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Oil Pressure Issues


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Hi all, I just picked up this basket-case 06 LGT for super cheap and got it running well enough to at least drive (LOTS of little things). But now when it's at hot idle, the oil light flickers. I measured oil pressure with a mechanical gauge under the alternator and measured 40 psi on cold start, and 4 psi hot at 750 rpm.

 

I looked through here for advice and saw that the most common causes are a cracked pick-up and screws backing out of the oil pump back plate. Took out the pick-up and didn't see any cracks but replaced it anyway with a new OEM one and a new gasket. Took the oil pump off and those screws are not budging. I did notice that whoever was in here last didn't use an o-ring on the high pressure port, just RTV. So I put a new o-ring in there thinking that's the problem, threw it all back together, and I've gotten nowhere.

 

Banjo bolts are all clear of filters, turbo had been upgraded to a VF52 at some point so I don't know if the stock one blew up or the owner just wanted an upgrade. Both new OCVs for the AVCS, still only 3-4 degrees max advance. Tune is set for 20 max. I think the low oil pressure is causing it to not be able to push the cam pulley enough. Either that or the pulleys are stuck. The car bucks and kicks below 3,000 rpm and it's pulling timing for knock. I turned down the boost for the time being to 14 psi I think. The map that was in it had boost set to 19 or 20 psi.

 

I'm trying to fix this cheap, but I'm trying to completely fix it. Next step for me is to replace the oil pump because I didn't take the rotor out to inspect it. Should I go with an 11mm pump or just another 10mm? Would an 11mm just mask the issue if the current pump is fine?

 

Any other ideas on what's going on here would be a massive help. Thanks.

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I don't have a lot to add, but I'd be very hesitant to just slap a new oil pump on hoping that will fix the problem.

 

I've heard horror stories here about turbos blowing up, sending metal fragments into the lubrication system, only to have big problems after they slap a new turbo on. So I guess what I'm saying is, I wonder if something like that has happened with the previous owner, obstruction(s) in the lubrication system.

 

Towards the bottom of the first post you'll see "Preventative measures after failure."

https://legacygt.com/forums/showthread.php/turbo-failure-wiki-173358.html

 

 

The turbo owners will probably be able to help you out more, just wanted to throw that out there for now.

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Get the 10mm pump. The only other thing I can think of besides the pump would be that the bearing clearances are so loose that your oil pressure is low. Your pump could have the bypass plunger stuck open as well which would cause low oil pressure.

 

One other thought is to check the turbo oil feed line to be sure the correct orifice bolt is being used. I don't think the change in size would cause such a drastic change in oil pressure though.

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So I guess what I'm saying is, I wonder if something like that has happened with the previous owner, obstruction(s) in the lubrication system.

 

Towards the bottom of the first post you'll see "Preventative measures after failure."

https://legacygt.com/forums/showthread.php/turbo-failure-wiki-173358.html

 

Thank you. I totally overlooked the oil cooler. If a new 10mm pump doesn't fix it, then I'll try a new cooler. I used to work heavily with the Toyota 3S-GTE and if an engine had a bearing failure, the oil cooler would get clogged and wouldn't be able to be cleaned. I just don't know if this engine has seen a turbo failure. It probably has, but there's a small chance that it's clean. And I like being hopeful. Although it almost never works. :lol:

 

Get the 10mm pump. The only other thing I can think of besides the pump would be that the bearing clearances are so loose that your oil pressure is low. Your pump could have the bypass plunger stuck open as well which would cause low oil pressure.

 

Ah, forgot to mention in my original post that I'm not noticing any bottom end noise at all, which leads me to believe that the bearings might be okay. The only noise I'm noticing is a slight ticking from the heads, but I think it might be valve clearances. I haven't checked them yet and they probably haven't been checked in a long while.

Is there a way to check/unstick the bypass plunger without taking the pump off again? If I have to take it off, I'll just slap a new one on there. Not worth doing it a third time.

 

 

Thank you both for your replies. This is why I still love forums. :icon_chee

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Low oil pressure cause the cams to over advance. Not under advance. If your oil pressure was as low as you measured the engine would have already siezed. Check oil pressure at the AVCS valve if you want to see whats getting to the cams. You could very well have an obstruction. Oil passages are as small as <1mm.

 

You are all over the place with troubleshooting and not verifying anything. Your just throwing parts at it.

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Subaru or aftermarket oil filters?

Purolator PL14612

 

Low oil pressure cause the cams to over advance. Not under advance. If your oil pressure was as low as you measured the engine would have already siezed. Check oil pressure at the AVCS valve if you want to see whats getting to the cams. You could very well have an obstruction. Oil passages are as small as <1mm.

 

You are all over the place with troubleshooting and not verifying anything. Your just throwing parts at it.

 

Could you please explain how low oil pressure causes over-advancing? I tried looking for diagrams or information on it but I only got generic descriptions.

 

Isn't the port that's under the alternator before the heads? I thought it's one of the first things after the filter.

 

The only part that I've replaced so far that wasn't broken or faulty was the pick-up. I've replaced an ignition coil that was open, a TGV sensor that was faulty, the OCV's which were stuck, the driveshaft U-joints that didn't have any needle bearings left, valve cover gaskets that were leaking, rear end links that were separated and a front ball joint that was worn out.

I'm all over the place with troubleshooting because I'm checking the most common causes of my symptoms. And I'm pretty sure verifying a flickering oil pressure light with a mechanical gauge is classified as verifying the issue.

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Yes, low oil pressure causes the cams to over advance. Avcs operation is well documented.

 

You already pulled the oil pump and mentioned buying another. If done properly removal of the pump should also mean replacement of the timing belt tensioner at a minimum.

 

There are multiple locations to take an oil pressure reading. No matter what you are low. I mentioned reading from the oil control valve to get a better reading of oil pressure to the cams and turbo.

 

If the ocv's were "stuck" a good cleaning should free them up. If the magnets are burnt and no longer attracting the slide, then its time to replace. If they were just gunked up, I would have expected the oil pan to have gunk too. Was there any debris in the oil or pan?

 

There are many possibilities of the cause of low oil pressure. You risk major damage troubleshooting without a decent knowledge of the ej255/7 engine and heads. In most instances if the oil pressure light comes on, its too late. Engine is done.

 

I am sorry the car is a basket case. Many are, it is a turbo Subaru. Chances are based on the condition of the rest of the car that there is an engine and turbo rebuild in the near future.

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I don't have much to add, m sprank knows these cars extremely well. I just hope you keep us posted.

 

I also wanted to say that I now understand your logic in looking at the oil pump after looking at the oil flow charts below. I'd be very suspicious of that oil cooler, and while I know it's not smart to just throw parts at a car, I'd replace your oil cooler before replacing the oil pump.

 

 

https://legacygt.com/forums/attachment.php?attachmentid=181940

https://legacygt.com/forums/attachment.php?attachmentid=181941

 

That oil filter doesn't have the correct bypass valve spec, but I don't think that makes any difference at all here. It could actually be helping to keep the engine lubricated with such low pressure, since less pressure is required to open the bypass valve, and allow more oil to bypass the filter element.

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There must be more debris in the oil passage, like RTV. PO did this car no favors. You keep digging will probably find more shortcuts.

 

More band aids are not going to to heal it. Surgery. Stat.

 

To truly fix it? Dig deeper.

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Even if the engine is considered "dead", this is an unusual problem so it's worth pulling it apart to see if the problem can be located.

 

 

Personally I'd start to suspect a spun bearing or something similar.

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