remove thermostat when flushing w123 diesel cooling system

I don't know if I am reading the MB manuals correctly, but it seems to me that in the topic (20-015) on cleaning the cooling system (deoiling and decalcification/derusting) they say to remove the thermostat when
performing this. Is that correct? What is the reason? I can't imagine the t-stat being damaged by a bit of cleaner. If it is neccessary to remove the thermostat then what do you do--reassemble its housing without it before doing the flushing? I am assuming you have to leave the seal in?
Oh, and what kind of place sells citric acid? (for the decalcification)
This is all for a 1980 300 non-turbo diesel (W123 with a 617.912 engine).
George
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Calcification is pretty rare if the coolant is MB coolant and regularly changed... Pep Boys and alike should have citric acid cooling system flush.
Thermostat removal is a must or whatever you pour into the cooling system will not circulate to the radiator... only the engine if it ever gets there... so by removing the thermostat, you allow the whole system to circulate regarless of engine temperature.
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Ditto (for the t-stat removal).
Whether the seal is put on during flushing does not make much difference. The seal isn't very tight without t-stat anyway. Also, flushing is only a short period. There will be some dripping.
If I remember correctly, the MB manual mentions citric acid for deoiling. I guess that may be necessary after a head gasket failure. I have never found any retailer selling citric acid, thought in most cases it is mentioned in food/grocery/chemical trade so I was a little bit surprised when I saw MB manual mentioning this. There are some people selling citric acid on eBay but I am not sure if there are different grades for food or industry usage.
Tiger wrote:

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the problem is i don't know exactly what's inside--this is a used car and on top of that i just installed a second-hand radiator. i thought it can't hurt. i don't really see any signs of calcification but i do see some rust and the citric acid flush is for derusting, not just decalcification.

got it. thanks!

"neutral or mildly alkaline cleaner" for deoiling. "citric, tartaric or oxalic acid" for decalcification and derusting.
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