oil presure
 

hi all what is best concerning oil presure.is more better than less.only because i might have a few issues.any help much appreciated.:thumb:

Tell us what you have, both cold and hot, tickover, cruising and under power.

Then we can comment.

Otherwise you'll just get a list of what others have.

Don't get me started on oil pressure. I made the mistake today of letting the van washer get rid of half the sahara off of my car today. I ended up driving home with the gauge reading 8 bar, pooing my pants. Thanks to Gaz's advice I cleaned the sender and all now seems fine.

I asked about a bit when I fitted gauges and the common theme was around 6 bar cold and 2 bar once warm. This is what I get when monkey's aren't washing my car.

You need enough pressure to ensure the internal engine components are properly lubricated, under all running conditions (idle and high revs)

It will always be higher when cold

So, to little is bad and too high puts unnecessary strain on the pump and can blow gaskets and cause oil leaks

hi i have a 1998 terz0 .when its cold it reads 7.2 bar,idle 4 bar cruising 6.6 and under power 7.8-8.holp this helps.

Mine has stopped working and i'm glad, sick of worrying and watching it. I have come to the conclusion that they are a total waste of time as by the time it gives you any warning the engine is fooked and needs to come out anyway, so may as well not be there making me fret all the time. I'll be replacing it with a fuel pressure one, much more use than a "your engines fooked" gauge.:lol1:

Tell me about it. I've had high readings again today, so it's either the sender or I have a buggered pressure release valve. I can't get hold of a sender quickly, so if i end up stripping down the oil pump for nothing I'm going to get rid of the gauges.

Surely a pump issue is more likely to cause low pressure readings

A stuck relief valve can cause a high reading.

My my 2 penny worth

It should be higher when cold and then drop.

Also a constant pressure whatever it is, as long as is not too low is good. Or pehaps a better way to put it is, a smooth delivey of pressure.

IF the guage starts to flicker, as the pressure begins to fluctuate....that is a sign that something is up.

Sure, are these in the pump nowadays then

I remember my Mini Cooper, with the pressure relief valve in the block (a spring and a ball bearing) it was a common trick to put stiffer springs in

That is what I was thinking. The reading doesn't drop at idle either.
What do I need to do to the prv to check it/modify it?

hi guys new today cant find how to post new thread can u help please thank u

Top of the page on the left in what ever section you want to put it in.:thumb:

http://i1215.photobucket.com/albums/...ps48a87c27.jpg

This is the pressure relief valve from the original CDB i stripped.

the needle on my preasure gauges bounces very slightlly when its warmed up and at idle.should i be worried.or should i just get rid of the gauge and stop looking for problems.not sure if it makes a difference but last week i had a stage 1 clutch fitted and a bigger alloy radiator and a light weight alloy pulley kit.

What gauges are they?

hi motor meter dials .they have been in the car since i bought them.iv never heard of them before.just another point.last year i put a 2.5 lit engine in .but never got it mapped.i cant re-map without getting a piggy back chip .iv been told you just cant remap the standard ecu on the terzo.not sure if this is causeing the problem:wonder:

It could possibly be the same problem I'm hoping I've got - dodgy pressure sender.

ill keep an eye on it and keep you posted.thanks for the advice

Pressure relief valves are designed to open when high oil pressure is detected, usually when very cold, the oil bypasses the filter and goes straight back to the sump

So during normal "hot" running, even under load the oil pressure should not get to the pressure needed to open the valve , to relive the pressure

Do you know at what pressure the valve opens?

Well a good point and relevant

But if you look at the use case for a relief valve, the Subaru engineers must have defined a pressure that is potentially harmful to the engine, so a relief valve is set at the limit of this value to prevent too much pressure, so lets say that this pressure is 100psi, any more and potential harm is done - blown gaskets etc

So the valve is there to stop pressure building up past 100psi - this would be the idiot who gets into a very very very cold engine and revs the t1ts of it - the theory is that the potential harm is greater than letting some oil pass back into the sump (bypassing the oil filter) so relieving the pressure.

So why would Subaru engineers set a pressure any lower than the top end of the pressure range

So on a warmed up engine, with the correct grade oil the fact that the pressure relief valve does not open is not a problem

But I do add that I know fvck all about the Subaru set up - just curious that's all

OK, so if mine is truly running 8 bar of pressure, what can be done to "relieve" that pressure?. What would cause a engine to have low pressure?.

Low pressure would be caused by the engine tolerances becoming to big (essentially bigger gaps so requires a higher flow rate to create the desired pressure) or a fvcked pump that can't generate enough pressure

If your is running 8 bar of pressure when hot the i would suspect a faulty sender

But more important than actual pressure (a number) is how the pressure readings behave

So the they will be high when cold - in fact if very cold they will stay high regardless of revs because the relief valve will be opening to relieve the pressure I,e, it will not go any higher revved or not

As you drive and the car warms up the pressure will drop - to a level that is consistent when idling, the when you rev the engine the pressure will go up - but rarely enough to open the relief valve

If that is the basic operation I would forget the actual figures, that maybe just a calibration issue

My Toyota Landcruiser has a oil pressure gauge and it does not even have numbers

The symptoms of a stuck relief valve would be getting in a very very cold car and starting the engine then revving it and seeing the oil pressure rise, I.e the valve is NOT opening hence the pressure increasing

They've been 6 bar up until Friday afternoon. Now they have been sitting at between 7-8 bar whether it's hot or cold, driving or at idle.
It fluctuates very slightly with revs, but only .1 of a bar up or down.
I hope its a faulty pressure sensor, one should be here Tuesday. Until it's fitted It won't be started/driven.
I found an old thread where Merlin was telling a chap who was getting 150psi readings (about 10 bar) that his oil filter would have ballooned so I've checked and mine's fine.

I've also found that RCM and Advanced Automotive sell oil pump's with modified pressure relief valves. Id like to modify mine, just in case. Is this just adding a washer under the spring?. Wouldn't that mean it would run a higher pressure before opening?.

Yep, those symptoms look like a faulty sender

Coz in a well warmed up engine, the pressure will be relativity low (thin hot oil, low spinning oil pump) at idle (slow spinning engine - not much heat/friction)

But as soon as revs are applied - oil pump spins up and creates much more pressure, which is obviously needed now that the engine is turning faster (more heat/friction - more need of oil)

The readings should go up significantly

I hope that isn't the case literally as typed!?!?

So just to add Kwik, given the fact that the engine oil requirements at idle are vastly different to the oil requirements at high revs and yet your engine is still (hopefully) going strong would indicate a duff sender/gauge