So, Is this What I should expect after some very spirited driving in my 2006 MCS..........


Or do I just need a new cap?

Oh, and this has just recently happened to me twice. Otherwise, the cooling system seems to work as intended and the engine does not get hot ,etc.

 

either air got in system causing the overflow or cap could be bad . also see if tank weeps at seam midway , common problem with tank . you could go with a canton (very nice) or i'll sell you my used almost new oem .

 

Terry:
I had this happen to me, too. It was the coolant cap--but the sad news is that the dealer would not sell me a cap alone, but they said it only comes as a tank/cap kit. I convinced them to cover it under warranty.
It could just be the rubber gasket on the cap, but you'd have to fabricate a new one I guess.
The cap is also a pressure valve, so it could be that that failed, but your dilemma remains the same.
I wish someone would make a replacement cap--more useful than the darn tank, which you can get anywhere...

 

Terry,
the day after I saw your car at the dealership I went back and bought a cap. I think $12, my leak was not like yours but it did fix the leaking that was occuring in my car.

 

OK, just ordered a Canton. Cheaper than the Forge (170) or the GTT (205) at 140 with a cap -- it doesnt accept the Mini cap, which might be a good thing...

Will report when it arrives.

btw, do you have to bleed the system if you replace the overflow tank?

 

My car is at the dealership now getting some last minute warranty odds and ends addressed. I expect to get a new cap at least, and hopefully a whole new tank. However, the Canton option looks like a nice alternative. It sure does look better than ever darkening and hardening plastic.

I would not expect to have to bleed the system for just the tank replacement. I mean for a thermostat yeah, but not for the expansion tank.

Actually, air will eventually work itself out of the system anyway. Although sometimes the result is very similar to the original pic in this thread as noted in the posts.

So, since it is relatively easy to do......might as well bleed it.

 

I had the same problem with my coolant tank (not as bad as yours) and power steering tank. Dealership replaced my coolant tank/cap and power steering cap. Both still tend to leak slightly at the caps. When I wash my car I always have a little fluid around the power steering cap.

I wonder if the coolant tank cap rubber seal could be replaced with an o-ring to seal it a little better. I also wonder if a slightly different size o-ring would better seal the power steering cap. I have not tried to change either seal.

 

u dont have to bleed the system i replaced the tank and cap in my moms mini and all i did was suck the fluid out of the tank and unclamped the hose and pulled it out...though u might want to take off ur spark plug ign box...makes it easier

 

Be sure to check the coolant level; it should be ~1/2 inch below the seam while engine is cold. When coolant temp is at normal operating temperature, it will expand a good 1-2 inches. Service techs have a habit of over-filling fluids (oil, brake fluid, coolant, P/S). Mine did and coolant was leaking from the cap while the engine was idling. The cap will vent at a certain pressure level.

 

you should not have to bleed . do yourself a favor and get the morroso 27-29 lb. cap . i used 16 , 18 , 22? and all vented . the 27 has yet to vent for over a year .

 

My Forge tank leaks at the cap like this with spirited driving, but so did the old plastic tank, before it split in half.

 

BTW, It looks like you can get the cap by itself at ECSTuning for $8.50 + shipping. I'm interested in this Moroso cap though, that might be somthing I can pick up locally, does anyone have a P/N? I didn't find anything on their website except STD radiator caps, I don't think those will fit our expansion tanks.

 

BTW, for my OEM tank and cap as described originally, the dealership solution was to install a new cap. I am sure it can only help, but the plastic tank still looks a bit nasty.

 

Darn it--HRP is sending me a 22-24 Stant cap along with the tank...
btw, why are caps so expensive--they all look like they are made from tin cans...

thanks,

 

cool try the 22-24 if it works all the better. they do looke like junk lol . some guy gave awell informed race proven dissertationon pressure caps and swears bye the higher pressure caps for the aluminum cans . he also recommends running a hose to the area above the header so if you ever did vent it'd be apparent immediately. or use a cool aluminum overflow bottle . do a search in mods and find what one nammer did to this end , very nice work . was a hikers water bottle or something looks very good .

 

Here's what the Canton looks like installed:



Install was relatively easy except for one glitch. And this is a heads up for the install. There is a vertical lip on the bracket that holds the tank to the firewall on the left side (passenger side of engine bay). This interferes with the Canton and prevents it from sitting properly. And don't force that sucker...
You have to bend the vertical lip back and to the left out of the way of the new tank. Once done, the two locator pins under the tank fit perfectly, the 10mm nut goes on cleanly and you have a nice last-a-lifetime overflow tank.

Do it, Terry...you know you should.
PM for details on purchase.

 

Wow, looks great Phil

I don't need it BUT that has never stopped me before.....

 

Of course, that's the spirit!! You don't really need those tires, ... go on, get one of these suckers

 

looks nice man . everynow and then open it when cold to make sure no air got trapped . i flushed all my coolant and a year later still had a bit of air . the canton will hold it like oem .

 

A very nice looking engine bay upgrade that also increases reliability.

 

This happens to me after track sessions when there's too much coolant. I wait until it cools then take some out using a turkey baster or whatever that cooking tool is called. Problem solved.

That said, if a new cap from MINI is $12, I'll probably do that, too.

mb

Edit - looking at this pic closer shows me that the cap looks to be pretty loose with the arrow still on the left of it. I tighten all of the way so that the arrow is on the other side. Just an observation.

 

Actually the cap was very snug and checked by several people, including myself. None of us moved it at all. I do have a new cap from the dealership now, but no further incidents to report. I am sure though that my post new cap spirited driving no where near matched what was done for the original symptoms to show.

So, I am good for the moment and the new cap is tight.

 

BTW, just to add a little more info to this thread, if anyone ever reads it...there's a downside to fancy alloy tanks like the Canton, compared to the stock tank. Of course they all get hot, but you can really burn yourself on a metal tank, for quite some time after you turned the engine off and began working on the ignition wires... I never even thought about the heat from the stock plastic tank, but I am certainly aware of the little thermonuclear device sitting up there center stage now.

 

Did an oil change on our 03 MCS on the Saturday, decided to check all the fluids. Realized the PS was low and had to search to find a bottle of the CHF 11s fluid (which was a mission). Then i decided to check the coolant and i was shocked at how low it was. So I topped it off with the BMW blue coolant which I already had a ton of. The car was not driven more than 60km's (40 miles)since saturday, and when I checked it again just now i saw it was at the same level as it was, which was VERY low. This was not spirited driving, it was just regular driving to get back home.

This is starting to worry me now since the weather is starting to get hotter. Is there enough coolant in flowing throughout the system that the tank running on low will not cause and overheating issues? I believe the manual says the entire coolant system is about 6L or so. Can the car still be driven with this low coolant in the tank while i figure out a replacement.

I'll try to snap some pics later tonight, I can't tell if it's the cap that I'd need to replace or the tank. I have some dry residue at the top of the tank but the seam in the middle looks a little green.

Yet another stupid Mini design. Do the ones from the dealer FIX this issue or are they still sealed in the middle?

 

So how are those Canton expansion tanks holding up? More importantly, how are those caps holding up? I noticed that HRP is now offering their tank with a 30 lb cap.