[Blanc89]

Just had the heads machined and new rings in. After starting up the oil pressure measured on the block went up to 100 psi which is really scary. Verified this with another mechanical gauge. Is this a real problem or does the engine need to be run a while?
This is an '07 2.5 liter non turbo

 

[plain OM]

The oil pump has a relief valve that is set around 85 psi so pressure in the oil passages after the pump should not be at higher levels. (See diagram below.)

Do you know if the pressure was as high before the work on the heads?

Was anything done to the oil pump during the head and ring work? Wondering if the relief valve was affected in some way.

I guess it's remotely possible the relief valve piston could seize in the valve bore. . . .

Are you getting oil to the heads (camshaft, AVLS solenoid)?

 

[Blanc89]

Thanks for the great diagrams and info. Unfortunately I didn't measure the oil pressure before I started the rebuild. The block sat around for about a year before I reassembled it so there could be the possibility of the oil relief valve in the pump being stuck. Is it possible to take the plug off the relief valve and remove it without having to remove the whole oil pump assembly? I am also looking into verifying that the oil is going to the cylinder head. What is the best way to do this? I did remove the oil sensor switch next to the AVLS solenoid. No pressure was measured there but I'm not sure if being at idle and the position of the solenoid would effect that. I even left the port open expecting to see oil spurting out but that didn't happen. Could this be a telltale sign of no oil getting to the head or should I remove the solenoid assembly to see if oil comes out?
Thanks,
Mark

 

[plain OM]

Is it possible to take the plug off the relief valve and remove it without having to remove the whole oil pump assembly?

I think the timing belt tensioner is in the way. If it's removed then there might be enough clearance. There's a gasket on the plug that might have to be replaced -- it's supposed to be one-time use.

I even left the port open expecting to see oil spurting out but that didn't happen.

That seems odd to me, but I've never actually tested it.

Oil from the head supply (arrows point to the lines in the diagram above) goes to the solenoid mount at the end of the head. It goes through a small screen filter inside the mount and into the spool valve. When the solenoid is off, the oil flow is essentially off, but any leakage/bypass through the spool valve goes to a passage in the head that drains into the camshaft area and from there down to the sump. In contrast, when the solenoid is on, the spool valve directs the bulk of the oil to a pressure passage that goes to the camshaft, and from there to valve lift mechanism. The oil pressure sensor switch is in a vertical "T" line off the pressure passage.

When the engine is running the solenoid is always operating. At idle it's still being switched on and off by a 300 Hz duty cycle signal at 15%, so it's actually "on" 15% of the time. That leaves the question: At 15% duty cycle, would there be enough oil in the pressure passage to come up and out the open pressure switch port?

Perhaps not. When the solenoid is off the pressure passage is connected to the camshaft area drain, so the switch pressure passage might drain back faster than the time it takes for the oil to go from the solenoid up all the way up to the open switch port. At 15% duty cycle, each "on time" is only 500 micro-second followed by almost three milli-seconds of drain time.

(Incidentally, the solenoid duty cycle changes from 15% to 65% when the car is being driven and the rpm passes 1600 rpm or so. With the car stopped, in P or N, it doesn't switch to the higher level until the rpm passes 3100 - 3300.)

Did you check if oil does, or doesn't, come out on both sides, or only one?

Another way to test test the oil supply to the AVLS system might be:

Disconnect the harness connectors from both the solenoid and the pressure switch (installed in the head).

At the pressure switch, connect a multimeter set to read Resistance between the small center pin of the connector on the pressure switch and a good ground. With the engine off, (low pressure) the switch should be closed (low resistance between the pin and ground). (Or, remove the pressure switch and install a pressure gauge in its place.)

Connect clip leads to each of the pins in the solenoid connector and connect the other end of one of the leads to one terminal of a 9 V battery.

Start the engine. (This will probably cause a trouble code and the CEL to come on.)

With the engine idling, touch the other lead from the solenoid to the other terminal of the battery. This should turn the solenoid on. At that point there would normally be high pressure in the pressure passage that is being monitored by the pressure switch. If there is high pressure, the switch should change from closed (low resistance) to open (high resistance), or the oil pressure gauge should go from low to high pressure.

If there's little or no change, that could mean there's a blockage in the AVLS supply passages, or oil isn't getting to the head, or heads if the tests on both have the same result.

What head gaskets did you use (brand, part #)?

 

[Blanc89]

I think the timing belt tensioner is in the way. If it's removed then there might be enough clearance. There's a gasket on the plug that might have to be replaced -- it's supposed to be one-time use.



That seems odd to me, but I've never actually tested it.

Oil from the head supply (arrows point to the lines in the diagram above) goes to the solenoid mount at the end of the head. It goes through a small screen filter inside the mount and into the spool valve. When the solenoid is off, the oil flow is essentially off, but any leakage/bypass through the spool valve goes to a passage in the head that drains into the camshaft area and from there down to the sump. In contrast, when the solenoid is on, the spool valve directs the bulk of the oil to a pressure passage that goes to the camshaft, and from there to valve lift mechanism. The oil pressure sensor switch is in a vertical "T" line off the pressure passage.

When the engine is running the solenoid is always operating. At idle it's still being switched on and off by a 300 Hz duty cycle signal at 15%, so it's actually "on" 15% of the time. That leaves the question: At 15% duty cycle, would there be enough oil in the pressure passage to come up and out the open pressure switch port?

Perhaps not. When the solenoid is off the pressure passage is connected to the camshaft area drain, so the switch pressure passage might drain back faster than the time it takes for the oil to go from the solenoid up all the way up to the open switch port. At 15% duty cycle, each "on time" is only 500 micro-second followed by almost three milli-seconds of drain time.

(Incidentally, the solenoid duty cycle changes from 15% to 65% when the car is being driven and the rpm passes 1600 rpm or so. With the car stopped, in P or N, it doesn't switch to the higher level until the rpm passes 3100 - 3300.)

Did you check if oil does, or doesn't, come out on both sides, or only one?

Another way to test test the oil supply to the AVLS system might be:

Disconnect the harness connectors from both the solenoid and the pressure switch (installed in the head).

At the pressure switch, connect a multimeter set to read Resistance between the small center pin of the connector on the pressure switch and a good ground. With the engine off, (low pressure) the switch should be closed (low resistance between the pin and ground). (Or, remove the pressure switch and install a pressure gauge in its place.)

Connect clip leads to each of the pins in the solenoid connector and connect the other end of one of the leads to one terminal of a 9 V battery.

Start the engine. (This will probably cause a trouble code and the CEL to come on.)

With the engine idling, touch the other lead from the solenoid to the other terminal of the battery. This should turn the solenoid on. At that point there would normally be high pressure in the pressure passage that is being monitored by the pressure switch. If there is high pressure, the switch should change from closed (low resistance) to open (high resistance), or the oil pressure gauge should go from low to high pressure.

If there's little or no change, that could mean there's a blockage in the AVLS supply passages, or oil isn't getting to the head, or heads if the tests on both have the same result.

What head gaskets did you use (brand, part #)?

I tried your suggestion of activating the AVLS solenoid to see if the oil would come out of the pressure sensor port. So I tried the side closest to the battery and the results were like cartoonish; oil shot out of that hole and hit the hood! Alot of oil pressure here.
Well, that tells me that oil is going to the head, is it safe to assume that it is traveling though the rocker journals? (These heads don't use hydraulic lifters.) This was my main concern because I don't want to wreck the heads.
The gaskets are Felpro.

 

[plain OM]

. . . oil shot out of that hole and hit the hood!

I actually suggested having the oil pressure sensor switch, or a pressure gauge, in place for that exact reason, but I guess the experience is a good visual verification instead!

The pressure at the engine oil pressure sensor on the engine block is downstream of the pump and the oil filter. Given that it doesn't appear the lines to the heads are blocked, the pump relief valve should be controlling the pressure at the engine oil pressure sensor location. If that's measuring the 100 psi, then the relief valve might be stuck.

I've seen only a few discussions where the oil pressure had been gauged and reported. I don't recall any suggesting 100 psi (when the engine and oil are started cold and the engine is running at a high idle) but I'd have to find them again. I do recall that on cold starts, the pressure can be fairly high, but I wouldn't think it could be well above the relief valve target.

EDIT 2022-05-17 0700 EDT: Looking for 2006-2012 2.5 (NA or turbo) oil pressure data does mention reports of pressure being as high as 100 psi on "cold starts", despite the relief valve specification. Some are from LegacyGT.com where there are posts with pressures in the 90s on cold start. These might be specific to the 2.5 turbo engines usually discussed there, but perhaps that's what you're seeing after all, and with some warming, it comes down.

 

[Blanc89]

 

[Blanc89]

This is the piston that came out of the oil pump pressure relief valve. I was able to remove it without much resistance. The barrel looks clean except for a minor scoring line where the valve spring would be.
Does the piston look worn enough that it could cause a problem?

 

[plain OM]

I don't have any reference for that, but would think that wear on the side of the piston would have the opposite effect.

If it came out without resistance I'd think it's probably okay. But then the price appears to be around $5 (2007 subaru Outback Valve Oil Relief -E/#294070 - 15019AA040 - Genuine subaru Part) if there's any doubt.