Auxiliary Water Pump

My 1987 300E has a leak in the cooling system that appears to be coming from the Auxiliary Water Pump. I understand that this is used to pump water into the heater core during engine idle. I called the local MB
dealer who quoted me a price of $357.50. I found a new one online for $118.69 which looks very similar but says that it is for Chassis: Up To: B 527022. My Vin is WDBEA30D3HA357927 - the last 6 digits indicate chassis, right? I asked the online store and they said it would not fit, but I'm not sure if they are correct and I am tempted to try it anyway. What do you think?
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Save your money for more important repairs.
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I am not sure for your particular model.
But for the later engine (104) the auxilliary water pump in normal operation of course ensures circulation through the heater core, but it also ensures circulation of the entire engine cooling, after engine is switched off, to avoid hot spots and the formation of vapor bubbles.
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Perhaps you don't need it at all. If it's not gushing just unplug the motor it and see how well the heater works without it.
I found there was no heater performance difference, removed the pump and substituted a 1/2" copper 90 degree turn and short piece of copper pipe for it.
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"Perhaps you don't need it at all. If it's not gushing just unplug the motor it and see how well the heater works without it. I found there was no heater performance difference, removed the pump and substituted a 1/2" copper 90 degree turn and short piece of copper pipe
for it. "
I'd love to know why they ever put these aux pumps in to begin with. The motor went on mine in my 80 300SD and like TG, I haven't noticed any difference in heater performance. The only scenario where I think it might make a difference is when its cold and you start the car and leave it idling instead of driving off. Then, at low RPMs I think it might get heat to the cabin faster, but I've never tried it to find out.
And beware of the replacement ones that people are selling on Ebay and elsewhere. If you do want to replace it make sure it's a Bosch or similar quality manufacturer. I bought a couple from Adsit Company and they were China junk, only lasting a few months before leaking.
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