Hey!

I've been enjoying my Cooper S for over a month now, but today it overheated pretty bad on my way to work (rush hour). There's been a weird smell now and then coming in from the engine bay ever since I got it and I've known that couldn't be a good sign. I've examined the area around the coolant expansion tank and have come to the conclusion that it's leaking slowly from its seam (something I've read is a very common problem with these cars), dripping coolant onto the heat shield from where it ends up on the hot parts causing it to steam up creating the weird smell in the cabin.

I had to drive it a few meters while overheated, couldn't just stop it in the middle of the freeway at rush hour. As soon as I could, I got off the road, parked it and shut the engine off. I let it cool down while googling for help on my phone. I then walked to the closest burger joint, asked for water and received two large cups of it. After having the engine cool down for 20 minutes or so, I carefully opened the cap on the tank. I tried to see if there was any coolant left, and the expansion tank was almost empty. I then poured all of the water into the tank and nervously started the engine up again. The temperature didn't rise and I got to work without further problems (3 km or so).

While at work, I ordered a new coolant expansion tank. It will be available for pickup on thursday (I'm writing this on monday).
When it was time to leave work, I poured an extra half litre of clean water into the tank, and the car didn't overheat at all on the way home.

I know this topic has been discussed to death, but I have a few questions:

1. Is it ok to drive if I keep an eye on the temp gauge and top the tank off with water before I drive? No long trips, about 10 + 10 km.
2. Should I be worried about any damage the overheating could've caused today? I feel nothing strange driving it.
3. Is it plausible that the tank is the (only) cause of the overheating?
4. After replacing the tank, do I have to "flush" the whole system or will it suffice to just fill it with proper coolant/water mixture?
5. After replacing the tank and filling the system up with coolant, is it necessary to "bleed" any trapped air out?

When I parked my car at home just now, I kept it running for a minute while looking at the coolant tank area. I can see how the coolant (now mostly water, I guess) keeps leaking out little by little from the tank's seam.

I'm absolutely no mechanic, but from what I've seen (watched a bunch of videos on YouTube) replacing the tank isn't that difficult of a job. I should be alright with a wrench and pliers, right?

Thanks!

Bonus pic with explanations @ https://i.imgur.com/Osz8KAF.jpg

 

I had the same issue just a few months ago. You will want to take care of this as soon as possible.
1. Yes BUT make sure you keep the car moving to help keep the engine cool. Open your windows and turn on the heat to help keep the temps down. Water is not the best coolant.
2. You should be OK but will want to consider replacing all coolant.
3. Yes and No. The lost coolant will have contributed to overheating but if the coolant wasn't doing it's job, you may have had additional pressure that helped the tank seam fail.
4. Replace the tank, fill with the proper mixture then have it checked. A garage has equipment to determine the quality of the coolant and if it needs replacement. A coolant service is recommended ("flush" and replace).
5. No, the system will bleed itself using the coolant reservoir. Just check it after running the engine for a couple minutes and turning on the heat.
CORRECTION: See louie12345's comment below.

I had my tank replaced then had the coolant service done. It takes a while for the coolant smell to go away.

 

I would flush the system. I assume you used tap water to fill reservoir. Tap water has mineral that can build deposit inside you cooling system. Get the correct coolant and mix with distilled water (50/50). BMW water pump needs the correct coolant to lubricate.

 

Bleed the system per manual, there is a bleeder valve in the upper coolant hose.

 

I have coolant leak all over the place. You're lucky that it's from the reservoir,mine occurred at the flange connection between the engine block and water pump. If you can crawl under the car to inspect if there any drips from above that would be ideal.
To flush and refill,turn your heater all the way up at the lowest range,it might take at least 15mins for the coolant to flow in the system,then from the bleeding valve you will start to see coolant overflow which means air has been evacuated,close the bleeding valve as well as fill the coolant to the max level. Hope this help

 

Flush and bleed the system after you replace the expansion tank. Mix the MINI coolant 50 / 50 with distilled water for most areas, moarsecode in Finland so its cooler up there. Mix 60/40 , heavy with coolant.

Might take a couple times to bleed:

https://www.northamericanmotoring.co...endations.html




Coolant:


http://www.ecstuning.com/Search/SiteSearch/82140031133/

 

Thanks a lot for all the replies!

 

Welcome.

 

Be advised that there are two bleed screws; the obvious one up front, and one virtually impossible to find alongside the driver's end of the engine block, in the vicinity of the thermostat. Opens with an 8 mm socket, as I recall.

 

Update: Drove it to work today, no problems. Made sure the coolant temps didn't creep up over 99°C or so (Bluetooth OBDII adapter + Torque for Android). Also drove ~20km to get the new expansion tank and then back home.

Now I'm waiting for the engine to cool down enough for me to replace the tank. I decided to let "my" mechanic flush and check the whole system on monday, so I won't need to do the bleeding and whatnot.

Thanks again for all the pointers!

 

Good point, but you shouldn't have to mess with the back bleeder screw--just work the one in the hose flange next to the radiator and you'll purge all of the air.

 

Got the tank replaced after a bit of swearing.

I poured some coolant into it and let the engine idle for a while until the temperature was bouncing back from ~97°C a few times. I then took the car for a short spin, revving it up good and watching the temperature -- nothing special.

When I parked it I popped the hood and took a peek. There was some steam coming off from here and there around the tank, but I'm hoping it's just "old" water/coolant from before that sat on the heat shield etc.

Let's see what the mechanic says on monday.

 

Thanks for the update.