FGT vs BMW Oil Filter Cap & Cage


HighHP

GT Owner
Jun 3, 2019
434
Spokane, WA
In the late 90's and early 2000's some plastics used for Genral Motors hot engine parts deteriorated and crumbled. These problem plastic parts were changed to metal. With this in mind, I thought it might be a good idea to have a spare oil filter cap and cage assembly for my FGT, since, I could get the identical replacement assembly from BMW for only $33, thanks to the great tips and posts on this SUPER forum. Also, bought a couple spare BMW green o-rings.

A buddy of mine races BMW's, has many spare parts and loaned me a BMW oil filter canister assembly for comparison. Upon inspection of the FGT and BMW parts, all looked identical with one small exception. The bayonet on the FGT cage had a plug in the lower end, plugging the two side holes located between the two o-ring slots. See Picture. From what I understand, Ford only uses one o-ring in the slot closest to the filter.

On the BMW bayonet, these two side holes are ported to the top of the bayonet and open to pressurized oil in the filter cap. The end o-ring has a smaller installed diameter as seen in the attached diagram. The BMW bore for the bayonet is stepped to a smaller diameter for this end o-ring. This end o-ring is smaller in diameter than the FGT bore and results in space between the o-ring and bore. If the BMW cap assembly is installed as-is in the FGT, two possibilities exist:

1) Oil will flow down thru the bayonet, thru the two holes and then past the open o-ring space. The oil pump may have excess capacity to supply this under most conditions. However, at a critical time when the oil pump is barely keeping up with need, this leakage would result in a reduction of oil pressure, or

2) Oil pressure may expand the o-ring to seal against the bore, however, w/o R&D bench tests, who knows?

I found that a 3/16" dowel fits the bayonet inside hole. I took a small flat bladed screw driver and filled the lower portion of the inner hole with epoxy (not the quick 4 minute cure), then inserted the dowel from the open end. Actually, once I filled the lower portion of the inner hole with epoxy, it looked like the epoxy would work great by its self. But, since, I had already prepared the dowel, I did insert it. This worked so well, that I think I will install this one in my FGT and keep the original as a spare.

11421744000 - BWM Oil Filter Cap Assembly, Dorman also makes one #917-013

11427549573 - BWM Green Bayonet O-Ring

11427512300 - BMW Oil Filter - Mann HU 925/4
 

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Art138

GT Owner
Mark II Lifetime
Jan 4, 2011
624
Weston,FL
Do you have a close up pic of the dowel you are referring too?
 

HighHP

GT Owner
Jun 3, 2019
434
Spokane, WA
It is shown in the pic with the cages. 3/16" round stock cut to length.