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SR3 RSX Oil Temp Sensor Failure and GDU Temp Sensor Install...


Rod Bender
(@rjbender)
Estimable Member
Joined: 4 years ago
Posts: 173
Topic starter  

Hi All,

Wondering if anyone can help me with a couple of oil temperature and wiring loom related questions?

At the last event I had some dubious oil temperature movements, that in once case on the warm up lap showed the temp dropping suddenly (over less than 2 seconds) by about 15 deg C... and then recovering back to 'normal' a few seconds later.  I first noticed it because it bought on the 'Engine Cold' alarm.  Once I got back to the pits and downloaded all the data I noticed that this had been happening quite a bit, including in the previous racing heats, but not enough to make the alarm come on.  Because the temperature drop was so dramatic (big steps and very quick) I assumed it couldn't actually be the oil temp changing, but suspected something wrong with the sensor or loom.  After fiddling around for a few minutes, I put my hand down onto the connector on the sensor and wriggled the wires a bit.  When doing this the temperature on the dash did almost exactly what I had been seen while running.  I took the Bosch connector off to have a closer look, but without removing the diffuser and getting under the car couldn't see too much. I ran the next two races and just ignored the lower temps that would display a few times each lap (in different places on the circuit - it wasn't repeatable)

Once I got home and put the car up on the service stands with the diffuser off I was able to have a closer look this is what I found... It looks like the sensor has cracked (maybe effected by the heat?) and started to let oil into the connector.  The oil residue (assuming that's what it is) is extremely hard and is almost like a resin, and wont come off easily.  I have cleaned the terminals using a small screwdriver with fine emery cloth on it, and the sensor now works fine again.

image

Given it's likely that there will be more residue form over coming events, I'd like to get a replacement sensor.

Firstly I'd like to try and identify the thread size on the oil temp sensor that goes into the threaded socket welded onto the bottom of the dry sump tank? (the sensor has the 2 pin '2 Way Junior Timer' or 'Bosch' connector on it).  That would allow me to source a local supplier of a suitable sensor with the same electrical connections.

Alternatively does anyone know the OEM manufacturer and part number?

On another oil temperature related topic, I'd like to install an oil temperature sensor into my GDU and was thinking that if I did this I would use the identical sensor as used in the dry sump (saves carrying too many spares).  I would like to wire this so that it displays/logs on the MXL2 Dash.  

Does anyone know if there is an easy way to make that work from an electrical point of view?

Are there any spare connectors in the engine bay that I could use to connect to the Dash at the other end of the car?  I could easily make a patch cable in the engine bay to get from the new temperature sensor to wherever there might be a spare connector into the loom, but I'm not sure what would be needed at the dashboard end of the car.  I'm assuming there are one or two analog inputs into the Dash and was hoping I could use one of those.... I'm not sure if it's possible to go through the Life ECU, but would be fine for it to go straight into the MXL2. 

Thanks in advance for any help...


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DavidF
(@davidf)
Estimable Member
Joined: 2 years ago
Posts: 214
 

You may be able to see a part number on that sensor if you take it out.  I searched Bosch oil temperature sensor and found a few like the one below.  You can use a thread pitch gauge and dial caliper to determine the thread size.  I don't know anything about oil temperature sensors, but my guess is that this is a fairly standard item for liquid temperatures.  But who knows?  Perhaps some work with 5v, and some with 12v.   The one below is part number 0280130026.

Looking at this part, I does not appear that there is a path for an oil leak unless perhaps something broke off?  Does not seem likely.

 

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John Parsons
(@parsonsj)
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Joined: 4 years ago
Posts: 569
 

@rjbender It's a Bosch (as mentioned by David). At Amazon: AmazonSmile: Bosch 0280130069 OEM Temp Sensor for Select 1987-1995 Porsche: 928; Saab 9000; Volvo: 240, 244, 245, 740, 760, 780, 940 : Automotive

These temp sensors are resistive ... the sensor itself changes resistance based on the temp of the liquid (or air) at the tip. One prong goes to earth, and one goes to the device that "knows" how to interpret a temp based on the ohm reading it measures.

As such, the MXL2 has some extra analog ports that can be used for it. Have a look under the dash -- Radical often has an unused connector for that. 

Microsoft Word - Cablaggio_StandardMXL2+MXG+MXS_106_eng.doc (aimtechnologies.com)


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John Parsons
(@parsonsj)
Honorable Member
Joined: 4 years ago
Posts: 569
 

@rjbender Here's another link to that sensor (same color too):

Bosch Temperature Sensor - Race Spec (racespeconline.com)

Note that it's available in two different threads. One metric 12x1.5, and one 1/8" NPT. You'll need to remove it to see which threads you have. I have 4 of these in my SR8. One each for oil, gearbox oil, coolant, and fuel. 


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Dan Phillips
(@rlm-dan)
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Joined: 4 years ago
Posts: 213
 

Just to add to this it is the M12 x 1.5 for the Radical.

Oil and water temp sensors are the same.


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Rod Bender
(@rjbender)
Estimable Member
Joined: 4 years ago
Posts: 173
Topic starter  

@rlm-dan - Thanks so much Dan,

That will help as I would have had to drain the oil to remove the sensor and check the thread, and I'm not due for an oil change until after the next sprint event.

I had wondered if it was part number LS0028 which is the water temp sensor unit.

You're a champ!

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