Here's where actual pressure measurement would have helped...

The pressure switch for the factory warning light works by grounding that wire. If (BIG IF) that wire were rubbed bare somewhere, and occasionally touching something metal on your car, it would occasionally light up the warning light. In that case, the pressure measurement would show that everything is OK and no need for diving into the actual engine. In that case the search would be for a wire rubbed bare somewhere. That can be tested with a multimeter and wiggling the wire harnesses.

Another possibility that should be considered is sludge obstructing the pickup screen in the oil pan. Maybe(?) your mechanic has already looked at that or somehow convinced himself that it's not the problem. A good look at old oil draining when you change oil will probably answer that question. Another way is to poke a wire into the drain plug after the oil drains out & scrape it around on the bottom of the pan. It shouldn't pick up any sludge.

 

He did mention that he would check a couple of engine ports for any blockage. RE: my earlier oil pump question, does reusing the old oil pump plate ( I referred to it as frame / matrix ) vs. installing the new plate make any difference ? Thanks.

 

After all that work..you should have checked the oil pressure itself..i know from experience that my light would flicker when the idle would drop low

 

Using a complete new pump vs. just replacing the gears depends whether the pump housing is worn. I'm not sure I could find accurate dimensions for the cavity where the gears fit, but if that's worn (enlarged) then the new gears probably won't help. I think the housing is aluminum vs the gears being steel. And its already been mentioned about the possibility of the bypass valve sticking.

And re: hondaslave, if the idle occasionally drops to a low RPM, then the thing is to figure out why the idle is dropping & fix that. If the idle isn't really dropping, then you want to know whether the oil pressure is actually dropping.

BTW, in post #3 the photo of the tachometer shows it at just barely below 750rpm. The scale is kinda funny, there's no mark for 250, the first small mark is 500 and the needle is just about at the 750 mark where it belongs. I don't think that's low enough to cause a problem, but a well-equipped mechanic probably has a tachometer to plug in that's more accurate at low speeds.

 

Do mechanics usually replace just the gears and use the old housing or do they usually replace the entire oil pump housing ? It sounds like trying to replace just the gears in the old housing could be tricky. Maybe if the fit isn't good that could cause an intermittent drop in oil pressure when hot ? Anyway, he's replacing the housing this time. And, a new oil pressure switch. It looks like the gears come mounted in the oil pump housing ready to install. He said that the ports look okay. He did comment this evening that there was some play in the gears that he had just installed a week ago. That's not good to hear. BTW, this must be time consuming work. The car was at the shop all day and won't be ready for pick up until tomorrow. Then, it needs to be road tested big time !

 

I don't know how common it is to just replace the "gears" without the housing. Seems like the aluminum housing might be more likely to wear but I don't really know.


I just looked at the parts drawing & it seems like you can't buy just the gears from Honda. That seems to imply that Honda doesn't want you to do it that way.

It's a big job, because you have to remove a lot of stuff just to get at the oil pump. You have to remove everything related to a timing-belt job just to expose the oil pump for removal. That right there is motivation to replace anything that might go within the next couple years.

 

Personally, if I'm digging in that deep to pull the pump, I'm replacing the whole pump. The aluminum housing could have excessive side wear, the gears could be worn, the steel plate could even have wear. When you add up all of those possible wear points, it doesn't make sense to just swap the gears. Especially since you have to pull the pump out to access the plate to remove the gears. Then when you really get down to it, a pump goes for around 50 to 100 bucks, depending on whether you get a Honda pump, or an aftermarket pump, it doesn't make sense to just swap the gears.

Honestly, your mechanic should have tested the oil pressure right from the beginning. He should have also tested the switch, to make sure it was operating correctly, and the wiring harness as well.
Since he's now replacing the pump again, and the switch, this means that you'll have to wait until you get it back to find out if it's fixed. It's possible that it could still be the same, due to a wire rubbing against a ground spot turning it on, or it could be that the main bearings are worn out due to a lack of regular oil changes in it's past (before you bought it).

 

Thanks to all of you for the helpful advice !