Hi to all,
Hope you can help with this,
I have a 99 uk turbo waggon (no mods yet). It has oil temp, oil pressure and boost gauges. The oil pressure has always been rock solid at 30/40 psi at tickover rising to 80/90 psi when moving (depending on temperature).

When accelerating or crusing the pressure has started to drop rapidly, sometimes in steps, to around 50 psi then builds back up to 80 again.

The Subaru book gives minimum oil pressures of 14psi at 800 rpm and 43psi at 5000 rpm which it is above (just), but that is not the point. It wasnt doing it before so something has changed? Any Ideas?

I have checked all round the engine for oil leaks, removed the under tray and checked underneath, no leaks.
Its not burning oil, no smoke also clean spark plugs.
Doesnt seem to be loosing any oil or water and isnt making any strange noises (yet).
Im kind of hoping its a failing oil pump or pressure relife valve.
What say you all

 

when was the last oil change? and what kind of journeys does it have? Oil wil lose its properties over time.

Anyway, something to check is the wiring for the presure sender, when I first put mine in it would fluctuate wildly, I found it to be a dodgy earth wire to the sender unit.

 

Remove, clean, & inspect the oil pressure sensor, and see if that helps, but it sounds like it could be a sticky oil pressure relief valve.

Have you had a recent oil change ?


Be VERY careful, until you identify the cause, because if it is a sticky valve, it can jam open at any time, causing a complete loss off oil pressure, or the opposite, where the pressure goes to well over 10bar, and blows the oil seals.


Mark.

 

Thanks for that.
Last oil change was about 5 months ago (4000 miles).
Is there any way of cleaning the valve to stop it sticking or is replacement required?
Just pleased I had a pressure gauge fitted or I would'nt have known anything was wrong.

 

Oh yeh and I will be checking the wiring and cleaning the sender unit, just in case, although the gauge has been working fine for ages.
Many thanks.
Any more thoughts?

 

The valve is a pain to get to. It's part of the oil pump, and behind the front covers. Work is the same as a cam belt change, plus swapping the oil pump.

Very occasionally you can remove the valve without needing to remove the cam belt, but it's rare.

Checking the sensor is a quick job, and I would do this first. Then I would double check the gauge isn't playing up.


Mark.

 

Right, yesterday I removed and cleaned the sensor and made sure it has a good earth. I also removed the gauge and made sure it was operating properly. I am happy that the gauge and sender are now working correctly.

Just been out for a short test, even just driving along at 30mph in 4th the oil pressure starts of steady at 80psi then droped to 60 then to 55 then back up to 80 for a while.

As Im now happy with the gauge I guess that means its probably the valve.
Will have to have a look this weekend.

If I have to do the oil pump is there any thing else I should do while Im in there?
Also what parts will I be needing any sudjestions?

Many Thanks

 

you'll need a new cam belt