3000m radiator is stubbornly cold

[laikathedog]

Hello,

Wile scratching my head about brake bleeding that should have been a straight forward job ! I decided to run the engine and check my otter is working.... Which it isn't, the temp goes to the end of the gauge and the otter doesn't engage.. But then I checked the lower hose ( the one that runs from the bottom of the rad across the wishbone to the pump) and it is COLD, so no water is being drawn through the rad, and explains why the rad is cold and the otter thinks temp is fine! The aluminium Coolant reservoir is hot. I initially suspected a stuck thermostat, but if the reservoir is hot that means it is open,?so now I suspect the water pump... Which has about 100 miles on it...
Is there any way to check the pump ? Have i got a blockage somewhere ? Where should I start ...

Thank you all

[Astacus]

If your pump is more or less new then you must have recently drained the system to fit it , no? I would suspect an air lock in the coolant system. I take it you checked the pump was running? if thats the case then there should be at least some movement of water. If the header is getting hot then the 'stat is probably open and convection is moving the hot water upwards to the tank, slowly.

ETA - welcome to the site. Just spotted this was your first post.

Post up a picture of your M when you have a moment, we'd love to see it

[GAjon]

Take the stat out, fire it up with the filler cap off, rev it gently and see if you've got flow through.


ETA. the stats can be a right pain in the arse.

[laikathedog]

Discovered the real problem:

My temp gauge sits at 90 when cold and then rushes past 140 quickly
An independent temp sensor tells me the real temp is 75degrees less than the gauge which is rather a lot !

Will I be able to calibrate that level of error out ?

[Adrian@]

Order an electronic version of the voltage stabilizer... that way your fuel gauge AND your temp gauge will read properly.
Adrian@

Edited by Adrian@ on Friday 31st May 14:16

[tomtrout]

Still doesn't explain why your bottom hose is cool. I had the very same issue with my vixen and it turned out to be a duff thermostat. Why don't you whip it out and see if the bottom hose warms up.

[laikathedog]

I replaced the thermostat
On testing I found that it takes along time to get up to temperature, the gauge says the engine is way past 88 degrees, but in reality reaching that point takes much longer.

I have a separate stat for fans from kenlowe so I can ignore the dash gauge until I get around to ordering and fitting an electronic regulator, it seems my fear of overheating is uncalled for.

The fan does work, but I noticed that it is not ignition switched which means it runs even when the engine isn't, is that a good idea ? Seems like a pointless waste of battery to me.

Thanks to all for their help and advice