Benjamin4456

Just a quick question to level my sanity here. About a week ago now I had to pull the front cover in order to replace a crushed thrust bearing. Upon reassembly it was a bit tough convincing the front cover o-ring to stay in place, but eventually it did and I got it all back together. This was all done with the engine in the car and I used a new front cover gasket, no rtv. My only concern is that o-ring, since it popped out on a couple attempts. This is on an SA so no oil pressure gauge, but I'll verify it with an external mechanical gauge before I get to driving again (engine bay is still disassembled).

So with the backstory done my question is this: If the oil pressure checks out when testing it, what is the likelihood that the o-ring could pop out, or migrate, or something after the fact? If it's at all out of place/pinched is it even possible to have pseudo-correct oil pressure? I know I ought to get a gauge for the car but right now that's not in the budget. Anyone have a thought on this? I'd think that if it's good it's good, but I'd appreciate some input.

Benjamin4456

I've made a good bit of progress on the car in the past couple days - should be running by Thursday, or at least that's the plan. Anyway, I have the oil system all hooked up and tested the pressure while cranking with the plugs out. It takes a while to start moving but once the needle is on it's way I reach 30psi within ten seconds or so. Upon stopping cranking the oil pressure bleeds down within about 15 seconds, not sure if that's normal since I've never had an oil gauge on a rotary before. Any thoughts on this? The oil cooler was completely drained and the oil pressure gauge has a long, rather 'large' diameter hose, so perhaps that's part of it? To me it'd seem that if the front cover o-ring was gone or pinched, I wouldn't be able to see 30psi. I suppose I won't know for certain until it's running, but do things sound on track so far? This is being tested with an external mechanical gauge of course.

Benjamin4456

Ok, the car runs and I've got oil pressure. For context I'm using 10W40 dino oil. Now here's the breakdown:

~50 psi at cold start idle
20 psi hot idle (as in a little too hot, I haven't gotten the rad full yet so temps should go down - rear housing hit 190F), 750rpm
18.5 psi with headlights on (idle drops to around 700)
60 psi by 2500rpm (I need to roll the car out before I can test any higher as it's just too loud)

The engine in question is an '82 block with the updated 17mm oil pump. Stock regulators both front and rear.

From what I understand the spec is 20-40 psi at warm idle, and 70 psi at 3k rpm and above. Given that, does my oil pressure sound at all suspect or just that of an engine with about 90k miles? Most important to me is that front cover o-ring. I'd say it stayed in place - does that conclusion sound reasonable? Even if it's okay now, how likely is it that the o-ring isn't sitting quite right and could blow out sometime? Or perhaps that it's the paper gasket holding the pressure and that it would blow out? Just trying to settle my conscious since I don't have an in-car oil pressure gauge yet (it's on the list).

Lastly, is 18.5 psi at idle too low? It jumps up fast and is quite responsive. I suppose I could run 20W50 if that seems warranted, however if I meet the 3k rpm spec it would seem I might not want to do that. Thoughts on this? And even though there's been no responses yet, thanks all for the info in older oil pressure threads, they've been quite helpful so far.

GSLSEforme

Use 20W50 oil. All I’ve ever used in my rotary engines is Castrol 20W50. Warm idle 58-60psi. 3k rpm@85 psi.
Original engine 85 SE.142k,no oil system mods.

Benjamin4456

Yeah, I had been thinking of switching to 20W50, sounds like this is a good reason to do so. Given my climate a 20W40 oil is theoretically optimal (based on the manual at least), but it's not an easy thing to find. Unfortunately I have enough 10W40 for another change and a half so perhaps I'll use that up in the winter.

Anyhow, thanks for the reply. I take it by the lack of a mention that the front cover o-ring is probably fine?

Oh, and I did test the 3k spec and I do indeed hit the 70 psi mark.

GSLSEforme

O ring should be ok. After reading your thread it seems yer a bit paranoid. Oil pressures look ok. 20W50 will bump pressures up across rev range.

Benjamin4456

Ha, paranoid? Yes, most definitely. This is my daily so something like a critical o-ring taking leave makes me a little concerned. Thanks for the reassurance.