Does anyone have any ideas what would cause a motor to start fine and maintain normal oil pressure (30ish at idle, 60ish at 3k rpm) but as the motor warms up, the oil pressure dies off till theres nothing left. Im at a loss of what could cause this and if anyone has any idea, i would greatly appreciate it.

I should also mention that this is a 12a (freshly rebuilt) that developed a dowel pin oil leak between the rear plate and rear housing.

 

Low oil level?

Loss of temper in the spring in the oil pressure regulator, or other failure there, like a heat-biased internal leak?

That's a tough one.

 

what oil is in it??

 

debris getting sucked into the oil pickup screen until it blocks it off and looses pressure. I have seen this happen mainly on higher mileage engines or engines that werent properly cleaned out before assembly.

 

Could be the connection at the sender. Clean the prongs off and see if it helps. My FC would have erratic OP readings and I found out that there was oil all over the connector. I guess the last time I changed the oil the filter dribbled oil onto it and it got baked on and gummed it up.

You could buy an RB adapter plate and Autometer gauge and sender for roughly $130 or even cheaper used. It will be far more accurate then the simulated factory gauge.

 

I use 20w50 oil in it. Could this have anything to do with the oil control rings? I put new rubber inserts in the outer rings but not the inner rings because i could not get them to seat properly with the new seals. Should the inner ring be loose in its slot? They actually fall out when i move the rotors around on my work bench.

 

is it new oil?

I think you may still have a leak somewhere that is expanding as temps increase. a bigger hole will give you less pressure

 

Yeah its brand new oil with my rebuilt motor. First rebuild resulted in me putting in my apex seal springs upside down cause im an idiot, second resulted in this oil issue and a dowel pin oil leak thanks to a popped dowel pin o ring.

 

Oil rings are supposed to fit snugly in their bores... whether or not your problem originates here, I don't know, but assembled properly they need to be carefully pressed into the groove (usually using the old ring to press them in) to avoid pinching the rubber. Once in, they shouldn't just fall out.

Least, that's how I remember them behaving each time I've built an engine.

 

Yeah thats kind of what i figured. Also, do you think that my problem could have been a blockage in the dowel pin line? I may have over hylomared the o ring and cause it to block around the outside of the dowel pin. I know the holes in the dowel pins were open however

 

1st step would be to put a mechanical gauge on it.

 

Ok I get the idea that the stock gauge isnt strictly accurate. Mine has always been correct-ish however. I know for a fact that the oil pressure dropped off as the gauge showed thanks to some burning on my housings that was luckily repairable

 

There shouldn't be enough oil flow around the outside of the dowel pin to matter one way or the other, considering how tightly they normally fit.

 

Stupidly the low oil level appears to be the most plausible thing at this point. I filled it to the full line but i never bothered to check it after the car lost pressure, also because im an idiot. Is it plausible that it would drop below the pickup tube after the oil is sucked into everything in the rebuilt motor?

 

ok.... wanted to be shure that you didnt have 5w30 or some thing in it

 

Oh no, im a true rotorhead. Im just stupid sometimes =D

 

Yes, that's possible; between the oil filter, the cooler, and all the various oil passeges, that first fill can be a couple quarts short once the motor has run for a few minutes post-rebuild.

Easy enough to check it; just do a proper oil-level check now that everything's together. Warm the motor to normal temp, shut down, let sit for a few minutes, and check level. Should be on the checkered part of the dipstick.

It's also possible that you've got a leak in your oil pickup tube that's sucking air as RPM increases and oil gets warmer. This is most likely around the connection point of the pickup; gasket didn't seat, got left off, or attachment screws weren't torqued properly and got loose, fell out, or cracked off.

 

well ill have to double check all that. the motor is in pieces in my garage thanks to that dowel pin leak, waiting for my parts to come friday

 

since its apart NOW is the time to get the book out, and take some extra time and measure/spec everything out, it does make a difference....

couple little teeny things, put a little dab of silicon on the oil pump to engine flange.

 

Everything is to spec as far as i can tell from the three times i pulled the engine out so far this summer =(. Im going to double check the oil pump again though just to be safe

 

If the oil pump is even close to failing specs, replace it with an SE pump. Same goes for the oil pump chain. Then look into bumping up the pressure by modding the rear oil pressure regulator. You are the first member I've heard of that had a rear dowel pin o-ring failure. Aren't you special, lol. Good luck on the re-assembly.

As a side note, check all the main bearings for any new wear along with the e-shaft. If the o-ring is still in place and shows no sign of damage, you may wish to have the rear iron magnafluxed and the rear housing dyed to check for cracks. Lastly, make sure the o-ring between the front iron and front cover is in place and that the thermostat in the FMOC is opening at temp and installed correctly, it you have an FMOC.

 

Make sure you install the new oil control rings that you failed to install before. I cover the o-rings with petroleum jelly, put the rotor on the floor, 2 X 4 flat on top and stand on it to press the control rings into place. They will not seal properly if they fall out when the rotor is moved around.

 

Well my gasket kit, viton oil ring inserts, and video came from atkins today. I think I alone am keeping them in business this summer =P. Time to get things right.

The dowel pin leak was caused by a broken seal. Somehow my brand new dowel pin o-ring snapped and obviously leaked. Sucked too cause i took special care to hylomar them to prevent it from leaking lol.

I still cant figure this thing out. After the first rebuild, the oil pressure was regular. After the second, where i got the apex seals to seat properly, it dies off as the engine runs, what gives?! I blame the oil control rings not seating properly. Sound true?

 

So its doing the same thing after my third time rebuilding the motor. All seals were good, replaced all the gaskets and the oil ring viton inserts.

Starts fine cold, shows oil pressure, then after a couple minutes, it dies off. What the hell. I need help. Now. I go back to school in 3 weeks and I havent driven the car since may so I'd like to get it going again...

 

put a different/mechanical gauge on it