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Old 03-28-2009, 08:16 AM   #1
DoodieHead
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Default Low oil pressure

I have been reading posts for the past couple hours and I have yet to find an answer. First off I will post what I have for a setup to eliminate 90% of peoples posts.

2001 EJ25 block resleeved and semi-closed deck
Pauter rods w/ Cosworth 100mm pistons
TWE Stage III prototype heads
ACL coated race bearings
Stock crank
Stock oil pan and pickup
WRX oil pump (shimmed .80mm)
Processwest oil cooler
Mechanical Autometer oil pressure gauge (in RED for the people that cannot read)
Royal Purple 15w 40
Autronic SMC
Perrin GT35r kit

For the most part that is everything that I can think of which would affect oil pressure. Now for the problem.

When first starting my car my oil pressure light is on for the first 5 seconds or so of cranking. I actually crank it till the light goes off in order to eliminate the motor from being starved. I am able to do this as I am running the Autronic w/o the idle air control solenoid and my car will not start w/o giving it throttle. I know it is not the pressure sender as my Autometer gauge shows no pressure during this time.

After the car is started my max oil pressure (cold) is right about 65psi @1500rpms. When the car is warmed up @ idle my pressure is about 14-16psi. What really worries me is the old 'RULE OF THUMB' 10psi per 1000rpms. Under normal driving around 3000-3500rpms pressure is just above 40-45psi and goes no further. If I continue through the powerband even to 6000rpms there is still no additional pressure, it is almost like hitting a brick wall. 45psi is as much as I have seen past 3500rpms.

The main reason I am posting is that I am worried about getting high into the RPM range and loosing some bearings. My setup is good for 9000rpms and I worry about taking it beyond 5000rpms, because of the 'RULE OF THUMB'.

A few of the posts I have read seem to lean me more toward my oil cooler setup. Seems that running an external will make less pressure, but I dont know.

My Autometer gauge is plumbed into the top rear oil galley. From what I am told there should be more pressure on the highend.

I have been searching for an answer to this and I have come up short. Seems as though most peoples problems are in their bearings, but I am almost 100% sure mine are fine. I have had bad bearings in the past and know the signs. Motor sounds amazing and runs like a raped ape. There are absolutely no external leaks and I also have no blow-by. Spark plugs all look good with no signs of burning oil, all look light brown.

What I have concluded thus far from reading other posts is that:
- Pickup tube is fine, as it would show fluctuation in oil pressure
- Possibly bearing clearances, but that would not explain why oil pressure goes no further than 45psi.
- Oil pump might be done for (my only possible conclusion). Planning on buying 08 STI pump, but I dont know the warning signs of a dead/dying pump and dont want to waste money.
- Crack in the block (checked before I put together).
- Processwest oil cooler is killing my oil pressure. UPDATE: (20+psi difference after oil cooler disconnected)

I am sure someone out there has had this problem, I hope. Really looking forward to some replies as I am @ a complete stand still.

I have done 100% of the work.
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Last edited by DoodieHead; 03-30-2009 at 01:05 PM.
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Old 03-28-2009, 09:49 AM   #2
silver-duck
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Iam not an expert but I know your pressure is too low[my 06= 100 cold idle/35-40 hot idle and 4000rpm=100+ cold 90+ hot]with amsoil 15-50 race oil and filter with guages[pressure and temp] reading of sandwich between oil filter.
TRY THIS; disconnect oil cooler and record pressure's
Put in amsoil 15-50 racing oil and filter and record pressure's
Take pressure reading off of sandwich adapter and record
Tear motor down?
good luck
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Old 03-28-2009, 10:09 AM   #3
moorebl
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i seriously think you have a oil pump problem. with all that motor you should have slapped a modified oil pump or a cosworth unit. but there is a problem in there. i would suggest get a new pump. i have a sleeved motor and my ar FABRICATION MODIFIED OIL PUMP IS A MONSTER. i still have the stock 05 sti oil pump in pristine condition with 5 k miles on it. if you are interested in getting it hit me up.
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Old 03-28-2009, 11:09 AM   #4
jigga
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well... it is a rule of thumb, not a law... Nascar engines don't run 90psi of oil pressure up there either.. IIRC, they get by with 60psi up top without grenading themselves.

Where are you reading the oil pressure from?

You are correct in that oil pressure does drop a tad with the use of an external oil cooler, but you usually are able to get that pressure back in the form of the higher oil pressure you see when running cooler oil.

Are you sure your oil levels are correct? Some tend to use a WRX dipstick with an STi pan, and don't realize that their oil readings are off... lower than they should be.

Why do you think your bearing clearances could not explain why your oil pressure goes no further than 45psi?
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Old 03-28-2009, 11:15 AM   #5
blkwagon
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Maybe bearing clearances too loose??? what did you set your clearances to??
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Old 03-28-2009, 12:09 PM   #6
DoodieHead
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Default

Thanks for the replys guys.

I will try and disconnect the oil cooler and see if that yields something.

I am unable to connect my oil pressure line to the sandwich adapter, as the line is the exact length and my oil pressure adapter is -6an and dont have a fitting for it.

Oil pressure is being taken from the top rear oil galley plug, under the throttlebody.

I really do not see too much difference in oil pressure with the oil cooler. After boosting/tuning (3-4 hard pulls) oil pressure drops about 4lbs. After a couple minutes of normal driving it will bump back up.

Fortunately my oil levels are correct. I have an RS pan w/ an RS dipstick.

The bearing clearances, regardless of being tight or loose should still go up with the RPM range. I guess it is possible that they could max out @45psi. Not sure what the clearances were, all I know is that they were ACL Race Bearings which are sightly loose compared to the STD. I think on the box is said .001, IIRC.

The main thing I want to know is why I am not getting oil pressure right when I crank the car over. That I am sure is where the problem begins. Might be the thick oil, but I still think the problem lies in the pump.

Thanks again guys.
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Old 03-28-2009, 12:22 PM   #7
andya
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From what I've read here, everything points to the oil pump or sending unit for the gauge. Loose bearing clearances will still show high pressures when cold and a big drop when hot. The pressure would still rise in proportion to RPM instead of stopping at a particular reading. The regulator in the pump controls max hot pressure.
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Old 03-28-2009, 12:27 PM   #8
DoodieHead
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Quote:
Sending unit for the gauge
IF YOU READ CLEARLY, YOU WOULD NOTICE I HAVE A MECHANICAL GAUGE. LOOK AT MY FIRST POST.

Yes, I agree, the pump is probably shot.
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Old 03-28-2009, 12:31 PM   #9
andya
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OOPS.... My bad....
Did you bleed the air from the feed line to the gauge first? Air causes those Gauges to do weird things.
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Old 03-28-2009, 12:32 PM   #10
DoodieHead
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Lets just ahead and say the gauge is fine and it is reading correctly. Back to the real problem. I just installed the gauge a month ago. It is very consistent on a daily basis.
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Old 03-28-2009, 12:46 PM   #11
DoodieHead
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What are the symptoms for a bad oil pump? This might be a good start.
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Old 03-28-2009, 12:52 PM   #12
Patrick Olsen
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What size are the lines for the Process West oil cooler?
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Old 03-28-2009, 01:20 PM   #13
andya
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Quote:
Originally Posted by DoodieHead View Post
What are the symptoms for a bad oil pump? This might be a good start.
From experience, the first sign is slow pressure build on hot startup. I have also seen a broken regulator spring do the same thing, but it was not a subaru engine. The regulator could also be stuck partially open as noted with some of the new pumps.
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Old 03-28-2009, 08:39 PM   #14
Patrick Olsen
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Quote:
Originally Posted by Patrick Olsen View Post
What size are the lines for the Process West oil cooler?
In searching for something else I found this old thread and figured I'd post it here. If you're using -8AN lines then that could be the cause of the low peak pressure.
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Old 03-28-2009, 11:00 PM   #15
jigga
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Quote:
Originally Posted by Patrick Olsen View Post
In searching for something else I found this old thread and figured I'd post it here. If you're using -8AN lines then that could be the cause of the low peak pressure.
he mentioned earlier that he didn't notice much change in oil pressure with the oil cooler in place... Must be something else..
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Old 03-28-2009, 11:27 PM   #16
wrxwhat
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I've had this problem for 2 years now. My car makes ~10psi at idle warm, and never ventures above 60psi even at 7500 rpm. Cruising at 3000rpm my oil pressure is about 40psi. So yeah, 2 years and 35,000 miles of getting the absolute **** beat out of it, my built motor is just fine. Run some thicker oil, though.
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Old 03-29-2009, 08:55 AM   #17
DoodieHead
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How thick of oil do you recommend? 15w 40 is too thin?

Thanks for the replys, the posts were very informative.
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Old 03-29-2009, 03:49 PM   #18
wrxwhat
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With 5w30 my oil pressure is on average at any given RPM above idle about 8-12psi lower than when I use 10w40..
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Old 03-29-2009, 04:03 PM   #19
generalee69
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Your symptoms sound pretty close to my symptoms... unfortunately I have an electric O/P gauge. My problems went away when I grounded the body of the sender to the intake manifold. And I verified I had good pressure with a mech gauge.... Sorry not of much help -- just trying to post some info for people in the future who may be searching for low oil pressure questions.
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Old 03-29-2009, 04:48 PM   #20
Patrick Olsen
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Quote:
Originally Posted by jigga View Post
he mentioned earlier that he didn't notice much change in oil pressure with the oil cooler in place... Must be something else..
He did? I see in his original post...

Quote:
Originally Posted by DoodieHead View Post
...
A few of the posts I have read seem to lean me more toward my oil cooler setup. Seems that running an external will make less pressure, but I dont know.
...

What I have concluded thus far from reading other posts is that:
...
- Processwest oil cooler is killing my oil pressure.
He followed that up with this...

Quote:
Originally Posted by DoodieHead View Post
Thanks for the replys guys.

I will try and disconnect the oil cooler and see if that yields something.

I am unable to connect my oil pressure line to the sandwich adapter, as the line is the exact length and my oil pressure adapter is -6an and dont have a fitting for it.
He has not posted back about trying that since making those comments.

This comment...
Quote:
Originally Posted by DoodieHead View Post
I really do not see too much difference in oil pressure with the oil [running] cooler. After boosting/tuning (3-4 hard pulls) oil pressure drops about 4lbs. After a couple minutes of normal driving it will bump back up.
... was in response to your comment about how the pressure changes when the oil is warm vs. when the oil is cooler. I've added the "[running]" to show what he meant.

I still think the smart thing to do is to try running without the oil cooler and see what oil pressure does.

Pat
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Old 03-29-2009, 07:44 PM   #21
DoodieHead
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Thanks for clearing things up Pat. Unfortunately my area is under a winter storm warning right now and we are expected to get up to a foot of snow, which is why I have not posted any new information. My car is not winter worthy or even partially wet road worthy. Soon as the roads clear I will post my results.
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Old 03-30-2009, 12:44 PM   #22
DoodieHead
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Just disconnected the oil cooler and I am allowing it to drain. Will have some info here in awhile.
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Old 03-30-2009, 01:03 PM   #23
DoodieHead
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Well, seems at though the oil cooler is responsible for the oil pressure problem. I have about 82psi without the oil cooler on startup, as compared to the 62psi I had with the cooler on.

I also think the oil pump is bad, as the oil pressure light still takes about 10 seconds to turn off during startup (I dont allow the car to start with the light on).

We got quite a bit of snow last night, so the roads are horrible. Just need a little sun to get the snow melting so I can go for a ride and see if the oil goes up with the rpms.

Hope to have some results this afternoon.

Thanks again for all your suggestions and information.
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Old 03-30-2009, 01:13 PM   #24
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Quote:
Originally Posted by DoodieHead View Post
Well, seems at though the oil cooler is responsible for the oil pressure problem. I have about 82psi without the oil cooler on startup, as compared to the 62psi I had with the cooler on.

I also think the oil pump is bad, as the oil pressure light still takes about 10 seconds to turn off during startup (I dont allow the car to start with the light on).

We got quite a bit of snow last night, so the roads are horrible. Just need a little sun to get the snow melting so I can go for a ride and see if the oil goes up with the rpms.

Hope to have some results this afternoon.

Thanks again for all your suggestions and information.

More likely than the pump being bad, is that the o-ring between the pump and the block is compromised. This will cause the pump to lose its prime. It can take several seconds of cranking in order to build pressure. It's fairly easy to damage this o-ring during the pump install if you're not careful. I use a little bit of grease to hold it in place when I slide the pump over the crank.

-Duncan
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Old 03-30-2009, 01:47 PM   #25
DoodieHead
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That is the exact same way I installed the pump. Just put a little grease on the o-ring after it is in the hole and push the pump on.
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