Has anyone tried this with their pickup screen?
www.saabservices.com said:Prevent SAAB 4 cylinder engine failures.
SAAB 900, 9000, 9-3, and 9-5 can all benefit from this modification.
One solution for SAAB oil pickup screen becoming clogged with sludge and/or oxidation product particles.
We are not the first to use this method, but we felt that an engineering explanation of the method was in order. The author of this document (blue text) is D.O. Schultz.
Mr. Schultz is a retired engineer, pilot, and FAA licensed airframe and powerplant mechanic, and has driven Saabs for many years. Currently he owns a 9-5 wagon.
The existing wire mesh screen has an open area on the pickup of 62mm diameter, which equals 4.67 sq. inches of area.
This particular screen, called 30 mesh, is manufactured .011” diameter wire, spaced .033” on centers, in a square pattern. Openings are .022” X.022” and .031” on the diagonal. This equals an open area of 40.8 % or 1.91 sq in which is about 410% of the pickup tube ID area.
Replacement screen vs original. Placing a strong magnet on the back of the pickup is advised.
The proposed replacement screen is based on proven history in the Continental TSIO-360; a 220 hp turbocharged, intercooled aircraft engine that has been is use for over 30 years. In this application, there is only 1.1 sq in of total screen area and the perforations are .081”diameter, resulting in an open area of .385 sq in. Normally this screen remains clean at oil change intervals of 50 hours (which equates to about 3,000 miles of highway driving) unless there is an internal part failure in the engine.
Using this historical example, the screen shown is made from 22 gauge mild steel using .079” diameter perforations, staggered on 7/64” spacing.
This equates to an open area in the modified SAAB pickup, when directly replacing the wire screen, of 46% or 2.15 sq inches, which is 474 % of the pickup tube ID area.
The factory screen allowed passage of a particle of up to .022” and the replacement screen allows passage of particles up to .079” diameter.
This equates to a 260% increase in particle size and a 12.5% larger open area for less overall screen restriction.
Careful examination of the ”sludge” reveals that it is primarily composed of small granules of what appears to be cooked oil and is not a hard substance like combustion chamber carbon particles. These granules should not cause any harm to the oil pump and will be trapped in the full flow oil filter and thus not continue to circulate in the oil system or serve as a clogging agent for the pickup screen.
It goes without saying that the oil filter must be changed at each oil change and in our opinion this period should not exceed 3 to 5,000 miles or every 90 to 180 days.