Dave,

my point it that I can't see, or have seen proof, that closing the rear heater valve will cause any harm to the heater, given that the van has a good charge of coolant. There is no proof that anything will precipitate out as you think it would. What suspended matter is there in the coolant? If you can tell me that then we can have a discussion. Perhaps take a sample of your coolant and let it sit for a while and see what drops out? 

alistair

On 2012-11-19, at 12:38 PM, <mcneely4@cox.net> wrote:

> Alistair, while I agree that chemical environment matters to chemical processes, I am not sure that the facts you cite would prevent precipitation of suspended matter in a static setting with tiny passages.  But, I (like others) have been wrong before.  mcneely
> 
> ---- Alistair Bell <albell@SHAW.CA> wrote: 
>> Dave,
>> 
>> the comparison you make between a car's cooling system:  
>> - closed loop, low O2 (if not anoxic), water, ethylene glycol, corrosion inhibitors 
>> 
>> and a dishwasher:
>> - open loop, O2 rich, water, caustic cleaning solution
>> 
>> doesn't warrant much more thought than just how bad an analogy you made .
>> 
>> :)
>> 
>> alistair