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Old 01-16-2006, 09:02 PM   #1
Javier
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Exclamation All possible causes for low oil pressure...

Well, I just got my S3L built and installed in my car with V7 heads. However, now my oil pressure is low. At Idle after a nice long warmup I get ~50-75 kPa (~7-11psi) and at 3000rpm cruise I get ~225 kPa (~33psi).

According to the FSM I should get at least 98 kPa (14psi) at 800 rpm and 294 kPa (43psi) at 5000rpm. I'm pretty sure that I would be over that at 5k rpm but since the motor is new I'm not gonna go up there and find out.

So before I strart going crazy looking for stuff, what could be causing my low oil pressure. Any and all possiblities are welcome as I'm gonna go over everything sometime this week.

BTW - all the readings on my defi gauge were confirmed with a mechanical gauge, so the Defi unit is working correctly and these readings are correct...
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Old 01-16-2006, 09:54 PM   #2
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Sounds like a bum oil pump. Replace it ASAP.

Stock is TYPICALLY 25ish at idle and 80+ at 5000rpm (even if spec is much lower)
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Old 01-16-2006, 09:58 PM   #3
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Well at least it's got ok pressure This is with a new pump or a recycled WRX pump? If it's the 2L pump (new or recycled) they aren't shimmed under the valve spring like the STI pumps are. That would definitely cause you to have lower pressure. I've got an STI pump already shimmed with the addition of an extra shim. It's about 15psi at idle on 5w-30 oil and after my oil change the other day (1800 miles) I decided to mix 5w-30 with and equal amount of 10w-40 and the pressure is a little higher at about 17psi idle. I'm guessing the new mixed weight is about 7w-35 equivelant or so.


Edit: I'm at about 75-80psi at 5k rpms.
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Old 01-16-2006, 10:03 PM   #4
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I believe its a shimmed oil pump from an ej22t. Correct me if im wrong steve. Never know with crawford though
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Old 01-16-2006, 10:35 PM   #5
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Quote:
Originally Posted by norexyet
I believe its a shimmed oil pump from an ej22t. Correct me if im wrong steve. Never know with crawford though
Correct, it's a shimmed oil pump from an ej22t that I got from axis
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Old 01-16-2006, 11:00 PM   #6
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hahaha so its both of them, how them piston to wall clearances doing. About .035"?? Well if thats what you got.
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Old 01-17-2006, 02:02 PM   #7
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First thing: Establish what stock oil pressure is on a stock engine.

Next: Call your engine builder. It's possible that the trick oil pump you bought from Axis is not working properly. It's possible, but not likely, that Quirt used larger clearances in the rod/main bearings, which would show up in the oil pressure....but not likely. I'm pretty sure he uses close-to-stock clearances.

If you have oiling issues, STOP. Talk to Quirt.

S.
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Old 01-17-2006, 02:59 PM   #8
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Quirt didn't build the motor. I bought the s3l package and had it built locally. The bearing clearances were all within factory spec (albeit I was told on the high side of factory spec). I don't think that would cause the pressure to go as low as it is. I'm still thinking it's the oil pump at this point...
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Old 01-17-2006, 03:17 PM   #9
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Quote:
Originally Posted by Javier
Quirt didn't build the motor. I bought the s3l package and had it built locally. The bearing clearances were all within factory spec (albeit I was told on the high side of factory spec). I don't think that would cause the pressure to go as low as it is. I'm still thinking it's the oil pump at this point...
Ask the builder if he made notes during assembly, and if you can have a copy.

You can bet your behind the oil clearances on the bearings will in fact cause what you are experiencing.

I'm hoping it's the pump, but I'm betting it's not.

S.
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Old 01-17-2006, 06:17 PM   #10
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I'll ask him.

How would clearances that are within factory spec cause the pressure to drop below what the factory calls for?
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Old 01-17-2006, 07:05 PM   #11
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Quote:
Originally Posted by Javier
I'll ask him.

How would clearances that are within factory spec cause the pressure to drop below what the factory calls for?

They wouldn't, IF they are within factory spec during operation. I'm sure I don't have to tell you this, but I'm going to pretend you don't know:

-Unless you've measured the clearances, you have no idea what they are at the time of assembly

-Unless you assembled the engine, you have no idea how clean the assembly process was kept, i.e., did the guy grab his greasy flashlight to check for a piece of breakfast muffin he sprayed into the bearing saddle....there goes that bit of dirty wheel bearing grease into the next bearing he grabs...."extra" clearance, no charge

-Did he decide to clean the head mating surface after assembling the short block?

My point is, one has no idea what the bearing clearances are when the engine is running, much less what they were during assy, unless one was there taking notes and doing the measuring oneself.

Please don't take offense. I'm sure you are a sharp guy, but I'm doing this more for the folks considering assembly, rather than you personally; Like I stated, I hope I'm wrong.

S.
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Old 01-17-2006, 07:24 PM   #12
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No offense taken. There's always the risk when you have other people do things for you that they cut corners or are just plain wrong. I have a lot of faith in my builder and I know he's very meticulous about things and very experienced. That being said, people can make mistakes. ***** happens. I'm aware of that too. That's part of the reason I posted this up. I wanna educate myself to what the possible reasons could be so that when we start tearing things down I know what to look for that no one can take me for a fool. I appreciate your candor as that's exactly what I'm looking for.

That being said, I beleive that they were within spec during assembly (like you said, things can change for any number of reasons after that). I'm fairly confident that no shortcuts were taken, especially since the build was put on hold several times because some things were "good enough" which my builder didn't think was really good enough.

The oil pump is being replaced this weekend so we will see what happens after that.
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Old 01-17-2006, 07:31 PM   #13
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Quote:
Originally Posted by Javier
The oil pump is being replaced this weekend so we will see what happens after that.

Make sure to open up the old pump and look for any damage before you put the new one in. That would at least give you an indicator of any foreign matter that might also be damaging the rest of the internals. The piston/valve comes out with a hex key. The plate on the back of the pump will need an impact screw driver. If you don't have one you can find them at Sears or Harbor Freight Tools.
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Old 01-17-2006, 07:54 PM   #14
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Will do. Thanks for the tip.

The good news is I dropped the oil in the car and it came out clean (other than some assembly lube). I didn't find any large particles or anything that was picked up by a magnet. I ran it through a tight strainer and din't see anything come out either. We'll see what happens...
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Old 01-17-2006, 10:42 PM   #15
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Quote:
Originally Posted by Javier
Will do. Thanks for the tip.

The good news is I dropped the oil in the car and it came out clean (other than some assembly lube). I didn't find any large particles or anything that was picked up by a magnet. I ran it through a tight strainer and din't see anything come out either. We'll see what happens...
Based on that then I'd bet it's straight then. Get the new pump anyways, but still check out the old one for problems. If the old one looks to have a tight seal on the internal parts and no scarring then suspect the clearances of the engine internals to be off. Let us know.
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Old 01-17-2006, 10:49 PM   #16
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Quote:
Originally Posted by n2xlr8n
First thing: Establish what stock oil pressure is on a stock engine.

S.
Did you miss where I already posted that?

Everyone I have talked to with an STI has roughly the same pressures +/- 5psi
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Old 01-17-2006, 11:54 PM   #17
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dnow,

25psi sounds on the high side for idle especially w/ 5w-30 oil. You sure about that? I'm just seeing 17psi with the extra shim mod and an equivelant oil weight of 7w-35. My engine is within in spec clearances of the manual but I've got dry film coated bearings.
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Old 01-18-2006, 11:51 AM   #18
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Quote:
Originally Posted by tmarcel
dnow,

25psi sounds on the high side for idle especially w/ 5w-30 oil. You sure about that? I'm just seeing 17psi with the extra shim mod and an equivelant oil weight of 7w-35. My engine is within in spec clearances of the manual but I've got dry film coated bearings.

Im heading out in a few min, Ill tell you when I get back I could be a bit off, I am going off memory and I have a crappy memory I know the upper number is spot on.

I know I have been in 3 other STIs with OP gauges, and all 3 had the same readings I do +/- 5PSI.

There was also a thread a while back where people reported what they see, and most saw the same kind of pressures.
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Old 01-18-2006, 11:55 AM   #19
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Quote:
Originally Posted by Davenow
Im heading out in a few min, Ill tell you when I get back I could be a bit off, I am going off memory and I have a crappy memory I know the upper number is spot on.

I know I have been in 3 other STIs with OP gauges, and all 3 had the same readings I do +/- 5PSI.

There was also a thread a while back where people reported what they see, and most saw the same kind of pressures.

Make sure you get it nice and warmed up. Mine will show in the low 20's even after it's warmed up and driving for a little while and then slowly get to abot 17psi when hot (well maybe not hot )
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Old 01-18-2006, 01:04 PM   #20
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Quote:
Originally Posted by tmarcel
Make sure you get it nice and warmed up. Mine will show in the low 20's even after it's warmed up and driving for a little while and then slowly get to abot 17psi when hot (well maybe not hot )
25psi Idle and anthing over 3500 shows 80+psi.

That is after a 30min drive to work on 10w40.
As Davenow said, this is about what all Sti's I have been in run +/- ~5psi depending on oil weight.

TMS
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Old 01-18-2006, 06:03 PM   #21
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possibly could be slightly to much main or rod bearing clearance.
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Old 01-20-2006, 02:59 AM   #22
Javier
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Well, bad news. We changed the oil pump today and the pressures are still the same. I'm getting 11psi at idle (max), 32psi at 3000rpm cruise, and 86psi at cold start.

Tomorrow we need to figure out what the plan of action is from here on...
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Old 01-20-2006, 03:05 AM   #23
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After trying another pump and its still down on pressure its got too much clearence.
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Old 01-20-2006, 03:23 AM   #24
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Exactly.. like I had said... excessive main and rod bearing clearance.
Thank you crawford for supplying the wrong bearings...oops
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Old 01-20-2006, 04:26 AM   #25
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Exclamation

Plastigauge is less than a buk a stick and saves alot of misery later on.
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