I need some help here. My '69 has been very slowly showing lower and lower oil pressure over the past 6 months or so. When I bought it a year ago it seems to me that the oil pressure guage sat somehwere around 45, the midle of the gauge or slightly below. Now it barely clears the mark towards the left (it has no number below it but it looks like it should indicate around 15). It isn’t any higher when I start the car up nor does it move when I rev the engine. The engine doesn’t seem to be making any weird noises but it is a convertibe and it has Flowmaster 40’s on it so it is hard to hear much or anything when I am driving. The last time I had it running with the hood up I didn’t hear anything out of the ordinary. The oil level is right where it needs to be, it has only been driven about 2000 miles since the last oil change but it has been about 8 months so I am overdue there.
I know the gauges in some cars don’t actually give you a real time reading of the oil pressure, just a general indication to keep you aware of the range it is running in. But I am used to the gauge in my Miata that gives me all kinds of real time data.
From what I have read online it could be nothing to worry about, just a clogged filter, a bad oil pump or time for a new engine! Can anybody give me a bit more nuanced a diagnosis based on a better understanding of Cougars and their engines and gauges?
I plan to take it in for an oil change and a look-see this weekend but I wanted to be armed with a bit of Cat science before I go!
From what I understand none of the following should matter but just in case: the engine is a 351W which has been stroked, balanced and blueprinted with a pretty aggressive cam, makes about 500hp and produces very little vacuum (which makes braking a lot of fun!).
I get that, but is it normal for the gauge to not move much when the rpm’s change a lot? And is it “normal” for it to indicate pressure in that lower area or is that a sign of a problem?
Well, like he said, the only way to know for sure what your real pressure is would be to put a mechanical guage set up on using the port your electronic oil sensor screws into.
That being said, your guage should definitely not be reading that low. With no apparent lifter noise from lack of oil, you might be safe to drive it, but do you really want to risk damaging your engine to the point of a required re-build because you ran it with a lack of lubrication?
Don’t run it tillyou put a mechanical guage on it to see what your actual oil pressure is. If it shows low pressure as well, you have got some issues internally that need to be addressed before running it more. If it shows around 45 or higher, then your electronic sending unit is likely bad and your are ok to drive it.
I agree with the other guys. Go to your parts store and buy the $20 mechanical gauge and find out what your true pressure is at the sensor location port. The low indication on the pressure gauge does indicate a problem!!! However, that problem could be something as simple as a bad sending electrical unit? Or a bad electrical gauge? Could even be an electrical wire grounding out someplace between the two? So, until you get the mechanical gauge, you’ll just be worrying about phantoms…
What is next after finding out the gauge is reading correctly? I had a 69 XR7 Convertible with a 351 Windsor 4bbl engine. It had oil pressure issues just like the ones you are describing. I did put a mechanical oil pressure gauge on it and that gauge showed bad pressure also.
The cause was bad main bearings. I pulled the engine and installed a new bearing set without doing anything else to the engine. I cleaned and repainted the engine. The oil pressure was like new. This fixed the problem at a very minimal cost and the engine looked new again.
You could also replace the oil pump while the engine is opened up.
I went down to Harbor Freight and picked up a mechanical oil pressure test set, it has a 6 foot hose so I could tell as soon as I fired it up that the engine doe not have a pressure problem! I replaced the sending unit and the pressure now reads higher than before but still noticeably short of the 50+ lbs the mechanical gauge showed at start up.
My instinct is the get it so it reads more accurately but how do I troubleshoot it now? Or is this just part of the fun of owning a 45 year old car?
It is the joy of owning 45 year old technology… This old tech would lose some signal between the sending unit and the gauge. Plus the sending units themselves weren’t all that great to begin with. These are a few of the reasons manufacturers created the “normal range” gauges…