I'm planning on changing the coolant in my M103 for its 90,000 mile service. I've got the service CD and a gallon of MB coolant (from here) but though I'd query this vast wealth of knowedge regarding any tips. For what its worth the car seems to be running a little hotter in this cooler weather, its been getting down into the 60's here in So Cal. I've only had the car a year and a half so I'm not completly familiar with its seasonel perks. Could it be its just keeping itself warm, or is it the old coolant?

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)

After changing my radiator due to the neck breaking, and replacing the coolant with mb coolant. My car runs at 85-90 maximum in 100-110 degree weather.

Normally in anything else it is usually around 80-85.

And I have the AC on all the time. it never goes off at all.

I'm in Los Angeles, and in stop go I have yet to see my car break 90 at all in the heat.

With the current temps, my car is at 80-85 as always.

Alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon

How about some answers to some specific questions. Could anybody define “flush?” What I’ve done before is fill and drain with water a couple of times. Does that technique hold water? And what about draining the block? And where exactly is the drain plug? I was also wondering about the thermostat, would replacing it for maintenance be a good idea? I foggingly remember something about a plastic housing that should be replaced. Is that something else to do?

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Jim,

You want to drain the block as well as the radiator. Be sure to set the heater to max heat, to allow the heater core to drain. You will probably want to do the citric flush. The MB stuff is recommended, but others have posted some off the shelf citric acid cleansers. The citric acid will help in removing the scales and crust from within the system.

After flushing you'll want to rinse and drain the system probably three or more times. This can be a pain on your car, as you have to fill the system through the expansion tank, I think. It may be a pain, but you'll have to do it.

Not sure exactly where your block drains are on the 103, on the 117 they are near the motor mounts (left side in front of/right side behind the mount) and should take a 17 or 19mm socket. Let the car cool a bit before taking out the block drains or you may get scalded.

You shouldn't need to degrease the system if you haven't had a head gasket leak (another flushing using degreaser).

It couldn't hurt to replace the T-stat while doing the coolant change. Be sure to index it correctly.

For refilling, you will find it easier to pre-mix your coolant and water before filling the system. Shoot for about a 60/40 mix and you should be fine. Might want to add a bottle of water wetter to the mix.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

I did a full flush just the other day. As mentioned above, you'll need to drain the radiator, and the block itself. A picture of the block drain on the M103 is attached below. I think it's 17mm and with about a 6 inch socket extention you can reach it from above without going underneath the car to turn it.

Drain all coolant then flush with appropriate agent (citric for buildup; degreaser for any signs of oil -- SHOUT! works well, 3 bucks at your local grocer)

After the flush, fill with regular water and run engine some more. Drain again. Now take a water hose with both drain plugs open and stick it in resevoir filler until you see clear water draining from both locations. Tighten drain plugs and fill'er up with coolant/water and you're good to go.

FWIW you'll find that your auto climate control works better after a good flush. Don't ask me why but I actually get fan speed changes now when in auto mode, where before I didn't. Maybe someone else can explain this one.

Good luck!

~Paul

Looking at left side of engine:

In my case,t he car had hardly any fluid left in int after the radiator broke.. and I did a flush my way, I ran water through until all the green stuff was gone... hehe

I refilled from the raditor top hose to make it easier and used the expansion tank.

Alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon

You can refill coolant by removing a threaded plug on the head on the intake side near the rear. (that rhymes )

That is what I believe I read in the service manual yesterday.

I wondered what that plug was under the exhaust manifold when I had my engine out the other week. I should have removed it and anti-siezed the threads when I had the chance while the block was on the stand.

Still waiting for the darned chain crimp tool!

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

pmizell: Thanks for that picture, thats exactly what I need


The service CD says "For draining and filling of coolant, see repair
instruction 20-010." (Cut & Paste right from CD) Where and what is "instruction 20-010."

And what about the plastic housing?

TIA