Outer Limits 4x4 Board

I fitted an oil pressure, oil temp and water temp gauge to my 4.5L 80s.

The water temp probe is fitted inline with the top radiator hose and because the cooling system is in good nick, water temps have consistently stayed between 80-90degC.

What I am concerned about is that the Gregory's Service Manual recommends the following oil pressures with the engine at operating temperature

Idle (650rpm) 29KPA or 4.2psi

3000rpm 245-490kpa or 35.5-71psi

On cold start, oil pressure goes straight to 90psi and and when driven on a cold motor, pressure can get to 120psi with 3000rpm gear changes.

When oil temp gets up round 80degC a 1st gear run at 3000rpm holds a constant pressure of 90psi. and when idling it sits on 27-30psi.

This vehicle has always been fitted with the smaller Z418 oil filter and I just tried the bigger Z9 filter. On cold start I noticed it went to 90psi but settled to 65psi within a few minutes as the high idle started to slow. When at operating temps, it idles at 20psi. I noticed the anti drain back flaps are quite stiff on both filters and would contribute to increased pressure. Ideally it would be best to have the filter mounted vertically without the one way rubber flaps, I suspect.

I then changed the oil from 20w50 to 15w60 and noticed only a very slight reduction in oil pressure up to 5psi max.

Comparing this information to what the FSM says, my oil pressure is somewhat excessive. However an idle pressure of 4.2psi wouldn't inflate my blowup doll so I have some reservations regarding their listings.

Oil pressure and temp are taken from a fitting that fits inline with the oil filter. I believe the reading is actually taken just before the oil enters the filter.

Considering oil pressure has never dropped below 20psi at idle and with the engine consuming next to bugger all oil or blowing any smoke with 230,ooo km on the clock, I admit to being somewhat confused as to what should be normal oil pressure.

On another note, oil temps have never gone past 95degC during slow city driving conditions. I suspect this would increase noticeable when in the humid conditions or soft sand driving etc.

If I was to fit a remote oil cooler, what would be the ideal thermostat to fit so the oil wouuldn't get too cool? I wat thinging somewhere around the 85-95deg mark.

Thanks in advance.

Regards,
Nathan

Any advice wiuld be much appreciated

What brand are the gauges? Unless they are really good ones they can be quite a bit out.

Your using the wrong oil too. Too thick.

Castrol netlube suggests a 10W-40 or maybe a 15W-40.
http://www.datateck.com.au/lube/castr_au/default.asp

Jas.

Yeh thats pretty thick oil for a DOHC multivalve donk which wasn't designed in the stone ages.

I got beaten to it, but you should be using a 10 weight oil.
You do even notice very slight performance and economy gains using 10W.

Secondly 120 psi is way to much, in fact it's problematic.
Try thinner oil first, but if you get over 90 psi i'd suspect you have an internal problem, presuming the gauge is correct.
Dan

Oh and yes, 4.2 psi isn't enough.

I just figured the 15w60 would give me better protection when the engines working hard off road, especially as it's so damn hot lately.

I'll change to a 10w/40 today and note any changes. I guess if there is none, it's off with the oil cooler and oil pump for a gander - it might have a sticky pressure relief valve etc.

I'll post up the results this arvo.
Cheers,
Nath

I swapped over to Nulon 10w40 full synthetic this arvo.

Oil pressure dropped to 85psi on cold start and still sat at 19-20psi when warm. Didn't really get the change I was hoping for after spending $100 on oil, but you get that I guess.

Will pull the oil pump pressure relief valve this weekend as it may be stuck.
Might even pull the oil cooler too...

Cheers.

i would make sure the gauges are accurate before pulling it apart just to save labour most mechanics will have a "test set" you could compare the two raedings and if they match/similar start looking at pulling it apart.
i am amazed at how far out some gauges are

Yeah good idea.

I was planning on doing that along with putting the aftermarket gauge in the same location as the factory gauge.

At the moment, the aftermarket gauge is fitted to an adapter plate between the oil filter and the block.

Cheers,
Nath

It is not uncommon for the oil pressure to be as high as 90-100 psi on a cold start as the bypass valve in many engines are not large enough, the thick oil cold oil dosen't escape past the bearings and alike as it does when warm so it relies on an internal bypass to regulate the pressure. Its one good reason not to rev up a cold engine. If the oil pressure dosent go increasingly high with higher revs (above 4000 rpm) and stabilizes between 60 and 70 psi when hot (at least 15 minutes driving) maximum, then I wouldn't be worried.

Joel

guzzla wrote:I just figured the 15w60 would give me better protection when the engines working hard off road, especially as it's so damn hot lately.

I'll change to a 10w/40 today and note any changes. I guess if there is none, it's off with the oil cooler and oil pump for a gander - it might have a sticky pressure relief valve etc.

I'll post up the results this arvo.
Cheers,
Nath

An old myth which is no longer really revelant. The level of protection between the honey you were using the and normal oil you're now using is probably very little.

Its only when the oil quality is poor you will have issues.

Keep an eye on the oil pressure the hotter it gets. Its normal for it to drop a bit but if it drops too much you should change oil as the type you're using obviously isn't stable enough at high temps or is just a poor quality blend. Don't think you'd have issues with the Nulon though.

goodluck with it anyway

i wouldnt be aiming for lower than 20psi at idle, 4psi at idle will eat bearing very quickly. trust me, i learnt from experience.
what oil pressure do you get when hot at revs? 2 or 3K for instance?

cheers, andrew

Some Toyota motors have had a history of wearing the housing around the relief valve allowing oil to bypass and pressure to get too high. I've heard of a few blowing oil filters apart. It may be necessary to strip it and check. No matter what viscosity of oil you're using the max pressure should be the same.

min requirements for oil pressure is
10 PSI per 1000 RPM throu out the rev range

11_evl wrote:min requirements for oil pressure is
10 PSI per 1000 RPM throu out the rev range

that for any engine? what about on a 1.6 4cyl? is that a hot or cold start too?

I T'd the aftermarket gauge of the same hole as the factory gauge and oil pressure is reading perfect.

60psi on cold start, 60psi at 3000rpm when warm and 16-20 psi at idle and that was with after replacing the Z418. The Z9 was going to be too much hassle long term for little gain.

Pulled the piston and spring relief valve assembly and they were like new and were easy to remove. I will remove the factory oil cooler as service the pressure relief valve there too (when I remove the extractors to fit the turbo manifold over Xmas)

I still cant explain the excessive oil pressure when fitted to the oil filter adaptor except that it must be a major restriction point as the oil transferes through the filter element.

Anyway, considering oil pressure is reading as per the FSM, I guess there's nothing further to worry about. Not sure if I'll continue to use the 10w40 at $11 per litre though - time will tell if it's worth it eh...

Cheers,
Nathan