Low oil pressure! Help! - Toyota Nation Forum : Toyota Car and Truck Forums
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#1 Old 05-14-2008, 03:33 AM
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gen 7 Low oil pressure! Help!

Hi guys,

i have a problem with my engine, hope you guys can give some solutions or suggestions.

Here's the situation:
When my engine is warmed up (after half an hour's ride), the oil pressure will drop to less than 10psi and the warning light on my oil pressure gauge lit up. However, when i am driving, or as long as i step on the gas, the pressure will go up to 30psi or more. This only happens when the car is warmed up. Otherwise, the oil pressure is between 30-60psi. Also, i notice there is some slight knocking sound coming out from the valve cover, on the timing belt side when the oil pressure drops below 10psi. Sometimes, when i clutches in to down-shift, the oil pressure will drop together with the rpm. I could smell engine oil when the engine is started up, probably came from the exhaust, but did not see any blue smoke out from it.

Prior to this, i found a bad PCV valve (wouldn't rattle) and had it replaced, and did an oil,spark plugs and oil filter change after that. The throttle body was cleaned on the same day too.

Now the question is, what could be the cause of low oil pressure on hot idle? Is there a possibility that fuel has entered the engine and caused damaged because of the bad PCV valve? Before the oil and PCV valve change, the oil pressure appeared to be more than 15psi (still low?). Some research on the web suggests replacing engine bearings as it might be worn. Will this solve the whole problem or do i have to re-build the whole engine?

Is it ok to continue driving it as long as i minimise the need to idle when hot?

My current mileage is 290500km and running 4A-FE with 0W40 Mobil 1 engine oil.

Any help will be appreciated. Thanks in advance!

Last edited by technica; 05-14-2008 at 03:35 AM.
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#2 Old 05-14-2008, 04:15 AM
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Run non-synthetic oil and the low oil pressure issue will probably be gone.
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#3 Old 05-14-2008, 07:53 AM
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First, try running the grade of oil specified by the manufacturer for your engine (10W30) and go from there. Also, change the filter while you are at it.

Last edited by blb; 05-14-2008 at 07:55 AM.
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#4 Old 05-14-2008, 12:27 PM
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ok well for reference toyota specifies "At idle 4.3 psi or more" , "at 3000 RPM 71psi or more"

-a slow idle can effect this if your idleing below 750 take care of that first

-also if your oil is dirty change it oil wears out and loses viscosity on a cold start comparing old oil versus fresh i notice like a 15 psi difference in pressure cold and like a 5psi difference warm

-filters also can effect pressure some have more internal resistance than others play around some will have less than others

- it is possible to have fuel contamination thats definately a factor for losing viscosity,

-i donno what oil your using, try the next grade if your 5w 30 or 10w 30 try a 10w 40, if your 10w-40 try 20w 50 your pressure should go up.

-if your low for both idle and 3000 rpm check your oil pump could be warn out, or the engine could just be worn out in general

- i dont think its readily acessible but you could also check the relief valve on the front of the oil pump it could be sticking.

Ah when she was in her glory, Not so nice anymore 358k 17years old her time is getting short ....


Last edited by 94_Rolla_Guy; 05-14-2008 at 12:28 PM.
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#5 Old 05-14-2008, 08:16 PM
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Quote:
Originally Posted by 94_Rolla_Guy View Post
ok well for reference toyota specifies "At idle 4.3 psi or more" , "at 3000 RPM 71psi or more"

-a slow idle can effect this if your idleing below 750 take care of that first

-also if your oil is dirty change it oil wears out and loses viscosity on a cold start comparing old oil versus fresh i notice like a 15 psi difference in pressure cold and like a 5psi difference warm

-filters also can effect pressure some have more internal resistance than others play around some will have less than others

- it is possible to have fuel contamination thats definately a factor for losing viscosity,

-i donno what oil your using, try the next grade if your 5w 30 or 10w 30 try a 10w 40, if your 10w-40 try 20w 50 your pressure should go up.

-if your low for both idle and 3000 rpm check your oil pump could be warn out, or the engine could just be worn out in general

- i dont think its readily acessible but you could also check the relief valve on the front of the oil pump it could be sticking.
Hi 94_Rolla_Guy,

I've heard about it but where is the oil relief valve you mentioned? Do you have any pics for my reference?

You also mentioned toyota specifies "At idle 4.3 psi or more" , "at 3000 RPM 71psi or more". Is this information for 4A-FE engines in all kinds of climate? I'm worried coz im hearing slight knocking noises from the valve cover (timing belt side) when the pressure is lower than 10psi. But it is so slight that i can only hear it when i pop up the hood. Is it a sign i should be worrying about?

i have replaced the PCV valve and oil and filter are new. The pressure is still low. Any other possibilities? Will vacuum affect oil pressure?

Last edited by technica; 05-14-2008 at 08:17 PM.
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#6 Old 05-15-2008, 01:58 AM
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the pressure relief valve: if you follow the dipstick tube down to the pump its in almost the same location just mirror'd to the front of the pump

it specifies those pressures regardless of climate.

If your really concerned about the knock i would buy one of those mechanics stethoscope things and poke around and try to find the noise. most likely its a valve clearance out of spec issue and probably isn't a concern, youtube "rod knock" if you have never heard it before

the only other thing i can think of is that you bought some shitty or mislabled oil and no vacuum shouldn't effect oil pressure..

Ah when she was in her glory, Not so nice anymore 358k 17years old her time is getting short ....

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#7 Old 05-15-2008, 04:13 AM
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Quote:
Originally Posted by 94_Rolla_Guy View Post
the pressure relief valve: if you follow the dipstick tube down to the pump its in almost the same location just mirror'd to the front of the pump

it specifies those pressures regardless of climate.

If your really concerned about the knock i would buy one of those mechanics stethoscope things and poke around and try to find the noise. most likely its a valve clearance out of spec issue and probably isn't a concern, youtube "rod knock" if you have never heard it before

the only other thing i can think of is that you bought some shitty or mislabled oil and no vacuum shouldn't effect oil pressure..
Will adding oil treatment to the engine oil enhance it's viscosity? thicker oil should bring the pressure up if i'm not wrong? I'm thinking of adding STP oil treatment. What do you say?
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#8 Old 05-15-2008, 09:16 AM
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that could work but the only thing i can think of is that lucas oil stabilizer http://www.lucasoil.ca/prodofseason.htm

other than that i would go up a range from 5w 30 or 10w 30 try a 10w 40, if your 10w-40 try 20w 50

Ah when she was in her glory, Not so nice anymore 358k 17years old her time is getting short ....

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#9 Old 05-15-2008, 08:47 PM
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I would first do the obvious, change the oil and filter and use either 5 or 10W-30 oil. as for the knocking at valve cover, it could be oil is not reaching the valvetrain fast enough/lack of lubrication, that would be my guess, also when was the last time u changed the timing belt? it could be worn/cracked. take a look at the timing belt and the tensioner too.
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#10 Old 05-16-2008, 12:25 AM
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I couldn't find Lucas Oil in my country. However i have added in the STP oil treatment. the hot idling pressure is raised to about 20psi. Think you guys are right, the 0W40 oil is too thin for my car, coz the pressure did go up after adding the oil treatment. i'll try the 15W50 next oil change. Will continue to monitor and see if it maintains at this pressure. Thanks for all you valuable inputs.
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#11 Old 05-16-2008, 07:39 AM
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how about trying 10w-30 or 10w-40. 15w-50 may be too thick and damage the pump and not flow enough volume to lubricate the top of the engine.
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#12 Old 05-16-2008, 07:46 AM
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Quote:
Originally Posted by blb View Post
First, try running the grade of oil specified by the manufacturer for your engine (10W30) and go from there. Also, change the filter while you are at it.
I don't understand why you are now pouring STP into that engine. Did you ever disassemble an engine where someone was using that crap? Its not pretty. You've already created your own problems by not using the correct viscosity of oil as specified by the manufacturer. Now you are pouring thick crap into depleted oil that was too thin to begin with. Just change the oil and filter, use the correct viscosity of oil, and stop creating problems.
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#13 Old 05-16-2008, 10:56 AM
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Finding the root cause of the oil light problem would be my first mission, not use some bandaid repairs, that will end up costing more. Oil grade wont matter, unless you're really using LOW VICOSITY 0W40/5W40 should be fine, though I'd go a bit higher for summer, but mines turbocharged so I get low oil pressure due to several things.
And your idle oil pressure should be up even if you have low idle.

To forum readers:
You do realize the lower number indicates cold viscosity and the latter number hot viscosity.
Basically 5W-40 and 0W-40 should be the same viscosity when hot, however some variables might exist.
going to 10W-30 would actually lower the hot viscosity and the oil would be thinner than 5W-40.

Last edited by Flashmn; 05-16-2008 at 11:00 AM.
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#14 Old 05-16-2008, 01:04 PM
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Quote:
Originally Posted by Flashmn View Post
To forum readers:
You do realize the lower number indicates cold viscosity and the latter number hot viscosity.
Basically 5W-40 and 0W-40 should be the same viscosity when hot, however some variables might exist.
going to 10W-30 would actually lower the hot viscosity and the oil would be thinner than 5W-40.
In theory, the above is exactly correct.

In reality, and after several thousand miles when the additive packages tend to break down, the multi viscosity oils tend to perform more toward the middle of the specified range rather than at the lower number when cold, and the higher number when hot. This was proven as a result of a study I was a part of, performed at General Motors, in my younger years.
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#15 Old 05-16-2008, 01:47 PM
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Yes true, but that means the oils are long gone. Oils have gotten alot better since the early 2000's, now that long life oils have emerged this has gotten alot better. Mercedes service interval is 15k km, vw has 35k km, thats alot for oils. (ok ok, the mobil from the mercedes runs out at about 10k km, and its a noted deficiency in mobil 1 oils as per dealership workshop).
Personally I'm not a fan of Mobil products, they have a good reputation, but in tests they have fallen short and in practice, if my mercedes runs dry before the service interval, I think thats a pretty big shortcoming. Now that warranty is over, I think I'll be servicing it with my preference now on and that does not include mobil oils.
I'm using Motox (euroil product I think, as it comes from holland and theres one oil refinery there), which is the oil our shop has manufacteured. I've been satisfied with them, although alot of people consider it a "cheap brand" when its not.
Also another company to look at is LiquiMoly, seems like they're pretty good and I think in the past mercedes used them as well as other german companies.
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