Oil pressure Line routing and type

[Laz]

I am down to the last few Items in the panel area. I have an original oil pressure gauge. It has a flair fitting on the back ( they are SEA 45 deg NOT AC 37 deg.) I think that they used 1/4 inch copper to the firewall then some sort of rubber to the engine fitting. The original engine fitting was a brass elbow with a Barb for the rubber and a clamp. What I need to know is how the tubing ( think it was copper. was routed from the gauge to the firewall. My AI said it is wise to put a small coil in the copper line between the gauge and the firewall to allow for expansion and contractio. I have also heard that that lone needs to be bled to get rid of air . An y thoughts or photos would be of great help. Thanks.

[M Towsley]

Re: Oil pressure Line routing and type

I have an original US Gauge instrument, but do not have it rebuilt or installed yet. The flair is definitely bigger than the one I have on now. My aircraft has aluminum tubing from the gauge to the firewall fitting, no coil required.

Laz, Also meant to tell you mine has a firewall fitting with a hose with fittings from the firewall to the engine.

[Forrest Barber]

Re: Oil pressure Line routing and type

copper and I use the coil . Use a grommet thru the firewall and today I use RTV on it.

[Hank Jarrett]

Re: Oil pressure Line routing and type

Mine is run from the back of the gauge to the right side of the tank and runs down the fuselage tube on the right lower corner of the tank. I put some felts between the fuselage steel tube and the oil line and secured it to the steel tube in several places with zip ties. There is a loop in the line close to the firewall and zip ties to hold the line to the firewall steel tube and to hold the line clear of the controls. I used to have a piece of split hose over the line (it was a copper line then) that was tight on the line inside and tight on the grommet through the firewall outside. The copper line attached to a plugged elbow fitting with a weep hole (so all the oil wouldn't be lost if the line broke) that was screwed into the engine case.
When I rebuilt the cockpit forward I replaced the copper line with a high temp oil hose with stainless braid which eliminated the split hose through the firewall and have a firewall fitting there that divides the line into two sections and, seals the firewall better. There is still a plugged angle fitting at the case with a weep hole.
Hank

By the way, make sure you have a rag under the fitting when you hand pull the engine to prime the line. Crack the fitting at the instrument and pull the prop through till oil comes out of the instrument fitting. It beats having your blood pressure spike and hyperventilating while the engine runs with no pressure on the gauge!

[Robert Lees]

Re: Oil pressure Line routing and type

The engine fitting I used was an AN840-4D modified with a threaded insert in the end (and also staked) with a tiddy hole drilled through.