Our W123 ('81 300TD) has a new old motor that sat for many years in a warehouse. This motor seems to run about 10-20^C higher than its predecessor so I decided it would be a good idea to clean the cooling system. Thanks to all the folks who have posted their procedures and the excellent information in the shop manual, it was a successful day (or 2).

I started at about 9:00am on Saturday and finished at about 1:00pm on Sunday. I drained, flushed once, de-oiled, flushed twice, decalcified and derusted for 100+miles, flushed 5 times, and filled.

The most time consuming bits were waiting for the solution to cool after each cycle. That and looking for the drain bolt and washer when they went missing in the engine and frame and in the gravel a few times.

Something that was useful to know, but not explicitly noted in the threads here, is that you need to run the defroster and run the motor until you get hot air coming out of the vents to make sure you have solution reaching the entire system.

Another thing I would like to know is what others have done to redirect the engine block drain flow. It runs down onto the frame and spreads the flow all over the place. It's worse than changing the oil on our '85 Mustang where the drain plug was right above a frame member.

I used an temperature sensor gun to check the temperature sensor and gauge. It reads about 10^C to 20^C high. Is the sensor replacement difficult?

The drain plug takes a 19mm wrench. I used a 4in extension to remove it and an 8in extension to remove it (to keep my fingers further from the hot solution). There is plenty of room to get to it from the bottom.

I had the front wheels on ramps and that gave me enough space to work comfortably, although I was lying in muddy gravel every hour.

All in all, it was a straightforward, yet time consuming job.

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Mike

1980 300SD
1981 300TD
1998 E320 Gasser Wagon
2000 SL500

Did you read some of the horror stories of flushing? Sounds like you lucked out.

You can install a drain valve on the block drain, put a hose on it, turn the valve and drain it into a jug without spilling any.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Either he lucked out, or in about a month....he will be tearing the inside out of the car to replace the heater core

To the op...

The thermostat may be an after market, causing the temp reading differences. You may not have bleed all the air out of the system. You may need a new fan clutch and radiator.

Did you replace a non Turbo engine with a Turbo engine or visa versa?

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Yes, I did. Wouldn't be the first time I was lucky.

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Mike

1980 300SD
1981 300TD
1998 E320 Gasser Wagon
2000 SL500

firstly - love your nick - lambretta.,, my dad had one of them.

anyway

if you are seeing a consistent hot running engine - its usually a case of a faulty thermostat, For flushing I always use a 5% solution. not too aggresive and easily flushes out.

I have even flushed GM dexcool rust deposit cars with it and they come out squeaky clean.

The horror stories of system failure are usually due to extreme neglect and on the verge of failure - and IMO you dont want yourself rolling in that car for any duration of drive.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I have a vintage scooter sickness, we have 4 of them from 1961 to 1967.

I was pleasantly surprised with how much stuff didn't come out with the flush. I know that any issues would have been in the block because the radiator is a couple years new and the car was well maintained and running and cooling and heating well. Based on the reported mileage of the donor motor, it had been sitting for 15-20 years. I wanted to clean that junk out. I know I didn't need to do the heater core, but wanted to know if it had any issues.

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Mike

1980 300SD
1981 300TD
1998 E320 Gasser Wagon
2000 SL500

Ok. It's been 2 weeks now. We can put my vehicle in the "tolerated the acid flush" column. I appreciate the concern.

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Mike

1980 300SD
1981 300TD
1998 E320 Gasser Wagon
2000 SL500