Oil Pressure Query

Alex170984
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Oil Pressure Query

Postby Alex170984 » Fri Dec 19, 2014 3:20 am

I wonder if you can shed any light on this potential issue…

My engine is from a corolla originally putting out 115hp, even though I was told it was the same engine from the MR2, this is not the case. The sump on the engine obviously doesn't come with the MR2 factory oil cooler outlet on it either.

I then rebuilt the engine, with bigger OEM pistons, changed the sump to an MR2 sump, so it’s got the outlet for the oil cooler pipes and installed the rest of the oil cooler recirculation components.

When the car was running before, I had no oil pressure issues and the gauge read correct when it was securely fastened to the sensor.

Since it’s been rebuilt, running but before the cambelt snapped, I had low oil pressure when the car was hot. There was a knocking noise, but I have since identified this as the cause to my cambelt issue (don’t ask!).

What I'm asking is, can the addition of the oil cooler, reduce the oil pressure?

sirdeuce
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Re: Oil Pressure Query

Postby sirdeuce » Fri Dec 19, 2014 7:37 am

The oil cooler system is a 'bypass' type. The oil going through your oil cooler is taken downstream of your oil pump and bypassed through a pressure relief valve. In order for it to operate it has to be at a lower pressure than your pump's relief valve. I'm not sure of the pressure differential, but it shouldn't be much, but it will be lower than you're used to. If you want to check a few things try checking the spring and piston in the bypass plate. Make sure the piston moves freely and the spring isn't broken. Install a good pressure gauge. You can increase your pressure with shims on the relief valves, but you have to do both the pump and the bypass. Do just the pump and the bypass will pass even more oil and if you do just the bypass it won't send any oil to the cooler. Or, you could put your old oil pan back on the engine, take off the bypass plate, and run a full flow oil cooler. Put the cooled oil into the oil galley and not in the pan.
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Alex170984
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Re: Oil Pressure Query

Postby Alex170984 » Fri Dec 19, 2014 8:13 am

Hi Sirdeuce,

Thank you for your informative response!

The oil pressure must be something to do with hooking up the cooler. I am putting on a replacement pump tomorrow (taking from a working engine with good oil pressure), but will take apart the relief valve on the pump when I buy some circlip pliers, prior to install.

Is the other relief valve in the oil sandwich plate?

I can just put a bolt in the recirc line and put back on the old oil filter housing and block off the cooler. I haven't got the old sump any more.

Best regards,

Alex

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jondee86
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Re: Oil Pressure Query

Postby jondee86 » Fri Dec 19, 2014 3:06 pm

Here it is...

Image

The spring loaded relief valve is under the hexagon plug at the bottom, and
when the valve opens oil flows out thru the banjo fitting and tube clamped by
the other haxagon bolt. If you remove the banjo fitting and plug the hole with
a bolt and washer, there will be no oil going to the cooler... ever.

Just remember that there can be 50 or 60 psi of hot oil trying to get out of
that hole, so make sure whatever method you use to block it off is solid !!

Cheers... jondee86
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Re: Oil Pressure Query

Postby sirdeuce » Fri Dec 19, 2014 10:36 pm

If you are going to consider blocking the bypass, just remove the plate and go back to the original configuration. Safer than trying to block the hose. You could remove the banjo bolt and use a solid bolt in it's place.
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Alex170984
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Re: Oil Pressure Query

Postby Alex170984 » Mon Dec 22, 2014 8:47 am

I took the sandwich plate off and I cleaned it all up and removed the pressure relief valve.

It all came out fine. Which way does the valve go back in? I.e. does the hole in the valve line up with the hole in the plate?

I went to remove the pressure relief on my old oil pump and the valve itself didn't come out or want to come out. The spring was moving fine, but the valve didn't drop out.

I've still got to remove the pressure sender and refit a replacement to see if that makes a difference of or not as well.

If when it's up and running i've still got pressure problems, i'll remove the sump outlet and stick a standard bolt in place and block off of the oil filter housing holes etc

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Re: Oil Pressure Query

Postby Alex170984 » Mon Dec 22, 2014 8:55 am

My 27mm (socket) fitting union did not have a washer behind the head - is that an issue?

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jondee86
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Re: Oil Pressure Query

Postby jondee86 » Tue Dec 23, 2014 8:14 pm

The oil on the outside of the union fitting comes from the pump and
passes into the filter. The oil on the inside of the union fitting has passed
thru the filter, and is on its way to the bearings. There will be some
difference in pressure from outside to inside, but if the union fitting
is correctly seated and tight, the missing gasket will not affect your oil
pressure. Even if it was loose, your pressure would not be affected unless
oil was spraying out because the sandwich plate was no longer sealing to
the block.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: Oil Pressure Query

Postby sirdeuce » Tue Dec 23, 2014 9:20 pm

Like jondee said, but if the gasket is missing it could be a potential leak. The gasket is a softer material than the banjo fitting and the bolt, prevents galling between the bolt and fitting and fills irregularities between the same. If the joint is seeing pressure it's wise to have all gaskets in place.
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Re: Oil Pressure Query

Postby Alex170984 » Wed Dec 24, 2014 1:27 am

If I were to remove the sandwich plate, do I need a different union to screw into the block for my oil filter? It's been a while since I was messing about down there and I cannot remember how it was before the oil cooler...

Alex170984
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Re: Oil Pressure Query

Postby Alex170984 » Wed Dec 24, 2014 4:01 am

Can the pressure drop not be also down to the wrong choice of oil viscosity?

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Re: Oil Pressure Query

Postby PDB » Wed Dec 24, 2014 7:11 am

I also want to remove my sandwich plate, if anyone knows what/where to get the correct length fitting from please post up :)

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jondee86
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Re: Oil Pressure Query

Postby jondee86 » Wed Dec 24, 2014 1:38 pm

Alex170984 wrote:If I were to remove the sandwich plate, do I need a different
union to screw into the block for my oil filter?

Yes... it is a shorter one that you should be able to grab from any
dead 4A engine that came from the factory without an oil cooler.

Cheers... jondee86
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persists in trying to adapt the world to himself. Therefore, all progress
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jondee86
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Re: Oil Pressure Query

Postby jondee86 » Wed Dec 24, 2014 2:21 pm

Alex170984 wrote:Can the pressure drop not be also down to the wrong
choice of oil viscosity?

Nope. Your oil pressure is basically a measure of how difficult
it is for the oil to get into and out off the bearings. Just like a
garden hose without a nozzle. When the end of the hose is
unrestricted, water pours out easily and there is no pressure
inside the hose. But put your thumb over the end of the hose,
pressure builds up, forcing the water out past your thumb.

So if your gauge is not showing pressure, these are the possibilties...
- No oil
- Wire off pressure sender/broken sender/broken gauge
- Broken pump
- Blocked/loose/broken oil pickup
- Oil relief valve stuck open/broken spring
- Bypass valve to cooler stuck open/broken spring
- Excessively worn/melted crankshaft bearings

Thin oils like 0W20 or 5W30 may cause your engine to burn a bit
more oil, but will not cause your oil pressure to drop off the scale.
The factory bypass oil cooler is designed so that it only sends oil
to the cooler when the engine is at high rpm's (oil pressure gets
high enough to open the bypass valve). Otherwise, during normal
driving the valve stays closed and your oil pressure should be the
same as if there was no oil cooler fitted.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

Alex170984
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Re: Oil Pressure Query

Postby Alex170984 » Mon Dec 29, 2014 5:56 am

I did find when I went to strip the sandwich plate down, that all the bolts were loose...

Another thing; when I stripped the pressure relief down on the old oil pump, I could not get the valve out, the pressure relief in the oil filter plate came out / fell out when I stripped that.

Could that explain anything?

Cheers

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jondee86
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Re: Oil Pressure Query

Postby jondee86 » Thu Jan 01, 2015 10:23 pm

Here is an interesting thread Google turned up...
http://www.st162.net/forum/showthread.php?3376-JDM-TEMS-Corona-162-2-amp-4-door-and-many-more-jdm-oddities/page13

While the thread is not about the 4AGE, it is about a Toyota engine,
and the type of oil pressure relief valve is exactly the same. Therefore
the same type of failure could be expected in a 4AGE under the same
conditions.

The relief valve is a simple spring-loaded poppet type. When the oil
pressure exerts a force on the top of the poppet that is greater than
the spring force under the poppet, the valve opens. The valve actually
operates as a pressure sustaining valve, by-passing excess oil directly
back into the pan while maintaining the oil supply to the engine at its
nominal opening pressure. Once the engine rpm drops and the oil flow
reduces, the pressure drops and the valve closes.

If, as suggested in the referenced thread, the bore that the poppet
slides in becomes coated with a thick layer of carbon crud, a big rev
could push the poppet far enough to cause it to jam on the crud. Then,
for as long as the valve stays jammed open, you will have reduced oil
pressure during normal driving.

The fact that the poppet did not fall out suggests that you might have
had a buildup of carbon crud around the valve. Worth investigating.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: Oil Pressure Query

Postby allencr » Fri Jan 02, 2015 2:31 am

Alex170984 wrote:I did find when I went to strip the sandwich plate down, that all the bolts were loose...
Another thing; when I stripped the pressure relief down on the old oil pump, I could not get the valve out, the pressure relief in the oil filter plate came out / fell out when I stripped that.
Could that explain anything?


No. It's just got a ridge in there or smegma. Even it its worn a ridge in there, you should be able to scrape that ridge down&out with a knife or scissors.
Loose, was it leaking. seeping. weeping? Then it's nothing and if it was, it's just a leak.

Sure, that valve can get stuck open resulting in about zero pressure at low rpms or stuck closed & peg the gauge if it doesn't blowup the filter, or inbetween intermittently. It moves a lot during its life and can wear out, the relief valve wears&tears&scrapes&gauls into its bore a lot of times, even though they seems to be right next to a tremendous lube supply, they aren't lubed much cause it takes the easy way out.

Alex170984
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Re: Oil Pressure Query

Postby Alex170984 » Wed Jan 07, 2015 3:36 am

jondee86 wrote:Here is an interesting thread Google turned up...
http://www.st162.net/forum/showthread.php?3376-JDM-TEMS-Corona-162-2-amp-4-door-and-many-more-jdm-oddities/page13

While the thread is not about the 4AGE, it is about a Toyota engine,
and the type of oil pressure relief valve is exactly the same. Therefore
the same type of failure could be expected in a 4AGE under the same
conditions.

The relief valve is a simple spring-loaded poppet type. When the oil
pressure exerts a force on the top of the poppet that is greater than
the spring force under the poppet, the valve opens. The valve actually
operates as a pressure sustaining valve, by-passing excess oil directly
back into the pan while maintaining the oil supply to the engine at its
nominal opening pressure. Once the engine rpm drops and the oil flow
reduces, the pressure drops and the valve closes.

If, as suggested in the referenced thread, the bore that the poppet
slides in becomes coated with a thick layer of carbon crud, a big rev
could push the poppet far enough to cause it to jam on the crud. Then,
for as long as the valve stays jammed open, you will have reduced oil
pressure during normal driving.

The fact that the poppet did not fall out suggests that you might have
had a buildup of carbon crud around the valve. Worth investigating.

Cheers... jondee86


That may well have happened to me.

I'll have another go at getting the valve out tonight. But all the valve is, is a bucket with a small hole near the top...

allencr
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Re: Oil Pressure Query

Postby allencr » Wed Jan 07, 2015 8:40 am

Alex170984 wrote:...I then rebuilt the engine, ...I had low oil pressure when the car was hot
What I'm asking is, can the addition of the oil cooler, reduce the oil pressure?


Yes, it is possible that the addition of a cooler could reduce the pressure, but it's very unlikely to be enough to be observed on the factory's dash gauge and is not the source of it. Sure about the gauge??????
It is about 98% more likely to be because of 'I then rebuilt the engine'. Plus or minus 1.5%, and 1% the relief valve.

Alex170984
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Re: Oil Pressure Query

Postby Alex170984 » Thu Jan 08, 2015 1:43 am

I find it hard to believe the gauge was working, then all of a sudden it's not because I rebuilt the engine.

I had been suffering from electrical issues as well, so a grounding problem may not help things.