that car has a balance tube from the top of radiator to the expansion tank.it sounds to me as though the tubes have shrunk in the radiator and it needs replacing.

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David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
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