Coolant Temperature Sender on BMW Sportster with M50B25 engine.

[Colin Barratt]

Hi,

Recently my coolant gauge started reading low. The fan would come on at what the gauge said was 75 degs rather than the 85 degs it had done since I bought the car from Rob Dorey. The running temperature was also lower than previously.

Thinking that it may be the Coolant Temperature Sensor I disconnected it. The gauge still gave a reading so that couldn't be where the signal originated. The only other temperature related sender is the on/off wax cartridge one on the rad to start and stop the fan and this doesn't send out a variable signal suitable for the gauge.

Somewhere in the cooling system there is another sender but I can't find it. I emailed Rob without success.

Can anyone think of where this other sensor might be sited?

Neil Meakin at Caerbont Automotive who made the gauge is happy to test the gauge but would like me to send him the sender as well.

Hear from you soon.

Regards,
Colin.

[dogoncrazy]

Re: Coolant Temperature Sender on BMW Sportster with M50B25 engine.

Hi Colin
Don't know about your engine but M20 in mine has 2 temp sensors close to each other almost next to and above thermostat housing. One feeds info to the ECU and the other one is for the temp gauge. Are you disconnecting the correct one? Again on mine one is brown, the other blue.

[Mike]

Re: Coolant Temperature Sender on BMW Sportster with M50B25 engine.

Hi,

Recently my coolant gauge started reading low. The fan would come on at what the gauge said was 75 degs rather than the 85 degs it had done since I bought the car from Rob Dorey. The running temperature was also lower than previously.

Thinking that it may be the Coolant Temperature Sensor I disconnected it. The gauge still gave a reading so that couldn't be where the signal originated. The only other temperature related sender is the on/off wax cartridge one on the rad to start and stop the fan and this doesn't send out a variable signal suitable for the gauge.

Somewhere in the cooling system there is another sender but I can't find it. I emailed Rob without success.

Can anyone think of where this other sensor might be sited?

Neil Meakin at Caerbont Automotive who made the gauge is happy to test the gauge but would like me to send him the sender as well.

Hear from you soon.

Regards,
Colin.

Hi Colin

As Alan has suggested for the M20, the M50 has two senders at the front of the head just below the inlet manifold.



The front Blue one - shown here on the left - is the sender to the ECU. Its the rear one you require, which is connected to the Temperature guage.

It is interesting that Caerbont made your guage.

I had an original Smiths classic sender/guage but was not happy with what it told me - very little!
Ian John is Caerbont's technical boffin - very good guy - and explained most guages are designed to sit on "Normal" across a wide temperature range, and by the time they read "Hot", you've cooked your engine!

Ian suggested a digital guage calibrated to the BMW VDO sender would offer a true temperature readout, and provide much better information about the engine temperature so this is what I had made.

It sounds like Rob Corey had something similar, and Caerbont are offering to test the calibration of the guage to the sender.

If it helps, they should have the information from my BMW VDO sender to check for comparison.

[Colin Barratt]

Re: Coolant Temperature Sender on BMW Sportster with M50B25 engine.

Thanks Guys.

I shall send gauge and second sender to Caerbont and I'll let you know what they find.

Regards,
Colin.