Oil Pressure Switch and Vanishing Oil


#1

Our oldest daughter came home for the Memorial Day weekend. While here, she told me her oil pressure light had come on. When I checked the dip stick it was as dry as a bone. It took 4 quarts of oil to bring it to the full mark. She has since had to add 3 more quarts. The garage she took it to when she returned to her home said the problem was the switch. Is that possible? They had also performed some previous work on her car…including, what appeared to me to be a new oil pan. Are they accurate about the oil pressure switch, or are they covering for some previous sloppy work…possibly not tightening the bolts for the oil pan enough. Thanks for your help.


#2

If the question is ‘Can oil leak from a bad oil pressure sending unit?’, then, yes, it is possible for an oil pressure sending unit to leak oil. I’ve seen it first-hand myself. Once on an 2-year old truck still under warranty.


#3

You may also want to teach your daughter about that light. When it comes on, it indicates you already have NO oil. Pull over, ASAP. Not in two miles, three miles, or when you can. You need to shut down the motor now. As in right now. Neutral or clutch in, motor off.

It takes seconds for a fine running motor to seize without oil.

The only time I’d not pull over (which could very likely destroy the engine) is in extremely heavy traffic, in a middle lane, or a gang of thugs with automatic weapons chasing me.

Keep a bottle of oil in the car at all times, and if you need oil on a regular basis, keep two.

This is not meant to scare you nor her. Just to save your motor. I had to replace a motor with my Dad years ago because my Mom “thought it would be OK, and Dad can fix it when I get home”…she didn’t make it. It was a long tow, too.


#4

Something doesn’t add up here. If the engine was “dry as a bone” when you checked it the oil has to have gone somewhere. If she has since had to add 3 quarts, then either the oil is going somewhere or she’s added enough oil to cause foaming, and that too can cause loss of oil pressure. And now they’re saying the problem was the pressure switch? Or was it the pressure sender?

And what’s the deal with the possible new oil pan?

The bottom line is that it sounds to me like she’s hemmoraging oil. The dipstick, by which I assume you determined that the engine was bone dry, would not have been affected by any new switch or sender. A new switch or a new sender would not fix oil loss.


#5

The switch part is attached to the oil sending unit and yes they can leak and leak badly. I have had at least 3 go out on me for leaking. Sometimes they just leak a little but other times they can push the oil out big time. They may have made a mistake thinking the pan was leaking, or she could have both problems. A bad oil pan gasket can leak quite a bit too and it may have looked like the pan gasket was bad.


#6

More info would help. Type of car, how many miles on it, what was the reason for replacing the pan, how many miles since that pan was replaced, etc, etc, etc.

Oil light on means the engine is damaged so I’d start thinking about another motor or another car.


#7

If the oil pressure sending unit is leaking, it will likely leak only when the engine is running, and may only leak noticeably when the engine is running at higher RPMs, and the oil pressure is higher. I had one leak a visible stream once when the engine was revved, but only seep at idle.

If you can get at the sensor, clean it thoroughly, take the car for a drive, and inspect it again for signs of leaks.

A bad rear main seal can leak like this too, while under pressure. You would almost certainly be noticing drips on your driveway with this though.


#8

Bing, Oblivion, while I’ve never run across a badly leaking sending unit, I’ve no doubt that it happens. My impression from the OP was that because the oil was filled when the shop looked at it they were blaming the sender for the light coming on when in fact the oil has disappeared.

She’s losing oil somewhere. lots of it. The “new oil pan” combined with the new sender assembly gives me a really weak feeling that someone might be throwing parts at the car without figuring out where the oil is actually going. I was hoping for some more definition.

Perhaps another shop is in order?


#9

It’s probably coming from a leaky sending unit and they thought it was the oil pan. They’re only about $15 and ten minutes so just replace it.