When I parked in the garage today I noticed the temp gauge was pegged with a trail of coolant behind the car. Why didn't the MINI beep or something?

I put the R53 into front-end service mode just to help diagnose where the issue is coming from. I noticed fluid by where the hose connects to the lower elbow on the radiator. I ripped the hose off, but didn't notice any cracking on the hose, and the elbow seems to be fine.

I would love some advice on how to proceed. I'm not sure if I should just replace the elbow and lower radiator hose and hope for the best? How concerned should I be about the temperature the engine reached?

Thank you!

 

Is is dripping down the hose from the water pump or block?

 

When I looked I didn't see anything dripping down the hose from the water pump or block. It was concentrated by the elbow.

 

The plastic radiators are notorious for failing. Before doing anything else, I would re-fill the system with water, then pressure test the system to specifically localize the leak. As for the effect of high temp on the engine, it all depends on how long and how hot. Keep in mind that it may not be the radiator or hoses but could be a bad head gasket that caused excess pressure to the cooling system.

 

Thank you for the reply. I'm doing some research now to figure out where best to get the tool to pressure test the system. I'll keep you posted.

 

So, I pressure tested the MINI and it had no leaks. Put in new coolant, flushed the system, and found out the thermostat was functioning just fine. The dummy temperature gauge was saying the temperature was fine, but I decided to bust out my computer to find out what was really going on. It turns out it was running at 105 degrees celsius. I read that the first stage fan kicks on at 96 degrees, but I didn't see it running. With my computer I found out that the ECU was trying to turn on the fan, but wasn't able to. After ripping apart the fan, I did find the bad resistor. I ordered a new one at pelican parts along with the foam surround for the radiator.

I'll be bleeding the system again with MINI coolant and testing once more. I'm not sure that the fan is the only problem, but it certainly was a problem.

 

So a quick update. I installed an external resistor and made sure that the fan kicked on for stage 1 (stage 2 works as well). It kicks in just fine now. However, it is still overheating. I am completely stumped now. The upper radiator hose fills up with pressure, and I can bleed it. Wouldn't that indicate that the thermostat as well as the water pump are fine? I'm not sure what else it could be at this point.

 

There are two places to bleed the system, one in the front by the radiator, left side of engine that is a large plastic screw that turns into a hose coupler. The other is by the T-stat.

A t-stat does have a very small by pass that will allow water passage. Talking a hole like 1/8" so it will not allow enough coolant through to properly cool but could pressurize the system. Also remember that coolant system is open to the engine in one direction and that heat can backup into the radiator thereby pressurizing the system as well. It could be the t-stat.

How many miles on the car and has the water pump been replaced??

 

It currently has 61,000 miles on it, and the previous owner had the water pump replaced at 38,000. The thermostat was replaced at 21,000. After my post last night I decided to bleed it again and monitor it closely. I could see the temp hit 106'ish, the fan kick in, and temps were brought back down. I saw this happen a couple of times. I think I might be doing ok

Bleeding the system sucks. You never quite know if you have all of the air out, and always wind up with a mess. It almost makes it a joy working on the cooling system in my Subaru Any good tricks with bleeding? I found that I had to keep the reservoir cap on, but the first time I bled I think I ran the expansion tank dry when the thermostat kicked in.

I'll be trying again tonight.

 

When the temp gets to between 190-195°F you should start to see coolant coming from the UPPER bleed screw. That indicates that the thermostat has opened - returning coolant to the radiator.

Another way to check a thermostat that is stuck closed, is after running the engine - if your lower radiator hose is cool to the touch, coolant has been blocked (by the stuck thermostat) from entering and circulating through the radiator. If the lower hose is hot, the thermostat is working properly.

A faulty expansion tank cap can also cause overheating.
I know, because mine failed recently.

The MINI's coolant system is designed to be under 15-16 psi of pressure, so if the cap (or the tank itself - due to a split in the seam) isn't holding that pressure in, the boiling point of the coolant drops exponentially. For every 1 psi of pressure, the boiling point of the coolant raises 2°F, so if you have a properly functioning cap holding 15psi, your boiling point raises to 242°F. With a leaking tank or bad cap, the boiling point is 212°F, which of course will lead to coolant boiling and engine overheating.

 

I have never had an issue bleeding the coolant system. First, I use a wet/dry vac to suck out the coolant through the refill tank. Take the bleed screw out in the coolant hose first. I can usually get everything but 4-5 ounces out. I then know how much to put back in.

When I refill, I use the top coolant hose by rotating to top the radiator out. I then rotate it back and connect it back to the coupler. I then use a funnel that I tape a straw into and fill through the bleed screw hole. I put more in and then put the rest in the refill tank.

Start the car up with the bleed screw out. Let the engine warm up until you see water start to circulate and when the water is getting high enough to start wicking the bottom of the bleed screw, put the screw in.

Remember to turn the heater on high while the engine is warming up.

 

Thank you for the guidance. Thankfully the thermostat seems to be acting fine since the lower bleed screw is bleeding. I ran the pressure test as my first diagnostic tool, and it kept pressure. I'll be driving it back and forth this week to work to make sure it holds coolant.

 

Thanks! Love the wet-vac idea. Keeping the bleed screw out as a visualization is a great idea, too.

 

I put some masking tape around the vacuum hose where it fits into the white filling tank. A good tight fit and removing the bleed screw makes it easing pulling the coolant out.

 

Just want to clarify - and I've edited my post - that I was referring to the UPPER bleed screw, as you'd only see coolant bleeding from that screw if the thermostat actually opened, thus allowing coolant to flow through the radiator.

If the thermostat isn't opening, there will be no flow through the radiator.

 

I've read both! But which is accurate does stage 1 fan kick in at 96° or 105° Celsius?? ?

 

Low speed (Stage1) fan comes on at 105°C (221°F).

 

Crap, forgot to update this post! After about two weeks or so I noticed a tiny bit of coolant leaking from the reservoir and a faint coolant smell when I parked it in the garage. At first I thought it was some coolant that I spilled but quickly learned the reservoir was bad. I replaced it with an aluminum one from Way Motor Works, and haven't had an issue since. Thanks again!