Just bought a 1995 mustang gt (5.0). Car has 43k miles on the clock. After bringing it home i noticed the oil pressure is always high. Even when you first start it after sitting the gauge goes almost all.the way up. I changed the oil pressure sending unit but nothing changed. I checked pcv valve and screen but they look new. I havent checked it with a mechanical gauge and i also havent changed oil since i bought it since oil looks new. Any ideas?

 

Yeppers, there's a couple that come right to mind...


Definitely need to do the mechanical gauge next. You MUST know what's going on. If the gauge says 'all's good', then the problem is the wiring to the gauge in the dash or the gauge itself. And thank your lucky stars, fixing that issue because it's the lesser one of the possibles left.

If it's still reading high on the mechanical gauge, then I'd go ahead and do the oil change with new correct oil and new filter if you don't absolutely know the weight that's in there now. New or not doesn't matter, correct weight does. That said, I'm betting the oil's fine, and what you've unfortunately got is a pressure relief valve gone bad, probably, and the oil change won't matter. And soon there won't be oil in it, and you'll need new oil anyway, maybe...

I had it happen in the 3.8 V6 of my '97 HoopTBird, and it sprayed oil out the filter gasket. Fun times cleaning that up twice. Why twice? Because I just spun a new filter on thinking double gasket or something, and immediately no-oil happened again. Whee. Stuck relief valve, and the stupid thing is part of the timing cover. Funny enough, it turns out they sell 3.8L timing covers *specifically for this problem*. Because you could rebuild the valve, or not, but either way, the timing cover is coming off to fix the issue. Hilarious job that one. Also, idiot lights on that car, not gauges, so of course I didn't see it until the dang thing blew oil everywhere. They only light up when there's low pressure... which happened right after it lost all the oil. SUCH a good feature... Idiots lights are not great.

Anyway, for your engine, the oil pump might be doing the same thing, but hasn't gotten to critical and blown out the filter gasket yet, just sorta flirting with the notion. Which is why you should absolutely do the mechanical gauge and know what's up.

The fix for that is a new oil pump, or rebuild the current one, either of which will require pan off fixin'. You *could* run some 'inside engine oil system cleaner outer' stuff which may or may not do the job, but... I'd be looking at a new pump. It is a '95 after all, probably could use one, even with the low miles...

I'm hoping its the gauge/wiring myself...

I do hope that helps, and good luck!

 

I hope its its just a bad filter. I really dont feel like taking the pan off right now. Ill change the oil this week if its still the same ill buy a pressure gauge from harbor freight to see what it actully is

 

Just changed oil with 10w30. Pressure is still the same. Im starting to think the gauge is right

 

Update: stuck a gauge on it today(psi not a fun task with larger hands).
55 psi cold start. Holds that untill temps starts to get up. Factory gauge must be wrong .

 

I'd rather that than the oil pressure be wrong all day e'ry day.

Probably a grounded/shorted wire or the gauge cluster innards might be messin' up. Might be simple as disconnecting/reconnecting the gauge cluster's connectors. Whatever it is, that's much better than the alternative and a win for sure for ya, right? Right!

 

Definitely a win . Thanks for help