not sure where to put this post,, still new to this forum. After my car heats up, my oil pressure is reading zero psi at idle,, when crusing, i am lucky if it gets up to around 20 psi. the car has around 126,000 miles on it and i am planning on putting a new oil pump in it, the sending unit has been replaced and it did no good. I have a dent right in the middle of the oil pan and i was curious wether or not i needed to replace the oil pan, as that may be the reason also for the low oil pressure, any suggestions would be great!!! thanks

 

well first of all... STOP DRIVING THE CAR !!! lol. My car was doing the same thing, and I decided to change out the oil pump, well yesterday I was trying to take out the oil filter (i'm still in the process of fixing this btw), and it was soooo tight, I bet 5 dollars that it was my FRAM oil filter (fram sucks beyond all recognition btw)... so since you already replaced your sending unit, why dont you give it a good oil change including good oil filter first.

Also, depending on how big and deep the dent is, it certainly could be effecting your pump pickup... if the pickup is too close to the pan then it wont get enough room to suck from, if it's too far away from the pan then it wont have enough oil to suck out at high RPMs.

My suggestions (in order of preference)

1)do oil / filter change and see if it makes a difference

2) add 1qt of automatic transmission fluid to the oil, this has a detergent in it and will clean up your oil valley's and such, only rev it up a little bit in park and change out the oil after you do this, dont drive it like this (and by add, I mean w/ 10w-30 in the engine already )

3) Take out the dent in the oil pan... but since you've already gone that far (the hardest part of replacing the oil pump is taking off the pan, believe me!) you may as well replace the oil pump, pump pickup, get a high pressure spring, and a lightweight driveshaft for it.

the list for the oil pump things are as follows:

Melling M-55 Oil Pump
Melling M-55A Oil Pump Pickup
Mr. Gasket #26 Pressure Spring
Melling 55-SA (think that's the one atleast) Lightweight driveshaft

the oil pump is standard, you dont need a high volume oil pump, matter of fact it would only be BAD for the car at the top RPMs when your oil pump has all the oil in the top of the motor and none at the bottom lubing.

The 55A is the high-volume version of the oil pump... you are getting the pickup that is made for the high-volume pump because it is made to pick up larger amounts, thus obviously over-kill is better for this standard oil pump.

the pressure spring raises the pressure that your oil pump will release oil at, pressure should not be confused by volume! Pressure is how hard and fast the oil will hit the needed lube spots, volume is how MUCH oil will hit the lube spot.

the lightweight driveshaft is just that, a lightweight driveshaft, it'll take less energy from the motor to turn the oil pump, therefore saving you horsepower (though not much of course )

4) re-do your bearings (you really dont want to do this, i can almost guarantee it )

 

Uh oh!! Low oil PSI!! Stop, drop, and roll!! Once you get up, dust off, and check the actual oil pressure with a mechanical gauge. Verify that the pressure is actually what the gauge tells. Our senders are absolutly notorious for going south.

If the pressure IS verified, I agree with MOST of what sellman says.

A high volume pump will NOT suck the pan dry though. Excess oil is merely circulated back through the pump. The lifters have metering systems which limit oil travel to the top. If the pan is sucked dry, then the drain back holes are clogged up.

In short, you only need a HV pump if:

You are running insane RPMs and need lots of oil
Running a remote cooler/filter (factory doesn't count)
Increased bearing clearances

If you aren't doing any of these, then HV is just overkill. It won't hurt anything.

 

check it with a mechanical gage, factory set up isn't know for accuracery or relibility

 

thanks for the advice. Im not looking forward to having to take the engine off it's mounts to get to the oil pan, gotta do what i gotta do. I might change the bearings,, car has around 130,000 miles on it after all.;.. so it dosent suprise me that it has low pressure. Thanks again!!! Oh yeah, is there any other sending unit for oil pressure other than the one at the back of the engine around the manifold?? i saw a sending unit of sonme type near the oil filter,, wasn't sure what it did,, if anybody knows please let me know!!!
Thanks

 

It could be either as both are possible locations. How many wires were coming off of it?

1 wire: oil pressure sender for gauge
2 wire: oil pressure switch for fuel pump relay backup
3 wire: combination sender/switch

Did you verify the pressure with a mechanical gauge?

 

did you do the simple things on the list already? Getting the engine off the mounts isnt that difficult (have a breaker bar and 5 - 8 inch extension for it handy though! Also a deep socket 5/8" 1/2" drive is the size you'll need)

if you actually do end up needing to pull the oil pan, here is a quick run-down on what to expect while you do it.

1) Take engine off mount (driver side is easy, extension needed to pass the crossmember; passenger side a lil more difficult, the breaker bar is needed on the side away from the engine, instead of towards the front of the car like on driver's side.

Also, you'll need a adjustable wrench to put on the back nut of the bolt for the engine mount bolts, they will just spin freely if you dont have it. You'll quickly learn to become a contortionist as you keep one hand on the wrench to keep it on the nut, and one hand turning the engine mount)

2) take out starter, and the viewpan (or whatever you'd like to call it lol) for the flexplate and torque converter. No problems there unless you have an aftermarket y-pipe.

3) un-bolt the y-pipe from the headers/manifold (this isnt too hard either, it'll require a breaker bar or 1/2" drive ratchet and the 5 inch extention, if you can get a 8 or 9 inch extension too that'd make your life a lot easier for the passenger side, driver side is really easy)

Also, take off your distributor cap!

4) lift engine up by balancer (with a piece of wood under it) lift it until you can put two pieces of 2x4s in between the engine and the engine mounts. Then proceed to put a 2x4 in between each engine mount and engine.

5) unbolt the oil pan (should be rather simple, i didnt have any problems)

6) now at this point you will need to rotate your crank over manually until #1 piston is at TDC (if you can see inside the crank through a little gap when you unbolt the pan then you can tell where it's at sorta instead of having to take out that spark plug) You'll need a 5/8" 1/2 inch drive for this, breaker bar or ratchet.

7) This is where it gets tricky and painful... you'll have to attempt to get your oil pan out now. You might not be able to though, which is what happened to me, and I just sawed out my y-pipe. I dont care because i'm getting headers and y-pipe anyways, but if you've got a y-pipe that you care about, then i suggest cutting it off right where they would do replace your cat, then just take it to a shop or friend later and weld it back up there. (I didnt have a sawzall, so i had to use a regular saw that i had laying around, let me tell you that was not fun! 2 hours of sawing, but it finally came out, just gotta stay the course)

So basically you have to take out the y-pipe at this point if you cant get the oil pan to drop.

8) Now you'll see the oil pump there and i'll leave it to Mr. Haynes manual from here Remember to torque everything to proper specs and such when you work on the car like this.


This is if you plan to work on the pump while the engine is still on the car (since not all of us have 500 dollar engine hoists ) If you DO plan to take the engine out, then just ignore everything that i just said

 

thanks for the help,, haven't been able to get on here for a few days,, gonna work on getting that sensor out and finding out if that is the problem...

Thanks!!