Replacing the Oil Pressure Sending Unit
 

My 2.4L had a pretty bad oil leak down the front of the engine (2.4L) just below the Oil filter housing which was traced to the Oil Pressure Sending unit, which is screwed into the front of the block.

Replacing the sending unit requires the starter motor be removed, as it is not accessible from the top side (at least not with any of the tools I have available).

The process to replace it was as follows:

PREP WORK:

- disconnect the NEGATIVE post on the battery
- manually flip the latch inside the bottom of the hatch to the closed position so you don't lock yourself out of the trunk - OR, throw a piece of carpet over the latch point
- jack up the drivers front side of the vehicle and block it securely

REMOVE STARTER MOTOR:

- using a 8mm wrench remove the small nut on the end of the starter (I believe it is the trigger wire for the solenoid), and remove the wire
- remove the power lead nut (it will probably be 12 or 13mm depending on the specific starter), and remove the two wires from the bolt, and push them aside
- there are two bolts holding the starter in place, one that is at the bottom, and one on top but totally hidden. I believe they are 14mm, so use a ratchet and an extension to remove them both
- pull the starter free of the block and place it aside (no shims were noted between it and the block in my case, but keep an eye out for them in case)

RE and RE OIL PRESSURE SENDING UNIT

the sending unit's nut on the base is 27mm if I remember right, but the only one I had was not a deep socket, and I didn't have a 27mm wrench handy, and there is limited room to play with..... soooooo....

- disconnect the connector from the oil pressure sending unit
- disconnect the black connector from what I believe is the crankshaft position sensor (lift the red tab to enable removal)
- use a 14mm wrench/socket to remove the bolt that holds the anti-knock sensor against the block (located just below the oil sending unit)

- remove the oil pressure sending unit with a suitable tool (I used a crescent wrench - ok.... shame on me, but it was all I had) - be prepared for some oil to leak out of the hole that it comes out of

- install the new oil pressure switch - 16 lb ft and attach it's connector
- reinstall the anti-knock sensor and it's bolt - 18 lb ft
- reattach the connector for the anti-knock sensor, and push the red tab in to lock it in position

REINSTALL STARTER:

installation is just the reverse of the removal -

- install the starter with the two bolts (14mm socket) - 39 lb ft
(do the top bolt first loosely as it seems easier to get it located as it is done all blind)
- place the two big power leads on the stud, and lock them in place with the 13/14 mm nut - not sure of the torque on this - just be careful not to strip the stud as it is not exactly heavy duty
- place the solenoid driver wire in place on the small stud and tighten it in place with the small 8mm nut

FINISH

- reattach the negative battery post in the trunk
- use the fob or turn on the ignition key and use the touch pad on the hatch to unlock - it will flip the lock in the bottom of the hatch to the open position - the hatch can now be safely closed
- lower the car back to the ground
- start the engine and look for any leaks
- reset the time on the radio

Nice , thank you for the write up.

Good write up.

Sorry, but we'll have to deduct 1/2 a point for no pictures. :nuts:

His directions and expression bring pictures to the mind and imagination A+

I agree Oldblue. Just picking on him. Probably would have been hard to get a camera up in there any ways.

And dangerous, if it's a camera phone S7!

Yeah but Oldblue that S7 doubles as extra light! A torchlight!

I did this today, the knock sensor had a 10 mm bolt holding it
The starter mounting bolts were 15 mm
The battery cable to the starter nut was a 13mm
That top bolt was a treat to get into position, the oil pressure switch was only finger tight , and leaking where the plastic body meets the metal nut piece that threads into the block.

Thanks again for the write up, it was starting to sprinkle rain so I did not take pictures either.

Okie, dokie, a month, almost and 2,000 Kim's or 1,245 miles there abouts and no pesky oil loss, no drips on the oil or transmission pans, I can back into my sloped driveway and park nose down , no oil drops on the driveway! Yeah, it's like I have my HHR back!!
Next is Sweetie's GT!! It sits level in the garage , no drops, if I dare park it nose down outside over the course of an afternoon, a small drip or two!
And I always thought the leak was spillage from changing the oil filter!

Cool - mine was leaking the same way (an internal leak, not from where it screws into the block). So far so good with mine as well. My old starter had a 12mm nut on the power connection, and the new one was 13mm I believe.

FMG - no pictures? I just kept it to the written word, trying to expand your vocabulary ya know? ;)

Thanks for the expansion of my brain whopper. :lol:

Mine was leaking where the Bakelite mets the metal body

Any time lad. I even typed a slower for you! ;)

Hey Happy New year man - all the best to you and yours in 2017. :thumb:

Mr. Whopper,

Just so I am not making un-needed new threads, this oil pressure sensor is driving me nuts. I have replaced it 3 times and after a month it starts leaking again. I have tried two sensors from Autozone and then one from the chevy dealer (thinking it was just cheap sensors). Dealer one did last a bit longer though. I did torque the sensor back in properly, and I religously change the oil and I assume there is not a PCV valve, given that the crankcase gasses are sent into the intake.

So my question is, am I missing something? Or am I just having really bad luck with new Oil Pressure Sensors? And if you know of any sensor that might be stronger and not made cheap, could you please provide me a manufacturer and part number?

Nope - no idea which would be a better unit - the one I picked up was an Autozone part if I remember right. The important point I would expect, would be to not over tighten it.

Maybe put some thread sealer on it. I've never heard of anyone having to replace it more than once.

Could it be the leak is not from there, the filter cap is famous for leaking or getting cracked. They are cheap and readily available.

Some people refuse to change the O-ring. They do wear out.

I did order the AC Delco oil pressure switch, still not leaking.
My OCD dictated a wrap of Teflon tape to seal the threads, however, the part comes with thread sealant already applied.

Well be doing this this coming weekend. Oh what fun.

I believe it can be done from up top , but I followed these directions and removed the starter.

https://cimg4.ibsrv.net/gimg/www.che...f7aa8a8a9f.jpg
Well got my pressure switch and tools ready to go. Removed oil pressure switch noticed it had a crush washer on it and my new switch doesn't. Went back to Auto Zone the other two they had are missing it. The computer description say it should have it. Contacted Chevrolet dealer they say it should have it. So now I'm on hold for two hours till the dealers gets one in. I won't be a happy camper if I to put the old one back in.
Crush washer

Are you sure it is a crush washer looks like a copper banjo fitting washer to me, maybe oil drain. Unfortunately they sell them by the bag.

My service manual does not show any sort of washer or gasket.

https://cimg2.ibsrv.net/gimg/www.che...ae3542ca09.jpg

Brand new from the Chevy dealer. They call it a crush washer. It is installed and done. If you do this make sure to use electrical cleaner to get the oil out of the plug.

CHECK THE PRONGS TO MAKE SURE THEY ARE NOT OUT OF ALIGNMENT - don't ask me how I know.... The plug would not go in.... I coated the threads with GM head bolt sealer because I had it.

Good tip!!! :thumb:

so is it no way just tighten this sensor - anyway should I find the new one? Maybe just the washer? Not sure I'll find it so fast tomorrow - I have no car yet, motorcycle is garaged, don't want to take off starter one more time... I know if the oil was leaking from oil pan bolt on the trucks - I was replacing just a new copper washer.

Does somebody know what is the thread diameter on that sensor? - I had some copper washers in my toolbox.

Yes. If you're going through the trouble of pulling it out, just put a new one in. Why take any chances on an old sending unit. They don't cost much anyhow.
Better safe than sorry.

what does it mean "1/4 pipe thread"?
I understand in standard international metric system. I remember all those stupid sizes in wrenches like 1/2 it's 12.54mm, 3/8 it's close to 10mm etc.

I'm not sure will I find it(sensor) tomorrow because I will walk to the junk yard and especially -- it's Saturday.

Also one more question about torque starter bolts - is it really just 16-18 lbs? I want to add blue thread locker - is it a good idea?

Mine was dripping from where the plastic meets the metal. I have had this type of unit fail on other cars as well.

On my 85 it failed when the metal corroded and the plastic blew out - what a mess....

https://mdmetric.com/tech/metnptcomp.htm

- oil pressure switch - 16 lb ft
- anti-knock sensor - 18 lb ft
- reattach the connector for the anti-knock sensor, and push the red tab in to lock it in position
- install the starter with the two bolts (14mm socket) - 39 lb ft

didn't use torque wrench. Starter has 15mm bolts.

Took out an old oil sensor - there was oil inside connector .

Installed used sensor from 2011 HHR

yes, why it shouldn't?

Here is the pic you were all waiting for!
https://cimg6.ibsrv.net/gimg/www.che...24fef0107b.jpg