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Old 02-04-2014, 11:53 AM   #1
TyranosaurusWRX
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Default Low oil pressure

Been trying to troubleshoot a low oil pressure situation. I have a simple Autometer gauge with an electronic sender. The sender is connected to a braided line going to the block. Normally when all is working the gauge reads between 75-80psi when the block is cold and once it warms up it idles between 15-20 psi and revs up to 70 psi while driving. When I first start the car up cold I'm getting almost 75psi but once it warms up fully I get about 12psi on idle and am lucky to hit 45psi when revving it up driving. It's a recent motor build so I really haven't ran this hard at all. It only has a little over 700 break in miles boosting to about 5lb on the average keeping the revs under 4k so I really didn't notice the problem right away.

I've replaced the sender and the oil pump, and even changed the oil just in case there was an issue with viscosity. The old oil really wasn't in bad shape, not a lot of metal or flakes outside of normal break in. I would think that if the oil pickup was cracked it would not be getting any pressure, or relatively none. Not sure really what else could cause it....maybe one of the two grommets/seals in the oil pan?
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Old 02-04-2014, 12:20 PM   #2
atomicfire
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What kind of oil, and where was the oil pressure sender installed? What are the specs on the block build? DAVCS? Oil pump? What internals were used, and what was the rod and mains clearance?
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Old 02-04-2014, 12:57 PM   #3
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The gauge could be bad, it sounds like all your readings are low. You need to either get the gauge and sender calibrated as a system or mount a temporary high quality gauge to check the pressure.
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Old 02-04-2014, 01:40 PM   #4
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Quote:
Originally Posted by atomicfire View Post
What kind of oil, and where was the oil pressure sender installed? What are the specs on the block build? DAVCS? Oil pump? What internals were used, and what was the rod and mains clearance?
Without getting too far off topic (I understand why you are asking tho) the specs/clearances are well within reason. The first oil pump was the oem 10mm. Also changed it out to a 12mm (because it was available) with absolutely no change in pressure. The short block (built 2.35 stroker) was previously used (and working) in another car before I sold it with a stock long block and kept this short block - and did not have these issues at that time. This is my 05 Sti btw, intake AVCS only.

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The gauge could be bad, it sounds like all your readings are low. You need to either get the gauge and sender calibrated as a system or mount a temporary high quality gauge to check the pressure.
LIChuck, I agree and that thought crossed my mind but why would it hit close to proper pressure at start up? Seems like it would either work or not but I've seen stranger things.
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Old 02-04-2014, 01:45 PM   #5
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Where was the oil pressure sender installed? You'll see different readings in different areas.
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Old 02-04-2014, 01:46 PM   #6
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Quote:
Originally Posted by atomicfire View Post
Where was the oil pressure sender installed? You'll see different readings in different areas.
Oh yeah, meant to mention that. It's on the back of the block in the port over the #3 piston. Pretty much had it in that locaton in many many builds.
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Old 02-04-2014, 05:51 PM   #7
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Couldn't a hairline crack in the pickup cause lower pressures, yet not cause zero pressure?

When mine started forming a crack, my stock light would flicker for a second every time I would start the car, but I didn't have a oil pressure gauge at the time to see what it was reading at higher rpm's. But I can imagine that it was lower than normal :P

I'm just kinda thinking out loud..
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Old 02-04-2014, 07:15 PM   #8
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It very well could be. I guess any way you slice it I'm going to have to pull the oil pan. I was just under the impression that when the pick up tubes cracked they opened up...but I could see a hairline causing problems like that.
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Old 02-04-2014, 08:38 PM   #9
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If the pickup has a crack you might have funky symptoms for an hour or a few days, or maybe more, if you're lucky enough to have any symptoms.

Definitely a good idea to pull the pan. Might not be a bad idea to get a cheap $15 mechanical gauge and verify the pressure you're seeing too. They are handy to keep in your toolbox too. Personally, I wouldn't continue to drive the car until finding out what's going on, that pressure is below the factory minimum spec, 14psi, which is horribly low.
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Old 02-04-2014, 09:23 PM   #10
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Check the pickup I just lost a motor in my WRX from the pickup tube failing at 58k.
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Old 02-04-2014, 09:44 PM   #11
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Thanks for all the input. The car is definitely not moving until I'm confident of the issue.
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Old 02-10-2014, 10:51 AM   #12
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Any updates?
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Old 02-10-2014, 12:02 PM   #13
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Not yet, it's been way too snowy and cold I used to be that ambitious but not so much anymore lol. I will definitely report back.

Last edited by TyranosaurusWRX; 02-19-2014 at 11:24 PM.
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Old 02-19-2014, 11:22 PM   #14
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I hooked up a different gauge to the oil pressure feed line and got the same results. Pulled the pan today and took a bright light and some fine sandpaper to the oil pickup tube and I don't believe I see any cracks. The o-ring that goes to the back corner of the pan to the block is looking a little gnarled so I'm thinking that this might be the issue.



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Old 02-20-2014, 05:59 AM   #15
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That's not your issue. That's just a vent line. The seal goes way back to N/A applications and has just stuck around. We have no seal on our pan there, in fact other aftermarket pans have NOTHING there. It's purpose is to reduce the effects of crankshaft turbulence on the PCV vent.

That looks about normal for them, they are not an o-ring. Did you pull the pickup out?

You can have a very small crack that is difficult to detect. Sometimes impossible to see until you take it our and flex it some. Examples...






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Old 02-20-2014, 07:21 AM   #16
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Thanks for the clarification, I was never really sure of it's function. I know that it's never been an issue before. I'll warm up the tube and put some pressure on it at different angles and see if something shows but at this point it's not obvious.
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Old 02-20-2014, 09:48 AM   #17
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No problem. If you've got the pan off and pickup out. You might as well just replace it, If an aftermarket piece is not in the budget, replace it with a new one every 20K miles to insure you don't have this kind of failure.

Here are some pics of what to look for in the braze flux, tell tale signs of stress...





The last thing you want is this to happen...

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Old 02-20-2014, 10:13 AM   #18
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The 2nd pic with the blue circle...that's a crack, not the flux?
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Old 02-20-2014, 10:38 AM   #19
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Stress in the flux/tube can cause the appearance of crazing (top pic) or flaking (bottom pic) typically in a line. Usually, but not always, it's seen at or near the tube's weld seam. You can see this well in the bottom pic where the weld seam runs up the tube, right under the area circled. Neither of these examples are a crack... yet.
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Old 03-04-2014, 11:09 AM   #20
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Just an update.... replaced the oil pick up (yes, with the Killer B ;]), pulled and cleaned out the oil cooler just in case, replaced filter and oil. I'm only getting about 5-10psi more out of it. I'm thinking that's more the 15w-40 rotella than anything. Maybe it's in the build but I'm not seeing where. I fount my notes regarding the ACL main bearing clearances and they were all right around .0015 via plastigauge....So not sure what else to look for but the search goes on.
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Old 03-04-2014, 11:35 AM   #21
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Quote:
Originally Posted by TyranosaurusWRX View Post
Just an update.... replaced the oil pick up (yes, with the Killer B ;]), pulled and cleaned out the oil cooler just in case, replaced filter and oil. I'm only getting about 5-10psi more out of it. I'm thinking that's more the 15w-40 rotella than anything. Maybe it's in the build but I'm not seeing where. I fount my notes regarding the ACL main bearing clearances and they were all right around .0015 via plastigauge....So not sure what else to look for but the search goes on.
Sad face for the plastigauge your clearances are probably off from what that sheet says.
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Old 03-04-2014, 11:39 AM   #22
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did you keep the old pickup tube? did you find any cracks?
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Old 03-04-2014, 12:11 PM   #23
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Quote:
Originally Posted by Razgeiz View Post
Sad face for the plastigauge your clearances are probably off from what that sheet says.
I know some people like to make that argument but plastigauge has always worked for me in the past. Not to mention even the manual states to use it. .0015 is a little loose for factory tolerances but it's not that uncommon I don't think for the ACLs depending on which ones you use.

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did you keep the old pickup tube? did you find any cracks?
No cracks, yeah I kept the old one. It looks a lot like the middle pic on post 17.
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Old 03-04-2014, 01:43 PM   #24
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5-10psi everywhere or just at idle?

So to review... You have a new pickup. Have tried different pumps.

What is you idle RPM? What port are you measuring oil pressure from?
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Old 03-04-2014, 01:52 PM   #25
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Actually everywhere but idle to be honest. Idle RPM is about 850-900. Pressure is measured from the galley above the #3 piston, near the breather outlet.
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