An old post, but i'll throw a few quick notes in here specifically regarding AD-21:
- I don't find it necessary to remove the entire pump, though, read further...
- Even with cooling water shut off, mine will still backflow, because
- my original AD-21 has 2 impellers (!!) and 4 hoses.
--on mine, even with cooling water shut off, one of the other hoses (which are intake and output for a bilge pump) will backflow. for impeller change, i remove that hose and stick a cork in it. easy, peasy.
- on mine, the 2 impellers are the same size. the important impeller -- which cools the engine, hides directly behind the first, and behind a brass plate. if you didn't know what you were doing, and didn't notice the extra hoses, you might quite likely completely fail to notice this very important impeller.
-
www.albinmotor.se, the swedish albin store, is the only supply i know of to buy these unusual impellers
- i find it difficult to remove the brass plate between the 2 impellers. i pry at it from the center hole with a long thin screwdriver, but there really must be a better way, like, some sort of clever extractor tool. (anyone??)
-- i have always found it quite easy to remove the impellers themselves, they just slide off. no extractor required. they have tiny round key-pins along the shaft that will fall out -- worth keeping some as backups in case you ever lose one.
- it also takes 2 o-rings, one in each impeller compartment, each the same size, which you may wish to replace at the same time.
- you may wish to remove the whole pump, because, deeper in, a seal between the waterpump and engine is prone to failing, which would leak fresh water into the engine oil. you don't want that, so it is worth replacing this seal proactively! again: parts from albinmotor.se
smooth seas-
