Impeller questions for 202 pump (FWC)

[Mr. Close Reach]

Hello,
I'm replacing the impeller on my Oberdorfer 202 pump and as you can see from the picture, the new impeller is sticking out a bit. Is this normal or do I just not have the shaft seated all the way in? (I removed the whole shaft, not just the impeller, so I could get at it with the snap ring pliers more easily.)

Also, do I have the blades oriented correctly? As I'm facing the pump housing it rotates counterclockwise, right? I'm trying to visualize the blades doing there job but I'm not convinced I've got this right.

[Marian Claire]

I do not think you need to worry about the fin oriantation. They will flip when the pump starts. The impeller being slightly proud of the houseing is also OK. Dan S/V Marian Claire

[marthur]

In fact, if there is a gap between the impeller and the rear housing, it might not pump.

[Mo]

There were two impellers with slightly different dimensions; both state they are for atomic 4... one as in the pic in post one and the one just a tad narrower. Both work, however, the one as in above pic is tighter and is said to move more water. It will also leave a score mark on the cover plate as it breaks in.

People who have had one of these slightly larger impellers (I think they are the original version) and a scored cover plate find a decrease in flow after putting in the more narrow version. The remedy to that is to sand the plate even again, however, MMI sells these new cover plates as well.

I changed quiet a few impellers past few years and some are the narrower ones and some the slightly larger ones....seems to be about a 50/50 chance of scored plate but with the larger one it doesn't matter.

[Skywalker]

Excellent info,Mo.

Thanks

[marthur]

If you were worried about the larger one scoring your plate, a minute with a belt sander would take care of the extra thickness : )

BTW was it random or were the thicker impellers purchased from a particular source?

[Mr. Close Reach]

Thanks guys! I think I'll leave the belt sander in the workshop for now...
The replacement impellor was ordered directly from Moyer and matches the old one so in this case I don't think there was a sizing issue. Dan's comments make since so I'll put the gasket/cover plate on there and move on to the next project.

[marthur]

Good plan!

[Mr. Close Reach]

Overheating now, trying to burp the system

I'm back in the water with two new impellers installed and the engine is overheating. I'm hoping this is just a 'burping' issue but last time I had to drain all the coolant (to do the water jacket side plate) I only had to burp it once and now I've done it a few times.

If I run the engine a bit and let it get hot, I can see the air bubbles coming through the hose to the expansion tank after shutoff. Do I need to just keep doing this - i.e. is this suffiicient to burp the air? Would opening up the fill cap on the heat exchanger help in any way (after she has totally cooled down, of course)?

[ndutton]

Ideally the reservoir portion of the heat exchanger should be the highest point in the system with all hoses running uphill to it without loops, sags or traps. Right, ideally.

If your installation is less than ideal, consider a radiator style bleed valve at the high points. With the engine running you can crack open the valve and bleed the air that accumulates there. I did it on mine and bleeding the air is quick and easy.

[Mr. Close Reach]

Ideally the reservoir portion of the heat exchanger should be the highest point in the system with all hoses running uphill to it without loops, sags or traps. Right, ideally.

If your installation is less than ideal, consider a radiator style bleed valve at the high points. With the engine running you can crack open the valve and bleed the air that accumulates there. I did it on mine and bleeding the air is quick and easy.

Thanks Neil, I did see that fix when I searched the forum and it is something that I will try to put in place - but b/c of the location of the HX it will be a bigger job. Any other guidance on effective burping for the short term? I'm assuming that my new impellor is circulating coolant, otherwise I wouldn't be seeing the air making it's way to the expansion tank.

[ndutton]

Any other guidance on effective burping for the short term?

Nope. About all you can do is keep running it and hope the flow pushes the bubble along but it's a leap of faith and gravity is working against you.

I'm assuming that my new impeller is circulating coolant, otherwise I wouldn't be seeing the air making it's way to the expansion tank.

Air bubbling to the tank is not by itself a reliable indication of flow although it is encouraging regarding the elimination of the bubble. I think a more reliable indication is you are not spiking the temperature.