1985-1998 [Subscribe to Daily Digest] |
1986 9000 turbo, 200000+ miles. Bought with inoperative odometer trip odo OK). Previous owner didn’t keep trip odometer mileage records.
Using a gauge known to be good, oil pressure (engine warm) is 32 psi @ 2krpm. Min spec is 39 psi.
Oil pressure relief valve opens at 55 psi. (Rpm vs. pressure curve goes flat at 1500 rpm.) Spec is 52 - 75 psi. When engine is warm, oil pressure doesn’t get to open the relief valve at reasonable rpm.
We can assume that engine wear is a contributor to the situation. The question is, how much of this problem can be attributed to the oil pump.
Sooo, prior to dismantling the pump, I did my usual literature search. (I don’t have the applicable section of the factory manual)
Factory Service Bulletins and Saab Network Archives, nothing relevant found.
Haynes and Bentley manuals each give pump clearance limits. In each publication, these limits are 0.03 to 0.08 mm. However, they each measure something different, and make no mention of the other’s measurement!
Haynes measures between pump outer rotor and timing-cover housing. They show a picture of a feeler gauge inserted parallel to the crankshaft.
Bentley places a straightedge on the pump body to measure the clearance between the pump body and the outer pump rotor. This measurement, of course, is perpendicular to the crankshaft. A drawing of this is shown.
Aside from this inconsistency, I have a more fundamental question. The pump body is alloy, while the pump rotors are steel. They wear against one another, both radially and tangentially. At least, that is my recollection from my last disassembly about a year ago. Would the wear not take place overwhelmingly on the alloy pump body rather than on the steel rotors?
However, when I went to the dealer for an “oil pump” (having had no luck with my usual aftermarket suppliers) I was offered a set of steel rotors.
Does anyone have insights on these (to me, anyway) puzzling questions?
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