K Series Coolant Temperature ECU Sensor Types - What Have You Got?

[revilla]

There seem to be two types of ECU sensor for coolant temperature uses on the Caterham K Series:

MEK100061 (Brown)	MEK000030 (Black)
[attachment=3837:name]	[attachment=3838:name]

The threads on both are M12x1.5mm so they are physically interchangeable but the "coding" of the connectors used on them are different, so you can't swap between them (the position of the raised key can be seen to be in the middle on the above picture of the brown sensor and offset to the left on the lack sensor, meaning that a connector suited to one will not fit onto the other). The corresponding connectors used on the Rover looms are BMW parts:

Rover YPC114900	Rover YPC114920
BMW 12-52-1-427-615	BMW 12-52-1-427-787
Code I	Code III
[attachment=3839:name]	[attachment=3840:name]

From Rimmer (in this case for the 1.8 MG ZR), the brown MEK100061 is specified for serial numbers up to 471564 and the black MEK000030 is specified for serial numbers from 471565 onwards. These same two serial numbers crop up here as the point when the EU2 VVC plenum LKB107060 switched over to the EU3 VVC plenum LKB109520.

So basically the brown sensor is for the EU2 engine and the black sensor is for the EU3 engine.

The oddity is that my car is an EU3 VVC but has the BROWN sensor fitted (and the correct connector for the brown sensor on the loom).

From memory other EU3 K Series Caterhams I've seen also had the BROWN sensor, but I may be wrong and it may just be my car that is odd. Caterhamparts do however list something that looks very much like the black EU3 MEK000030 as "Temperature Sender - Water Temperature to ECU - 1.6 EU3" which suggests again that an EU3 should have the black sensor.

I can't find any decent reliable data on the calibrations of the two to know if it really matters, but if it does my ECU will be getting wrong temperature information (although it can't be too far out as the temperature data read out from the ECU via OBDII looks at least believable).

My car did have an awful lot of oddities when I got it. From what I can gather the transition from EU2 to EU3 (MEMS3 ECU, COP ignition systems) did not coincide exactly with the transition from 143bhp to 160bhp on the VVC engine (52mm throttle body, head machining) and there was a transitional EU3 143bhp engine which retained some of the EU2 features such as the IAT sensor being on No 4 inlet runner rather than within the MAP sensor. My car seems to have been fitted with the engine loom from one of these, then retrofitted with a full EU3 160 engine which didn't quite match up. I'm just wondering if this is just another one of these cases where my loom retains an EU2 style sensor connector and the later EU3 engines then switched.

Just to help my research, if people have the time to look, could you please just post on here whether you are EU2/EU3 and whether your ECU temperature sensor (the one one the water rail or submarine pipe with two wires and looking like one or other of the above) is BROWN or BLACK? If EU3 only, it would also be helpful to know if you have a connected green IAT sensor screwed into the rear end of the inlet manifold.

Thanks

Andrew

[revilla]

For ease of identification:

EU2 ECU Looks Like This:	EU3 ECU Looks Like This:
[attachment=14408:name]	[attachment=14409:name]

 

IAT Sensor on Back of Manifold Looks Like This:

[attachment=14410:name]

 

[rj]

BRown, but my car is on an MBE and I honestly don't remember where I've got the sender from. Could be from the donor (EU3) engine but could also be from somewhere else. IAT sensor was taken from the VVC manifold and was connected.

[Seabea23]

Brown, Standard EU2 1999 1600K. Interesting thread. 

[CageyH]

EU2, fitted with two brown ECU sensors.

[SM25T]

Will check when home next week

[revilla]

Thanks for the replies.

Any EU3 owners who i can help me out here?

Just to add to the confusion I have a water rail here in front of me fitted with an ECU temperature sender with only a single wire connection. They should really be earthed to the sensor ground to avoid voltage drops around the engine earth path but this one must have been grounding through the rail.

[rj]

I've seen that on an EU2 car at some point. And it made me wonder too.

My Stack sensor is grounded through the water rail without any problems at all.

[Silver Machine]

Brown on an 1997 EU2/ Suppersport . 

[revilla]

An update ...

When I had a good look at my car, although it did have the brown temperature sensor it actually had the loom connector for the black sender.

This is the correct EU3 BMW connector for the black BMW sensor:

This housing takes ELA 2.8 (BMW style) terminals. It is Code III with the offset keyway.

Having checked an EU2 car, it doesn't use the Code I version of this connector at all but an AMP Junior Power Timer connector (which also has a central keyway like the Code I BMW connector). I guess the EU2 loom design pre-dated the BMW influence on Rover and there was a general move towards BMW engineering standard in the EU3 loom (for example the EU2 loom uses a 4-Way Econoseal plug for the lambda sensor where the EU3 also uses a BMW ELA 2.8 connector).

This is the correct EU2 AMP connector for the brown sensor:

The thing is, the EU3 BMW connector for the black BMW sensor, although it has the keyway in a different position, actually fits onto the EU2 brown sensor too. Although it's clearly wrong, it does fit without forcing, clicks into place anc connects correctly. So it is perfectly possible to fit an EU2 sensor on an EU3 car and get away with it, which seems to be what somebody has done on my car in the past.

So everything I have seen tells me that I had the wrong sensor installed. According to all the Rover documentation I have found, the EU3 engine ALWAYS used the black sensor. All the EU3 looms I have seen have the correct connector for the black sensor, even my own car which had the brown sensor fitted.

So today I swapped the sensor. 

I was planning to check the calibrations of the two against each other but I haven't found the time yet, although I still plan to check them later when I get a chance. However, I have checked the performance of the new sensor in the car with the following observations:

Previously, the temperatures reported by the ECU over OBDII live data agreed pretty much exactly with the temperature gauge. However, I had reason to believe that my teperature gauge under-reads (I have two sensors, one for oil and one for water, on a switch. Both oil and water seem to run cooler than expected, especially taking into account the teperature ratings of the coolant thermostat and the oil cooler thermostat).

With the new sensor, the ECU reports temperatures around 7°C higher than the gauge shows. These temperatures make a lot more sense, and in addition the fan switches on with the ECU indicating 92°C over OBDII and switches off again with the ECU indicating 88°C, which is in almost perfect agreement with the fan thermoswitch rated temperatures of 92°C and 87°C.

These are the ECU and gauge readings when the fan switches on:

These are the ECU and gauge readings when the fan switches off again:

So I'm comfortable that I'm now running the correct black BMW sensor for the EU3 ECU and that it is reading accurately. I'm also a lot happier that my oil and water running sensible temperatures and no over-cooling, I just know that my temperature gauge reads about 7°C on the low side. It's also been a mystery to me in the past why my engine temperature doesn't seem to cycle on the gauge when the fan cuts in and out, but this is also clearly just the gauge being lazy and the temperaures are actually cycling between the on and off points of the thermoswitch as expected. This makes a lot more sense.

Interestingly, after seeing Nick Basset's post on here about low oil pressure, I lent him a spare mechanical oil pressure gauge. I checked the calibration of this against the pressure gauges in my leak-down tester on a compressor. I've always thought my car ran slightly low oil pressure, which was a bit odd as it's had three different engines (long story!) and the pressures have always been the same. So I checked the calibration of my oil pressure gauge in the same way and that under-reads too, by about 5psi. Allowing for the 4psi drop I got through the oil cooler when I fitted it, that means I'm actually running about 30psi into the oil cooler at hot idle and 60psi on the road, which is not too bad.

Completely unrelated issue as the gauge is purely mechanical, but now I know both gauges read low!

[StevehS3]

Black on my standard 120hp EU3

[revilla]

Thanks StevehS3 ... I was really hoping for some feedback from EU3 owners, so much appreciated. That just helps to confirm what I thought, black for EU3 - looks like mine's just had the wrong sensor fitted since I got it.

[Jonathan Kay]

EU2 1998 1800: Brown.

And it sends its best wishes. ;-)

Jonathan

[revilla]

Another EU3 with Black BMW:

[rj]

I've got a spare BMW sensor somewhere

 

[revilla]

Thanks Regin but I've got spares already on order :)

[revilla]

In a final bizarre twist, the odd single-terminal temperature sender I found screwed into a water rail in post #7 turned out to be ... a low oil pressure warning light switch!

[garybee]

Surely that can only have been functioning as a blank.  

[revilla]

Or somebody had just stuck together some spares in their garage at random and it was a complete red herring? It wasn't in very tightly when I came to remove it. It certainly can't have been doing much useful. I can't see much use for a low coolant pressure warning. It was a used water rail I bought. The seller had bought it used himself and just passed it on without using it, so no idea how it ended up like that.

[garybee]

Will remain a mystery then.  I'd only just seen this thread, I presume you are no longer interested in sensor types.  In case you are I have standard EU3 1.6 and EU3 VVC engines and looms in my workshop.  I removed these myself so am certain that they are unmodified.

[revilla]

No I think that question is resolved now, the brown ones were fitted to EU2 and the black ones to EU3, my engine had the loom plug for a black one jammed onto a brown one. I've swapped over to a black MEK000030 and all is as it should be. Thanks anyway.