This morning my MCS got "boiling" mad. I was at a stop light in 90+ temp. It looked as though smoke was whisping out from under the hood. I popped the hood and saw the overflow tank was gushing around the lid. I got back in and started the car and the temp guage was normal, dead center where it always is. I drove the car a block or two and once again a boil over occured, temp gauge still reading normal. I let the car cool for an hour. The overflow tank coolant level was normal. I drove the car the rest of the day and it was fine, with the temp gauge normal as always.

A few years earlier I replaced the cracked coolant tank. This one isn't leaking at the defective seam where most original MINI's are known to leak.

Any suggestions? 2002MCS

 

My guess would be that your water pump is failing; have you ever overhauled your supercharger? How many miles on this car?

 

125K miles. Never touched the supercharger or water pump. I also thought it might be a pump but it worked perfect the rest of the day despite the 100 degree temp today. I thought perhaps the thermostat stuck for a brief period, but the temp gauge was always normal.

 

Ignore the temp gauge, it is designed to stay in the middle. Go buy a scan gauge two or an blue tooth OBD reader if you have an i-phone or android phone.

A water pump failing with the supercharger usually is accompanied by a very audible rattling sound. That sound being the gears that drive the pump starting to disintegrate. If you have that then the DRIVE is still okay for now.

I would wager bad thermostat. Easiest way is to pull it out and drop it in boiling water. It should open.

 

Is the gasket reusable?

 

Sort of. It's a rubber/polymer gasket, not paper, so it should be reusable. But given that it's likely 9 years old, probably worth getting a new one (unfortunately (or not) the gasket is only sold with the thermostat. If you have more time than money, you can try to R&R and test it. In the end, it's only $35 or so.

 

Is your low speed fan working? that could also cause the radiator and expansion tank to go wild. If it is not going on when you turn on AC you need to repair fan relay. Many threads on how to fix relay.

 

Not certain if its the low or high speed fan thats not working, however the fan does come on with the a/c. I think I have the issue narrowed down to the thermostat as it hit a high temp yesterday while on the interstate with the a/c on. I have been watching the temp gauge so I caught it the moment it indicated high temp which was right at an exit with a gas station. It took about 4 pints of water and ran cool on the return trip home.

This weekend I'll replace the thermostat. I'll also research the threads on checking and fixing the low speed fan.

Thanks again for the information.

 

You can access the instrument cluster to monitor coolant temp. On my '06 the procedure goes as follow...

1. Hold down the odometer trip reset button while turning the ignition key till "Test" lights up on the LCD screen. (Don't start the engine)

2. Press (repeatedly) the odo trip reset button till you've reached "Test 19". The options will alternate between On and Off. At Off, press the odo rest button again. This unlocks the other tests.

3. "Test 0" appears. Press repeatedly the odo trip reset button till you get to "Test 7". The LCD will display the current/live coolant temp in Celsius.

4. You can start the engine and drive in this mode.

I've been monitoring the coolant temp because I thought my Fan Speed 1 is dead... but it isn't! Normal operating temp should be around 88-92*C. Most of the time, mine sits at 89-91*C. If you sit in traffic or let the engine idle for test purpose, the temp will rise to 105*C and the ECU should activate Fan Speed 1. At 101*C it should turn off. In mild ambient temps (70-82*F), the coolant operating temp should be very stable in light traffic driving. If it's not, the thermostat is the culprit.

 

Thanks for the tip on how to read the coolant temp. I'll try that on my '02. What else will the test read?

I have a new thermostat with gasket on order as well as a new oil pan gasket. Looks like the 4th of July will be non-stop fun.

 

Here you go...

https://www.northamericanmotoring.co...924-post5.html

 

Hi guys, I have the same problem too....
my car is about 7 years old now with pretty low millage (45 000), i cannot stand still with it, it goes boiling crazy. When driving no problem, when I stop a light it starts boiling.... I thought bad fan... so I got a new one fom mini... problem still there.
I saw your post here, replace the thermostat this morning... problem STILL there!!
Any other suggestions PLEASE....I'm lost...

 

Is the seam on your overflow tank cracked? Mine cracked a few years ago, I replaced it as many had to do. If its not holding pressure it will boil over prematurely.

 

I forgot to mention I changed the overflow tank for a new aluminum one too.... but tank cap is old one... could this be the problem?

 

The cap would make sense. Do you know the coolant temp when it boils? High fan doesn't kick in until 234 degrees, which is way above boiling if not pressurized. Even the low fan doesn't go until 221.

 

It starts leaking at 210, fan kicks in when 221 and stop at 195 on my recent tries.

Eric, What do you mean, if I get new cap and pressure goes up... boiling point is higher? could this be that simple?... I just spent $500+ for parts... and my solution might be a $10 cap...?

oups... just reminds me my physic's class.... PV=NRT... huh.... I'll give it a try tomorow....

 

Some Guy,
Can you provide a source for this? Also, are there any threads on here that deal with installing the peripherals (the water temp sending unit)? I'm just curious how much is involved with adding this to my R53...

Any info/help will be appreciated...

 

No peripherals, anitan1 - that's the beauty of OBDII. While the 'gauges' are analog idiot gauges, the OBDII computer knows the true temperature via an OEM water temp sender. Installation is as simple as plugging into the OBDII port on the lower left driver's side. Scangauge works well, and the Ultragauge (though that one appears to have possible issues.) Not sure about bluetooth options.

 

JHrea, Stuck fan relay?

Aam having a similar problem, has not gone into boil over mode though.

I believe for my car it is either bad relay and or the low speed fan resistor failed.

 

Little update on my car... went to dealer this morning anf bought a new overflow tank cap... IT VOILA... IT WORKS!!!

 

Gotta love when the simple stuff works. Love it more when it works first!

My Scooby is still sporting a 'new' made-in-mexico rad cap . Which the shop put on just before it replaced the head gasket...
Glad to hear your MINI doesn't blow anymore.

 

PLX Kiwi plugs into your OBD II port and talks to your smartphone via Bluetooth.

http://www.plxkiwi.com/