: Low Oil Pressure 1994 SLS 4.6 144k



MDH1994SLS
07-11-04, 09:35 AM
Folks, Driving the caddy yesterday and the Low Oil Pressue / Stop Engine Warning message reared it's ugly head. Car has plenty of oil and was running fine. Stopped the car immediately. I am going to have a reputable shop ckeck the oil pressure to determine if no oil pressure is truly the culprit. Is the oil pressure switch easy to replace once you take the oil filter off on this model? Haven't tried overfilling the engine with the 8 qts of oil yet to see if debris in the oil pump is the culprit. I did change the oil myself in this car two weeks ago. Any words of wisdom out there? Thanks for any help.

growe3
07-11-04, 05:23 PM
My first check would be the electrical connection to the oil pressure sending unit. You may have damaged the connection and/or wires in your last oil change.

If the sending unit does turn out to be faulty, make sure the replacement is for the 4.6 engine. The low oil pressure setting is different than the 4.9 engine. I understand some have used the wrong sending unit and were getting low pressure warnings, but the oil system was actually working as designed.

It is also possible you have a defective oil filter.

BeelzeBob
07-11-04, 11:55 PM
Idle the engine and take the oil fill cap off with the engine running. If you look carefully you can see the cam bearing cap at the front of the camshafts...if there is oil oozing out of the cap while the engine is idling then you have oil pressure.


Most likely it is the oil pressure warning light switch on the oil filter adapter.

If you do have no oil pressure the engine should start to get pretty "clicky" at idle as the lifters slowly collapse... If you are starting to hear noise idling it for a little while then do the 8 quart overfill to blow the debris out of the pressure bypass valve.

MDH1994SLS
07-12-04, 06:33 PM
Folks, thanks for the info so far.

Where is the oil pressure sending unit located? How much is it and is it easy to repair?

I'm scared to idle the engine at all to test the oil pressure and also see if there appears to be oil pressure. Am I being too cautious? A shop is going to have to run oil pressure diagnostics and I don't want them killing the engine.

Where does the sending unit hook up to the main computer (could be the wrong question to ask?) outside of the engine? I guess I'm looking for electrical schematic help. Just for grins I'll add that I had my left windshield wiper arm and the wiper linkage replaced after I changed my oil at a car shop I normally go to for service. But I found a roll of electrical tape inside the engine compartment when I checked my water levels, etc. last week and wondered why a mechanic would leave the tape there?????????

The engine was running fine. I'd appreciate some more help and thoughts on this matter.

MDH1994SLS
07-12-04, 06:38 PM
My first check would be the electrical connection to the oil pressure sending unit. You may have damaged the connection and/or wires in your last oil change.

If the sending unit does turn out to be faulty, make sure the replacement is for the 4.6 engine. The low oil pressure setting is different than the 4.9 engine. I understand some have used the wrong sending unit and were getting low pressure warnings, but the oil system was actually working as designed.

It is also possible you have a defective oil filter.
Need to know how the sending unit gets to the main computer - electrical wiring
schematic would help. Not sure how I could have damaged any wire or connection during the oil change, please elaborate. Oil change went smooth and nothing was forced or pulled on. A defective oil filter? Elaborate here too , please. Thanks for your insight and your help.

growe3
07-12-04, 09:06 PM
The sending unit is screwed directly into the oil filter adapter (just above where you screwed in the oil filter). With the oil filter removed it is easy to see, but there is no need to remove the filter, to service the sending unit.

The only wire damage likely would be where the wires plug into the sending unit.
The plug should be plugged in solid and no obvious physical damage to the wires themselves. No schematic necessary for this check.

Did you use a name brand oil filter or a "house" brand?

-George

sts96
07-12-04, 10:36 PM
Had a oil filter several years back the return holes were not punched out oil could not go thru. so filters can be defective. filter was not ac.
sts96

MDH1994SLS
07-12-04, 11:06 PM
The air filter is not an AC filter. Definitely OEM, but the last two seemed to work OK. I suppose this one could be bad. I probably will do an oil change and oil filter change again, just for grins and I will check the sending wires and replace the sending unit with the PROPER Cadillac only parts. I should know better that buying OEM parts is risky and certainly may not be the best for my car.

Thanks to Cal George & East Texas. I'll let you know what happens - Mark :coolgleam

MDH1994SLS
07-12-04, 11:09 PM
Idle the engine and take the oil fill cap off with the engine running. If you look carefully you can see the cam bearing cap at the front of the camshafts...if there is oil oozing out of the cap while the engine is idling then you have oil pressure.


Most likely it is the oil pressure warning light switch on the oil filter adapter.

If you do have no oil pressure the engine should start to get pretty "clicky" at idle as the lifters slowly collapse... If you are starting to hear noise idling it for a little while then do the 8 quart overfill to blow the debris out of the pressure bypass valve.
I appreciate your insight and will remember these tips and I'll let you know how things turn out - Mark

BeelzeBob
07-12-04, 11:48 PM
You aren't going to hurt it idling for a few minutes to diagnose the problem. The engine will idle a long time with no oil pressure believe it or not. Certainly will idle long enough to take the oil filler cap off and look inside to see if there is evidence of oil pressure..i.e..oil oozing from the cam bearing cap.