Low Oil pressure

[Mustang Leo]

So I figured my stock gauge was taking a dump on me the other day when under 1000 rpm it would not register anything. i bought a brand new auto meter mechanical gauge (thanks joe) and i am reading very low oil pressure at idle to the tune of 3 - 9 lbs. granted she idles low around 650 but rarely do the pressure top 20 lbs unless i am beating on her( a little).

So my question is what is acceptable and unacceptable limits on oil pressure on a motor with a melling high volume pump with just over 3500 miles since rebuild?

[1loudmouthpony]

So I figured my stock gauge was taking a dump on me the other day when under 1000 rpm it would not register anything. i bought a brand new auto meter mechanical gauge (thanks joe) and i am reading very low oil pressure at idle to the tune of 3 - 9 lbs. granted she idles low around 650 but rarely do the pressure top 20 lbs unless i am beating on her( a little).

So my question is what is acceptable and unacceptable limits on oil pressure on a motor with a melling high volume pump with just over 3500 miles since rebuild?


My teacher the other day was explaining this the other day... as dangerous as that sounds... some manufactures allow that low of a pressure at IDLE. he was saying that cars pcm's would flash up a low oil light unless it was even lower than that. but since your only able to get 20lbs thats concerning at least to me. i had 40 45 psi and about 30 to 35 at or around idle.

[NC STANG GUY]

If it's 3-9 lbs at idle something is wrong... Hate to say that but if you've already installed a mechanical gauge to verify it pretty much sums it up.

Even when I had a 393 set up with "loose" bearing clearances it had 20-25 at hot idle and 45-50 at WOT.

[cobra_4]

My 90 idles with pretty oil pressure. But it has 100k miles on the motor. Im no expert but I would think it should have a little better. What weight oil you running?

[Mustang Leo]

just changed the other week with 10w40 havoline

[cobra_4]

Yeah something isn't right. I mean you might try a thicker oil, maybe some lucas oil stabilizer and see if that brings the pressure up but the bottom line is something is wrong, and is shouldn't be with that fresh of a motor.

[Mustang Leo]

loudmouth pony knows why this erks me so bad as he too has had to watch his pressures for the same reason as i am. I get a little skittish because as some of yall know i have already replaced this oil pump and bearings once before due to the oil pump shaft shattering

[Notch93]

My car with a mechanical oil gauge reads 50-60 cold at idle, and around 25- 30 warm at idle. Under acceleration, it is always in the 45 - 55 range. Cruising down the interstate, it stays right at 40.

Sounds like something wrong.:sad1:

Are you 100% sure there is enough oil in the motor?

[cobra_4]

My car with a mechanical oil gauge reads 50-60 cold at idle, and around 25- 30 warm at idle. Under acceleration, it is always in the 45 - 55 range. Cruising down the interstate, it stays right at 40.

Sounds like something wrong.:sad1:

Are you 100% sure there is enough oil in the motor?

And that weight is what is in there? Did you do it yourself or at a quick change? If it was at a quick change or a garage you never know what kind you gat.

[Mustang Leo]

I guess it is always possible. changed the oil two weeks ago and put 4 1/2 quarts in. stock pan. have not seen any oil spots where i park and would not think they are getting by the rings yet... but iw ill double check in the morning.

[Mustang Leo]

And that weight is what is in there? Did you do it yourself or at a quick change? If it was at a quick change or a garage you never know what kind you gat.

yep did this one on Ed's lift myself for that very reason.

[Notch93]

I guess it is always possible. changed the oil two weeks ago and put 4 1/2 quarts in. stock pan.

Stock pan, you should still be putting in 5 quarts.

[cobra_4]

Stock pan, you should still be putting in 5 quarts.

Yeap. A half a 1/4 isnt gonna make a difference in pressure though. Not like that.

[Notch93]

Yeap. A half a 1/4 isnt gonna make a difference in pressure though. Not like that.

You might be surprised, at what a 1/2 quart difference will make. Especially at idle.

[Mustang Leo]

I was just thinking about the shimmy i had a while back and i ended up finding the input bearing was bad in the back of the crank. i wonder if the tranny bouncing around in there could have ate the bearings?

[Wayne's 88 GT]

just changed the other week with 10w40 havoline

10W40? Why are you running that weight?

[Mustang Leo]

what the old guy behind the counter recommended. been doing buisness with him for years and has not told me any untruths that i know of...

[NC STANG GUY]

10W40? Why are you running that weight?

Why not?

[1loudmouthpony]

loudmouth pony knows why this erks me so bad as he too has had to watch his pressures for the same reason as i am. I get a little skittish because as some of yall know i have already replaced this oil pump and bearings once before due to the oil pump shaft shattering

yes indeed. im not a expert as well. but id drain the oil. look at it, see if it looks like it should ( no gritty feel) and then fill it with 5w 20 or something a thicker weight. if no change.... then from my experience you have a huge problem that again based on my experience with op will ruin bearings. somethings not right. if its the pump again...

[Notch93]

Why not?

Agreed, I run 10W-30 with no problems.

[1loudmouthpony]

leo.. keep me informed on what happens. i feel your pain:sad1:

[Fox Rodder]

Are you are saying that your oil pressure is 9 psi at idle and 20psi tops at rpm ?? If so you have some bearing problems :thumbsdown1:. What kinda filter you running ....FRAM ?

[Mustang Leo]

yep good filter new oil. added lucas to it today and still have low oil pressure. I am figurig my brand new 3500 miles old bearings have taken a crap on me. soon as i get another daily i guess i will pulling her again to take another stab at it. just real frustrating after you spend all that money and time to rebuild a motor by the book just to see it do this. the thing is she does not tick or knock in the least little bit. does not feel like i have lost any power just really crappy oil pressure

[1loudmouthpony]

yep good filter new oil. added lucas to it today and still have low oil pressure. I am figurig my brand new 3500 miles old bearings have taken a crap on me. soon as i get another daily i guess i will pulling her again to take another stab at it. just real frustrating after you spend all that money and time to rebuild a motor by the book just to see it do this. the thing is she does not tick or knock in the least little bit. does not feel like i have lost any power just really crappy oil pressure

sorry to hear that.. but do you remember what your clearences were when installing the mains and rod bearings?

[cobra_4]

I'd keep driving it no point in tearing her down till she goes.

[Mustang Leo]

sorry to hear that.. but do you remember what your clearences were when installing the mains and rod bearings?

do not remeber on the first set before the pump failure but what ever the book said was what it was supposed to be. the second set was installed by my mechanic. there should not be any problems running an 89 rotating assembly in an 88 block.

[Mustang Leo]

I'd keep driving it no point in tearing her down till she goes.

True....

[1loudmouthpony]

x2 on that. life of the engine may be cut in half. but as long as it runs fine pulls hard id drive it too. no nosies at all? id let it go since its nothing but a factory 302.

did you say you had a high volume pump?

[cobra_4]

Something you might want to try but I won't recommend it its up to you to make your own mind up about it, my 79 doesn't have the best oil pressure in the world. At idle it gets pretty dang low. I run 20w50 and two quarts of lucas in it. Now she sits half way in between the H and the L at idle hot:thumbsup1:

Its thick stuff my if you read on the back of the Lucas jug it says you can do it.

[Mustang Leo]

yep melling hv pump came in kit from bucks engine parts. clevite bearings, new timing chain double roller, new hypernutic pistons 10 over, polished crank (original 89) and all the rings seals and gaskets to boot for like 4 something. wish i knew back then what i know now...

[1loudmouthpony]

i dont understand why the pressure is so low so soon. what was your pressure before this problem. possibly you spun a rod bearing or maybe more.. when i pulled mine two of my rod bearings were warped lost their shape. guess i wiped them out before i knew what happened.

[Mustang Leo]

before the problem it was reading middle of stock gauge that goeas from 0 to 100 so i figure 50 lbs

[1loudmouthpony]

could it be possible something is restricting flow to the oil sending unit off the oil pump log off the side of the block? maybe gasket material? but i dont think its likely it was missed by the screen and pump.

[Mustang Leo]

there was a little goop on the old sending unit looked like old teflon tape. we made sure there was not any restricting the new connection for the new meter. i could pull the log and just see .

[mustb50]

What kind of filter are you running on the motor?

[Notch93]

Could be that the melling hv pump is a POS, and went south. Remember reading over on the corral, about people having problems with the melling hv pumps going bad right away.:thumbsdown1: Just a thought.

[Mustang Leo]

Gonna replace the log off another motor that had good pressure just for kicks and giggles. tell you what, the next motor i build will NOT have one of those pumps in it. i hear the ford pumps are just fine.

[Mustang Leo]

had a fram on it but think its a purolator on there now

[Notch93]

had a fram on it but think its a purolator on there now

The only filter I will run, is a Motorcraft FL-1A.:yes1:

[Wayne's 88 GT]

The only filter I will run, is a Motorcraft FL-1A.:yes1:

Amen Brother! :yes1:

[stangster50]

Gonna replace the log off another motor that had good pressure just for kicks and giggles. tell you what, the next motor i build will NOT have one of those pumps in it. i hear the ford pumps are just fine.
i would try swapping pumps before tearing the engine down again... i too hear that the melling hv pumps are garbage.


and +2 on the fl1a

[Badass1993]

+3 on the oil pump,taking a crap......Id pull it apart,and replace the oil pump.....and check the bearings while you had it down....sounds to me like the pump is not doing its job

[wick22]

im with these guys if its not knocking or rattling id try a new stock ford pump first

[Mustang Leo]

Well i think she is done. Drove her till the lifters were chattering a bit. Had checked to make sure no debris in the line on the new mechanicle gage. Had just left Stable's shop and had to stop for a quick drive thru lunch today when she started chatterring in the drive thru. was able to get 15 lbs of pressure at 2500 rpm. finally read zero when backed her into her space tonight. I am pretty sure i have hurt the crank from previous pump issues. gonna buy a cheap replacement to get her going while I take my time and build what i really want. Just kinda sick to my stomach right now....

leo

[1loudmouthpony]

very sorry to hear that leo.

[Notch93]

That sucks to hear Leo.:sad1:

[JB_90LX50]

Oh no, I really hate to hear this Leo.

[midnight stang]

sorry leo:sad1:

[itsastangthing]

sorry to hear this.