friend has told me that when it has run warm before, he didnt have the same problem.

With regards to this, there is an idea of a fix...as the auxiliary fan has been quite erratic...sometimes it only stays on for a few seconds. A possible short or bad relay. However, like I say, I am not sure the heat is 100% of the problem.

2)Sometimes the transmission will start out in second gear. I have been told I am due for an tranny flush/filter change. Will this fix the problem?

3)When accelerating fast, and the transmission shifts, either up or down, I get a "loose" feeling from the rear end of the car. I took a look at the rear end suspension, and everything seems fine at first glance except the differential. The bushings that mount the differential to the subframe are comepletely gone. I plan on getting that fixed on wednesday...but I do have to ask if that is the problem with the loose feeling? Its almost a side to side motion, and I am a little curious if a loosely mounted diff can cause that kind of motion.

I believe that model transmission always starts in second, my '86 300E does. If you feel you need first gear from a standining start, place the selector in the '2' position. The transmission will now start in first. Then move the sector to '3' and let the trans shift to second, quickly pull the selector back to '2' and it will hold in second. Then you move the selector to '3' again and let it shift to third gear. Then move the selector to 'D' and it will shift to fourth.

This is sort of a manual shift method to get all 4 gears. I practiced it until I could do it fairly smoothly but it really doesn't seem worthwhile unless you just like to play with the trans. Later models use all 4 speeds.

Draining and replacint the transmission fluid would be a good idea anyway.

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1986 300E
1993 Volvo 940 Wagon
1984 Volvo 240 (daughter's)
1976 Dodge 1/2T pickup, gas hog

It is hard to diagnose a rough idle over the internet. It could be ignition wires, an injector, fuel distributer, or even engine mounts. I'd be more concerned about the temperature. You can start with the simple things like testing the pressure cap and replacing the thermostat. Check the radiator for redtrictions with your hand. The fan clutch may be failing, but I would reserve that for last. Fan clutches like carburetors are always blamed, but are rarely the problem.

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Auto Zentral Ltd.

What do you consider hot? 90 to 95 Celsius is typical.

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Norm in NJ
Next oil change at 230,000miles

Norm,

Agreed for later cars with electric fans, but this car should hang at 80*. This is still an early car with early technology.

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Auto Zentral Ltd.

My engine fan works perfectly fine. The auxiliary fan is problematic. It will switch on and then off in just a few seconds, and sometimes it works when the car is hot, and sometimes it doesnt. I am thinking a bad relay, but I am going to try to troubleshoot it with a friend who knows electronics.

The car runs impecable on the freeway, and the temp is 80C.

The engine mounts are okay it would seem. They are definitely old, but they are okay.

The car is carburated, so its not an injector.

I just put new Bosch platinum plugs in(although I have been told that it is better to stick with the OEM Bosch coppers). The wires might be a little old...

What Do You Mean Carbureted? Where Do You Live?

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Auto Zentral Ltd.

Stockton area(Manteca)...

Its not fuel injected...I believe they started injecting this engine in 93.

Nope, hasn't been a carburetored MB in USA since early 1970s.

Or carburetored anything else from Germany for that matter. (except motorcycles)

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

That is what I thought. If it is an 86' with the original engine, then it is definitely fuel injected. A lot of people get confused here because the air cleaner looks like it has a carburator, but that is just how it looked on the earlier models.

Something that hasn't been mentioned yet is that the above symptom on an M103 is a classic sign of leaky valve seals. How's the oil consumption?

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1989 300 SEL that mostly works, but needs TLC

This is why I get pis*ed when people don't state the specs on the car or where they live. I will actually be driving through Stockton tomorrow morning on my way to Angel's Camp which is were Mark Twain did a considerable amount of his writing. Manteca is a few miles off on Hwy 4, but I won't be doing any water slides this time of year.

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Auto Zentral Ltd.

Erratic electric fan operation can also point to a plugged radiator, which can be a bit tougher to diagnose. Plugged radiators will have hot and cool spots in the core. having a fan on the front and back of the 124 radiator makes it almost impossible to tell if that is what's happening. Test for electrical gremlins first, but don't rule out a bad radiator.

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Fourings

84 Audi Coupe GT with Turbo engine, EFI (buh-bye CIS), Jamex seats, Koni's/H&R's, e-code lights. 210k and counting.
1992 Anthracite 400E, 161k, "Grey Ghost".
1986 VW Quantum Syncro, 192k, gone to the crusher in the sky.
1989 300TE 172k. (Was mine, now also Mom's car)
72 280SE 4.5 (Mom's car)

1884 300d Turbo 135k
I Had A Olds Run Hot And The Engine Misfire It Was The Fan Clutch
$43.00 Pep Boys 15 Mins Done, Turn Off Engine Hot And Try To Turn
Fan If Loose Replace Fan Clutch

Same issue here, currently looking for a fix...