my car makes good pressure at idle 20 psi.
it quickly jumps to 45 psi at 2500 rpm.
then it just sits there through the rest of the rev range.
when cold it gets to about 60 psi at 2500 and as it warms up it drops to 45 psi.

Im thinking the problem could be one of 3 things
- front cover o ring failure.
- thermo pellet failure.
- oil pressure regulator failure.

does anyone know the symptomes of any of these 3 things.
I searched and found several posts where people "heard it was this" bu noone seems to have figured out what was actually causing their low pressures.

 

That's very consistent with a front pellet failure. Get the replacement plug that does away with that system all together - fc3s.org has 'em for like $15.

If that isn't it, it's a good idea to do anyhow, and is MUCH easier than a front cover job . If the pellet doesn't fix things, it's maybe a front cover O-ring problem, but they typically don't fail unless they've been messed with, installed improperly, etc. I would double-check the oil pressure with a mechanical gauge to make 100% sure before you tore into the front cover - that is THE most pain-in-the-*** job you can do!

Dale

 

Thanks for the reply. all my above pressure numbers are using a mechanical gauge.
That was the first thing I did.

Where is the front cover O-ring located? IE where does it seal. and when leaking where does the oil go.

does anyone else care to take a stab at what my problem it.

anyone think it's the pressure regulator just inside the pan?

 

Also, just incase you havent dont it check your oil and make sure its not just low hehe

STEPHEN

 

well here is a follow up and request for more info.
did the thermo pellet mod this weekend.
oil pressure is much higher when cold now (between 35-110 depending on RPM.
when the oil worms up the pressure drops steadliy to 50psi at 2500 rpm and NEVER goes any higher.

so it was not the thermo pellet. At least Im able to rule that out now. and will forever be able to.

so what would be causing this non linear pressure?

I'm hoping oil pressure regulator. It looks like an easy enough part to replace and teh pan gasket leaks anyhow. good chance to fix that as well.

 

What oil pressure are you now getting at idle?

Also, I'm assuming you've tried an oil/filter change - a bad oil filter can drop oil pressure as well.

Anyhow, the front cover O-ring is sandwiched between the front cover and the front iron housing of the engine. The oil pump draws oil from the oil pan, goes through a passage in the front iron, through that o-ring to the front cover, then to the front oil cooler line.

If the o-ring fails, oil will leak out around that o-ring back into the oil pan. You'll never see a leak externally, but it will bleed off oil pressure.

I've done a number of front cover jobs (most of them due to my screwups - that's a hard way to learn something!) and that is the LEAST FUN thing I can think of doing to an RX-7. Mind, this was on a 2nd gen, and was likely quite easier than doing it on a 3rd gen. Seriously, if I ever had to do it again, I'd just pull the motor out - takes much less time, and it's all right there easy to get to.

Does the stock gauge corroborate the aftermarket gauge? Is it an in-cabin aftermarket gauge that you've had for some time, or is it one you're holding in your hand hooked up to the motor for troubleshooting? I just want to make sure you can believe what the gauge is telling you.

Dale

 

at idle I get about 15-20 psi.



I hooked one up and held it in my hand. The stock gauge looks about the same som I know it's telling the truth.


as for front cover Oring.
the engine has run fine for 17K with no problems.
I can't figure why it would just start leaking now.
when you have needed to do front cover ring jobs, what pressure were you seeing?

 

I don't see where you mentioned the oil/filter you're using? Also, did your pressure just one day or was it a gradual thing? And just to clearify, you're saying that once the engine is warmed up (what's your normal temperature?) the oil pressure won't go above 50 PSI regardless of RPM?

 

Im using a Puroilater pure one filter. It has been about 1700 miles since I changed it.

and yes once the engine gets to ~85C the pressure just sits at 50 psi for anything above about 2500 rpm. under that id drops like it should to 15 psi and then when I rev it rises quickly to the 50 where it just sits through the rest of the RPM range.

This change was not gradual. one day I looked at my gauge and it was sitting at 50psi... then I later noticed when I rev it it no longer rose to nearly 100 psi.

Im really at a loss here to trouble shoot it without having some more of an idea.

Since MADS it coming up and Im registered... I would like to fix it. I also would like to leave it alone since 50 PSI won't hurt the turbo or probably anything else.

If I can get a better idea what would cause this I'd get right in there and fix it.

 

Well, I have a gut feeling it might be the front cover o-ring. You said you've had the motor for 17k miles - where did you get the motor from?

The symptoms are right in line with a bad front cover O-ring - 15-20 psi at idle, 45-50 at 3000 RPM.

Many years ago, the motor in my 10th Anniversary blew, and I decided to rebuild it myself. I messed up a LOT of stuff on that rebuild, but I learned a lot. A lot of the screwups resulted in the numerous front cover jobs I did to that motor.

Problems I had -

- I chose the wrong O-ring out of the gasket kit. None of the o-rings are labeled, and I used one that looked to be the right size, but was actually slightly too big, and it got pinched. I also used the wrong front cover gasket, but that's a 2nd gen problem.

- I eventually discovered that, when building the motor, I pinched the front needle bearing resulting in major e-shaft slop. Had to pull the front cover off to fix that.

- I had a mysterious oil leak that I thought was a bad seal between the front cover and the engine. Turned out I was a dumbass and was tightening the front oil cooler line incorrectly. Doh!

I would SERIOUSLY consider pulling the motor to tackle this job. Considering you have to drain the oil and coolant, pull off the oil pan, remove the power steering/AC bracket, etc. etc. etc. it's gonna be a lot easier with the engine out of the car. If you unplug the wiring harness from the ECU and pull the harness with the engine, you shouldn't have to go under the upper intake manifold and mess with any of that stuff.

I would definitely NOT track the car with low oil pressure. The high temperatures and extended high RPM use could result in a bearing failure.

When you have the front cover off, I would also inspect the oil pump. If the oil pump ate something somehow, that can also cause a drop in oil pressure. Look for scoring and damage inside the pump.

Like I said, it's a big job, but once you get the front cover off lots of questions will be answered.

Good luck!

Dale