This is the coolant expansion tank in my 2004 MC. I just bought it and realized my coolant levels are below the minimum, but I can't remember if it was full when I bought the car...stupid me. Does this just mean I have to replace the coolant expansion tank that I've read is a common problem?

I wanted to double check the forum before I went and bought one.

 

Not that I know anything, but that doesn't look like any tank I have seen on a Gen 1, is that a non S, guess I only looked as S cars?

Anyways yeah the white residue looks like dried up coolant, make sure you get the right kind, and while you are at it since it probably has been leaking for a while, make sure you get the proper mix and someone hasn't just been adding water...

 

Yes, it is a non S, just a 2004 MC. What do you mean the right kind? I mean the manual just suggests a 50/50 mixture, nothing special. I picked some up at WalMart and plan on adding it in the morning when the engine is nice and cool. Then, if it is leaking from the expansion tank, I'll know for sure. It's just there are no cracks or anything...so I'm confused.

 

I know it's still possible but most of the expansion tank leaks occur in the MCS since their tanks are pressurized. There are a lot of antifreeze threads stating not to use some brands because they can corrode some of the plastic parts in the coolant system. I couldn't find any of the recommended brands at my local auto part stores so I ended up grabbing the OEM antifreeze (unmixed) from the dealer for the extra piece of mind.

Since you bought it used, clean off the current tank and fill it up and just see what happens. Then you can start looking for leaks.

 

To me that tank looks like it leaked out the cap. When they break it leaks at the seam. Check cap tightness and if there is a rubber seal in the cap. Maybe something fell out that sealed it better. I would try to tighten or find/make a gasket for the cap first.

 

Hm, alright thanks a lot, how much is the OEM stuff? To menit sounds like a way to make more money haha.

But anyway, I cleaned off the reservoir and filled to MAX, no leaks, at least not at the reservoir. I'm guessing the guy I bought it from never used a funnel when filling it. However, I do wonder why it was low...I'll keep an eye on it this week, and if I lose some, it could be a slow radiator leak or a hose leak or something, that would suck.

 

The non-S tanks aren't especially prone to leaks or cracks as the S ones are.
An overheating event could make it look like that (boils over), as could a sloppy previous attempt at filling as you said.
I'd look around the thermostat housing for a leak, and since it's sometimes hard to spot unless you remove things,
look at the top of the transmission housing and the engine block/cylinder head seam at the back driver's side
of the engine - coolant from the thermostat housing often ends up running there with a leak at the thermo gasket.
With mine, it only leaked the first few minutes after starting up from a cold engine - the leak would stop as the
engine warmed up and parts expanded.
Also check if the low speed of the radiator fan is working.
Now that you've filled up, keep an eye on the level in the resevoir to see if it's slowly dropping - remember that the
level will vary a little between hot engine to cold engine.

 

A really common failure on the R50 is the thermostat housing. I had mine crap out shortly after I bought the car last year. Same symptoms, slowly vanishing coolant.

You don't want to mix different kinds of coolant, so get the "right" stuff from BMW/MINI. Top it up, see if it's leaking by putting some cardboard underneath your car and checking for wet spots the next day.

It's a pretty cheap fix. I managed to squeeze in under warranty so I got it for free, but I don't think the new part will cost you much.

 

I think I paid ~$25 for OEM unmixed antifreeze. And I saw where another member found the parts online to do the thermostat + housing replacement for a little over $100.

 

I just replaced my thermostat housing, thermostat gasket and thermostat. Got the parts from WayMotorWorks (gasket/thermostat) for like $41 shipped, and the housing for something around $38 elsewhere. Took me 2 hours, though I didn't bleed the radiator properly so even after I did the install it seemed like I still had a leak (though it has since stabilized). I had to remove the battery box, and air box and that's about it, very straightforward install. I also bought some screw-style hose clamps to use on the thermostat housing hoses because I hate the spring steel style clamps.

I also used Peak Advanced coolant, my Dad got me some of it and says the only real requirement for the MINI is sulfate-free coolant. He also just flushed the system for me before I got it (Dad picked the car up for me 1000 miles from where I live, younger sister drove it down to me) and used Peak Advanced, so I knew that was the stuff in the system.

If my engine looked like that, I'd top it off with coolant (ensuring 50/50 mix when its cool), clean off the expansion tank and drive it for a few days then check it.

If you have an OBC, you can monitor the coolant temperature quite easily. Let me know and I'll see if I can find the link for you about how to do that.

 

Awesome, thanks everybody! Super helpful. I have the reservoir topped off now so I'll keep an eye on it while driving. If I notice the level starting to decrease I will check all the areas that everyone has recommended, especially the thermostat housing.

Thanks for the good info on where to buy too. I'll keep everyone posted!

 

So I had some time today and decided to take out the battery box and air filter. I didn't know exactly what I'm looking for but you guys might. It seemed pretty clean under there, though I have only run the car once since I topped off the coolant. What do you guys think?

 

Just a point to remember. You may have a bit of air in the hose if it ran too low. What I mean is the level may drop a good amount at first filling the radiator and hoses (that you can't see). So the point is if it lowers at first, I would ignore the first day or so. From then on it may be leaving the system rather than just topping it off. Don't go to crazy if it lowers in the first day or two.

 

Couldn't agree more. After swapping my thermostat stuff because I had air in the system, I checked the level in the mornings (for the prior days heating up cooling down cycle) and it was low. After adding coolant for several days it finally stabilized. I was definitely freaking out when it kept dropping (find my thread about it lol) but it takes a while for it to be noticeably stable. Because it has to heat up and then cool down to suck coolant back in the system, and that can take hours. There's really no point to checking the coolant more than once a day, I checked mine first thing in the morning before I left for work (6am when it's 50*F at my house).