Yanmar 4jh2e Impeller Problem

[journey1]

We removed the impeller from the water pump">raw water pump but have been unable to get the new one to fit all the way back in. We have done the tie wrap lots of lube and all that. It slides in easily for the most part but hangs up just shy of being all the way in to get the face plate back on. We have a 98 caliber 40 LRC. The pump is behind the alternator which we happen to have taken off for other reasons which was why we figured it would be a good time to check the impeller. We have been struggling with this for a while and thought maybe we needed to remove the pump completely to get the impeller back in. Much to our dismay, we realized two of the four bolts holding the pump on are located behind one of the motor mount brackets. We are at the point where we will néed pofessionals unless anyone has any suggestions.

[DeepFrz]

You are absolutely positive you have the correct replacement impeller?
Have you tried putting the old one back on to see how it fits?

Tried different rotations etc.?

Any castings or burrs that are blocking insertion?

Without a clearer description or pictures those are the only things I can think of. Good luck.

[perchance]

Step 1 measure impeller thickness.
Step 2 measure pump housing depth.

[Charlie]

Compare the two impellers with a pair of calipers to see that they are the same. Is it possible that a Previous Owner changed the type of water pump? If so perhaps it needs a different model impeller.

[journey1]

We physically and visually compared the two and checked the part number in the manual, and they apperception to be a match. I also measured the depth and it should fit. Is it possible to move the shaft out while pulling out the old impeller? A few people have mentioned that. Also corrosion behind the wear plate was mentioned. Anyone know of issues with either of those things.

[DeepFrz]

You didn't mention whether the old one fits or not?

[journey1]

You mean that if the old doesn't go in something must have changed in the pump when we pulled it out? That is a good thought. Will try that next. If it doesn't fit do you think the shaft movement is the most likely culprit and if so will we have to take out the pump to fix it?

[four winds]

Yes, as advised, re-install the old impeller.

Obviously it fit when removed. If it won't go back in then you can assume something happened to the shaft position as you mentioned.

And triple check that the new one matches the old one.

[perchance]

If there is end float in the shaft it will move in i.e. shorten and not interfere with the fit. There is a possibility that the last part of the impeller bore is tapered due to a manufacturing defect. A vernier will tell you one way or the other. Carefully inspect the bore of the impeller for anything obvious especially around the keyway if it has one.