Engine oil pressure fitting

[Robert Lees]

You know the old AD...87-03-08...requiring the replacement of the oil pressure fitting at the engine.

Mine does not have a small orifice...in fact it is a bog-standard AN840 fitting.

Is this OK? Admittedly no problems in the last 15 years, but you never know.

1946 BC12D

[jgerard]

Do you have a special fitting in the back of the gauge with the small hole?

I want to make a new O.P. line for my plane and install a bulkhead fitting at the fire wall. I think the cessna 150 parts manual shows the proper O.P. fitting with the small oriface.

Jason
N43643

[Dick Huish]

The small oriface should be at the engine end. The purpose of it to prevent the loss of all your oil in the case the line or gauge breaks.

[Robert Lees]

Reply to Dick and Jason:

Dick, you are correct, the orifice is to reduce engine oil loss in the case of oil line failure. [as you know, the orifice has no influence upon oil pressure, because there is no oil flow]. I know that the original B-1071 fittings had the orifice for this very reason.


Jason, no I don't. If the Cessna 150 (0-200?) manual has a plan, please scan it in and share!


To all: does the modified fitting B-7071 have an orifice? Or did the higher oil presures of the later Lyc engines get rid of this?
How come this AD came out in 1987, when A-65's had been flying for 40+ years?

[Len Petterson]

Engine oilpressure fitting

In hydraulics we made orifces from
:1 A allanhead set screws 10/32 or 8/32 whatever was suitable size for the fitting it had to go into.
Tap the fitting and drill a 1/32 hole in the setscrew. Use LOCKTITE on the tread and/or peen over the end of the tread with a centerpunch.
:2 The best is to use a 1/16 inch pipeplugg and tap as the pipetread is taperd. Locktite it to! They can be found at a good hydrulic supplier
:3 As there is no oilflow and therefore no wear in the orfice you can silversolder or brass a steel fitting shut and drill out the orfice in the solder.

The orfice is there to prevent massiv oilloss i case the hose brakes.
Len

[Robert Lees]

Still looking for technical info regarding the B7071 oil pressure fitting, as suggested by AD87-03-08

Does it have a small diameter orifice?
How is the oil pressure hose attached? Hose clamps?
Anyone got one with the "T" stamped on one of the hex flats?
Anyone got a drawing?
Anyone got one without a rubber hose, but with a coiled copper pipe to the firewall?

Rob

[yerich109]

Mine is copper all the way. I think there are two or three hex heads at the back of the acc case because of this and I always get confused when it's time to change the oil. Can never remember which one to turn first...


Blue Skies,

[Robert Lees]

Mike...I think you are looking at the oil temperature bulb and oil screen housing, where there are three hex fittings.

The outermost one is the first to undo, but holding the centre one stationary, to prevent twisting of the oil temerature capillary.

Then when loose, the middle one can be undone, allowing the largest one closest to the engine to be undone to get at the oil screen.

Rob

[jrzangger]

The small hex fitting is for the oil temp bulb, and you are correct to hold the second hex fitting to prevent damage to the capillary tube. The second hex need not be removed as it is just the adaptor for the temp sense bulb. The oil screen itself is not a hex but a square of 1" or maybe 1 1/4". The second hex or adaptor always seems to be less than tight, but be warned not to overtighten it as it will easily fail grounding the aircraft until a replacement can be found!

[alwaysoar]

Re: Engine oil pressure fitting

RE: the oil pressure fitting on the engine. I've just re-read the posts and have made a fitting with a small orifice by taking a 1/8-1/4 brass union for the engine end of the oil pressure line, then taking about 3/16 off the end of an AN 3 bolt and putting that into the orifice which is a perfect fit into the brass union. I then drilled a 1/16 hole into the piece of AN 3, and then soldered the piece of AN 3 into the brass union. This was easy to make and very cheap. As soon as I find a smaller drill (1/32) I'm going to make one with a smaller orifice. Attached to this is an Aeroquip hose with standard fittings that attach to a through fitting on the firewall. Anybody see anything wrong with this?

Ed@BTV VT
TF 527

[Mark Julicher]

Re: Engine oil pressure fitting

I just inserted a rivet body (sans rivet head) into the AN fitting and squeezed (squoze?) it to stay tightly in place. Then drill a 1/16 hole through the rivet. This has been working fine for over 10 years now.

Best Regards,
Mark Julicher

[Robert Lees]

Re: Engine oil pressure fitting

The original B-7071 (banned now) was a #60 (0.040") drilled hole into a solder plug in the end of the fitting. I have no reason to think that the hole size changed during the AD process, it was the attachment of the flex rubber hose that caused the problem.

I will be plugging my fitting, and then drilling to the above size.

Ed I see nothing wrong with your version.

Rob