BigAl Posted May 10, 2010 Share Posted May 10, 2010 So finally got around to doing an oil change on the hatchback and am seeing some weird symptoms. Before the oil change, the oil pressure sat around 50-60 PSI at cold idle and dropped near 30 at warm idle. When up to temp it would run 60-70 at highway speeds (2800-3500 RPM). After the oil change, it sits well over 70 PSI at cold idle, and even after allowing the engine to warm for 6-7 minutes, it does not drop. If I try to drive it like this, I can not take it above 1200 RPM or the pressure spikes past the top of the gauge (75 PSI+). After a few minutes of gentle driving, the oil pressure will drop down near 50 at idle, and will sit right at 70-75 PSI under highway load, but it will not return to its original levels. I have triple checked the oil level and it is perfectly at the full mark, not over, not under. I used a NAPA Gold oil filter and Mobil 1 10w-30. According to the manual, 10w-30 is a recommended viscosity, so I don't think the oil is to thick. Also, I figured that even if I had used an incorrect viscosity, the pressure would come down after allowing the engine to warm, so I dont think that is my problem. Any ideas? Is this engine really that sensitive to synthetics? Any help would be appreciated, continuing to drive it at these high pressure levels is making me uneasy. Thanks in advance guys (and gals) Al Quote Link to comment Share on other sites More sharing options...
dyellowninja Posted May 10, 2010 Share Posted May 10, 2010 Call that guy you know... he can help. Quote Link to comment Share on other sites More sharing options...
asis Posted May 10, 2010 Share Posted May 10, 2010 What type of oil pressure gauge do you have? If electric could be sending unit or gauge itself... 60-70 @ temp @ highway speed, sounds a bit high to me to be normal, even with a fresh rebuild...but I don't have a gauge on my EA81, just my EA82, and 40-45 @ temp @ highway speeds is all it has ever run. Might try an engine flush...I think Riselone ....? has been recommended also. I have used GUNK engine flush before and it does a good job, just follow the instructions. Worse case if you do have a blockage, could use an old aviation trick. Drain the oil, fill to the low mark with diesel fuel, start the engine for 15-30 seconds, drain and refill with oil. Quote Link to comment Share on other sites More sharing options...
BigAl Posted May 10, 2010 Author Share Posted May 10, 2010 The car is an 84.5 EA81 hatch, it came equipped with a factory oil pressure guage. So does it sound like I have a clog in the pickup or in my oil channels? Quote Link to comment Share on other sites More sharing options...
asis Posted May 10, 2010 Share Posted May 10, 2010 The car is an 84.5 EA81 hatch, it came equipped with a factory oil pressure guage. So does it sound like I have a clog in the pickup or in my oil channels? I would imagine it is electric but I honestly don't know for sure. I would suspect the sending unit or gauge tho as being off even prior to the oil change. Any blockage in a direct feed oil pressure gauge should result in a lower reading. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted May 10, 2010 Share Posted May 10, 2010 Unless you verify the gauge reading with a second reading from a shop gauge (mechanical would be the preference), anything you do or do not is based on speculation. TEST - then hypothesize. It may be nothing more than a bad sending unit or mis-calibrated gauge. GD Quote Link to comment Share on other sites More sharing options...
BigAl Posted May 10, 2010 Author Share Posted May 10, 2010 Unless you verify the gauge reading with a second reading from a shop gauge (mechanical would be the preference), anything you do or do not is based on speculation. TEST - then hypothesize. It may be nothing more than a bad sending unit or mis-calibrated gauge. GD Thanks GD I actually did things backwards and searched after making the post, seems the high readings and faulty sensors are all to common on these engines. Looks like I need to hook up a mechanical and verify what I am seeing. Any idea on what a 'Safe' range should be when its up to temp? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted May 10, 2010 Share Posted May 10, 2010 No less than 20 to 25 psi when hot at idle. Cruise should be up around 50 to 70 psi. That's as read from a low-mileage EA81 hydro lifter engine in my wagon. New oil pump and Autometer gauge for oil pressure. And the gauge has real numbers calibrated in psi on it's face. GD Quote Link to comment Share on other sites More sharing options...
asis Posted May 10, 2010 Share Posted May 10, 2010 Thanks GD I actually did things backwards and searched after making the post, seems the high readings and faulty sensors are all to common on these engines. Looks like I need to hook up a mechanical and verify what I am seeing. Any idea on what a 'Safe' range should be when its up to temp? How many miles on the motor? Any rework been done? If you can idle at temp at 15 or so I would say that to be a safe min. Highway speeds @ temp 40 to 45 min. Can run and be fine with less but, is also an indication of tired motor. Quote Link to comment Share on other sites More sharing options...
asis Posted May 10, 2010 Share Posted May 10, 2010 No less than 20 to 25 psi when hot at idle. Cruise should be up around 50 to 70 psi. That's as read from a low-mileage EA81 hydro lifter engine in my wagon. New oil pump and Autometer gauge for oil pressure. And the gauge has real numbers calibrated in psi on it's face. GD Have you actually measured those numbers on any ru engines with over 150k? just curious...seems pretty high expectations. Also is there a bypass for the filter??? If so, what is the release pressure? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted May 10, 2010 Share Posted May 10, 2010 Have you actually measured those numbers on any ru engines with over 150k? just curious...seems pretty high expectations. Being that the oil pressure reading is taken directly at the pump, the only variables that affect the reading are the condition of the pump, type of oil, engine speed, etc. Mileage and internal engine wear have basically zero effect on the pressure reading at the pump. It has been my experience with the EA81 that a 20 psi hot idle reading is possible on any engine providing the pump is within specified wear limits. They do wear - sometimes a LOT. Depends on how the oil and filter have been treated. My hatch engine has low compression on the #2 cylinder and about 260k on it. The oil pump was trashed when I got it and the first thing I did once I got it driving was replace the pump. The oil pressure went up to about 20 at hot idle which was at least a 5 to 7 psi increase and the cruise went up by about 15 or 20 psi easily. No - I didn't verify any of this with a seccond gauge but I'm very comfortable with the EA81's and their oil pumps. I know what bahaviour to expect and where the pressure should be - that coupled with what I saw when I dissasembled the pump as well as the differences in the readings from old pump to new tells me it's right where it should be now. Also is there a bypass for the filter??? If so, what is the release pressure? I think you are refering to the pressure relief valve inside the pump - the one in the filter is a differential pressure valve and opens with very low differential - probably 5 psi or less. The one inside the pump is based on the calibration of the relief valve spring - I do not know what it's setting it but it's probably somewhere in the 60 to 70 psi range as I have never seen a verifiable reading higher than that. GD Quote Link to comment Share on other sites More sharing options...
asis Posted May 10, 2010 Share Posted May 10, 2010 (edited) Being that the oil pressure reading is taken directly at the pump, the only variables that affect the reading are the condition of the pump, type of oil, engine speed, etc. Mileage and internal engine wear have basically zero effect on the pressure reading at the pump. It has been my experience with the EA81 that a 20 psi hot idle reading is possible on any engine providing the pump is within specified wear limits. They do wear - sometimes a LOT. Depends on how the oil and filter have been treated. My hatch engine has low compression on the #2 cylinder and about 260k on it. The oil pump was trashed when I got it and the first thing I did once I got it driving was replace the pump. The oil pressure went up to about 20 at hot idle which was at least a 5 to 7 psi increase and the cruise went up by about 15 or 20 psi easily. No - I didn't verify any of this with a seccond gauge but I'm very comfortable with the EA81's and their oil pumps. I know what bahaviour to expect and where the pressure should be - that coupled with what I saw when I dissasembled the pump as well as the differences in the readings from old pump to new tells me it's right where it should be now. Hmmm. Reading is taken at the pump...? Internal oil pump..? I know the one on my EA82 is. I am used to the sending unit being in an oil galley in the block or at the oil filter mount. I think you are refering to the pressure relief valve inside the pump - the one in the filter is a differential pressure valve and opens with very low differential - probably 5 psi or less. The one inside the pump is based on the calibration of the relief valve spring - I do not know what it's setting it but it's probably somewhere in the 60 to 70 psi range as I have never seen a verifiable reading higher than that. GD same as above, relieve valve inside the filter mount so if the filter clogs, oil can still bypass to supply the bearings.... thx for the education....just trying to transpose my knowledge to these critters...as you know I have a couple of EA71 to refurb Edited May 10, 2010 by asis Quote Link to comment Share on other sites More sharing options...
BigAl Posted May 10, 2010 Author Share Posted May 10, 2010 (edited) Motor is a hydraulic lifter EA81 with 211k. Not sure if any rebuild or refresh work has ever been done on it. Watched carefully on the drive home and it looks like I am right on with what GD is saying. Sitting right at 25 PSI at idle when hot and resting at 70 PSI during cruising speeds (55-60mph). Guess I was just being paranoid. I will still get a mechanical to check it out just in case. Thanks again guys Edited May 10, 2010 by BigAl Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted May 10, 2010 Share Posted May 10, 2010 Hmmm. Reading is taken at the pump...? Internal oil pump..? I know the one on my EA82 is. I am used to the sending unit being in an oil galley in the block or at the oil filter mount. All the Subaru engines use an external oil pump. Either driven directly off the end of the cam (in the pushrod engines) or driven by the timing belt in the case of the EA82/ER27 and the EJ engines. All the EA engines have the sending unit mounted directly to the pump housing while the EJ engines have the idiot lamp switch attached to the oil gallery on top of the block - but they have provision for mounting sending units to the pump as well. I'm sure in other countries this is probably done but all US models have an idiot lamp only. Here the threaded boss for the sending unit is blocked with an alan plug. same as above, relieve valve inside the filter mount so if the filter clogs, oil can still bypass to supply the bearings.... Right - but it's a differential pressure valve - it opens in response to the pressure created by a clogged element. If the element is not clogged then the pressure could be 1000 psi - as long as it's 1000 psi on both sides of the element the valve will still be closed.... so it has no relationship to the pressure being put out at the pump. thx for the education....just trying to transpose my knowledge to these critters...as you know I have a couple of EA71 to refurb No problem - you definitely should be taking the oil pumps off for a look - they can and do get really chewed inside. GD Quote Link to comment Share on other sites More sharing options...
asis Posted May 10, 2010 Share Posted May 10, 2010 (edited) All the Subaru engines use an external oil pump. Either driven directly off the end of the cam (in the pushrod engines) or driven by the timing belt in the case of the EA82/ER27 and the EJ engines. All the EA engines have the sending unit mounted directly to the pump housing while the EJ engines have the idiot lamp switch attached to the oil gallery on top of the block - but they have provision for mounting sending units to the pump as well. I'm sure in other countries this is probably done but all US models have an idiot lamp only. Here the threaded boss for the sending unit is blocked with an alan plug. Right - but it's a differential pressure valve - it opens in response to the pressure created by a clogged element. If the element is not clogged then the pressure could be 1000 psi - as long as it's 1000 psi on both sides of the element the valve will still be closed.... so it has no relationship to the pressure being put out at the pump. No problem - you definitely should be taking the oil pumps off for a look - they can and do get really chewed inside. GD Come to think of it I was remembering the pick up in the oil pan...and not really taking my time to think of where the actual pump is. I am used to the oil pump being ran off the cam/distributor gear, internally. It has been 15 yrs tho since I had the pan off my EA82 :-\ since you won't come visit me , guess I will just have to tear into one now... PS At least it seems we agreed on an error with the gauge or sending unit to the OP Edited May 10, 2010 by asis Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted May 10, 2010 Share Posted May 10, 2010 since you won't come visit me , guess I will just have to tear into one now... Just busy is all. Always busy. I'll get up there eventually PSAt least it seems we agreed on an error with the gauge or sending unit to the OP Yes - the diagnosis is correct. Always verify gauge readings..... well shut down the machine you are working on THEN verify gauge readings. Faulty gauges are not an uncommon failure in any type of machine. GD Quote Link to comment Share on other sites More sharing options...
asis Posted May 10, 2010 Share Posted May 10, 2010 Just busy is all. Always busy. I'll get up there eventually No worries:) etu Yes - the diagnosis is correct. Always verify gauge readings..... well shut down the machine you are working on THEN verify gauge readings. Faulty gauges are not an uncommon failure in any type of machine. GD I got sumin right weeeeeeeeeeeeeee! Quote Link to comment Share on other sites More sharing options...
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