Mechanical Oil gauge tubing?: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Feb. 26, 2011 10:15 p.m. benzbaron HalfDork

Ok I accidently broke the plastic line to my cars oil gauge while installing fuel lines. I am currently looking at patching the line as it uses barbed fitting and was curious which type of tubing you would use? The stock plastic tubing is probably nylon but I was thinking about changing to a teflon tubing. I also have the opportunity if I want to to use an M12 x 1.5 to either AN or JIC fitting then I can buy a braided SS teflon line from grainger or other.

What type of tubing would you use? I hear you can also use copper tubing but there are concerns with the copper hardening and cracking.

Thanks for any help or suggestions, I have the oil gauge line patched for now but don't trust the tubing I used. Damn Polyethylene tube is only good for 160F.
Feb. 26, 2011 10:18 p.m. aussiesmg SuperDork

Copper FTW, metal doesn't harden with age, but you have to take care bending it so it doesn't kink.

However I prefer electronic.
Feb. 26, 2011 10:39 p.m. Gearheadotaku Dork

+1 for copper. Nothing worse than a plastic line full of hot oil bursting under your dash.
Feb. 26, 2011 11:52 p.m. geoffscott

Why not replace the tubing instead of a patch up job. Nylon is good. You can buy a gauge line kit and its very cheap and comes with all the fittings you will probably need. Look in your local parts store. Good Luck Geoff
Feb. 26, 2011 11:54 p.m. geoffscott New Reader

What year is your Benz. I have a mint 84 300d td
Feb. 27, 2011 12:15 a.m. benzbaron HalfDork

It is a 1978 280slc. I can buy the line but it is 100$. The line is repairable as it uses barbed fittings so I might as well just upgrade the tubing and either reuse the old fitting or change the fitting so it is easy to repair in the future need be.

Thanks for the suggestions and keep them coming. I did find some bitchin teflon tubing in the correct size that I can use. It sounds like a good material to use in place of nylon.

I also have some aluminum tubing I could use if I want to. I'd just have to figure out the fittings.
Feb. 27, 2011 1:42 a.m. Keith SuperDork

Doesn't copper have real fatigue problems in a high vibration environment - such as, oh, a car? If you want to use metal, use steel.
Feb. 27, 2011 7:01 a.m. 44Dwarf Dork

Use SS tubing under the dash to bulk head fitting use plastic or copper in engine bay. Copper will harden from heat and vibration over time but so does the plastic. Or use more SS but make at least a 360 loop around a broom handle or bigger to allow for engine movement.

Small Dia SS tubing can be purchased from Swagelock http://www.swagelok.com/downloads/WebCatalogs/EN/MS-02-191.PDF
Feb. 27, 2011 8:19 a.m. Leach SuperDork

Is the plastic you have long enough to cut where the hole is and put a fitting in with a barb on each side?
Feb. 27, 2011 8:55 a.m. porksboy SuperDork

The plastic under the hood of a Bens will harden and become brittle with age, If it broke when you touched it doing something else I wouldnt patch it, I would replace it. Use braided steel line if you can find the fittings, Its not like the car is lightweight to begin with so the extra weight of say a couple of anvils wont make any difference. Let alone a few ounces of stainless steel.
Feb. 27, 2011 9:14 a.m. novaderrik HalfDork

i don't know about other makes, but GM used copper tubing in the stock oil pressure gauges they put in all their cars and trucks until they went to electronic sender in the late 60's (cars) and early 70's (trucks).

you can buy way more nylon tubing than you will ever need with a bunch of fittings for a few bucks at any auto parts store and some places have the same kit with copper tubing. but the popular thing to do these days is to upgrade to braided stainless hose which can be purchased in kits just for use in mechanical oil pressure gauges.

looky here and see what catches your eye.
Feb. 27, 2011 9:51 a.m. motomoron HalfDork

Teflon (PTFE) from McMaster-Carr works great. Huge safety factor for pressure, easy to route. Get the correct fittings, also from McMaster. An infinite number of labs run all sorts of hot, compressed nasty dangerous stuff through it 24-7-365. It works great and isn't terribly expensive.
Feb. 27, 2011 11:35 a.m. porksboy SuperDork

An advantage to a steel braided or copper line is you cant see the air bubbles in the line. Not that you shouldnt bleed it its just I never seem to get all the air out, I see the bubbles and it drives my OCD crazy. It doesnt seem to affect the guage works any way.
Feb. 27, 2011 11:39 a.m. minimac SuperDork

What Keith said. Steel lines are easy to bend, cheap to buy and will probably last as long as the rest of the car. They'll take the pressure easily(same as brake lines) and will handle any temperature you'll ever make with an oil line. Flair or even compression fittings will work, are readily available and inexpensive.
Feb. 27, 2011 12:44 p.m. benzbaron HalfDork

OK after all the information being presented I feel there really isn't a perfect solution. Right now I am leaning towards using the teflon tubing as it is easy to install, clear so I verify oil is in there and cheap. I figure the operating temperature of I think -200F to 500F will work. Teflon in inert also as Motomoron pointed out. There is also another tubing type called PTA which is like PTFE with better durability.

Or I will use metric to (JIC, NPT, ?) adapter and just buy braided stainless line with fitting. The expensive part is finding the adapters, although I only need too buy 2 of them. Grainger sells ss braided PTFE tubing in varying lengths but it uses JIC 7/16 20 fittings which are kind of expensive to buy adapters for. I'm not much for the stainless boy racer look, buy I am being forced in this direction.

I also have access to stainless line if I want to use it but most of it is already bent. I guess you don't flare stainless you use the swage locks. My old man actually burst tests tubing using swagelock fittings. I guess if you hook them up correctly they work very well. I also have access to both copper and aluminum line if I decide to go that direction. I have teflon tubing but not in the correct size as usual.

Thanks for the tips and suggestions, I do appreciate it.