mercmad6.3
WOW, That was a rifle shot right to the bullseye! When I dug in I found that the hose to the auxillary water pump and the return from the heat exchanger, were connected to nothing. In their place a hose had been installed that connected the the two spigots on the heads together, thus leaving the heating system completely insolated.

My poor old, cold fingers couldn't be made to work in such a confinded space so I'm letting my local mechanic hook it it right tomorrow. Hopefully the second half of your prediction will be true also, and that it was done to correct a heater that wouldn't go off and not for a leaking heat exchanger. I'll post the results.
Thanks again,
Bob

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire