oil pressure gauge pegged
 

So I had my 1969 coupe on the Kerbeck Toys 4 Tots run a few months ago. Had the little small block running pretty well down the expressway; a lot of fun. The car did get a little hot waiting to be directed into the parking area but, she didn't overheat or anything.
The following day I go to take it for another drive and just as I start down my street I look at the oil pressure gauge and notice that it is pegged so I immediately bring the car home and park it.

I posted about the issue on another collector car site and a few people mentioned that the problem could be with the gauge or, worse, a pressure relief spring could have broken in the oil pump. I finally got around to pulling the gauge out of the dash and it seems to be fine; no corrosion or binding of any kind.

With that having been said do you think the issue could still be the gauge or am I looking at something more serious?

I think you're getting good info in that culprit could be either gauge or pump.

Send your gauge out for confirmation.

Or temporarily swap into your C3 a known good gauge ... does not have to be C3 correct.

My first guess would be a sensor or wire damage.
Just as a test, disconnect your sensor and see if the gage moves. Then ground the connector and recheck the gage. If it swings from one side to the other, I would believe the gage is OK. You have to do this with the key in the run position.
After that, pull the sensor and connect a mechanical gage, start the engine and check pressure.
Most likely, its the sender at the block.
Just my opinion, I could be wrong.
Good luck, j
​​​​​​OOOOPS. I forgot the earlier C3's used mechanical gages. My apologies to the OP.

My understanding is 1969 C3 has mechanical gauge with a small oil line from port on top of sbc block's rear china wall (adjacent to distributor) to mechanical gauge in dash.

Not electric and No sender.

I thought the 69 had a mechanical gauge. If so, check for blockage in the line from the engine to the gauge. If it's your oil pump, it's not very difficult to change. If you do change the pump, consider changing the rear main seal. Once the pan is off, it would only take a few minutes to change the seal and pan gasket. Jerry

^^This^^^

I have a cheap gauge and tubing in the garage for this.

If its pegged, change the pump. Melling.

If it is oil pump overpressure ... reference this thread link... particularly the mentions of plastic bits in oil pump and plastic cam gear & plastic intermediate shaft collar


https://www.corvetteforum.com/forums...-blow-out.html

I added some pictures Jackson.

69 is a mechanical gauge unless someone decided to swap it to electric. Factory was mechanical.

NCRS should except this just for safety sake.

A couple of questions; regarding the gauge; as I said it is not corroded or stuck at all. The needle moves freely and doesn't show any signs of binding. Knowing that would you still say that the gauge could need rebuilding / repair as detailed in the Wilcox repair document?

If it is a pump problem does the engine have to come out to make the repair? I have never done any type of engine work so I am not equipped to pull an engine which is one reason I ask.

Where is the oil pressure sending unit on your 69? Above the oil filter or at the top of the block behind the distributor? Which ever port is not being used, I would hook up a mechanical gauge and sending unit and verify the oil pressure reading on the car. I would NOT do anything until you verify the oil pressure of the engine.

My guess is it is NOT an oil pressure issue but a gauge/sending unit one if it is a mechanical gauge. If you are running 80+ PSI as the gauge is telling you, my guess is the engine would be leaking oil from various places, show excessive blow by at the PCV and even burn some oil through the exhaust....I doubt it......

If you have the gauge out of the car, just use your air compressor to shoot 30-50 psi into the gauge to see if it works OK. If it does, your problem is not the gauge. In that case, the issue is likely with your oil pump/psi regulator valve. No problem with the oil filter (pop-off valve, or not) would cause an 'over-pressure' condition with your gauge.

The biggest issue with the mechanical gauges is that the bourdon tube will fill full of crud just like the top of a cylinder head, especially if the owner doesn't change the oil in a proper manner. Covering the face, brake cleaner seems to work best for me. I spray it in there (wearing protective glasses) over and over and let it settle inside for a while until the cleaner runs clear out of the tube. You'll get the cleaner everywhere when you spray it so you'll also want to lubricate the gears on the back side once completed. You can work the gears by hand you must be careful not to bend the lever arm attached to the tube.

Willcox

Maybe I am missing something; the back of my gauge doesn't have any tube. The back has something that looks like a block with a threaded fitting where the oil line goes. Is that what it should look like or is it missing something?

The Bourdon tube is internal. Just hold it fitting down and squirt in some brake cleaner with the little tube.

Gotcha; gonna try that tomorrow. Thanks guys; wish me luck.

Again, in my opinion, I would not have touched the stock gauge until you had verified that the issue was the gauge and not an engine oil pressure issue. I sure hope that it is the gauge since you all ready started down that road.....