Low hot idle oil pressure?

[AcIdBuRn02ZTS]

Hey guys...

Was getting ready to repair the bhg in my car but I decided to check the oil pressure with a mechanical gauge as the stock gauge was iffy at times...

Cold, the mechanical gauge was reading 30psi higher... around 60psi with 10w40

Once hot, the mechanical gauge dropped to 0-2psi.. anything off idle was good... 2k and below was 10-25psi... 3k+ was 45+psi.. come off a rev and the needle would bounce off the 0 pin on the gauge.

So... its not making any noises... not knocking or ticking... oil is fresh cheap stuff (supertech from walmart just to get the car running)

I had the mechanical gauge tapped into the port forward of the stock sending unit just behind the water pump. Took a 1/8" bspt adapter.

Ideas?

Thanks
-Chris

 

[AcIdBuRn02ZTS]

Could the oil cooler valve/spring be sticking causing low/no pressure at idle? Anyway of testing this?

-Chris

 

[Nick M]

Hey guys...

Was getting ready to repair the bhg in my car but I decided to check the oil pressure with a mechanical gauge as the stock gauge was iffy at times...

Cold, the mechanical gauge was reading 30psi higher... around 60psi with 10w40

It is too high because of the wrong grade. Unless it is 120 degrees where you are.

Once hot, the mechanical gauge dropped to 0-2psi

One of two things are possible. The pump is worn or the cavities the oil flows through is worn. The cavity is the bearing clearance. Put the correct (grade) oil in it and check warm operating pressures.

 

[AcIdBuRn02ZTS]

60psi was cold @ 1300rpm fast idle... my one 7mge did that with 5w30. 10w30 and 10w40 shouldnt show a pressure difference when cold.

So there is nothing else in the system that could cause low idle pressure but the pump itself or bearings? What about the piston coolers and check valves in the pump and cooler and what have you?

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[Nick M]

my one 7mge did that with 5w30.

It doesn't have a designed internal and external controlled leak.

So there is nothing else in the system that could cause low idle pressure but the pump itself or bearings?

Yes, the oil. The pump provides flow. The bearing clearance controls the flow and raises pressure. As it wears, the expanse for the oil opens up and there is less restriction to flow, and it shows on the gauge as lower pressure. Since pressure is resistance to flow.

What about the piston coolers and check valves in the pump and cooler and what have you?

It is harder for them to open when warm.

Have you ever read about oil particles and oil change intervals? When the additive pack goes bad, you are left with the first number. It would not "thicken up" when warm. Thicker isn't really the goal anyway. If it was, Toyota would have told you to use 20W-50 like they do in G.C.C. countries.

Your winter in Indiana is more than cold enough to use 5W-30. It flows twice as well as 10W when it is cold.

 

[AcIdBuRn02ZTS]

.... actually you are correct the oil doesn't thicken up when hot, however the 2nd number is the oil weight at temp. The first number in a multi weight oil is what it should flow compared to when cold... 10w30 flows as good as a straight 10w when cold due to the additives... at temp, it doesn't get any thinner then a straight 30wt oil. Its not winter here btw... it was 83 yesterday. When it gets cold, I'll use 5w30... but oil isn't playing a part in the low idle oil pressure... considering 10w40 is thicker then 10w30... it should have higher pressure when hot... and it doesn't explain why it has good pressure at any rpm besides idle.

I've heard multiple complaints about stuck piston oil squirters and relief valves.... but you are saying that's not possible?

I want to know if there is something simple along those lines before I pull the engine for rebuild.

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[Nick M]

however the 2nd number is the oil weight at temp.

Actually, it isn't. Gravity (weight) has nothing to do with it. The SAE classification is grade. I know, many people refer to it that way.

10w30 flows as good as a straight 10w when cold due to the additives...

I am not even sure what you are trying to say. Are you claiming 10W and mono-grade 10 are the same thing? I assure you, they are not. The SAE charts are posted all over the internet. Some even show kinematic rating just for reference, even though 10W is not rated that way. And mono-grade 10 flows slower.

at temp, it doesn't get any thinner then a straight 30wt oil. Its not winter here btw... it was 83 yesterday. When it gets cold, I'll use 5w30...

The difference between 5W-30 and 10W-30 is that 10 does not flow as well cold. About half in fact. And they are the same at operating temps.

but oil isn't playing a part in the low idle oil pressure

How do you know the "cheap stuff" is not?

considering 10w40 is thicker then 10w30... it should have higher pressure when hot...

Why would you want that? That is rhetorical. Higher than what?

and it doesn't explain why it has good pressure at any rpm besides idle.

Idle will be your lowest pressure, and the spec is 4.3 psi. The pump which produces flow is moving at its lowest speed. And on the contrary, heat very much effects oil pressure, as oil viscosity changes with temperature.

I've heard multiple complaints about stuck piston oil squirters and relief valves.... but you are saying that's not possible?

If they are stuck open, they would not have such high pressure like you posted. Tearing the engine apart to get to squirters is not my idea of a cheap easy fix. Acknowledging that an engine has wear is much easier. They (bearings) do wear out over time.

 

[AcIdBuRn02ZTS]

You told me to put thinner oil in the engine and report back... thinner oil will decrease oil pressure and low pressure is the problem.

I'm well aware that bearings wear... I wanted to know if there were any other common issues that are easily fixed... I didn't want an oil debate.

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[AcIdBuRn02ZTS]

Piss on it.. lol

What should I put in it... ill do it tonight and report back.

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[DeMoN2318]

0W30 german castrol...

Hace you read through the oil and lube section?

http://www.supramania.com/forums/forumdisplay.php?108-Motor-Oil-Lubricants-amp-Filtration

 

[suprasick]

How is the condition of your turbo? When I switched to a BB turbo my pressure shot up significantly.

 

[AcIdBuRn02ZTS]

turbo has a bit of play... not excessive and its not leaking/smoking that I'm aware of. Produces boost normally and doesnt make any odd noises.

The reason for the pressure spike is the tolerences in a bb turbo are much tighter then a journal bearing turbo... and I assume you run a restrictor.

As far as german 0w30 goes... not gonna find that locally and I'm not ordering oil that I'm just going to be dumping back out of it.

-Chris

 

[super51fan]

I would run Rotella T6 15W40 synthetic diesel oil. Sounds to be just what you need in your aging engine. Good for high heat and turbocharging and lots of cleaners in oil. Should help increasing your oil pressure as well. IMO.

 

[MK3pizzadriver]

Just got the Cx Racing T61 Lipp Boss knock-off, came with a restrictor and is journal bearing.. Have no idea if I should drill it out though lol.

 

[AcIdBuRn02ZTS]

For giggles... changed the 10w40 for 15w40...

Same problem.

Then I decided to swap my new mechanical gauge for a used one from a buddies truck... 7-10psi after a HARD run @600rpm idle... apparently my new gauge is dead under 10 psi... it just rests on the 0 pin. On the different gauge, its showing basically just a bit over 10psi per 1k rpm... at 3k, it showing 45-50psi... 4k ~ 52psi or so... 5k was 55-60psi... didn't feel the need to push it any higher (these were no load RPMs)

Pressure is within spec so head gasket repair is under way.

Just a note for anyone else that may be having the same issue... always double check the gauge. We were actually getting ready to pull the engine today but decided to play around a bit first... glad we did.

I'd say oil pressure would still be in spec with a 10w30 or 5w30. Considering the higher mileage, I'll stick to thicker stuff until the new engine is complete.

 

[Nick M]

You told me to put thinner oil in the engine and report back... thinner oil will decrease oil pressure and low pressure is the problem.

I'm well aware that bearings wear... I wanted to know if there were any other common issues that are easily fixed... I didn't want an oil debate.

There is a very large difference between 10W when cold and 40 at operating temps. Of course there is a large drop when it warms. You are stating things that are supposed to happen. The oil cooler and piston jets open with pressure. If they were stuck open, you would not have 60 psi when cold.

 

[Nick M]

I'd say oil pressure would still be in spec with a 10w30 or 5w30. Considering the higher mileage, I'll stick to thicker stuff until the new engine is complete.

Penzoil has a formulation for high mile motors. They use 30 grade mixed with 5W-30. That will make sense if you understand how multi-grade works.

 

[AcIdBuRn02ZTS]

I always thought it worked like this....

10w30

No thicker then what a 10wt would be when cold and no thinner then a 30wt would be when at temperature. I'm always up for learning so if that is incorrect, please school me. In turn, the high mileage version would have a higher viscosity overall if its blended with a straight 30... right?

Since that is the case... and the coolers are opened by pressure... at cold idle, they would be open anyways since pressure is the highest... so when cold (60 psi)... it wouldn't make.a.difference if they were stuck open as they would be open anyways due to the high pressure... since temp doesn't come into play with them. Am I thinking wrong here?

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[Nick M]

That is right. They open more when cold. As temps increase, they close unless you have more rpm (pressure). The thought being open up with increased engine speed.

 

[AcIdBuRn02ZTS]

So if one was sticking... it could cause low idle pressure when warm... as pressure drops and the coolers close... one sticks or has a weak spring would show up as low pressure on the gauge wouldn't it?

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