ColinRX7

Okay just about every older motor I get develops a low oil pressure symptom before too long (front cover o-ring problem).



Today I hooked up a mechanical gauge to my oil system and verified the problem.



I connected it at the front cover (mainly because I was suspicious of the o-ring).





At start up, 32 lbs cold, idle. Something that shocked me was if I revved it up to above 4k (was not looking at the tach, sorry), it was spiking 140.



I waited until it was warmed up further and the oil was hot, and verified my low oil pressure due to the o-ring.



12 lbs at idle, warm, and still spiking 140 psi when revving.





At first I thought it was just the o-ring due to age, is this possibly a blown o-ring due to a regulator malfunction?



The gauge is accurate, I couldn't believe what I was seeing. I was under the assumption the stock regulator was 90 psi or something.







Any input is needed, I expect to tear down the front cover to replace the o-ring shortly, I might as well replace the regulator too? Or is this not the regulator's fault?



Thanks

ColinRX7

Excuse me, I'm used to saying pounds, or lbs, when I'm referring to psi.



All these numbers are in PSI.

mazdaspeed7

You read the pressure at the front cover. The pressure regulator is at the far end of the system, after the oil passes through the oil cooler and the oil filter.



Theres a thermostat in the oil cooler that bypasses the cooler below 140 degrees F. That could explain the normal readings when cold, and if your oil cooler was clogged partially, it would explain the high pressure coming off the front cover. That high pressure from a partially clogged oil cooler might be the cause for early failure of front cover o-rings in the past.

ColinRX7

Okay but 12 lbs is obviously too low for idle right? I have to aid something?





I run an FD3S cooler now, I don't have verified oil pressure readings from before



But I was using the stock FC3S cooler in the wintertime when suddenly my oil pressure took a dive at idle (I believe you remember me telling you about this, Adam, a while ago)



So where should I look to cure this spike? I don't want to reassemble a new o-ring and then have it blow again....

ColinRX7

Also I was under the impression the oil circuit began at the front cover because it's right near the oil pump..



I assumed the front cover was (essentially) the outlet and then it hit the cooler and ran to the back of the motor..



It is the other way around I take it?



Should I measure at the back and repost the numbers?



The main thing is the oil pressure gauge in the car is reading low, I am not sure of the accuracy of the stock gauge, so I hooked up this mechanical at the front cover. I am suspicious of the front o-ring. Those are my readings. Should I bother replacing the ring, or is there any problem at all? 12 lbs acceptable for warm oil at idle?

mazdaspeed7

[quote name='ColinRX7' date='Jun 1 2005, 06:54 PM']Also I was under the impression the oil circuit began at the front cover because it's right near the oil pump..



I assumed the front cover was (essentially) the outlet and then it hit the cooler and ran to the back of the motor..



It is the other way around I take it?



Should I measure at the back and repost the numbers?



The main thing is the oil pressure gauge in the car is reading low, I am not sure of the accuracy of the stock gauge, so I hooked up this mechanical at the front cover. I am suspicious of the front o-ring. Those are my readings. Should I bother replacing the ring, or is there any problem at all? 12 lbs acceptable for warm oil at idle?


[/quote]





The oil circuit does start at the front cover, which is why the pressure will be the highest there. Every restriction in the oil system will decrease the ratio of pressure at the end relative to the pressure at the beginning of the system. The more restriction(s), the bigger the difference will be.



12 lbs at idle is too low. You should have 30 lbs at idle at the stock oil pressure sender, which is very close to the pressure the bearings will see.



Id flush your oil cooler before tearing the front cover off.

ColinRX7

Okay well I will take a measurement at the rear oil cooler line fitting then, closer to the filter/pressure sender assembly.



I have no qualms about taking the front cover off if need be, but I don't want to replace the ring then have it blow again due to a malfunctioning regulator or something.

ColinRX7

Okay after a retest with the gauge at the back of the motor (oil cooler line again)





I am seeing 40 lbs cold, 10 - 11 lbs at idle warmed up, and no more than 85-90 lbs.





So, I take it I have the blown o-ring, due to high pressure spikes, caused by a clogged oil cooler?

ColinRX7

I see BDC lurking, I hope you can come up with something for me Brian!





I just don't want to replace the ring then have to replace it again in a few weeks