Re: 89 3.7 cooling questions
Yes the raw water impeller is the same as any other Alpha I. Change it now, as a matter of fact I would recommend the whole kit, impeller and housing, and I would use OEM parts. If the old impeller is not intact (fins missing) look for them under the front end cover of the heat exchanger. Next locate the weep hole on the lower starboard side of the engine waterpump and make sure that it is clear (poke it with a wire or toothpick). Once you have the new impeller in, start it on muffs and bring it up to operating temperature and check for antifreeze leaking out of the weep hole. This will tell you (if it is leaking)if you need new cam seals. Next you should evaluate the condition of the head gasket and cooling system by doing a compression check and cooling system pressure test. You can borrow the tools from autozone for free. Your system uses a heat exchanger where raw water circulates around tubes containing the antifreeze. Ok those are the basics, here is how the system works: It is a pressurized system, just like your car. The raw water is pumped by the impeller in through a hose through the water cooled voltage regulator into the front inlet of the exchanger and circulates back and forth a couple of times cooling the antifreeze flowing through tubes in the exchanger. The raw water exits the exchanger through the aft hose and flows up through the power steering cooler (if you have one) and into the exhaust elbow where it cools the exhaust on its way out. The antifreeze side is just like your car with a pressure (radiator) cap and an expansion tank. Keep your antifreeze at about 50/50. To winterize (freeze protect) all you have to do is pull the aft plug on the exchanger and drain the raw water (5min job). Welcome to the "470 club":facepalm:
