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Old 05-19-2017, 10:01 AM   #3
Live, eat, and sleep by TSL
Join Date: Mar 2005
Posts: 1,819
Oil Pump Gear Set

Next I try a new oil pump gear-set. Years ago when I dealt with a similar oil pressure issue in my first 9-5 I remember reading that some manufacturing issues had caused some timing covers (oil pump housings) to be out of spec. So when I built this motor I thought "if it ain't broke...." and re-used the original timing cover and gear set.

Saab is not terribly good at giving any measurements to inspect the oil pump either.

According to WIS, they spec "End float between oil pump rotor and housing" and spec 0.03 to 0.08 mm. No ilustration is given, and clearly there are more measurements than that! So out comes my manual for my Honda Civic! The 1.5L civic uses the same oil pump design, and slightly smaller. I am a big Civic fan, and think that the D15B7 motor is a fine little machine, it is just not much to brag about! Honda is much more detailed with three measurements:

Radial Clearance on Pump Rotor:

This is the clearance between the inner and outer rotor lobes. It is easy to understand that if the gap is too large, the lobes seal off as they close and oil will just run past into the next open lobe. It seems to me this would be the most important measure and Saab does not even check it! It turns out for me, my OLD (276k miles now) gearset is actually better than the new one i bought!! I measured with feeler gauges somewhere between .14 mm and .15 mm with the old set, and .15 mm with the new set! This is slightly out of Hondas "new" spec, but well within their sevice limit of .2 mm.

Axial Clearance:

I think this is what Saab means by "End float".
This was extremely hard to measure in the car but I did my best. Because of the pump design you need some sort of straight edge, but it is really short. I cut a piece of angle aluminum and used it to get my feeler gauges in there.

I am an Engineer by trade and I am very familiar with high precision measurment and I will declare this was not! An aluminum piece of angle is not a straitedge but it was the best I could do. Again, my old gear-set was better than the new! I measured somewhere between 0.08 mm to 0.09 mm with the new, and 0.08 mm with the old. Again, this is right on Honda's "new" spec of 0.08 mm but well below the service limit of 0.15 mm.

Radial Clearance (Housing to outer rotor):

This was easy to measure, just start sticking you feeler gauges in the gap. Again my old set was better than the new pump! I measured 0.25 mm to 0.28 mm with the new set, and 0.18 mm to 0.20 mm with the old set. This was because the OD of my old gearset was bigger than the OD of the new gearset! I measured this is digial calipers (not the best tool for this but what I had) and the OD of the new outer gear was 89.74 mm and the OD of the old gear was 89.82 mm.

Honda's spec is tight here, 0.18 mm is the upper limit for "new", but the service limit is right on top of that at 0.20 mm. So I am right on the edge here.

Pump scoring: the only significant scoring I have is on the pump cover, shown here:

Honda says" "Inspect both rotors and pump housing for scoring or other damage. Replace parts if necessary". That's not much help!

Since it is easy to swap the gear-set, I do it anyway and there is no change. I think at some point I will change the pump cover for good measure. But my conclusion here is my pump is NOT shot, and should be producing some oil flow!
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