Oil temp sensor & pressure sensor

[thejobrien]

Hi all, been doing some research on my oil temp and oil pressure sensors and have a question or 2. I have a 77, but it was swapped with a SC engine. From everything I've seen, 77 seems to be the black sheep of all the years with sensors being different from previous years etc etc. Recently my oil temp gauge stopped working (well, sometimes it works sometimes it decides to take a nap for a few days) so naturally I am going to check all the connections and wires etc. However, doing some research I saw that sensors from the engine need to match the gauge, so I was wondering if mine might be wrong? I've uploaded some pictures, the temp sensor reads 11.78 so I assume its the stock sensor from the SC motor swap, which would mean the pressure sensor I assume is also the stock SC sensor. My gauge cluster I've seen is correct for being a 77..? But ive seen gauges with the 0-340 temp as well. The SC pressure sensor is a 0-5 bar I believe while my 77 would have been a 0-10 bar? I guess I'm just wondering if my sensors arent matched correctly? - since I need to check the wiring on them anyways since theyre finnicky.

-Jordan

[John2244]

Hello Jordan,

I also have a 1977 911 with a 1983 3 L engine. When I purchase my car the oil temperature sensor and gauge seem to be matched OK. My oil pressure sensor was definitely not correct. If your oil pressure is reading 100 or more you probably need to switch it out with a one pole 0-10 bar 1974 to 1977 sensor. That’s what worked for me. Now my oil pressure is reading 60 as it should.

[John2244]

My oil temp sensor.

[thejobrien]

Hi John, thank you for the insight. The pressure sensor was reading really well up until 2 days ago. Before it was sitting around 60 almost constantly (except for higher RPM revs etc) but now it seemed to be idling around 80ish at same RPMs it was previously sitting around 60. I'll check again after I clean all the connections and check all the grounds if things are back to normal or not matching again.

[thejobrien]

Do you have the same gauge cluster as mine?

[John2244]

Yes.

[icarp]

Jordan you are on the right track , sensor must match gage , year , type.

Well done
Ian

[thejobrien]

Originally Posted by icarp

Jordan you are on the right track , sensor must match gage , year , type.

Well done
Ian

Trying! Haha. So putting the correct year sensor in, even if its in the incorrect year engine case doesnt matter..

[winders]

Originally Posted by thejobrien

Trying! Haha. So putting the correct year sensor in, even if its in the incorrect year engine case doesnt matter..

The sensor must match the gauge….the engine could be small block Chevy and it would not matter.

[spuggy]

Originally Posted by thejobrien

The pressure sensor was reading really well up until 2 days ago. Before it was sitting around 60 almost constantly (except for higher RPM revs etc) but now it seemed to be idling around 80ish at same RPMs it was previously sitting around 60. I'll check again after I clean all the connections and check all the grounds if things are back to normal or not matching again.

That's the failure mode I saw on mine; 930/60 oil pressure suddenly started reading that high a few years back - replaced the 40 year old sensor and it went back to normal. SC's will probably read lower at idle than that as their oil pumps are lower capacity.

The 3.3 930 10 bar oil pressure & temp sensors match the '77 gauges (140 PSI/0-340F). I was initially concerned the gauges weren't working correctly with the 930 transplant in my car until I cross-checked part #'s.

Sensors have to match the gauges if you want the numbers they read to mean anything.

[thejobrien]

Originally Posted by spuggy

That's the failure mode I saw on mine; 930/60 oil pressure suddenly started reading that high a few years back - replaced the 40 year old sensor and it went back to normal. SC's will probably read lower at idle than that as their oil pumps are lower capacity.

The 3.3 930 10 bar oil pressure & temp sensors match the '77 gauges (140 PSI/0-340F). I was initially concerned the gauges weren't working correctly with the 930 transplant in my car until I cross-checked part #'s.

Sensors have to match the gauges if you want the numbers they read to mean anything.

Ah okay. I have the 140PSI gauge but my temp is 80-340, any difference there between what youre saying with the 0-340 gauge?

[icarp]

All temp scales are 80-340*
ck pics

Ian

[thejobrien]

Hi all, can you advise on the best way to remove the oil pressure sensor? I've seen some people use the crows foot wrench and some people swear on removing the sensor while it still inside the block and to replace the pass through o-rings. Pros and cons of each? And if removing it while its still attached to the block is the best way, any part numbers for the new o-rings needed? Have no idea what to search for.

-Jordan

[spuggy]

Originally Posted by thejobrien

Hi all, can you advise on the best way to remove the oil pressure sensor?

Some are reported to come out fairly easy. Some require the block in a bench vice, lots of heat and hard core reefing on the old sender with a breaker bar.

It's a large diameter (17mm) hollow through bolt (banjo fitting) through a hollow block, screwing into an oil gallery in the crankcase. So it's not an assembly you want to be putting large amounts of force into (if you even can while the motor is in the car), given that any distortion of the bolt or block means a leak later (high-pressure).

Stuck Oil Pressure Sender

Added to which, if you break the crankcase oil gallery, you'll be very unhappy. Not a myth or a scare story - pictures of this on this very forum.

There are many, many threads on removing this part...

Originally Posted by thejobrien

any part numbers for the new o-rings needed? Have no idea what to search for.

Look into downloading PET for your car, and another for your motor - Porsche provides these as free PDFs. Searching various part suppliers web sites for part #'s will be confusing - and quite often yields contradictory results, so then who do you believe...

I see no o-rings in PET. I see a pair of crush washers ("A 12 x 18" - so aluminium, 12 x 18mm) on the banjo bolt/block - one on the outside, and the other between the block and the crankcase.

Sender has a crush washer between it and the block it screws into, which should be replaced if disturbed.



If not leaking, I'd be tempted to leave the sender undisturbed and replace the low oil pressure switch (#47 in the diagram of the "triangle of death) with a combined pressure sender and low oil pressure switch, like the factory used for 993.

VDO make combined switches/senders in a variety of pressure ranges and thread sizes - they all have much the same trip point (about 7-15 PSI, IIRC) for the "low pressure" warning. The combined switch/10 bar sensor with M10x1.0 thread is VDO #360-023. $40 from your FLAPS.

[thejobrien]

Originally Posted by spuggy

Some are reported to come out fairly easy. Some require the block in a bench vice, lots of heat and hard core reefing on the old sender with a breaker bar.

It's a large diameter (17mm) hollow through bolt (banjo fitting) through a hollow block, screwing into an oil gallery in the crankcase. So it's not an assembly you want to be putting large amounts of force into (if you even can while the motor is in the car), given that any distortion of the bolt or block means a leak later (high-pressure).

Stuck Oil Pressure Sender

Added to which, if you break the crankcase oil gallery, you'll be very unhappy. Not a myth or a scare story - pictures of this on this very forum.

There are many, many threads on removing this part...



Look into downloading PET for your car, and another for your motor - Porsche provides these as free PDFs. Searching various part suppliers web sites for part #'s will be confusing - and quite often yields contradictory results, so then who do you believe...

I see no o-rings in PET. I see a pair of crush washers ("A 12 x 18" - so aluminium, 12 x 18mm) on the banjo bolt/block - one on the outside, and the other between the block and the crankcase.

Sender has a crush washer between it and the block it screws into, which should be replaced if disturbed.



If not leaking, I'd be tempted to leave the sender undisturbed and replace the low oil pressure switch (#47 in the diagram of the "triangle of death) with a combined pressure sender and low oil pressure switch, like the factory used for 993.

VDO make combined switches/senders in a variety of pressure ranges and thread sizes - they all have much the same trip point (about 7-15 PSI, IIRC) for the "low pressure" warning. The combined switch/10 bar sensor with M10x1.0 thread is VDO #360-023. $40 from your FLAPS.

spuggy - always appreciate the info and insight on this thread so far, so thank you for that. Glad we have the same year car haha. The oil pressure sensor isnt leaking thankfully, its just the wrong sensor for the gauge cluster thats why I was considering the switch. I've purchased the correct 10 bar sender here and oil temp sender here so they can match (based on the previous posts and info from everyone). The temp sensor is more important to me since it simply just doesnt work anymore but that seems pretty straightforward with less room for error lol.

Sealing rings is what I mean, sorry for that not o-rings - and the PETs have now been downloaded for both the car and the engine, had no idea about these.

I think my plan of attack will be to gently see if the sensor comes off with no issue like others have had success with, and if it doesn't then I guess it will stay in the car for now. The combined switch/sensor on the triangle of death sounds pretty tempting, but from what I've gathered would be pretty difficult to access with the engine in the car? So for now, I think I'll just be ultra gentle with the sensor and see if it budges.

[spuggy]

Originally Posted by thejobrien

the PETs have now been downloaded for both the car and the engine, had no idea about these.

Yeh, some form or other of the PET is pretty much essential...

Originally Posted by thejobrien

I think my plan of attack will be to gently see if the sensor comes off with no issue like others have had success with, and if it doesn't then I guess it will stay in the car for now.

It's not that big of a job to take the block off and do it in a vice. Fiddly, awkward and time-consuming, perhaps. Get used to it - or start taking it to a shop. Because many things on a 911 are like that

Some report breaking the through bolt just tightening it up on the crush washers. It's hollow, so not strong. And the void in the crankcase it threads into is not strong either - or designed to take sideways loads or shocks. If you break the crankcase, you will be extremely unhappy.

Originally Posted by thejobrien

The combined switch/sensor on the triangle of death sounds pretty tempting, but from what I've gathered would be pretty difficult to access with the engine in the car?

Just about everything on the motor is difficult to access with the engine in the car, LOL. The more you take off, the easier it is, generally.

Doesn't mean it can't be done. The airbox needs to come off - but it's supposed to be a half hour job to replace the pressure switch.

Originally Posted by thejobrien

So for now, I think I'll just be ultra gentle with the sensor and see if it budges.

Your car, your choice.

I encourage you to read this thread. https://forums.pelicanparts.com/porsche-911-technical-forum/582593-broke-piece-metal-how-fix.html

Because that shows pretty much exactly what can go wrong with that plan.

[thejobrien]

Well, with looking at those threads I think I'm just going to take it off with the block LOL. Two of the 12x18 crush washers have been ordered for each side. I'm used to fiddling and plenty of awkward things with my 67 VW type 3 so it shouldnt be an issue fiddling with this as well. If its safer and less risky might as well go with that option if it takes a lil more time. spuggy, again thank you!

[John2244]

I tried to remove my sensor with a crows foot and it was a no go. Finally took the sensor and block off as one unit and put it in a vise. Even with that it was still very difficult to separate.

[thejobrien]

Originally Posted by John2244

I tried to remove my sensor with a crows foot and it was a no go. Finally took the sensor and block off as one unit and put it in a vise. Even with that it was still very difficult to separate.

Seems to be the way to go. Looks like I’ll tackle it this way. Was removing the block and sensor as one unit a pretty straightforward removal? Any advice?

Jordan

[spuggy]

Originally Posted by thejobrien

Was removing the block and sensor as one unit a pretty straightforward removal? Any advice?

Remove the A/C compressor & bracket first for better access, if fitted.

See these threads:

Question on replacing the oil pressure sender
Another Oil Pressure Sender Replacement Thread with pics

More reasons not to use a crowfoot on the sender while in the car:

Chain Housing Removal Without Dropping Engine?
Stripped mag case where oil line go's