Shop Talk–March 2013

MAR 2013 - Shop Talk by whidbeycruzers

OIL FILTER DESIGNS

Oil Filter Designs – Ron Teker

We will discuss only the following designs as there are numerous types of oil filters for engines and transmissions.

1. Spin-on canister types.
2. Full flow or 100% filtered where all the oil from the oil pump goes through the filter before lubricating the bearings and other wear parts.

As there are numerous companies who manufacture oil filters with their design and construction constantly changing, it would be a daunting task to rate each individual oil filter.  However, the following criteria should be examined by the user to determine if this particular brand of oil filter is doing its job for him.  I encourage everyone to examine his oil filter after changing oil by cutting it apart to see if it is indeed doing its job of filtering the oil and protecting the engine.

All oil filters require a “base gasket” which should be made of nitrile rubber to withstand the temperature changes and the oil pressure generated by the oil pump. This is the only thing that holds the "spin-on" oil filter to the engine and keeps the oil from leaking out of the engine. The base gasket will deteriorate with time, more than with mileage. It will either harden or soften, in either case the gasket tension that holds the filter to the engine is relieved. Engine vibration will "unscrew" the filter, and ALL the oil will be lost.

Desired Results:  No cracks or noted leaks.  Should exhibit some tension for sealing.

 Filter media can be made of cellulose or fibrous materials, or synthetic materials designed especially for this purpose. Media in an engine's primary filters pull out particles as small as 25 to 30 microns (a typical average human hair is about 45 to 70 microns in diameters).  The filter itself is pleated and needs to be secured inside the canister to a metal type cup on each end with an adhesive type material to keep the pleats open and prevent the pleats from collapsing together which would prevent the dirty oil from passing through and instead travel thru the by-pass valve into the engine as dirty oil. This is one reason the full-flow filter allows passage of the comparatively small contaminants; trying to catch everything would either restrict the oil flow or make the filter mechanically very large.  If filter media blockage occurs in the filter, by-pass valve will open at specified differential pressure, which allows oil to go around the filter media and back to the engine. In this situation, lubrication with unfiltered oil is better than none at all. 

Desired Results.  Pleats open and secured to end cup bases.  By-pass valve working.  Note: All oil filter media has to pass an SAE test for entrapping contaminates.

Anti-drainback valve: This should be a rubber or silicone seal with a spring to provide a positive seal to prevent the oil from returning to the engine pan after the motor has been stopped.  The intention here is that the oil filter should remain full of oil along with the internal oil lines in the motor. When the motor is started again, the lubricating oil will get to the bearings and engine components faster as the filter and oil lines already have oil in them.  If you here a knocking noise when you first start up your engine, you should try a different brand of oil filter to see if that corrects the problem.

Personal Note: I noticed that I had experienced this problem with a Fram oil filter and when I changed to a Wix filter, the noise went away.  I also noticed that when I changed out the Fram filter, it had very little residual oil in it.  When I changed the Wix filter out, it was full of residual oil.  I am now using an STP filter and will report on it in the future. Will not use a Fram filter anymore.

Desired Results:  Anti-drainback valve made of rubber or silicone with a positive pressure type spring apparatus for positive sealing.