[DrHoward]

Hey I am new here, but I am looking for a little advice


I am having a strange problem with my oil pressure, when I first start it up the guage reads fine right in the middle of "normal" but as the car warms up, the pressure will drop right off at around 1100 rpms and lower


I just replaced the oil pressure sending unit and it did the same thing, I can really tell by listening if it has low pressure at idle due to how loud it is normally

I really don't want to install a new oil pressure guage just for this, has this happened to anyone else? Any one have any advice


Thanks in advance

Cheers
Kev

[trueblue01]

Could be any number of things. How many miles on the engine? I don't trust electric oil pressure gauges I would at least install a mechanical gauge under the hood (use a tee fitting to keep the dash gauge also) to see what the pressure actually is in psi. How long since an oil change with filter and what weight oil are you using? Any lifter noise when the pressure starts to drop?

[91cobra5.0]

did you get the right sending unit? check your ire hookups. mine did the same thing, it would idle at normal right in the middle then when i put the engine under a load it would bottom the guage out.

[86gtconvert]

get a mechanical gauge hooked up and see what the pressure is,most cases if its fine at start up and bottom out after it warms up,its time for a rebuild,new cam bearings,mian bearings ect.. usually thats why you get low pressure after a motor warms up..to help it along till ya get $ you can add lucus oil additive and thickin it up..but its gonna need a rebuild at some point..

[DrHoward]

Its got around 160,000 km's on it (roughly 100,000 miles) seems strange that it would blow out the bearings so early....from what I've seen thats not a whole lot of km's for a 5.0

I have 5w30 on it right now and there is maybe 200km's on the oil and filter (I rarely drive it)

Its hard to tell if there is much extra lifter noise when the pressure drops off due to all the noise the engine makes, there is a tap but its been there since I installed my 1.7 roller rockers, not loud though, you pretty much need to put your head right next to the valve covers to hear it

[trueblue01]

Mechanical gauge is the first step. How many psi is it carrying when cold? When warm? At idle? At 1800 rpm? You don't know because the factory gauge is barely one step above an idiot light. 100,000 is a lot of miles for a 5.0 or any other engine, especially if it has not been properly maintained over that period. You need an accurate base line to go by. All engines are going to experience a decline in oil pressure as they wear and tolerances increase. Sludge build up can start to restrict oil flow so get a mechanical gauge and you will at least have an accurate oil pressure reading to go by............. 5, 10, 15, 20 etc is more accurate than N-O-R-M-A-L plus the reading is instantaneous

[crumbie50]

Originally Posted by 91cobra5.0 did you get the right sending unit? check your ire hookups. mine did the same thing, it would idle at normal right in the middle then when i put the engine under a load it would bottom the guage out.

mine has started doing something similar. engine under load the oil pressure drops. rebuild time soon?

[JBIGBOOTSY]

Take the tube between the engine and sending unit off and pull your coil wire and turn the car over. Debris loves to cake in that tube, then it makes it's way into your sending unit, thus ruining it, even a brand new one.

[DrHoward]

do you mean the electrical connector on the end?


And the engine has been very well maintained by both me and the previous owner, however I did blow a head gasket last fall and some coolant got into my oil.....that might have done it there