Interesting Oil Pressure

fiveliterdriver · Aug 26, 2008

My 95 gt with few real mods is acting strange. I never remember this being an issue but I am just doing some research before I tear this apart to see if anyone has anything obvious. So I did a cobra intake swap because my intake had a leak and I had it on the shelf. I figured no problem. Runs awesome and I drove it then noticed a problem. Not a drivability issue but now once the car gets hot the oil pressure is low. It fires up and idle's at approximately 40-50 cold and then when its get to operating temp it drops down to 10 then will work its way down to 7-5 then at idle eventually will drop to 0. unless i slightly tap on the pedal. I get 10 psi for every 1000 RPM up to 40. The car has 113000 on it and I am aware that it could be bearings however, since it makes no tapping noises and the oil has no metal or particles in it i am just looking to see if anyone has experienced similar. I changed the oil from 10w30 to 20w50 and it helped a little but its still not right. Obviously the shaft is not broken because the car fires and runs like a champ except for the oil PSI. I have a factory gauge and another gauge (mechanical). When the car sits at idle for lets say 15 secs the psi will drop to 0 on the mech gauge and then the factory gauge will bounce between normal and none. Since the factory gauge is basical a glorified on off switch its not really reliable. However, my added mechanical one seems to be fairly accurate. Sometimes the needle is delayed if i goose the throttle a little. Which i thought maybe a blockage in the sender oil tube. Nothing found there. Is there anything in the actual oil pump that anyone has found that goes bad. To my knowledge it doesn't seem like if I have oil pressure then the pump is at fault here. Either I have a bearing clearance issue or I have blockage.

I am going to pull the pan this week when I get done working on everyone elses cars and see if there is anything apparently causing this. I still have yet to hear any actual motor noises. No ticks no knocks nothing to speak of as far as the motor is concerned, nor have I found any material in the oil.

If anyone has experienced anything similar let me know.

95-stang · Aug 26, 2008

It does sound like general high mileage wear, but before you do anything, get a mechanical gauge on the car, electric senders and gauges are prone to weird stuff.

Paul · Aug 26, 2008

Cut your oil filter apart and look for metal particles in the element.

Paul · Aug 26, 2008

Silly question... have you checked your oil level?

fiveliterdriver · Aug 26, 2008

Haha, paul i apologize if this comes off wrong. But i feel like you didn't actually read my post . I stated i have both mechanical and factory gauges on the car. I have changed the oil to 20w50 and i did cut open my oil filter and it appears to have normal stuff inside. Nothing but oil.

Thank you for the reply haha but I am on top of all of the basic stuff. I was looking for more of the unknown forum kinda answers that only hundreds of people with these cars could come across. You time to answer is appreciated and I agree mileage on the bearings is most likely the issue.

Paul · Aug 26, 2008

No, I read through the whole post. Lots of folks look for particles in the oil, but not the filter, which is why I asked. The question about oil level is simply because sometimes the most complex problems have a simple solution.

Sucks that you have to pull the pan. That's not a fun job. Pull off a main cap and let us know how the bearings look.

Paul.

ryclef331 · Aug 26, 2008

WOw...this sounds exactly like when I roached my last motor. Dropped the pan and though I struck gold in the pick up. Pulled a main cap and the bearings were WIPED OUT...no noise...nothing. Just havoc internally. And NO looking at the dipstick did NOT reveal anything in the oil

fiveliterdriver · Aug 27, 2008

Well I decided to wait and pull the pan later in the winter when I won't be wanting to drive/enjoy the car (convertible). I bumped the throttle screw a little to prevent it from getting down to idling at 600-650 where it seems to want to be and its sits at around 890-925 with a slight slight surge obviously because the tps is like what the heck is going on. I put some lucas stabilizer in the new 20w50 and its back on the street. Drove it to work today in fact and torched a little punk in an Si Civic. Thats all it took to get 10psi of oil pressure at idle. Under load (approx 2/3 throttle at 3000 rpm it makes 30psi. ) Not fantastic oil pressure but its acceptable.

I don't have the time or the money to build a new engine right now so this will suffice until I get some cash set a side for a 331 build or something along those lines. However, whats funny is there was nothing in my oil pointing toward bearings and there is no noises under idle or load and the car runs fantastic. So that makes me think, I'll just run it until it dies and in the mean time prepare a new engine.

But Wycleff your right. Who knows whats in the pick up....