Oil pressure

DWMBMW

DWMBMW

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Uh oh. The engine sounded fine but my oil pressure light stayed on when I backed out of my driveway. I pulled back in and disconnected the sensor from the back of the cylinder head (the light went out) and then came back on when reconnected. I shut the car off and checked the oil level. It was fine but there seemed to be some obstruction when putting the dipstick back in. Has anyone ever had an oil pump dislodge? Guess its time to flatbed it and pull the oil pan.

Doug
 
Hi Doug, just for giggles you could replace the sender. You could take the old one out and remove the + from the coil and have someone crank it check for oil coming out, but if you really can't get the dip-stick back in then there may be a problem down below. Please keep us posted- problem/solution issues help allot and good luck.
 
DWMBMW said:
Uh oh. The engine sounded fine but my oil pressure light stayed on when I backed out of my driveway. I pulled back in and disconnected the sensor from the back of the cylinder head (the light went out) and then came back on when reconnected. I shut the car off and checked the oil level. It was fine but there seemed to be some obstruction when putting the dipstick back in. Has anyone ever had an oil pump dislodge? Guess its time to flatbed it and pull the oil pan.

Doug
Click to expand...

Without jumping to conclusions, if the dipstick guide tube is loose and possibly off-centered, it can result in dipstick interference.

Although not particularly common, oil pressure senders do go bad. In the field, you could remove the sender and crank (but not start) the engine. A "mess" would be a pretty good indicator of oil pressure. A cleaner approach would be to swap the sender for another or install a mechanical gauge. The unit could also be checked with an ohmmeter.

If the pump had become loose, or dislodged, I would imagine noise from the chain drive. Or a broken chain. The pump itself could have an internal problem . . .


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I should probably pick up and try a new sender first before assuming it must be the pump but when I looked in the oil cap everything looked pretty dry along the oil rail. The dipstick went back in but needed to be forced down. I will wait until next weekend to explore a little more in the daylight.
 
Sometimes the dip stick has to be rotated for it to go the final few inches. This is so it will end up with the handle pointing toward the fender so you can pull it out.
Try it.
The place where the sending unit mounts on the back of the head is the farthest from the oil pump so prone to be the lowest oil pressure reading you will get.
 
Experience from my aircooled VW engine, 2002's and M30's similar: when warm the oil pressure can be low enough to turn on the idiot light, on an engine that really doesn't need expensive internal work. I put in an oil pressure gage borrowed from an abandoned Audi and to my considerable surprise the cold oil pressure was near 80 psi.

Does the oil light go out if you rev the engine a bit (say 2000 rpm)? That's (to me) the decision point whether you have a worn bottom end or pump, or a bad sender.
 
Because the gage moves and even it you don't believe it's accurate, it gives you a relative sense of the oil pressure at various rpm's. The idiot light is a "last resort" and only significant if it stays on at over idle (to me, YMMV). I've changed my front seal and the oil pump, and it's no picnic. I had to raise the motor and get the Jesus Nut off and on again. This may be of no consequence for someone wealthy and/or who does not do their own work.

The Uro brand is not universally well regarded.
 
jmackro said:
What leads you to believe that the sender for the gauge is any more reliable than the sender for the light?
Click to expand...
1. It's a gauge, not a meter. It reads the pressure directly, there's no conversion to electric current then back to mechanical.
2. It reads pretty much the same all the time. You can see the change in pressure as the rpm and temperature change, as well as the change in pressure if you change the viscosity of the oil.
3. I still have the light.
 
Doug, that chain should rattle like crazy with no pressure. I agree with the gauge crew, definitely the first step.

Or maybe that ol' beater has finally given up! :eek:
 
Uro products are making me very unhappy these days.
Won't buy a bunch of their stuff now.
No fanclutches anymore.
 
Jeff, I think you are correct. I am still just paranoid about going up and down all those damn mountains on the drive to Monterey that something must have happened to the oil sump. I have changed the oil religiously every year for the past 32 years so there should not be any sludge but I have never had trouble inserting the dipstick before. Tomorrow I will get a new sender/sensor and change the oil and filter just for good measure this weekend. Hopefully no surprises come out of the drain pan.
 
Jeff, I think you are correct. I am still just paranoid about going up and down all those damn mountains on the drive to Monterey that something must have happened to the oil sump. I have changed the oil religiously every year for the past 32 years so there should not be any sludge but I have never had trouble inserting the dipstick before. Tomorrow I will get a new sender/sensor and change the oil and filter just for good measure this weekend. Hopefully no surprises come out of the drain pan.
 
Jeff, I think you are correct. I am still just paranoid about going up and down all those damn mountains on the drive to Monterey that something must have happened to the oil sump. I have changed the oil religiously every year for the past 32 years so there should not be any sludge but I have never had trouble inserting the dipstick before. Tomorrow I will get a new sender/sensor and change the oil and filter just for good measure this weekend. Hopefully no surprises come out of the drain pan.
 
Did you ever get the valves adjusted? They were rattling like hell when you left. Hope that wasn't the chain instead. Do an autopsy on the filter if you change it. You can cut the top and bottom of the pleats and unfold the paper filter section to see what it may have caught. If you've upgraded to a spin on, use a hack saw to cut the canister away from the mounting plate. If there's been a failure, it should be obvious in the metal bits on the paper. You can also carefully lay it out on some sort of screen, this will allow the oil to drain out and you can see any debris much easier.
 
No, I was actually about to drive and drop off the car at my mechanic for a checkup to assess the overall impact of the trip on the engine when the light came on.

Still have the original filter so while messy it should be easier to inspect. Thanks for the suggestions.
 
No gauge but I installed a new sensor tonight. The oil pressure light stayed on and the engine noise seemed to progressively get louder as I tried to warm it up. More forensics this weekend but it's not looking good.
 
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