C-3 Oil gauge

[Tony Roussos]

My previous message got cut off. Here I go again!!

My 1971 oil gauge reads less than 35. It has done this to me twice, I believe each time was after I moved the center cluster for restoration access. Currently, the reading varies, but hovers around 35.

My oil level is correct. Will certain weights or types affect operation? How much?

Also, what is the prevailing thought regarding oil line types? Sources for correct and high quality replacements?

I currently have a neoprene line that is seeping at the intake fitting. I had one like this on a 73 Vega that severed during a trip due to exhaust heat. Therefore, I'm considering replacing it with a copper line.

Thank you.

Tony

[Ed Jennings]

Re: C-3 Oil gauge

The conventional wisdom is that the line NEVER be replaced with copper. The copper line will work harden and likely break. At least on the older cars, the lines were steel, which had a copper coating in some cases. Not sure if GM ever went to the nylon tubes or if those are strictly aftermarket.

[Tony Roussos]

Re: C-3 Oil gauge-Correction and Update!

I incorrectly said my gauge hovered around 35. It hovers on the mark between 0 and 35. Sorry for the mistake.

Also, about the time my gauge screwed up, my headlight buckets and wiper door automatically open when I shut off the engine. I restart the engine for a second, then they fold down. There is no vacuum remaining when I shut the motor off for the second time to operate the units using the manual overrides.

Is there a connection? Can the oil gauge reading be affected by a vacuum leak?

Thank you.

Tony

[Joe L.]

Re: C-3 Oil gauge

Tony-----

ALL C3 small block oil pressure gauge lines were NYLON-----none were neoprene. Among other problems, neoprene would not have enough resistance to pressure-induced expansion to be used for an oil pressure line.

The nylon lines are usually very long lived. However, they do become somewhat brittle over time due to heat. So, it's a good idea to replace them from time-to-time strictly as a preventive measure. The line kits are no longer available from GM, but they are available from restoration parts sources like Dr. Rebuild, etc.

It's possible that during your under-dash excursion you "kinked" the nylon line. Usually, the nylon lines are very resistant to "kinking" (unlike the small diameter steel or copper lines used for some applications). However, I suppose that it's possible that you damaged the line in some way. It's also possible that you "disturbed" the connection at the gauge enough to cause a LEAK. That will "relieve" some of the pressure so that it can't register on the gauge. It will also cause an unholy mess once its "presence becomes known" (i.e. it starts seeping out from behind the dash area onto the floor). So, I'd recommend that you check this out.

Another thing is that C3 oil pressure gauges have a habit of reading a bit low. Are you sure that the gauge didn't always register as it does now?

[Tony Roussos]

Re: C-3 Oil gauge

Hi Joe,

Did I write nylon??! I know better. I thought I wrote neoprene. (Senility at work!)

I'll check again, but I don't believe the line is kinked or leaking out the back. I know for a fact that the gauge normally reads between 35 and the mark before 70. Sometimes a little higher than the 3rd mark before 70.

What's the possibility of junk clogging the gauge fitting? Broke Gauge?

Tony

[Harmon C.]

Re: C-3 Oil gauge

Tony Pressure in the line makes the gauge work and early in the life of the gauge the oil may have not reached the gauge. Over time it gets in the gage and gums it up as the oil is on a one way trip up the line unless it drains back. If the small hole in the gauge gets partially pluged the readings get less. I have had some luck cleaning them out and putting a little oil on the wheel on the back. Lyle