: 91 Brougham bad oil pressure sending unit???



Torr69647
08-24-10, 09:25 PM
I have a 91 Brougham 5.7 with 82,000 miles. My low oil pressure light came on and stays on after my mechanic just put a new oil sending unit in. It lights up very bright at idle, and it stays lit even at higher RPM's, although not as bright. The oil is clean and does not appear to be burning or leaking anywhere. The level is full too. The motor seems fine (no strange knocks or noises etc). Do you think this is just a bad sender, even though it's brand new? What should the PSI be?? Thanks!

csbuckn
08-24-10, 09:58 PM
What was the problem before you put the new one on?

Torr69647
08-25-10, 06:15 AM
The reason I put a new one on --- the other day (before replacing it), my light began to flicker at idle but would go out at higher RPM's. It ran that way on my way home on a several mile trip. I got it home, shut it off and started right back up (while engine was still at operating temperature) and the light was out and stayed out. I drove several days and light never came on while driving. Which made me think there must be something wrong with the sender. I looked at the sender and it was wet with oil. So I had it replaced yesterday and now it's on all the time, even at highway speeds!

csbuckn
08-25-10, 10:25 AM
Are you sure your oil isn't low? It happened to me and another member, we though for sure the oil level was good until we drained it. Wasn't much in there. Happens a lot to cars with high miles or leaking valve seals too. But you can check the sensor to see if its leaking again.

WMD
08-25-10, 11:19 AM
I have a 91 Brougham 5.7 with 82,000 miles. My low oil pressure light came on and stays on after my mechanic just put a new oil sending unit in. It lights up very bright at idle, and it stays lit even at higher RPM's, although not as bright. The oil is clean and does not appear to be burning or leaking anywhere. The level is full too. The motor seems fine (no strange knocks or noises etc). Do you think this is just a bad sender, even though it's brand new? What should the PSI be?? Thanks!

When this happens and you have the correct oil sending unit installed it is time to install a master oil pressure gauge on the engine to determine the actual oil pressure. A good shop will have a gauge for this purpose and will record the oil pressure after the engine is at full operating pressure. This will tell you if the engine is producing oil pressure or if your indicating circuit is at fault here.

wmd

Torr69647
08-25-10, 01:54 PM
What should the PSI be for this motor?

sven914
08-25-10, 02:58 PM
Hot idle should be around 15-20psi and highway speed should be around 35psi.

If the sender and connecter were coated in oil, there might be some residue on the contacts. If you can, try disconnecting the sender and cleaning the contacts.

Torr69647
08-27-10, 08:47 AM
Thanks for the info. I will try cleaning the contacts.

My mechanic installed another new unit yesterday, but the light is still on. So then he hooked up a pressure gauge and he said there was plenty of pressure....as good as new (thankfully!). He recommended unplugging the bulb. I will try cleaning the contacts before doing that.

sven914
08-27-10, 07:56 PM
Your mechanic just doesn't want to spend the time to find the broken wire (if there is one). With out the pressure sender working properly, you have no way of knowing when the oil pressured drops dangerously low. Not that the light means that much, but it could be the difference between mild, repairable, engine damage and a completly blown engine.

If you do just unscrew the bulb, install an after market oil pressure gauge. If you do that, consult my thread, The Dead Space Solution (http://www.cadillacforums.com/forums/rwd-19xx-1984-deville-fleetwood-1985/203968-dead-space-solution.html), for tips on making any digital gauge look like the car had it out of the factory.

jayoldschool
08-27-10, 08:29 PM
The FSM will have the procedure for determining where the problem is with the circuit. If your mechanic has Alldata, ask him for a print out.

AElayyat
08-27-10, 09:20 PM
I had a similar problem with my old DeVille. My problem turned out that the aftermarket sensor was no good, got a new one from dealer & no more light.

Torr69647
08-30-10, 09:17 AM
Here's an update....After I got the car back from my mechanic, the bulb doesn't light at all....not even with the motor off and ignitition key "on". I changed the bulb and checked the connection at the sending unit, and still no light--none at all. I also put a new tell-tale unit in (which I was going to do anyway because the woodgrain on my old one was deteriorated) which included new circuitry and it also made no difference. Still no light. I give up.

I thought about putting a gauge inside the car, but decided against it since the oil has plenty of pressure and I am meticulous about keeping the oil changed and checked regularly. The motor does not show signs of wear. If there was ever a situation where my oil pressure dropped, then I have more serious problems underlying the car which would necessitate a rebuild anyway!

jayoldschool
08-30-10, 11:21 AM
So, your mechanic disconnected the circuit because he is too lazy to fix the problem, and you are ok with that? Wow.

csbuckn
08-30-10, 11:32 AM
I didn't think it was supposed to come on at startup.

sven914
08-30-10, 01:25 PM
Without the light, your oil pump could fail, which a simple and non intrusive part swap, but you would have no idea, and continue to drive the car, until the pistons melted. Low oil pressure can indicate serious mechanical problems, but those problems can be fixed in a simple and reasonable manner. If the engine is driven without oil, it become a useless, non-reparable, paperweight. If your not going to get the light fixed, or put a gauge on it, you might as well pour a handful of screws down the intake; at least then you will know when it will fail.

Torr69647
08-30-10, 04:51 PM
Man you guys are tough! ;) No, my mechanic did not disconnect the circuitry. The light totally quit on its own after installing the 2nd switch. The light should light up when the starter motor is cranking but it doesn't even do that now. We're talking about a car I paid a $1,000 for. I suppose if I wanted to sink more money into the car I could get the light to work again. But I think you would hear something if the oil pump begins to fail....wouldn't the first thing you'd hear be the lifters tapping? Then you know there's a problem. If the oil pump quits all together, and you can't hear the motor screaming at you you're probably not going to notice a light either! Has anyone ever had an oil pump fail on a lower mileage engine? I suppose it could happen, but I have never known anyone having the situation, especially on a good Chevy 350.

Torr69647
08-30-10, 04:55 PM
Not to be "smart" - But besides, if your motor is worn bad enough that the motor has a low pressure situation, you might as well rebuild it. An oil light is going to tell you something you should know already.

sven914
08-30-10, 04:56 PM
Better get the screws ready...

Torr69647
08-30-10, 06:35 PM
Not worried. I'm content knowing the oil has plenty of pressure (as per the manual pressure gauge), not to mention the fact the oil doesn't burn. Oil is still nice and clean even after 1,000 miles since last oil change. I've driven many cars over the years in my experience and had several false warnings of low oil pressure only to find out the sending unit has always been defective (thankfully).

sven914
08-30-10, 09:36 PM
SCREWS

http://www.duckworksbbs.com/supplies/screws/ss/screws.jpg

Torr69647
08-31-10, 05:31 PM
On second thought, you are correct. I might as well just dump screws down the intake. Or, on the other hand, there's a used Prius for sale up the street and maybe he'll give me scrap value on trade.