No oil pressure after oil change

While I was away on a business trip the girl took the 95 XJ 4.0 2WD to get the oil changed. After this she drove it home and it seemed to be fine, but she only drove 3 miles home. On Friday on the way to pick me up, it overheated within 3 minutes and the oil pressure was at 0. I had it towed back up to the shop and they said my oil sending unit was cracked and it would be $70 to fix this. It sounds like they messed something up during the oil change, though I'm not sure how.

Any suggestions on how this happened? I'm not paying for their mistake.

It might be a little hard to proove now, but it's almost guaranteed that the oil pressure sensor was damaged during the oil change. Due to the proximity of the sensor to the spin on filter connection it is easty to happen when not being careful.

the oil pressure sending unit is right next to the oil filter... and if it worked before they touched it, they obviously XXXXed it up proper... only proper morons cant change the oil filter without damaging stuff in the vicinity. (heard a lot about it online)

PLUS, the sending unit is $16, tell them to fix it, but sure as hell dont pay them 70$, it screws off, is easy to get to, and only gets 1 electrical connector...

sounds like a perfect opprotunity for the shop to show you what theyre worth, if they say it's all you, thats just another reason NOT to return.

Would this cause the overheating that I mentioned? It did not overheat prior and there was plenty of coolant.

walkerc said:

Would this cause the overheating that I mentioned? It did not overheat prior and there was plenty of coolant.

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With the sensor broken there would be little to no oil pressure which would certainly cause the enging to overheat due to lack of lubrication.

CharlesS said:

With the sensor broken there would be little to no oil pressure which would certainly cause the enging to overheat due to lack of lubrication.

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Umm..... no.

The sensor does not create oil pressure, it simply reports the pressure readings to the cluster.

The overheating is likely just coincidence and needs to be resolved just the same. Is there oil in the overflow tank? Is there coolant on the oil? Frothy oil cap? These would all be symptoms of a bad head gasket. It could also be as simple as a stuck thermostat.

Glacialbass said:

Umm..... no.

The sensor does not create oil pressure, it simply reports the pressure readings to the cluster.

The overheating is likely just coincidence and needs to be resolved just the same. Is there oil in the overflow tank? Is there coolant on the oil? Frothy oil cap? These would all be symptoms of a bad head gasket. It could also be as simple as a stuck thermostat.

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If the sensor is cracked and dripping then there would be oil pressure, but if its broken off then there wouldnt be oil pressure....

CharlesS said:

If the sensor is cracked and dripping then there would be oil pressure, but if its broken off then there wouldnt be oil pressure....

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There also wouldn't be oil left in the motor, and the OP would likely have mentioned this in his list of symptoms, as well as an engine compartment covered in oil. *shrug* I supposed it's possible that he didn't, it just doesn't seem likely to me.

Plenty of oil, no leaks, plenty of 50/50 coolant. Prior to the oil change the car was running fine. No overheating or anything. She says the oil pressure was at zero before she left the location, but she didn't think much of it. Thank goodness our house is about 3 miles away. Before they even put the new sending unit on they told me I needed a new thermostat because the two issues, no oil pressure and overheating were two completely separate issues. The two have to be related and I'm just trying to find out before I get the car back on Monday. Is it possible the jeep just thought it had overheated?

The two issues don't have to be related at all. It is entirely possible that they are in fact, separate issues. Pull the thermostat and drop it in some boiling water to see if it opens. If it doesn't, then you know what's wrong there and can move forward. You can also replace the oil pressure sending unit yourself for next to nothing.

the oil pressure sender is about 15-20 bucks and a thermostat and gasket is around 10 for the pair. So thats 25-30 plus coolant (10-15 bucks depending what you get). Total of 45 on the high side. Labor is your choice of doing it yourself, cheaper way if you have the area to do it in, or a friends place to do it at as the thermostat could get messy, or pay some one more money to do something that you can do yourself. My choice is always do your own work unless you can physically not do it yourself which doesn't happen often around here....

Glacialbass said:

The two issues don't have to be related at all. It is entirely possible that they are in fact, separate issues. Pull the thermostat and drop it in some boiling water to see if it opens. If it doesn't, then you know what's wrong there and can move forward. You can also replace the oil pressure sending unit yourself for next to nothing.

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do not do this unless u know ur theromostats opening temp. and u have a meat thermomator on hand.. and watch the thermo when it hits the desired temp it should pop open .. if it doesnt open at the right temp it will cause a over heating problem no matter what .. if u place in into boiling water of coarse it goin to open no matter what but u want..

ur thermostat could be a 165-195 degree thermostat depending on if has been changed b4.. most shops dont care what degree it is just that it fits .

so ethylene glycol in a 50% mixture with water can change the freezing point from 32 degrees Fahrenheit or 0 Celsius, to –35 degrees Fahrenheit or – 37 Celsius. It moves the boiling point from 212 degrees Fahrenheit or 100 degrees Celsius to 223 degrees Fahrenheit or 106 degrees Celsius. Pressure is the second way that the boiling point is raised; most vehicles have between 13-15 psi (pounds per square inch) in the cooling system. This can raise the boiling point of the fluid mixture approximately 45 degrees Fahrenheit or just over 7 degrees Celsius.

your problem could be alot of diff issues .. such as head gasket, radiator cap,waterpump, or thermostat .. even a cracked block, and or head.. anything that can upset the pressure created by the water pump . or no pressure at all ..
i would do a pressure test on the radiator .. or (if u have on hand) a lazer temp gun .. and run the car and point the temp gun at the thermostat and the hoses and see where its starting to get hot at . (this is without having to take the theromostat out .

... or u can always fill the radiator ... run the car .. open the radiator cap watch the fluid .. when the thermostat opens the fluid should drop or start to swirl ..and at all times someone watching the temp . if the water starts to swirl or drop and suck then the thermostat is fine ..

and just another thing i learned..."never let ur girlfriend take the car for a oil change" lol

as for the oil pressure problem ..

look at it this way.. most oil pressure sensors are variable resistors which work of a ground and a diaphram .. if its a 1 wire take the wire off and touch it to the block .. if the oil pressure gauge goes up then its the sensor if it doesnt then its the wires. u dont have to start the car to do this just have the ignition key on

if u took it to a shop and they say that they ran a test.. that means they took the sensor off and connected a MANUAL gauge to it . then they should have gave u a reciept with...
COLD idle OIL PRESSURE --30-60psi
HOT idle OIL PRESSURE ---anywhere from 15-45 is good

if they did not give u those numbers then they didnt test it right

thats is the only way to assure u have significant oil pressure to to hook a manual gauge to it .. and also the basic procedure to check oil pressure

CharlesS said:

It might be a little hard to proove now, but it's almost guaranteed that the oil pressure sensor was damaged during the oil change. Due to the proximity of the sensor to the spin on filter connection it is easty to happen when not being careful.

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Yeah, I've broke one before. its pretty easy to damage.