What would cause a drop in coolant temperature and an increase in oil pressure?
Today took my 90 Toyota 4x4 w/3.0 for a short 14 mile round trip drive.
On my way to my destination I noticed the coolant temp was lower and the
oil pressure was higher then they should be given the distance. When I
started the truck back up for the drive back, the coolant temp and oil
pressure were correct, then a few miles in noticed the coolant temp drop
and oil pressure rise, then fall back to normal points. The after market
gauges and oem gauges both did the same thing.
It sounds like you may have a thermostat hanging up. Cooler engine temperatures will maintain a higher viscosity of the oil which would be the cause of the high oil pressures. Gauges are probably correct if you have aftermarkets matching the OEM's.
Have always ran 10/30 in it since it was new. Went ahead and pulled the t-stat, and it appears the inner gasket let go after 12yrs(abut 14k miles), and caused the valve to stick partially open, preventing the engine from warming up. Replaced it today with a new oem t-stat, and all gauges were back within their normal range. Thanks.
