Looks like it. If he behaves himself, fine.

Is BC back?

I had forgot about that heater thing.. never use in the sunny south..  buy proper thermostat .. the ones from Advance . Auto Zone.  are POS. and most times will NOT even open... use 165F.. PHD
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watch tv series

I also think there's something wonky with this post. It's disappeared and then returned to the forum several times (in my feed)???

One day its there ...and the next day its gone ...then....

Cheers, Ian

"......and temp sensor/fan switch from our host......"

Interesting new piece of data..... First mention (or did I miss it) of an electric fan??

I assumed from earlier comments that it has an engine driven fan??? If it has an electric fan only, it will overheat if the fan doesn't switch on when the engine temp demands it (ie defective fan switch). Several incidents have convinced me that if the fan belt breaks or the fan comes apart (don't ask) the flow of air caused by the car moving forward is not sufficient to cool it.

Cheers, Ian

I can't seem to view any of the later posts in this thread.

I'm only posting to see if it helps.  

Weird.

I cleaned out the overflow tank and reinstalled it. I topped it off to the proper level and let it sit for a few days. When I checked the level, it was right where it belongs. I just got back from a thirty mile jaunt and all went fine. I'll go back and check it again later this evening. I did however order a new radiator and temp sensor/fan switch from our host. I am also going to get the cooling system flushed out when the radiator is done. Thank you all for the good advice you have shared. I'll keep you posted as things progress. Take care. Mark

"...Easy - You could revert to a sealed cooling system same as earlier model minis by simply changing the radiator cap. This way coolant will only exit the radiator if it's been over filled making the expansion tank redundant.

Easiest way to identify a sealed system cap is it only has one seal on the foot of the sprung part whereas your recovery cap has a seal on foot and also where cap seals against rad filler neck...."

"...... Could I have added too much coolant to the system with it having nowhere to go but out the vent on top of the tank? The color of the coolant was pretty disgusting and very rusty. I then decided I was time for a new radiator and cooling system flush...."

Reverting to a sealed (non-recovery) cooling system is probably a retrograde step .... pretty much all modern cars have a coolant recovery system.

I would suggest you need to do a good reverse pressure flush of the block first. Then make sure the rad cap allows the necessary reverse syphon as the system cools (get a reputable brand from any auto shop ... nothing specifically Mini needed). And, finally, make sure the overflow hose reaches the bottom of the overflow tank (very important).... which should only be about a quarter full (but well above the bottom end of the overflow hose) when the system is cold.

Your problems are most likely related to a build-up of crud in the block which causes localised boiling. The resultant steam is then forcing water out of the system. Without that the water doesn't expand very much. If you overfill the system it will vent once. The extra water is pushed out and the correct amount remains (as long as localised overheating is not pushing it out).

A good clean out of the rad by a reputable auto cooling shop is a much better bet than a new cheap Chinese alloy rad. Better in both performance and $$$$.

BTD (all:)T

Cheers, Ian

I would bet dollars to donuts he's got a small leak.

Easy - You could revert to a sealed cooling system same as earlier model minis by simply changing the radiator cap. This way coolant will only exit the radiator if it's been over filled making the expansion tank redundant.

Easiest way to identify a sealed system cap is it only has one seal on the foot of the sprung part whereas your recovery cap has a seal on foot and also where cap seals against rad filler neck.

Are you using pre-mixed Prestone style "Coolant" or water ?

If you're using 50/50 'coolant' then you've created the problem by reducing the heat transfer ability of your cooling system - water is a far better means to transfer heat than the rubbish pre-mix designed for modern cars...

Run water with about 10% blue glycol for anti-corrosion and you'll probably be okay.

A friend of this message board, who does not currently have a login, sent me his experienced suggestions:

"my guess. the themomstat is stuck or has air bubble  in  line..  tell him to take thermostat  and drill six Small holes in it. so water will still flow..  ( do NOT take the thermostat totally out. as water will flow to quick..  then just heater one full blast..   last resort.. need to just replace water pump."

and later...
"also.. might tell him to buy proper alloy rad off ebay from Winning Spares from China.  4 core.about $125 with free shipping. I use Only alloy rads in all my minis and mokes..  ps. I have proper OZ moke and steel wagon for sale."


I can add: check the temperature sensor controlling the electric fan is functioning properly.

Yes you are probably overfilling it. See my previous post. The rad should not be completely full, but should have enough coolant to cover the tops of the tubes by about an inch, leaving an equal amount of air space. The overflow hose to the catch tank should extend to near the bottom so when it cools and siphons, it pulls fluid, not air. Add coolant to the rad, not the catch tank

It all started again when I decided to attend a cruise in event in a nearby town. I got out on the highway and after a little while the temp gauge began to rise. It was steaming from under the hood and spewing some coolant so I pulled off the road and let it cool down until the tow truck arrived. When I got back home I looked it over and found the electric fan wire was disconnected from it's terminal on the bottom of the radiator. I put it back on and it felt loose so I put a new connector on and it fit much better. I then topped the coolant and let it settle for a while. I drove it on several short trips and it was good. I checked it again and it was a little low so I topped it off. I then took it to a show about 45 miles away and everything went fine. I thought it was all good until I went to another show a week later and it overheated again. I let it cool off and drove it back home slowly as I wasn't far this time and it went better than expected. At that point I decided to remove the overflow tank to check it out. It was full of coolant and then found where it was leaking from. Could I have added too much coolant to the system with it having nowhere to go but out the vent on top of the tank? The color of the coolant was pretty disgusting and very rusty. I then decided I was time for a new radiator and cooling system flush.

I agree that an overflow tank should be able to vent to the atmosphere and not be pressurized. When working properly with, the coolant expands and with any excess pressure to the rad cap, it allows the air in the top of the rad (there should be some, like a car without an overflow tank) and then coolant escape to the overflow tank. When it cools down, the reduced pressure in the cooling system allows atmospheric pressure in the tank to push the coolant and some air back into the rad.

On some other cars, where there is a pressurized coolant tank, the rad should be full and the tank filled to the specified mark, to allow for coolant expansion. In this configuration, the pressure limiting "rad cap" is on the expansion tank and the rad, if it has a neck, gets a blank cap. It may or may not have an overflow tank as well.

Did you test the new thermostat when you swapped out the old? Did you buy a new 15lb  Rad cap?

So top of tank shouldn't be water tight should it ?  Tank shouldn't fill all the way up and/or be pressurized?  Suggests it is overheating and the tank filling and over flowing is a symptom and not the cause.  
I chased this rabbit down the hole on my mini.  In round one I flushed the cooling system full of black gunk multiple times. Better but still running hot.   In round two, I replaced the leaking water pump. I installed the fan blade correctly (it came installed wrong). I replaced the hoses and I replaced the radiator with an aluminum two core.  That worked too well- guess now is that the stat is stuck open....;-) but I don't need heat when the 'feels like' is over 100f every day.;-)  
So can you/ have you flushed the system? Oily? Black gunk?  (Prestone 'kit' at O'reilly) Next I would check the stat you installed. Defective new parts seem common these days. May wish to remove and run without it to see. (not long term but just long enough to rule it out)  You said you did the water pump.    Check fan belt - if it is slipping water pump ain't pumping. (I know obvious) Then it is hoses and radiator-Check that radiator is clean externally - not degraded with fan belt foo foo and dirt.  If still a problem then move to radiator- have it dipped or as I did just replace it.  Good Luck
Kim     

Well, my overheating problem has returned. This time I tracked it down to the coolant overflow tank that's mounted up inside the fender. I was getting a steady drip as the car sat. I removed the tank and found the leak. It has a pop-riveted bracket on the top with two pop rivets. I put water in the tank, tipped it upside down, and found the water was running out rather freely from those two rivets. A new tank will set me back about $150. Looking for suggestions to repair the existing one without shelling out that much money. Any suggestions would be appreciated. Thanks.

https://drive.google.com/file/d/1V_82CedEHZ4AQ1vml3sf0XecJgfsmcot/view?usp=sharing

URL: https://drive.google.com/file/d/1V_82CedEHZ4AQ1vml3sf0XecJgfsmcot/view?usp=sharing

Mark congrats..  enjoy your mini.  but me thinks you need to do some TLC to make a daily driver.  Cheers PHD>

It's been a week now and everything seems fine. There has been no overheating and the car even runs better and pulls strong. The weather here has been great so I've been driving the car whenever I can. It sure feels good to be driving a Mini again. Thanks again for all of your help. Mark