i recently purchased a "new" 87 190e 2.6 (158,000) seems to have a strong engine & trans. the interior needs a little tlc but functional. when i bought it i noticed the heater core was bypassed, not a big problem in so. cal. but i thought i'd check w/ you guys on difficulty of changing this, and/or how to test the aux water pump for proper output (maybe the only problem?) i've changed heater cores in other cars but this is all german to me!!