The last place I'd look for an oil leak...
05-02-2019, 01:03 PM
#16
Drifting
Harvey , are you using a turbo oil filter console with an external oil cooler ?
Let me know if it's the case , i'll send you some pics of how i plumbed my mechanical pressure gauge !
I'm not convinced mounting anything on the oil filter is a good idea ... but, that's just me !
Let me know if it's the case , i'll send you some pics of how i plumbed my mechanical pressure gauge !
I'm not convinced mounting anything on the oil filter is a good idea ... but, that's just me !
05-02-2019, 02:21 PM
#17
Rennlist Member
No, I'm not advocating this except to say that the first step in any oil pressure issue is to confirm the reading. And it is such a pain in the neck to install a mechanical gauge for a quick diagnostic check. The oil filter idea is not really serious but only to point out that its too bad there isn't an easy "spin on gauge" that we could all go to when we get to this point. Curt's reference to the adapter plate is probably the most promising way to plumb in a gauge, temporarily.
Since you ask, my car has a normal water to oil console. I have a turbo console and the remote cooler in my parts bin. I just haven't seen a need to go that route on my NA engine.
Since you ask, my car has a normal water to oil console. I have a turbo console and the remote cooler in my parts bin. I just haven't seen a need to go that route on my NA engine.
05-02-2019, 02:49 PM
#18
Rennlist Member
Thread Starter
OK Curt, you going to force me to get technical on you 
The reason I am suspicious of a 150 psi reading is as follows. I went down this rabbit hole last year when the oil pressure on my 944 was reading low. I wanted to rule out the sending unit and the gauge. So my thinking was that I could hook up my multimeter to the sending unit and read pressure directly, after applying some math. But what math. I consulted with Jason at Paragon and we came up with a part number for a sending unit manufactured by FAE. The one that he sells for much less than the Porsche labeled item. I'm sorry, I don't have the part number handy but it led me to a FAE catalog on-line. A portion is reprinted below. Now FAE is European and my best guess at deciphering their catalog is that Presion means precision and the number there is the recommended pressure measurement range for the sending unit in Bars. Part number 14110 is typical for what we use in the 944, which is a combination pressure sending unit and a switch to turn on the oil pressure light. That unit has a precision of 8 bars and the light turns on at 0.60 bar. And I'm pretty sure that the unit that I bought from Paragon has a precision of 5 bar, which makes sense as that is sympatico with the gauge, which reads up to 5 bars. Now 5 bars is roughly 75 psi.
Furthermore, I'm pretty sure the sending unit is a variable resistance. It doesn't read pressure per se, the resistance is converted back at the dash to pressure by applying the resistance to a voltage divider circuit. Now I'm really getting to the limits of my I&C knowledge so anyone, please, jump in here but my point is that the 944 was never set up to read 150 psi and your digital gauge has to make certain assumptions regarding the source of its information. But if for instance, your system voltage at the dash was degraded to say 6 volts rather than 12, the gauge would read incorrectly by a factor of 2. On my really old cars from the 60's, all the dash gauges make a sudden movement when cranking on the starter because the system voltage drops to 9 volts. Newer cars have a voltage stabilizer circuit to resolve this issue.
So all of this is a long winded way to say you can never be really sure of what your pressure is unless you circumvent all the stock parts and go with a mechanical gauge. Thus my crack about mounting a mechanical gauge on the oil filter.
In my case, the problem was the OPRV, but in your case, I still have to question if your pressure readings are real.
Just how close to the magnetic north pole are you, anyway
The reason I am suspicious of a 150 psi reading is as follows. I went down this rabbit hole last year when the oil pressure on my 944 was reading low. I wanted to rule out the sending unit and the gauge. So my thinking was that I could hook up my multimeter to the sending unit and read pressure directly, after applying some math. But what math. I consulted with Jason at Paragon and we came up with a part number for a sending unit manufactured by FAE. The one that he sells for much less than the Porsche labeled item. I'm sorry, I don't have the part number handy but it led me to a FAE catalog on-line. A portion is reprinted below. Now FAE is European and my best guess at deciphering their catalog is that Presion means precision and the number there is the recommended pressure measurement range for the sending unit in Bars. Part number 14110 is typical for what we use in the 944, which is a combination pressure sending unit and a switch to turn on the oil pressure light. That unit has a precision of 8 bars and the light turns on at 0.60 bar. And I'm pretty sure that the unit that I bought from Paragon has a precision of 5 bar, which makes sense as that is sympatico with the gauge, which reads up to 5 bars. Now 5 bars is roughly 75 psi.
Furthermore, I'm pretty sure the sending unit is a variable resistance. It doesn't read pressure per se, the resistance is converted back at the dash to pressure by applying the resistance to a voltage divider circuit. Now I'm really getting to the limits of my I&C knowledge so anyone, please, jump in here but my point is that the 944 was never set up to read 150 psi and your digital gauge has to make certain assumptions regarding the source of its information. But if for instance, your system voltage at the dash was degraded to say 6 volts rather than 12, the gauge would read incorrectly by a factor of 2. On my really old cars from the 60's, all the dash gauges make a sudden movement when cranking on the starter because the system voltage drops to 9 volts. Newer cars have a voltage stabilizer circuit to resolve this issue.
So all of this is a long winded way to say you can never be really sure of what your pressure is unless you circumvent all the stock parts and go with a mechanical gauge. Thus my crack about mounting a mechanical gauge on the oil filter.
In my case, the problem was the OPRV, but in your case, I still have to question if your pressure readings are real.
Just how close to the magnetic north pole are you, anyway
I decided to switch to a digital gauge because the VDO OE one pegged at 5 bars and I was left wondering what the actual number was. But now that I have discovered my 120 psi max gauge reads 150 it's time to try another one. Shopping time. Ordered! Bosch Sport.
I was also curious about the workings of an oil pressure sender. Seems pretty cool...
And as for my proximity relative to the magnetic north (44.2312° N, 76.4860° W), I've got that base covered. I never leave home without one form of EMF radiation protection or another.
Last edited by curtisr; 05-03-2019 at 09:39 AM.
05-02-2019, 03:52 PM
#19
Rennlist Member
05-06-2019, 06:30 PM
#20
Three Wheelin'
Harvey is correct, gauge is reading variable resistance from sender. I was able to borrow a test unit from a mechanic friend a year or so ago when I had pressure reading problems and needed to confirm. Hooked the variable resistor up to the leads at the sending unit per FSM and confirmed that gauge was fine, sending unit was the problem. So, fairly easy fix. If there was 150psi oil, it wouldn't just be a leak, more like a big spray.
05-06-2019, 09:19 PM
#21
Rennlist Member
Thread Starter
Harvey is correct, gauge is reading variable resistance from sender. I was able to borrow a test unit from a mechanic friend a year or so ago when I had pressure reading problems and needed to confirm. Hooked the variable resistor up to the leads at the sending unit per FSM and confirmed that gauge was fine, sending unit was the problem. So, fairly easy fix. If there was 150psi oil, it wouldn't just be a leak, more like a big spray.
Thanks for the input.
05-07-2019, 11:30 AM
#22
Rennlist Member
On my 85 car, I needed to buy a cheap set of crows feet to get the sending unit out. As I recall, it has 24 mm wrench flats on it and my standard open end wrench would not fit into the available space. The crows foot worked very nicely.
05-08-2019, 09:07 AM
#24
Rennlist Member
I got this set from Amazon for $14. At $14 obviously not high quality but it got the job done. The 17mm one is useful when torqueing the nut for the sump oil suction pipe.
05-08-2019, 10:19 AM
#25
Rennlist Member
Thread Starter
I got this set from Amazon for $14. At $14 obviously not high quality but it got the job done. The 17mm one is useful when torqueing the nut for the sump oil suction pipe.
TEKTON 2580 3/8-Inch Drive Crowfoot Wrench Set, Metric, 10 mm - 24 mm, 10-Piece
05-08-2019, 08:16 PM
#26
Rennlist Member
Thread Starter
Opened the new sending unit and gauge package and discovered the sending unit is 1/8 NPT. It looks like I'll have to find an adapter to make it fit. I presume it's a 1/4 NPT that I need (?) Anyways, that's a project for next week. 
05-09-2019, 09:01 AM
#27
Rennlist Member
Call me confused, Isn't the stock sending unit metric and much larger than that?
05-09-2019, 09:51 AM
#28
Rennlist Member
Thread Starter
05-09-2019, 10:13 AM
#29
Rennlist Member
Me understand now!
