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Hey all.

I've been experiencing some high oil pressure since I swapped out my dead engine with a NB6 engine. Warmed up, idle oil pressure is around 2bar. When cruising it sits just under 6bar. I've read this isn't normal at all, very high oil pressure.

Since doing the swap I've gone through two new oil filters, oil weight 10W-40 and latest oil is 5W-30. Both times they show the same high oil pressure. Oil pressure sender was taken from my old NA6 engine as the NB6 one doesn't work with the NA6 oil pressure gauge.

Engine sounds good and performs very well. There are no oil leaks, not burning any oil either. After draining, I put in about 3L of oil, making sure I don't overfill it.

The old engine had normal oil pressure, idle 2bar and cruising was 4bar.

Should I be concerned with this high oil pressure?

Maybe somebody shimmed the pump. it wont hurt anything.

dann

mrpham wrote:Hey all.

I've been experiencing some high oil pressure since I swapped out my dead engine with a NB6 engine. Warmed up, idle oil pressure is around 2bar. When cruising it sits just under 6bar. I've read this isn't normal at all, very high oil pressure.

Since doing the swap I've gone through two new oil filters, oil weight 10W-40 and latest oil is 5W-30. Both times they show the same high oil pressure. Oil pressure sender was taken from my old NA6 engine as the NB6 one doesn't work with the NA6 oil pressure gauge.

Engine sounds good and performs very well. There are no oil leaks, not burning any oil either. After draining, I put in about 3L of oil, making sure I don't overfill it.

The old engine had normal oil pressure, idle 2bar and cruising was 4bar.

Should I be concerned with this high oil pressure?

With the oil pumps so prone to failure on these engines I would be fixing the problem, 6 bar is way too high. I like to have my engines around the 60psi (4.28bar) mark hot and under load, no more than that. It is normal for the oil pressure to be high when cold, so I'm assuming you're checking it hot??

I would do this first though
-Get a master gauge or mechanical gauge and confirm your gauge is reading correctly, wouldn't be the first time a gauge read wrong.

If the engine does have high oil pressure then you need to find the problem, more than likely a stick relief valve in the oil pump, or someone has been playing around with it.

There are ways of fixing it without removing the engine. My race car runs a Peterson external oil pressure relief on it (fitted to eliminate the oil pump failure problem). This would cure the problem if you don't want to remove the engine.

Cheers
Woz

More details on the external oil relief please woz, pretty keen to prevent this problem if its relatively minor fix.

Sent from my GT-I9100 using Tapatalk

My apologies, my reply was much too brisk on such a serious topic as your oil pump, I should have given more info/suggestions or shut up.

Dann

Thanks mate!

All readings were taken when warmed up. Will try borrow a gauge and rule out the factory sender/gauge, I'll buy one if I can't. Fingers crossed that it's just that.

Too high pressure means that flow is reduced? So it's definitely something I have to look at if it's not a faulty gauge/sender.

Idle pressure is fine at 2bar when warm and 4bar when cold. But as soon as I go past 2000rpm, even just light driving, the pressure shoots up to 6bar (warm). It's never sat constant anywhere under 6bar while cruising.

Is it reasonable to think that an oil passage could be blocked? Or would that result in a high idle oil pressure too?


John.

Interested in our the remote relief valve is connected too.

mrpham wrote:Thanks mate!

All readings were taken when warmed up. Will try borrow a gauge and rule out the factory sender/gauge, I'll buy one if I can't. Fingers crossed that it's just that.

Too high pressure means that flow is reduced? So it's definitely something I have to look at if it's not a faulty gauge/sender.

Idle pressure is fine at 2bar when warm and 4bar when cold. But as soon as I go past 2000rpm, even just light driving, the pressure shoots up to 6bar (warm). It's never sat constant anywhere under 6bar while cruising.

Is it reasonable to think that an oil passage could be blocked? Or would that result in a high idle oil pressure too?


John.

Technically speaking even if an oil gallery was blocked the oil pump should still maintain pressure, as the oil relief valve is right it the pump and if a gallery was blocked it should just feed through the valve at the same pressure. The other thing to take into consideration is that if a gallery was blocked to that extent then it would be causing other issues (eg: engine failure!, lifter noise etc). So I would be thinking no, I'm pretty adament that you have a relief valve problem or a faulty gauge.

Cheers
Woz

wozzah1975 wrote:Technically speaking even if an oil gallery was blocked the oil pump should still maintain pressure, as the oil relief valve is right it the pump and if a gallery was blocked it should just feed through the valve at the same pressure. The other thing to take into consideration is that if a gallery was blocked to that extent then it would be causing other issues (eg: engine failure!, lifter noise etc). So I would be thinking no, I'm pretty adament that you have a relief valve problem or a faulty gauge.

Cheers
Woz

Thanks Woz!

Really appreciate all the info, can't seem to borrow a gauge so going to pick one up tomorrow.

My engine does make a bit of a ticking noise, but I've used a stethascope and confirmed that the ticking is from the injectors and not the lifters. Don't think noisy injectors are a real problem though.

Just read some info on the pump and relief valve here:
http://forum.miata.net/vb/showthread.php?t=55720

Don't the Mazda oil filters have a relief valve built in? Are you using MAzda oil filters?

J.

sailaholic wrote:More details on the external oil relief please woz, pretty keen to prevent this problem if its relatively minor fix.

Sent from my GT-I9100 using Tapatalk

Ok, to answer both you questions,

When I researched doing the engine for my car I was told about the oil pump issue (in mind that it is only a problem on engines turning at high rpm for periods of time, eg: constantly above 7000-7500rpm). I was made aware that there were performance oil pump internals available when I did my engine build. However, after speaking with some reputable engine builders I know it was explained that even the hi performance pumps were an issue an had the same problem (more reliable, but still break).

The issue is that the oil outlet on the factory oil pump relief valve simply isn't big enough to feed the oil away at high RPM, so the pump just over pressures itself and explodes (the crankshaft just literally tries to drive through the oil pump gear because of the high load). You probably need to pull an oil pump apart and have a look to know exactly the area I mean, but when you do you will see the return is small, and feeds directly back into the oil pump. So fitting expensive pump internals doesn't fix the problem, it only fixes the symptom for a longer peroind of time.

I have used the external valves on other engines that are difficult to remove to set oil pressure (sometimes it can be a guessing game on an engine build) and they work very well.

The brand of the external oil pressure relief is Peterson (scroll down on the link, its at the bottom)

http://www.petersonfluidsys.com/pump_acc.html

Basically you either shim up or "chock" the original relief valve in the oil pump. Then you need to plump the external valve in line by using a sandwich plate adapter under the oil filter

http://www.jegs.com/webapp/wcs/stores/s ... howValue=1

or if you have an oil cooler fitted, in line with that. The oil pump feeds directly to the filter mount on the block, then to the valve, then back into the filter at the set pressure (you'll note the grub screw adjustment and locking nut on the valve). There is also a third line that need to feed back to the sump pan.

So basically doing this increases the volume of oil bypassed at high rpm.

I hope I explained it well enough!

Cheers
Woz

Thats to stop the filter paper from bursting, its in series with the oil pressure so it doesnt affect it one bit.

Dann

aka_juffa wrote:Don't the Mazda oil filters have a relief valve built in? Are you using MAzda oil filters?

J.

Yes, but its nothing to do with the oil pressure. This is a different thing. Most decent oil filters have 2 valves. One that bypasses the element inside incase it should ever get blocked. The other is an "anti drain back" valve to stop oil draining off when the engine isnt running (cheap filters dont have this).

Cheers
Woz

aka_juffa wrote:Don't the Mazda oil filters have a relief valve built in? Are you using MAzda oil filters?

J.

Oil filter valve is different to oil pump valve.

{both Dann and Woz beat me to it}

T T T TRIPPPPPLE KILL !



Dann