I just replaced my leaking plastic coolant tank (2005 R53) with an aftermarket metal one. The one nice part about the OEM tank were the convenient little max and min marks on the side. How are you guys with metal tanks checking coolant level? Am I correct in assuming as long as you pop it open and can see SOME coolant in there when the engine is cold you're okay?

 

I keep the fluid level on our metal coolant tank between an eighth to a quarter of an inch above the center stand pipe. That fluid level is at 1.5 inches when measuring with a wooden dowel or wooden stir stick. That level works just fine. This tank uses the oem cap. I always make sure that the cap gasket including the rim and threads of the fill point are dry before screwing the cap back on. I check it weekly when in the local area and daily on road trips.

 

The instructions for my tank indicate that the level should be just above the top of a baffle (that may not be what they called it) inside.

 

I just stick my finger down there to the top of the baffle (cold) and if it comes back wet we're good to go.

 

Hmm, I'm going to go with I'm okay then as long as I can see something in there when the engines cold. How accurate are the temp gauges in these cars? If I have an issue with too little coolant that needle will swing past the middle point, right?

 

Mine has always gone to the same spot on the temp gauge and I keep a shop rag handy to clean m' finger. Another option is a narrow, clear straw. Stick it on the hole then a finger on the end of the straw, pull it out and see how high the water is.

 

The MINI temperature gauge is not very good - it will show 'normal' over a very wide range. If it ever peaks, the engine has already overheated.
There is a hidden menu on some cars that is more responsive.
I keep a wooden stick handy, a paint stirrer, to check the coolant level - about one inch is correct when cold.

 

That's clever! I never thought about some of these... Also, does anyone know what the extra nipple by the filler neck is for on these metal tanks? I noticed the plastic ones don't have anything, so why do these have it? Here's a picture of it: https://drive.google.com/file/d/1xiS...ew?usp=sharing

I'm a little worried because it seems to leak a little when I go on long drives, even if I have it filled up to the seemingly correct amount. Is this normal? Or should I figure out a way to block the nozzle off?

 

The radiator cap vents through the nipple. You could add an overflow tank to it.

 

Why doesn't the original one have this though? And adding an overflow tank to an expansion tank? Isn't that unnecessary?

 

I guess mini thinks venting onto the top of the tank is fine since it shouldn’t happen often on a street car. Track guys might want an overflow to avoid dumping fluid on the track.

 

ImASlowDriver
The extra nipple is really an overflow. If you were to completely fill the expansion tank, once the coolant heats up any excess is 'burped' out. You could add a tube exiting below the car, though it won't normally be used.

 

Hmm... so its normal then to dribble out a bit after its been driven for a while?

 

I wouldn’t think so, but I’ve never had a tank like that one.

 

Any harm in just blocking off the overflow nozzle? As the OEM tank didn't have this is it really needed?

 

I blocked mine off, I have had absolutely no issues.

 

What was your reason for blocking it off? Was yours leaking over long drives too? I'm thinking of sealing mine off with plumbers putty so if the pressure REALLY gets high it should be able to vent it by blowing it off.

 

On a long drive it would push a little coolant out the nipple and make a mess. So I took some JB weld and blocked off the end and made it smooth. Then I colored it black, now you can’t even tell it’s been done.

 

Putty wasn't doing it. I just put a vacuum cap on the end of mine. Fingers crossed it holds up with no ill effects.