GeneralDisorder Posted October 20, 2006 Share Posted October 20, 2006 Here's my understanding of the oil system.... 1. The pressure reading is taken directly off the pump. Therefore, nothing downstream of that point can affect the pressure reading. The EA81 in my Brat, with a main bearing knock still read 25 psi hot idle. When I tore it down the mains were scored, and starting to wear through the plating - they measured about twice the acceptable book limit. My 83 FSM (which doesn't cover the turbo, and your turbo has an oil cooler, as well as oil supply to the turbo itself.... so it very well could be different) indicates 25 psi as the lower limit of acceptable reading from the dash guage. 2. Because of the way the pressure reading is taken, as the engine wear's, the pressure remains largely the same. Only wear to the pump and the sending unit can cause the pressure change. This makes sense as the gauge is designed to warn the driver that the pump needs changing. The engine *can* run at lots of different pressure's, but if it starts to dip lower than normal, it's time for a new pump. 3. My expereince has been that if you allow the engine to continue operating at lower than 20 psi for too long, you will lose the rod bearings. The original engine in my wagon threw the #3 rod out the top of the block. It had a digi-dash without a pressure guage, and one time on my way home from some off-roading, the oil pressure warning light started to flicker just a little at idle. I replaced the pump seals but not the pump, and about 3k miles later it blew the rod. If I had installed a guage, and knew what I know now, that engine would probably still be running - I bought the car in perfect running order at 140k, and 165k it threw the rod. It's my fault because I didn't replace the pump. I changed the oil, but the pump was on it's last legs, and drowning the engine with swamp water a half dozen times and running with contaminated oil was the final straw for it. Now - you say the pump is new... what brand? I only use the Parut (OEM) pumps myself. I don't know if there are even any aftermarket pumps for the EA81, but I wouldn't buy one if there were. GD Quote Link to comment Share on other sites More sharing options...
beataru Posted October 20, 2006 Share Posted October 20, 2006 Now - you say the pump is new... what brand? I only use the Parut (OEM) pumps myself. I don't know if there are even any aftermarket pumps for the EA81, but I wouldn't buy one if there were. GD Yay, OEM, YAY smart people are here......... Quote Link to comment Share on other sites More sharing options...
Ross Posted October 22, 2006 Share Posted October 22, 2006 Here's my understanding of the oil system.... 1. The pressure reading is taken directly off the pump. Therefore, nothing downstream of that point can affect the pressure reading. The EA81 in my Brat, with a main bearing knock still read 25 psi hot idle. When I tore it down the mains were scored, and starting to wear through the plating - they measured about twice the acceptable book limit. My 83 FSM (which doesn't cover the turbo, and your turbo has an oil cooler, as well as oil supply to the turbo itself.... so it very well could be different) indicates 25 psi as the lower limit of acceptable reading from the dash guage. 2. Because of the way the pressure reading is taken, as the engine wear's, the pressure remains largely the same. Only wear to the pump and the sending unit can cause the pressure change. This makes sense as the gauge is designed to warn the driver that the pump needs changing. The engine *can* run at lots of different pressure's, but if it starts to dip lower than normal, it's time for a new pump. 3. My expereince has been that if you allow the engine to continue operating at lower than 20 psi for too long, you will lose the rod bearings. The original engine in my wagon threw the #3 rod out the top of the block. It had a digi-dash without a pressure guage, and one time on my way home from some off-roading, the oil pressure warning light started to flicker just a little at idle. I replaced the pump seals but not the pump, and about 3k miles later it blew the rod. If I had installed a guage, and knew what I know now, that engine would probably still be running - I bought the car in perfect running order at 140k, and 165k it threw the rod. It's my fault because I didn't replace the pump. I changed the oil, but the pump was on it's last legs, and drowning the engine with swamp water a half dozen times and running with contaminated oil was the final straw for it. Now - you say the pump is new... what brand? I only use the Parut (OEM) pumps myself. I don't know if there are even any aftermarket pumps for the EA81, but I wouldn't buy one if there were. GD On point one, down stream does have an effect on the reading - hydraulic pumps deliver a set flow rate, therefore a change in the downstream resitance will change the pressure at the pump outlet correspondingly. As you say, small amounts of bearing wear don't affect the pressure noticably , however, very worn bearings such as were in my engine before the rebuild do. It ran with a hot idle pressure of around 1-2psi with a brand new, oem pump. If you run contaminated oil through your engine, the bearings can suffer just as much as the pump, since oil supply is restricted by the oil filter getting blocked up. Its not really the pressure thats causing the problem with worn engines - its the increase in gap size. The bearings used on these engines dont rely on pump pressure, they operate using pressure created by viscous forces within the very small gap, which acts like a wedge since the crankshaft sits very slightly eccentrically within the bearing shells. The pump presssure simply has to be large enough to provide adequate supply to all parts of the engine. The pump i have is an oem one. Quote Link to comment Share on other sites More sharing options...
WheaT_BeeR_MaN Posted January 24, 2007 Share Posted January 24, 2007 well i thought since im having a problem with my oil i might ask y after i bought a new oil pump the light still comes on after it warms up. now its actully eating oil "alot of it!". i have ran the engine hard including threw alota ponds. so im not suprised its dying, just wondering what else i can do? Quote Link to comment Share on other sites More sharing options...
beataru Posted January 25, 2007 Share Posted January 25, 2007 what type and how old is the oil you are running? Quote Link to comment Share on other sites More sharing options...
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