Newbie With Coolant Problem On E46

[Bobbych]

hello, and hope you can help

I bought a 316 E46 in November. All was well, until recently, when I started to get a low coolant light. it was speradic at first, only coming on then going until this last week, where it comes on all the time

I always checked the level, and have Bled the system every day this last week. It always needed some more coolant, so today I did some more invest

I filled and bled the system and took it for a 16 mile run. I activated the OBC on the dash, so I could monitor the actual Temp during the drive

Anyway, during the run, the ANALOGUE temp dial, sat in the correct position, but as you can see, the actual OBC temp rose to 105/6 during,

it never dipped below 103 at any point, so I assume this is where my coolant is going, and is being boiled off

but, when I parked up, I popped the bonnet, and the radiator fan was not on, despite being at 104 at the time, but the DIAL was showing normal, so this tied in with the fan. After being parked, the fan did come on and off as I would expect, but the OBC readout stayed at 103

so, does the dial/fan get it's reading from a different sensor than the OBC? This would suggest so, and would also suggest the Thermostat is closed and not allowing coolant to the radiator? Or am I wrong and I have problems?

[Guest Mister Dabsy]

Yes there is a separate sensor on the Rad for the fan... The engine coolant temp sensor is usually on the cylinder-head (front near top-hose)

Worse-case scenario is the head gasket, check for fouling in both the coolant and oil...

[btmaldon]

Being new to this forum I have only just seen this. Before spending any money on cooling systems, always try changing the pressure cap first. If its not holding the pressure it will give you the same symptoms you are experiencing.

[melinamotor]

My E46 was losing coolant last month, the expansion tank had a small leak underneath. It only lost a cupful in 100 miles though so not a major leak but the expansion tank design looks pretty brittle with regards its location and exposure to extreme temperatures. Any way my analogue temp gauge also stayed stable throughout, it was by pure luck I found the leak whilst investigating my leaky headlight washers. Any way new tank on no more issues, as stated the caps are also a pretty naff design and also worth replacing if its your tank that's shot.