oil filter

[Anonymous]

can any one clarify how the oiling system works and why i had the the following symptoms.
i had changed to a bosch high performance filter last weekend along with a change to 15w40 mobil1. this was right after i changed the oil pump, cleaned out the pan and installed new rod bearings. the oil pressure was improved to a good state but during the week about 250 miles the oil pressure has started to sag. i was concerned but not alarmed. sunday we took the car up the hill from san bernardino to running springs. at the top i noticed my oil pressure was down to about 10psi at idle and about12-12 psi at speed. now i was concerned. i changed the oil before going any further. i could only get penzoil 10w40 and coudnt get a new filter. within a few minutes my oil pressure was at about 6psi at idle and at speed thre needle wouldnt move. i suspected the guage. i didnt hear any rod knocking!!!
we drove the 30 miles home at 6psi indicated. at home i slapped on a known guage and was getting also 6psi.
the culprit seemed to be the filter. i changed to a fram P8HA and rechanged the oil to durablend 20w50. everythinmg seems back to normal at 30psi hot cruising and 18psi hot idle.
i can only guess the bosch filter was a fine micron filter and loaded up quickly from the dirt shaken loose by the engine work and or synthetic oil??? Does this make any sense.
I read esewhere that some recommend the motorcraft filter. Is it better?

Lastly dont the oil filter have a bypass to prevent starvation?

Thanks Frankie

 

[80broncoman]

I found this from a old post it has a lot of oil filter info.
http://www.scuderiaciriani.com/rx7/oil_filter_study/

 

[Anonymous]

The filters typically have a bypass valve that would deliver unfiltered oil to the engine. If the filter was plugging up, the pump should have pressured up sufficiently to activate the filter's bypass, and restored oil flow. Assuming you don't have bearing problems, I wonder if you could have had a piece of trash in the oil pump that A) was restricting suction or B) stuck under the pump's relief valve.

I have been battling a similar problem on my motorcycle with the onset of a sudden intermittent oil pressure problem. Oil pressure is normally 30 psi at cruise and 10 to 15 at idle. Then it suddenly drops to 0 - 5 psi and the lifters start banging. (I also have an idiot light) Oil change helped one time for a couple hundred miles then it did it again. Next I replaced the relief valve spring & plunger. Worked for a little while. Sometimes it takes place when engine is hot, and others when it is cold. It may start up fine and then I get less than 1 mile down the road and it drops to zero. A week ago I tore into the gear case to make sure the pump key was not sheared and there was no trash. In a last ditch effort, I replaced the oil supply suction hose with a steel line. I've gone about 100 miles now. But who knows, the oil change may have "fixed" it.
Doug

 

[Anonymous]

that is an excellent website on oil filters!! that fram sure is cheesy copmared to most the others.
after seeing the general construction ...they all do seem to have a bypas valve. maybe the bypass valve in the bosch filter was set for a higher pressure than the 40 psi the 6cyl pump produces. so the pump bypass was blowing off before the filter. or the contamination in the pupm bypass scenario. at least i am learning a great deal. Thanks