Oil pressure just went to ZERO.

[Turbo Targa]

Ok I have been fiddling around with my Supra since the new HG and I have been fighting a oil leak. Well I took the turbo off for the 3rd time and finally got the leak fixed.

Get the car started and voila it runs. spudders and the idle roams, but i get the timing right and it cleans up its act. I am going to get the timing light out tonight when I get home from my finals.

Anyways when I fired the car up the first time oil pressure was good. Once it got warm I reved it up a little noticed the oil pressure gauge wasn't reacting at all. So for good measure I put in a quart of oil, and see positive results. So I add a 2nd quart for insurance and while the car is still running at idle I am walking around it checking for leaks. I decide to get in the car again to check the gauges and I have ZERO oil pressure. I then noticed a slight dribble of oil coming from right bellow the crank pulley. I didn't have time to trace the leak, but what just happened?

Did I do something wrong by adding oil while the car was running? If its not one thing its another.

 

[GrimJack]

If you are lucky, the oil pressure sending unit just got disconnected from the wiring harness. It's under the CPS, and it's a bit hard to get at.

If you're not so lucky, the oil pressure sending unit is dead. Still not THAT big of a deal, though it's a big PITA to change in the car.

From there we go to the unlucky possibilities. Dead oilpump, or worn clearances in the bottom end that eat at your total pressure. Both of those require you to pull the engine.

 

[Turbo Targa]

Under the CPS? Comes to mind as a coil pack system.

What are my ways of testing the sensing unit?

How could I mechanically check the pressure?

 

[Dirgle]

C-cam
P-position
S-sensor

Passenger side of the engine towarde the front of the head. The thing you use to adjust the timming. You know the one

 

[Turbo Targa]

Yeah i said it to myself a few times and I eventually remember what it is.

I took the wire off and plugged up again but had no luck with that. While the motor was running I did open the oil fill cap and the driver's side cam looked like it was getting plenty of oil.

 

[Satan]

Overfilling with oil can cause alot of other issues... replace the sending unit with a known-good one and check the wiring.... Do not overfill the oil/fluids... drain some of that out if ya need to.

 

[IHI-RHC7]

Yeah, for some reason frothy oil/ air foam doesn't make oil pressure...

 

[Grenadian7mgte]

TURBO TARGA! you said when you fired it up you had oil pressure yes?if so,how much and what grade oil are you using?When i start up i get about 42psi and at idle its about 4psi on a stock oil pump.:evil2:

 

[IHI-RHC7]

Uhm,, that's bad.

 

[Grenadian7mgte]

o shit man:aigo: ,what happen is that i spun some bearings and i had to do the cranck and bearings, i cant aford a comlete rebuild so i that i did enough to keep it running till the summer cuss i dont have a garage and jack frost is hear:1zhelp:and to think i was tryin to help? i need it myself now

 

[mkIIIman089]

Granadian, please try and use better grammer and spelling. I don't think I should have to concentrate that hard to decode someone's post.

 

[IJ.]

Granadian, please try and use better grammer and spelling. I don't think I should have to concentrate that hard to decode someone's post.

Go Colin!

 

[JDM 1JZ]

what preasure should the supra idle at ive been in alot of supras and they all idle at about 5psi and 40-45 on boost and driving

 

[SupraMario]

^^Wheres that damn pic with normal operation range,
but yea from 5psi all the way to 80 i think was the norm.

 

[JDM 1JZ]

damn 80 i dont think ive ever seen one up that high i think highest ive ever seen is 45-50

 

[Turbo Targa]

I am using 10W 30 Valvoline. I will drain the oil and throw a new filter on there tomorow when I get home from work. How does too much oil make the sensor go nuts?

Thanks!

 

[Dirgle]

If the oil level is to high in the oil pan the crankshaft whips the oil into a foam or froth. When the oil pump tries to pump this it can't generate pressure.

Oil in it's liquid form doesn’t compress so you can easily generate pressure, this is the reason hydraulic jacks work. The oil foam, on the other hand is like 80 percent air and 20 percent oil. The 80 percent air inside of the foam compresses easily so you can't generat any real pressure until you have compressed allot of it, so as you can see it would take a lot more of the foam to move the same amount of oil. Usually more than the 7m oil pump is able to move.

This causes the oil pressure sender to not read any pressure even though there is oil flow.

 

[JDM 1JZ]

so basically ur saying our cars suck for readin oil preasure

 

[Turbo Targa]

If the oil level is to high in the oil pan the crankshaft whips the oil into a foam or froth. When the oil pump tries to pump this it can't generate pressure.

Oil in it's liquid form doesn’t compress so you can easily generate pressure, this is the reason hydraulic jacks work. The oil foam, on the other hand is like 80 percent air and 20 percent oil. The 80 percent air inside of the foam compresses easily so you can't generat any real pressure until you have compressed allot of it, so as you can see it would take a lot more of the foam to move the same amount of oil. Usually more than the 7m oil pump is able to move.

This causes the oil pressure sender to not read any pressure even though there is oil flow.

Thanks for the great information. Its comforting to know that I may not have fubared my car up. I will continue with my plans on the oil change for tomorow.

 

[Dirgle]

so basically ur saying our cars suck for readin oil preasure

Na, they read oil pressure pretty good. However our lubrication systems are "Low pressure, High volume system" this means the even though the pressure is low the amount of oil being moved is very high. Most cars are a "High pressure, Low volume system" Even thought your getting a good oil pressure reading your not moving near as much oil.

It's because most systems are of the High pressure, Low volume type that people freak out when they see the readings on our system. On our cars idle oil pressure is approx. ~ 4psi. This is fine for our cars as it is a hell of a lot of oil at 4psi. But on any other cars this is a good sign that the engine is FUBAR.

I've tapped a manual oil pressure gauge into the 7M and found that the stock gauge is pretty damn accurate, so I took it off and just use the stock one.

As far as the foamy oil is concerned, don't get me wrong. Yes the motor is still being lubricated but it is only receiving 20 percent of it's normal lubrication. Also air is poor at absorbing heat and moving it away. This means that the air is basically trapping the heat and causing thermal breakdown of the oil and engine components. This is bad. So running the engine any more than necessary before you fix the level is not recommended.