Low oil Pressure at Idle

[Burnwithin]

i recently rebuilt the whole motor in my 98 camry and im getting low oil pressure at idle i have a new crank with barrings new oil pump new rings and a head from a 2001 due to my old head was really worn out. when driving ill get around 25-26 psi when at 2000 rpms but when i hit idle 600-700 rpms i loss pressure and oil light comes on. any ideas ?

[93celicaconv]

What engine (assuming 4-cyl 5S-FE, since you only mentioned a single head, not two heads)? What viscosity oil? Are you running any oil additives, or 100% fresh oil?

Sounds like you have an oil pressure gauge in that you provide a pressure range when driving and engine at 2,000 RPM. What is the pressure at idle when the light comes on?

What happened with your original engine? Looks like you had to do a lot of changes. What is the background of the 2001 Camry head? Did you take that head to a machine shop to make sure the mounting surface was flat, put in new valve seals, and check valve lash

[hill8570]

Sounds like your pressure is the suck across the board...25/26 at 2000 is pretty low, too.

You did clean / replace the oil pickup screen when you did the rebuild? How about the other end of the pickup -- is the gasket new, or at least undisturbed?

[93celicaconv]

Originally Posted by hill8570

Sounds like your pressure is the suck across the board...25/26 at 2000 is pretty low, too.

You did clean / replace the oil pickup screen when you did the rebuild? How about the other end of the pickup -- is the gasket new, or at least undisturbed?

For the record, that is about the running oil pressure of my 93 5S-FE after running an hour or more on the highway, then idle at 2,000 RPM (maybe a little higher, like 28-30 psi). Idle speed (700 RPM) pressure is about 7.5 psi. Cold start idle oil pressure is between 60-70 psi.

The shop manual for a 5S-FE in 93 has the oil pressure specs as follows:
- at idle (700 RPM): 4.3 psi or more
- 3,000 RPM: 36-71 psi

Measurements above are after engine has warmed up to normal operating temperature.

Assuming burnwithin checks his oil pressure at 3,000 RPM at the time he is getting 25/26 psi at 2,000 RPM, to see if he is in the target range for 3,000 RPM, that would be good (assuming he has a 5S-FE, but I'm not sure what engine he has yet).

[fenixus]

how do you check oil pressure ?
i can think of only by measuring terminals on oil pressure sensor. do you put some gauge somewhere or something ?

asking just out of curiosity. thanks.

[hill8570]

Originally Posted by fenixus

how do you check oil pressure ?
i can think of only by measuring terminals on oil pressure sensor. do you put some gauge somewhere or something ?

asking just out of curiosity. thanks.

Usual way is to pull the "you're screwed" pressure switch (which is just on or off) and either replace it with a sender wired to a dash gauge, or stick in a "T" fitting so you can have both the gauge and the idiot light. For one-sy two-sy diagnostics, you just pull the pressure switch and stick your handy dandy oil pressure gauge in it's place...kind of hard to drive around like that, 'tho.

[fenixus]

thanks gotcha

[73sport]

F,
to answer your question, remove the stock sending unit, grab an extender pipe (automotive store), a "T" and seal the T to the pipe, thread the pipe into the block. Insert the Stock sender in to the open T, insert a mechanical or electric gauge sender unit into the other open T.

PS - If you run a mechanical gauge, I suggest you use 1/8" copper as opposed to the common nylon tubing most mechanical gauges ship with. Heat, battery acid, won't kill it instantly.

Burn,
3 things come to mind:
1) don't run it any more until you know you are not doing harm to the engine. perhaps put a real gauge on it as mentioned above.

2) Don't quote me on this, but the sister engine has 3 check valves. 1 is on the oil pump body and is the pressure relief valve. Was the spring and ball checked? 2) is in the oil filter. If plugged it bypasses the filter. 3) and this one I'm not sure on by literature suggests there is a bypass valve inline with the filter near the pump. Was the spring and check ball removed, inpsected?

3) who checked the engine bearing clearances? Were they checked? A remanufactured crankshaft could be cut undersize to clean it up. This would require undersize bearings to obtain the correct clearances at the ROD and MAIN bearings.

As for the spec posted; that is what yota calls for. How they engineered it to run so low is beyond me. Does that mean the dash light comes on at 2.5psi as 4.5 is OK? Thats is very scary! What oil do you have in it and how many miles since the rebuild?


EDIT:

http://www.jegs.com/c/Gauges-Tachs/10331/10002/-1

http://www.jegs.com/c/Gauges-Tachs_G...10339/10002/-1

http://www.summitracing.com/brands/A...banner=HP50L04

[93celicaconv]

I have a setup much like 73sport described, with the sending unit for the idiot light and an electronic sender, all on a tee coming out of the oil pressure port on the head. I have 3 gauges in a pillar pod, one of them being oil. I made sure my oil pressure gauge was capable of measuring 1 psi (most start at 5 psi), because of how low the Toyota engines run oil pressure at idle speed when warmed up. Not too many oil pressure gauges that can read starting at 0 psi on up out there.

But it is a good idea to check idle oil pressure with a mechanical gauge at this poiint, as 73sport points out, given the oil pressure light coming on. Mine flickered too at times, put a mechanical gauge on it (before I put the electronic gauges in the piller pod), and found my idle pressure to be above the minimum all the time, so I bought a new oil pressure sending unit, and no more oil pressure light flicker (the previous oil pressure sending unit may not have been the right one, as I didn't own the car from new and don't know what someone else might have done).

[73sport]

93, So how far away is the head port from the factory sending unit? Is it at the pump end or further away?
The 1MZ V6 runs the sender off the front of the block right next to the pump (suck). I'm all for checking it as far away from the pump to see what the rest of the engine really gets!

Knowing both (a quick spot check) is best though (near pump AND away from the pump). Had V8 blow out a galley plug in the lifter area, held good pressure w/out it but a couple lifters ratteld. I could see it dropped some pressure but it wasn't like it went from 80 cold to 20. More like 80 to 50 at idle. When warm it dropped from its 50 to the high 20's! Anyway, more info is better!

Hmm - - if his switch got hot tanked, it could explain this. . . And maybe nothing is wrong. But I'd need to know with a real gauge.

[93celicaconv]

On the 5S-FE, the port where the oil pressure sender switch is located is in the head, opposite side of the oil pump. In this location, it is downstream of the oil filter, and on the head side of the oil galley (but the galley is also the same galley that supplies oil to the crankshaft). Given that oil has the viscosity of water when hot, since it is in the same galley, a pressure loss in the crankshaft area would show up in the galley feeding the head as well (the galley doesn't have much of any pressure variation in it throughout).

If you are asking how far is my gauge sending unit from the factory oil pressure switch, both are in the same tee, probably 1/2" apart at most.

I would bet that in your 1MZ V6, even if the oil pressure port is near the pump, it is still in the oil galley after the oil filter. My 4A-FE's oil pressure port is in the block, very close to the oil pump. But as I look at the oil galley path in the shop manual, the oil goes from the pump to the oil filter, then back out of the oil filter towards the oil pump, and splits off at the front of the engine (splitting meaning one galley goes up to the head, the other goes down to the crank).

[AlmightyCamry777]

is it within factory specs for the oil pressure, the rule of thumb is: 10 psi for every 1000 rpm. The toyota recommended minimum as quoted above is 32 psi at 3,000 rpm, the higher pressure limit is set due to such situations as too thick engine oil being used or the occasional pressure surges etc. (as you probably know the oil system has a high pressure cut out/relief valve.)

if you have the minimum pressure required then the only other thing to worry about is FLUCTUATING oil pressure. As 73sport said, it is possible that low oil pressure could be caused by excessive bearing clearances in the main bearings and connecting rod big end bearings.

You changed the crank and bearings, but who, if anyone, checked the clearances beforehand?
Whether the crank was brand new or remachined, a good machinist would have miked the journals on the crank and selected the proper sized bearings to match, that would provide the exact amount of bearing clearance (for both main bearings and connecting rod bearings). The answer may be that perhaps you did not have a good machinist check everything out for you before they sold you the crank and the bearings.

Too little bearing clearance and the crankshaft will seize up. too much clearance and you will get noise, premature wear and, low oil pressure (due to the oil pump having to pump greater volume of oil faster then it is designed to do, to fill in the excess bearing gap).
-did the place that sold you the crank and bearings give you any documentation? Was the crank used or remachined? Did anyone mike the journals and record the measurements?

-What size were the bearings, were they fitted for the crank or did some unknowing soul simply sell you stock replacements without measuring anything?

-is the low oil pressure also creating any engine noise? (constant rattle, tick, tock, or clunk from the bottom end of engine that varies with engine speed - possibly muffled by normal engine noise if it is slight.)

-did you replace the conecting rod bearings, reuse the old ones, or replace the bearings with OEM stock size? Did anyone measure these clearances either?

If you get a good oil pressure gauge and the oil pressure still seems too low to you, these may be questions you are going to have to find out the answers for, if you intend to get your money's worth out of this engine.

[Burnwithin]

its a 5S-FE im running 10w30 with a quart of lucas and the crank came remanufactured with the correct bearings as a kit i removed the engine balancer but that has no reason todo with low oil pressure i never miced the rod due to it came as a kit with the bearings assuming it was right the oil pickup tube was cleaned and new gasket. the car has only 30 miles on the rebuild the car sits till i find the problem the head was checked on a surface plate to mic and that was good along with the cams oil pump is new so im not thinking thats bad yet i could always take the crank from the 2001 motor i bought for the head and get new oem bearings for that and to find out if that is the problem and if not ill look into the oil pump and replace that again.

[73sport]

Do you hear any sounds that don't seem right? Does it sound totally normal?

Are all of the Engine Ground Strap Wires reconnected? Could anything have happened to that sensor? Dropped, pressure washed, hot tanked??

Off hand you really don't know if anything is wrong until you eliminate the sensor as defective!
Either replace it, test it, or install a real gauge even if its just under the hood. Mys suggestion is the later of the two. You will have an answer good or bad. I posted some links up above.

EDIT: You didn't by chance have any spare parts left over after the engine build did you?

Let us know if you have any questions but don't assume the worst just yet.
73

[93celicaconv]

Burnwithin, if you are reading this posts clearly, you may (and likely don't) have an oil pressure issue. You may just have an oil pressure switch that turns on your telltale light at too high of a minimum oil pressure. Its been suggested many times to go out and get a mechanical oil pressure gauge and check the readings. Don't ever tear something apart because a telltale light flickers - you need to the real pressure values to make any decisions.

Also,the Lucas additive you put in your crankcase will effectively reduce the viscosity of your oil. It is the same as the Rislone product I have occassionally used in my 5S-FE. And that product had the effect of lowering my oil pressure by about 5 psi (cold, warm, highway, etc.). So your Lucus additive may be reducing your oil viscosity just enough to trigger your oil pressure light when warmed up at low idle.

If your mechanical gauge testing tells you that your oil pressure falls within the range of normal (and you can see from earlier posts how low that is), then I would spend the money to go out and get a Toyota OEM oil pressure switch from the dealer. Getting one from an autoparts stores, you may be getting one that fits the application, but may not be at the exact pressure switching level that Toyota designed specifically for that engine. Replace the oil pressure switch with a Toyota one, and I think you won't have a problem, and nothing to worry about.

Why are you running Lucus additive in the crankcase anyway?