Caution--Danger--Alert on using mechanical oil gauges

[Skunkworks Challenger]

On another thread there is a discussion about adding a mechanical gauge in addition to the dash mounted instrument which is usually an electric unit.  This week I started my completely rebuilt 440 for the first time.  Working alone and not knowing for sure my instrument gauge would work I added a mechanical gauge under the hood so I could watch my oil pressure while testing the engine.  Unknown to me the bourdon tube in the gauge ruptured and I lost almost all my oil in a very short time.  I aborted as soon as I discovered the problem and do not believe I ever lost oil pressure or damaged the engine.  The point is the possibility was there.  Admittedly, I used an inadequate gauge and did not have a small orifice in the connection.  I just want to caution everyone that if adding a mechanical gauge that it be up to the task and is installed properly with an orifice size as small as possible. PK

[NC RMP]

Absolutely, you need to be careful if you use the mechanical gauge to not let the tube rupture.  For that reason, I use a copper tube not the nylon thing that comes with most gauges which can be melted or cut easily. 

Also, even though the term "idiot light" for the warning lights like the low oil pressure light are often used and is a derrogatory term clearly, I beleive that the idiot light serves a great purpose, which is to get your attention.  I know that I sometimes get distracted and don't check the gauges as frequently as I should.

[Skunkworks Challenger]

NC RMP,  Right on, I agree 100%.  This was a brass bourdon tube, on a new gauge but it was only graduated to 60 psi.  I have seen gauges go way over their graduation and not break but this one did.  Certainly the highest quality gauge the better.  This was a "box store" gauge.  PK

[tommyg29]

I agree about the idiot lights.
I rarely look at my gauges.
My stock oil pressure gauge always seems to read fairly high, which is a good thing, but I wonder how accurate it is.

[Super Blue 72]

My stock oil pressure gauge always seems to read fairly high, which is a good thing, but I wonder how accurate it is.

   Yeah, mine reads high all the time also, not sure how accurate it is but on the occasions it started to read low I knew there was a problem.

Good info about the mechanical oil pressure gauge.  Thanks!    I heard stories about those lines going but never ran into it.  Sorta like the nylon vs copper lines bringing water to the refriderator.

[72cudamaan]

Most companies went to the nylon because the copper tubing was so prone to cracking from vibration and motor torque. 

[CHL2T]

Had a nylon line pop off the back of the one in the Cuda, didn't notice till i felt the HOT oil on my leg, luckily I was just pulling up to the house......
Went with the copper after that

[73EStroker]

To use copper all one has to do is find a bottle or something round with a diameter of 2" or so. Then wind the copper about three turns around the bottle and slide off. This coily thing should reside near the motor connection. Gets rid of vibration fatigue problems.

[1970 RT Challenger 1970]

I've had a nylon line (oil pressure gauge) on one of my cars for 31 years and no problems yet.

[Brusco]

I use mechanical gauges for water and oil with copper tubing and as far as not looking at the gauges,call me paranoid but it's second nature for me.I have no mirrors on the g'fish so my eyes look at gauges instead.

[Skunkworks Challenger]

I would like to be clear on exactly what happened with my add on  manual oil pressure gauge.  I understand that nylon tubes, copper tubes or even steel tubes feeding the gauge can be problematic.  That is not what happened to me.  What happened and caused me to loose my oil was that the bourdon tube inside the gauge ruptured.  The bourdon tube is the curved brass tube that reacts to pressure, making the needle move. The whole gauge housing was filled with oil and was squirting out all around the dial face.  Like I said, I've never seen another one do that.  PK