For a few days now my temp gauge has been erratic. It doesn't climb past the half way mark, so no over heating, but it floats between the 1/4 and 1/2 marks. When the car sits over night and cools, it starts up and the gauge points at 1/8th as opposed to full cold, then it takes 4x as long as it should to 'warm up' to the half way mark.

There are no codes, the car runs fine.

I take it that if the gauge is broken that the whole gauge cluster has to be replaced. Could just the sender be bad?

This is probably just a coincidence but I noticed this a few days ago after running over a plastic bag. The bag shot up behind the rear window and blew away, so it didn't get stuck under there.

 

You may already know this but the temp gauge is more like an idiot light. With my scan gauge hooked up I can read a temp change from 180 all the way to 220 and the gauge wont move at all. As a result I basically ignore it. So if you have replace it use it as an excuse to get a Scan Gauge instead.

 

Yeah, I know it's a dummy light, but I still use it to know when I can get into the higher rpms.

Would replacing the sender necessitate draining part of the coolant? I just had it all flushed a few weeks ago. I'll replace the sender before even consider spending more than $600 on a new gauge set - which I won't do, the scangauge would be $400 cheaper.

 

So I was thinking about this. Could my thermostat be stuck open? I noticed the past few days the car will only take 2 or 3 times longer to warm up but be fine once it gets there, i.e. the needle won't fluctuate any more. Reading through the Bentley Manual on this it seems that the thermostat can fail open, partial, or closed.

Anyway, is it absolutely necessary to drain all the coolant to replace the thermostat? I do not want to deal with coolant again, that's why I had it flushed for me. I had a bad experience trying it myself once...

 

It is my understanding that the MINI uses a "closed loop system", as in if you get air trapped in it it will tend to stay there. So, I dont think you will have to drain all of your coolant, but you will have to bleed the system to get the air you introduce. That said, my knowledge does not extend far beyond that of the Bentley manual.

 

I described all these issues to my mechanic and I'll be taking the car in next week for diagnosis and repair. I don't like dealing with coolant. I got some in my eye once... longest 15 minutes of my life. It has a tendency to dry out more than the other, but I can still see.

 

Ouch! That is really awful, where you wearing safety glasses when it happened?

 

Not the science kind, so it was able to get around them.