Issue after oil change
- Thread starter 89Turbo
- Start date
Ok, I get it now...but shouldn't I be seeing a little bit more pressure before the valve starts opening? I'm guessing my relief spring is worn/weak?
There's 2 relief valves in the 7M (3 if you count the filter internal by-pass)...take a look at this:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?Section=LU&Page=2
The 1st is on the pump...this is the one you would shim for more pressure. Once shimmed though, you are going to see most of the effect at idle through 2000 rpm (remember the oil pump depends on engine speed)...once you hit pressure at ~40 psi, the oil cooler relief valve is going to open and have the effect I talked about earlier. This is also why a lot of guys don't see pressures above 45 psi or so with a shimmed pump (unless they use a lot of shims...4-5mm worth)...the cooler relief valve defeats it by by-passing oil to the pan.
What you should see is a steady rise in oil pressure with rpm. If the pump is shimmed, the pressure will be higher at idle and take a shorter time to get to the pressure where the cooler relief valves opens. Running a full flow, thermostat controlled cooler system does away with the stock filter head...this alone will show higher pressures as rpm increases. Even more so if the pump is shimmed. Clear as mud?
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?Section=LU&Page=2
The 1st is on the pump...this is the one you would shim for more pressure. Once shimmed though, you are going to see most of the effect at idle through 2000 rpm (remember the oil pump depends on engine speed)...once you hit pressure at ~40 psi, the oil cooler relief valve is going to open and have the effect I talked about earlier. This is also why a lot of guys don't see pressures above 45 psi or so with a shimmed pump (unless they use a lot of shims...4-5mm worth)...the cooler relief valve defeats it by by-passing oil to the pan.
What you should see is a steady rise in oil pressure with rpm. If the pump is shimmed, the pressure will be higher at idle and take a shorter time to get to the pressure where the cooler relief valves opens. Running a full flow, thermostat controlled cooler system does away with the stock filter head...this alone will show higher pressures as rpm increases. Even more so if the pump is shimmed. Clear as mud?
Tis true...the oil squirters are a "controlled leak". The spring in the squirters function at ~45 psi.
Keep in mind though the oil flow path...pump, filter, motor. The relief valve on the oil pump is the 1st pressure control...the cooler relief valve is the 2nd. Oil flow will follow the least path of resistance...with the relief valve in the pump, it goes back to the pan. The cooler relief, through the cooler back to the pan. The remaining pressure is for the motor...at high rpm, pressure will increase sufficiently to allow the squirters to function.
What can happen is the squirters function at a lower than designed pressure due to wear. This will rob your bearings of the oil flow they need. Since the oil pressure reading is at the block, this can be a cause of lower oil pressure on the gauge.
Keep in mind though the oil flow path...pump, filter, motor. The relief valve on the oil pump is the 1st pressure control...the cooler relief valve is the 2nd. Oil flow will follow the least path of resistance...with the relief valve in the pump, it goes back to the pan. The cooler relief, through the cooler back to the pan. The remaining pressure is for the motor...at high rpm, pressure will increase sufficiently to allow the squirters to function.
What can happen is the squirters function at a lower than designed pressure due to wear. This will rob your bearings of the oil flow they need. Since the oil pressure reading is at the block, this can be a cause of lower oil pressure on the gauge.
I still can't fathom why toyota would make the oil cooler dump into the pan instead of sending it back through the system so you don't lose pressure...
