Newly rebuilt engine only shows past 4 bar oil pressure when cold

[kyngfish]

As it says in the title. Before the engine was rebuilt - at cold idle the oil pressure would peg at 5 and when the car would get hot - I’d roughly get 1 bar per 1k rpm and it would top out pretty close to 5 bar when I ran it hard.

Last year the car had the valve guides redone - they went ahead and cracked the case - Ps and Cs were fine but we went ahead and re-ringed and redid the bearings.

Ever since - when cold the engine still roughly pegs at 5 at first. But once warm, the car idles slightly over 1 bar but even at redline the gauge reads either at 4 or maybe slightly over 4 bar. I’ve read through some old threads and it says i should be at around 4.5bar at 5k rpm. I also know the gauges aren’t the most reliable. But not sure if it’s something I should be concerned about.

Last thing is during winter when I’m running the heat - if I rev the car to redline - I get an oil smell in the cabin. Car doesn’t seem to be burning excessive oil. Oil smoke almost always happens on startup whether it’s been sitting or not.

Running Valvoline VR1 20w50.

[stownsen914]

Did they replace the oil pressure sender on the engine during the rebuild? One possibility is it reads slightly less than the old one.
Also, try a mechanical oil pressure gauge on the motor to verify what your cockpit gauge is telling you.

[fanaudical]

Definitely check oil pressure sender against a mechanical gauge. Also check electrical connections and make sure those are tight / no corrosion (as that may affect what the gauge reads).

I don't think you want to start thinking about engine internals until you have the gauge/sender verified...

[proporsche]

one thought........has the re-builder done anything with number 4 or 7??

Ivan

[kyngfish]

Don’t see anything about that on the rebuild sheet. Rebuilder is a reputable dude as well.

[kyngfish]

Originally Posted by stownsen914

Did they replace the oil pressure sender on the engine during the rebuild? One possibility is it reads slightly less than the old one.
Also, try a mechanical oil pressure gauge on the motor to verify what your cockpit gauge is telling you.

I don’t see a sender replacement on the parts list in the rebuild. Point me to a thread on how to measure the pressure with a mechanical gauge?

[stownsen914]

I looked for a few mins and couldn't find a thread explaining exactly what to do, but basically you replace the oil pressure sender with a mechanical pressure gauge. Usually it requires an adapter.

[Schulisco]

Originally Posted by stownsen914

I looked for a few mins and couldn't find a thread explaining exactly what to do, but basically you replace the oil pressure sender with a mechanical pressure gauge. Usually it requires an adapter.

Absolutely not!!! The danger of damaging/destroying the emgine caae while unmounting the oil pressure sensor is way too high!!!

Instead of unscrewing the oil pressure sensor use the temperature sensor bore instead! Currently don't know the thread size of it but you can google it easily.

[Showdown]

Originally Posted by Schulisco

Absolutely not!!! The danger of damaging/destroying the emgine caae while unmounting the oil pressure sensor is way too high!!!

Instead of unscrewing the oil pressure sensor use the temperature sensor bore instead! Currently don't know the thread size of it but you can google it easily.

?

Removing a sensor/sender isn’t that hard and if you do it right the chances of damaging anything are minimal if any at all.


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[winders]

Originally Posted by Schulisco

Absolutely not!!! The danger of damaging/destroying the emgine caae while unmounting the oil pressure sensor is way too high!!!

Instead of unscrewing the oil pressure sensor use the temperature sensor bore instead! Currently don't know the thread size of it but you can google it easily.

Settle down.

Outside of some highly unusual circumstances, removing and replacing an oil pressure sensor is not anything to get excited about.

[Schulisco]

@Scott&Julian: Really?

I don't wanna risk my engine case for such minor jobs. Probably very experienced mechanics may be able to do this quick'n'dirty. Most people here aren't that experienced and over time these sensors tend to get seized due to oil and too high torque during mounting...I prefer saftey first!

https://forums.pelicanparts.com/porsche-911-technical-forum/1012332-proper-method-safely-remove-oil-pressure-sender.html

These pictures you never want to see:


You have to dismantle the oil feeder line of the chain tensionse and the alloy block where the oil pressure sensor is screwed in...only then unscrew the sensor on the bench in a vice...

Again: Use the hole of the temp sensor instead to temporarily attach a mech oil pressure gauge...

Thomas

[john walker's workshop]

The little white spec book shows 4 bar is normal @ 5k rpm hot.

[Schulisco]

Originally Posted by john walker's workshop

The little white spec book shows 4 bar is normal @ 5k rpm hot.

Correct.

Probably the pressure relief valve was stuck before. Has this been replaced on the overhaul? There was tech bulletin from Porsche about them that they may get stuck iirc ... ?!?

Thomas

[proporsche]

I use this tool to remove the oil sending unit..most of the times without problem.But when it is tight i will remove it with the block
Ivan

[proporsche]

to the OP
have you done-the rebuild shop- the 1000 mile service after rebuild yet??You have oil smell, i would definitively go to those guys..

[winders]

Originally Posted by Schulisco

@Scott&Julian: Really?

I don't wanna risk my engine case for such minor jobs. Probably very experienced mechanics may be able to do this quick'n'dirty. Most people here aren't that experienced and over time these sensors tend to get seized due to oil and too high torque during mounting...I prefer saftey first!

https://forums.pelicanparts.com/porsche-911-technical-forum/1012332-proper-method-safely-remove-oil-pressure-sender.html

These pictures you never want to see:


You have to dismantle the oil feeder line of the chain tensionse and the alloy block where the oil pressure sensor is screwed in...only then unscrew the sensor on the bench in a vice...

Again: Use the hole of the temp sensor instead to temporarily attach a mech oil pressure gauge...

Thomas

I didn't say to not follow proper service procedures. I am pretty sure the correct procedure is to remove the block the oil pressure sending unit is threaded into first and then remove the sender.

It's not a big deal to do...but I would have new seals on hand before I did it.

I wouldn't do all that just to check the pressure with a mechanical gauge...I was talking about servicing/replacing the pressure sensor...itself.

[stownsen914]

No issue with putting the mechanical gauge elsewhere on the block. If you put the mechanical gauge at the flywheel end of the engine, keep in mind that you will get a higher reading as it's before all the bearings which bleed pressure somewhat. Nothing wrong with that, it just won't give a direct comparison to the cockpit gauge.

As for breaking the crankcase like shown in the picture above ... looks like someone wasn't being careful.

[Showdown]

I literally just did this and I’m not a pro or even semi qualified mechanic- I’m just an idiot who doesn’t know what he doesn’t know. #fullsend

I used PB blaster and a torch to heat the block and then slowly broke it free. Removing the sensor from the block was a chore and I had to destroy the sensor but I was replacing it anyways.

It’s not hard. Go slow, follow best practices and if you can’t do it take it to a shop where they’ll do the same thing as you with the same risks and might even damage the case…


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[john walker's workshop]

Just leave it alone, you don't have a problem.