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another oil pressure question..

Old 02-28-2011, 06:08 PM
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Default another oil pressure question..

so i tried searching, but didnt find exactly what i was looking for so i thought i would ask.

I recently rebuilt my engine, using a donor crankshaft from another motor (my cranknose failed) so i had to swap over the oil pump too. now im idling at about 15psi (which according to m.net is ok, but if it gets any lower is bad news) so im wondering if low oil pressure has anything to do with the engine still being in the break in stage? will it change once the engine has some miles on it, or should i start looking for a new oil pump? all seals were replaced so it shouldn't be a leak.

any insight would be appreciated

Thanks,
Chad
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Old 02-28-2011, 07:19 PM
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and i guess more importantly, where the **** can i get a 1990 oil pump? i cant find one anywhere. if they are only a couple hundred dollars, ill just replace it for piece of mind/prevent worse damage
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Old 02-28-2011, 07:30 PM
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Old 02-28-2011, 07:34 PM
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01+ motors have no more than 55-60psi tops and like 5-15 at idle. How much do you have at redline?
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Old 02-28-2011, 08:06 PM
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checked rockauto already, no luck. i havent taken it to redline yet, im trying to stay under 4k for the first couple hundred miles. (im only up to 150 miles so far)

i wouldnt be that worried about it, but the engine i stole the crankshaft from (short nose) was replacing my big nose, so i had to swap the oil pump. the donor engine literally had a melted rod bearing(see pic ), the #3 rod turned black from the heat so im thinking the cause might have been from lack of oil. that, or the fact that the previous owner tried rebuilding that engine, and LEFT OUT THREE MAIN BEARINGS. so it may or may not have been due to the pump. it had good pressure upon initial startup, and the first few miles. i then drove it for about an hour on the highway (i know that might be a no-no but i had to get from my parents house back to school). i noticed driving around today that it was idling around 15 and if i remember correctly, pre-rebuild i was idling at 30, crusing at 60. now i idle at 15, cruise at 30. also,im sure its unrelated, but it wasnt idling very well either. i shot the ISCV with some carb cleaner and that seemed to help.

im ok with replacing it if its not super expensive, but i guess ill have to call mazda in the morning to see how much they wanna rape my wallet for one if noone else has a source online for one?

thanks,
Chad
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Old 02-28-2011, 10:58 PM
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not super expensive but requires pulling the motor to replace

10psi per 1k rpm hot is generally accepted as being sufficient.
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Old 02-28-2011, 11:45 PM
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oh so i should be ok then it sounds like. idling (750 rpm) yields 15 psi, cruising (around 3k) is about 30 psi. guess i wont worry about it unless the pressure gets lower. if the oil pump is bad, will it get worse exponentially? or will it just gradually get worse over time?

Thanks,
Chad
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Old 03-01-2011, 01:04 AM
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uhhh

hmm your oil pressure is probably ok. flow not pressure!
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Old 03-01-2011, 01:16 AM
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Stop being a fuckign ***** and rev your bitch to 7000 RPM once and tell us what the oil pressure is.
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Old 03-01-2011, 02:01 AM
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My brand new motor with 400kms on it running the Maruha oil pump idles at 800RPM with 17-20PSI. Highest I see it is 60-62PSI with a current RPM limit of 5000RPM.
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Old 03-01-2011, 02:14 AM
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Originally Posted by falcon View Post
current RPM limit of 5000RPM.
What reasons were given for this RPM limit?
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Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 03-01-2011, 03:49 AM
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No specific reason other than I don't want to beat the **** out of a new motor. I've been driving it hard, just not high in the RPMS. Once I hit 500kms I'll bump it up some more. Once I hit 750-800 I'll be using it all.

Same way I've broken in all my motorcycles and I have never had an issue with ring seal or blowby with any of them.
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Old 03-01-2011, 07:36 AM
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Originally Posted by falcon View Post
No specific reason other than I don't want to beat the **** out of a new motor. I've been driving it hard, just not high in the RPMS. Once I hit 500kms I'll bump it up some more. Once I hit 750-800 I'll be using it all.

Same way I've broken in all my motorcycles and I have never had an issue with ring seal or blowby with any of them.
You're doing it wrong
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Old 03-01-2011, 09:01 AM
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what is your suggested break in method fooger? i have heard everything from limp wrist it around the block, to wail on it once its warmed up. im trying to take the center road and drive it average for a few hundred miles then beat on it. but ill check max oil pressure on my way to work and report back.
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Old 03-01-2011, 01:18 PM
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at 7k my oil is about 60psi. which seems kinda low to me. it used to peak around 90
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Old 03-01-2011, 01:45 PM
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Originally Posted by rigidbigelsworth View Post
it used to peak around 90
To me, that suggests that the pressure relief valve in your old oil pump may have been sticking.

There is a spring-loaded plunger in the oil pump which opens to bypass oil directly back to the crankcase when pressure exceeds a certain threshold, as would be the case when the oil is cold or at very high RPM. My recollection is that the target pressure is in the neighborhood of 60 PSI.
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Old 03-01-2011, 01:54 PM
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by target im guessing you mean target max pressure? if so, that is awesome news. so instead of installing a worse pump, i fixed a problem i didn't even know i was having! haha

thanks for the help everyone
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Old 03-01-2011, 03:26 PM
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Originally Posted by fooger03 View Post
You're doing it wrong
cool.
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Old 03-01-2011, 03:50 PM
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If it bothers you that bad buy a set of billet oil pump gears and shim the relief valve spring .030 and your oil pressure will be back up in no time. I shimmed my last pump and it would hold around 25 psi. at idle and 80psi at 7000k. On the other had my shimmed honda pump on my daily idles at 110-12 psi and maxes out around 75psi not that that matters for your mazda just a side not because that car has a donor crank in it as well.
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Old 03-04-2011, 10:41 AM
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15 psi at idle is not bad, and 60 psi at redline is acceptable.
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