E30 Temperature Gauge

[Boost Junky 1]

Hey guys, does anyone know where the collant sender is on the M50B25 motor? When i turn the car on the needle doesnt move unless i tap the cluster. When i tap the cluster it jumps to the cold position (have to do this every time i turn the car on). Now when i let the car warm up for like 10mins the needle stays at the cold position and never moves up. Would this be the sender or the gauge being faulty?

Cheers, Luke

[markb 0]

prob the guage itself, ive had the sticky needle prob too.

what i did was take apart the instrument panel from the dash, got the temp gauge and lubedthe needle up with some tamiya car lube. seemed to do the trick.

[ducatiss 1]

I agree its the gauge - mine does the same thing

[Boost Junky 1]

Yea i thought it may have been the gauge but i hooked up a spare sender and ran an earth wire off one pin to an earth point on the chasis and ran another positive wire from the other pin to the wire that switchs the gauge. I then held the sender on a hot surface and the gauge needle started to move so its either the sender on the motor or the wiring...

[hotwire 352]

Yea i thought it may have been the gauge but i hooked up a spare sender and ran an earth wire off one pin to an earth point on the chasis and ran another positive wire from the other pin to the wire that switchs the gauge. I then held the sender on a hot surface and the gauge needle started to move so its either the sender on the motor or the wiring...

Temp gauge sender should be a single wire - sounds like you have the engine management sensor. They both mount in same place. To test - pull wire off sender & give a direct earth - gauge should rise to top, that being so, the sender is faulty.

However if you need to bang the dash to get it to move from rest - as said this indicates a dash problem. If gauge moves then fails to rise above cold then possibly sender but is the engine getting up to temperature (thermostat jammed open)?

[Boost Junky 1]

Yea well on the M40 motor that used to be in there it was a single pin plug for the coolant sender. With the M50b25 it has two senders the front one being a fuel injector temperature sender and the back one being the coolant temperature sender, they both have two pins.... so im guessing they both earth with the loom not the head where they skrew in. Will earth the head tommorow and see if that makes a difference should be earthed anyway lol.

As you said hotwire i was trying to wire the fuel injector sender to the gauge and have since tried the coolant sender behind it but still no go, will try ur test in the morning. As far as the motor getting warm enough it should be, the thermostat is brand new. In saying that I have a thermatic fan switch which kicks in at 87deg which is rather low and the fan still seems to take ages to switch on... maybe i have a major air pocket somewhere... Lots of things to look at so will see what i can do tommorow.

One other question im still using the 4 cylinder gauge cluster in turn the rev counter is way out, does anyone know where i can read up how to rewire or whatever has to be done for it to work with the timing of the 6 cylinder motor. I know it can be done but cant find any info on R3VLimited or Bimmerforum...

Thanks for all the help guys, Luke

[Boost Junky 1]

Hey hotwire the needle flicked right round when i earthed the wire that goes from the sensor so it must be the sensor thats stuffed yet i have tried other sensors and still no luck so wether the car is actually getting hot enoug? I think I have a cracked head gasket tho so could that cause any issues? Also my overflow reservoir and radiator filler is lower than the top point of the radiator could that also cause something?

Cheers, Luke

[gmccormack 0]

One other question im still using the 4 cylinder gauge cluster in turn the rev counter is way out, does anyone know where i can read up how to rewire or whatever has to be done for it to work with the timing of the 6 cylinder motor.

Change the 4 cylinder coding plug for a 6 cylinder one. It is the white plastic block in the front of the instrument cluster

[hotwire 352]

Hey hotwire the needle flicked right round when i earthed the wire that goes from the sensor so it must be the sensor thats stuffed yet i have tried other sensors and still no luck so wether the car is actually getting hot enoug? I think I have a cracked head gasket tho so could that cause any issues? Also my overflow reservoir and radiator filler is lower than the top point of the radiator could that also cause something?

Cheers, Luke

Luke, Cant remember M50 setup off hand but you have confirmed communication between gauge & sender but being a 2 wire setup the other wire should be earth - ultimately somewhere, is it a brown wire? Try bridging the 2 wires in the plug - it should also make the gauge go high confirming the circuit to earth OK.

Make sure you get the gauge wiring & not the engine management sensor.

Has it ever worked properly since the transplant or is this a problem on the list to solve? E.G. if gauge doesn't read with wires bridged, where does the second wire go to - since the original system was a single wire?

Airlock will cause engine to overheat not under but may not show on the gauge as if the sender has no water behind it - it will not read. Is there a bleed screw around the thermostat area?

Cheers

Grant

[Boost Junky 1]

Grant, Yea the other wire should be an earth aye? The wire that communicates to the gauge is BROWN/Purple the other "Earth" wire is just straight brown. I shall try bridging the wire and see if it triggers the gauge also. But I have had the plug plugged onto the sensor in the head and re-routed the so called "Earth" wire in the plug to the earth on the chasis and still no go so i think its a sender issue or air lock issue also im damn sure the headgasket is gone aye.

Its definitely not the engine management/fuel injection temp sender. Nah man hasnt worked once since the conversion haha and its probably one of the most vital gauges i need of the lot so yea its one on the list to solve. I dont think there is a bleed skrew on the thermostat housing you would have to see my setup to understand how dodgy the cooling system is at the moment, heres the run down:

I have an M20 radiator with no expansion tank on the side of it where as my original M40 motor ran a radiator with expansion tank. So obviously I have no radiator filler neck anywhere because the M20 radiator has no expansion tank and the original setup did not have a seperate overflow tank.

What I have done is have a pipe made up with a filler neck and cap welded onto and then placed that inline in the top hose going to the thermostat, the way this is setup has the filler neck lower than the the highest point in the cooling system (lower than the top of the radiator etc) so I definitely need to sort a proper overflow tank where I can fill the radiator from that point.

Thanks Grant for being so helpful

Luke