(135,000k 91 350) I was giving the car the usual Sunday flogging and I noticed it smelled kinda hot, (it was cool out) so I looked over at my gauges and noticed the usually malfunctioning oil pressure gauge was stuck at the high end, about 60, while idling. It usually wavers at 30 while idling and jams to the top when moving. (A mechanic once explained to me that there are 2 sensors for oil pressure and 1 was malfunctioning thus the funny reading) At first I thought now it had completely broken, but then I saw that when it's idling, it's kinda wavering at the 60 like it's reading high pressure. Does that make any sense? If my gauge is working, is this a bad sign? I looked under the hood but nothing has exploded (yet), and the oil looks good for being 3000 miles old. That's about all I know.

 

well if you know the gauge doesn't work right you can't really trust it at any time or with any reading. replace the sender or install a mechanical gauge.

 

Okay. Well, assuming it does still work.

 

60 psi isnt really enough to blow gaskets or anything, but its very unlikely that your oil pressure just shot up for no reason, down maybe.. up.. probably not.. the stock gauges in these cars are quite possible the worst gauges i've ever seen in my life. They are horribly inaccurate even when in proper working condition. My oil pressure gauge would never read right, finally it did just what your's is now doing except mine was pegged past 80 at all times, i just replaced it with a mechanical gauge and forgot about it.

 

Yeah, low pressure would mean it was leaking somewhere, huh? Well I guess its just a bad gauge. I'll have to add that to the list of things that need fixing.

 

That is a bit high.... the problem with it being that high is not that it would blow gaskets, but that the pump tends to whip alot of air into the lube system at that high of a pressure. Not good for the engine.

 

mine did the same thing..


directly above your oil filter is a plug... that is the sending unit for both the gauge and the computer on our 91 cars.

wiggle the connector and wires and drive the car around.

i noticed that after i do that, mine works fine for a short while, then it goes wacky again... i think its the wire, not the sender or the gauge *shrug*

 

or the connector.. i just thought of that...

i'll look at my connector tomarrow

 

Makes sense. I'll check the wire. I'm due to get a ton of work done on the car in a month or so, anyway.

 

An external oil leak will not affect oil pressure 99% of the time. Oil pressure is what it is becuase of the pump design and the internal clearances of the moving parts.

It also won't make a drastic change like that without something fairly catostrophic being the cause - which is very unlikely as usually they will just lock up or blow up in short order and you wouldn't have time to notice a change like the one you describe.

What is most likely going on is that the oil pressure sending unit (at the rear of the intake towards the driver side, gold-ish colored can with one wire) has lost it's ability to send the proper signal to the gauge in the car. This is common and a new sender should fix it. That being said, the factory gauges, as stated earlier, often cannot be trusted to be accurate. They are more like an "idea meter".... As in they give you an idea of where the oil pressure could be... .

The other oil sensing element that mechanic told you about has absolutely nothing to do with the gauge. It is there to back up the fuel pump relay when/if it fails and will energize the fuel pump in such cases.

 

while this is true with a earlier model car, with the 91 this sensor doesnt exist.

the oil pressure switch and sensor has been condensed into one unit placed on the side of the block jsut above where the oil filter screws in. we have nothing in the back of the block.

 

Doh! Didn't notice it was a newer one... Forget what I said - the switch/sender is black and screws into the block above the filter, as MrDude points out .

 

I changed the oil yesterday and got a good look at the switch but I can't say anything except it's dusty but plugged in! I said so what. Well today I was driving doing errands and all of a sudden the temps went to the red and the car overheated! The oil gauge went back to 'normal' (30 at idle and maxed out while moving) and I stopped and looked around, thought Doh! maybe I lost all my oil! But it was ok, (but the coolant was looking about to boil, so I know that temp gauge is ok.) Both fans were not working, so they shorted out?? I know one fan was going to short out 'cause it died last month and only had a temporary used one to put in. Also just had the water pump replaced two weeks ago. (Until today the temps were great, I always keep an eye on it.)
Did anyone say catastrophic?

 

i doubt the oil change had much to do with your overheating prob.

 

I know. I just like how everything goes bad at once.

 

hey, id rather have it work great for a few months and have a feww things happen at the same time, then have stuff breaking on a constant basis.

 

So... a gage that reads off the scale when above idle is NORMAL? I got the digital gages, so it doesn't even show up idling cold, or running, but once it gets warm and idle, I see it hover above 30 PSI. Oh yeah, I also belch bluish smoke every time I start it, and it's eating oil, among other things.

 

I haven't gone 2 months without breaking something on it! Of course, my friend once figued out that i drive an average of 52 miles per day. Did I mention I failed my smog test on Friday? But I wouldn't trade the car in for anything. I was driving my dads V6 today and I actually got *tailgated!!* And some one passed me on the freeway!
Well, that's why we have two kidneys.