My R53 is continuously overheating at stop lights. I believe both fan speeds are functional. I'm not sure what the cause is. I don't know if the water pump is failing or possibly the thermostat?

I have to top off the coolant about once a week. When its full of coolant, it still can overheat, but it takes way longer, usually not a stop light, but like idling in a parking lot. Usually it's not a great deal of coolant, about 1 quart. I open the bleeders and stop filling when I can't hear air and coolant flows.

I looked briefly underneath and prolongedly from above the engine. I can't seem to pinpoint where coolant loss is occurring without pulling the bumper, it looks pretty dry until overheats. When the car overheats, the pressure cap releases spews of boiling coolant- it's possible that this is the only place I lose coolant. Sometimes when it overheats, the radiator is cold, most times it's hot.

I bought a water pump to have on hand and was thinking of replacing it as good measure.

Is there a way to tell if the pump has failed aside from the overheating? Is there a way to know if its actually the thermostat not opening causing the problem? I've read that you can squeeze the rad hose and feel it surge back at you. I squeezed it pretty hard while it was running, but it felt the same squeezing it when it was off too (pretty firm, but not sure if it was "surging" back at me).

When this all began I replaced the reservoir. The OEM replacement split two days later. I have since replaced it again with a metal one.

 

Without seeing the car and going through all the diag this will be hard. But you said the rad has been cold and the car overheated. That would indicate that either there was air in the system and the coolant isn't flowing, or the water pump isn't flowing, or thermostat is stuck or some other blockage. The supercharger could be broke not turning the water pump which is worse case on that. But if you have over heated it more than once cylinder head damage like warping or cracking could also cause it to continue to overheat. Have a MINI mechanic take a look at it and see as that will be much cheaper than throwing several parts at it to figure it out. As it could be as simple as an air pocket, or as worse as a back supercharger and cracked head.

 

Thank you for your reply.

I should note, that most of the times the car "overheats" the radiator is hot not cold. There was a couple of times it was cool, that may have been due to low coolant.

When I say overheat, the red light has come on about twice. The other dozen or so times the car has gotten hot, but the light hasn't come on... the pressure cap blows, steam pours out through the hood, then the temp starts climbing but doesn't reach high enough to trigger the light. Whenever that happens I pull over for twenty minutes and cool down.

Now of course when you say broken supercharger, and head gasket warpage, I could definitely have a heart attack (I'm already underwater on a loan for this thing). But, there has been no issue with power, the supercharger whines and the launches the car just fine and there's no milkshake in the oil or steam in the exhaust. So, I think I am okay- even if it's borrowed time.

I plan to put the car in "service mode" just to see if there's a hose leak or something. But I didn't know if the water pumps on these cars weep when they are failing. And I have no clue how to tell if a water pump is not spinning.

I am not familiar with any MINI mechanics in my area (Portland, ME). I tried a couple of the popular ones suggested, back when I wanted my tranny flushed, but the guys who answered the phone sounded sort of clueless about how to go about doing that so I wasn't quite feeling them. But either way, yes, I'd like to be able to go to a mechanic- I'm just afraid of labor costs for even diagnosing it, considering the bumper has to come off for almost everything. I know MINI's are high maintenance, I sort of turned a blind eye when my wife said she wanted one, so I am a bit over my head here- I know.

 

Weather has been cooler and I haven't overheated once in past week. If it stays this way I may delay addressing this issue until next spring. So that brings me to this simple question.

Is there any likelihood the pressure cap is shot? I was wondering if maybe the previous boil overs were due to the cracking plastic coolant reservoirs and perhaps these weakened the cap? The cap was replaced new with the last plastic reservoir and suffered about 10 boil overs.

 

I'd still find out why it's overheating. I'm always baffled at why people drive cars when they know something is really wrong that can cause expensive damage

 

I have to drive it to get to work. I'm even less likely to be able to fix it without a job!

 

It why a $35 thermostat swap turns into a $8500 motor....
To the op...
You have to start someplace.....and when you have the thermostat out...you can see if the water pump is running....
If the coolant went low, and you had to add coolant....it might just need a simple bleed...but a mini does not self bleed....that is why there are 2 bleed valves...
But DO SOMETHING ...
You fear of a $200 diagnosis fee might have already cost you a motor!!

 

I've come to the conclusion that's it only overheating when the coolant drops and an air bubble gets in.

I looked underneath car today while on ramps. Coolant seems to be originating from the front right region. I tried to peer up inside, it looks like the two hoses that are visible have coolant running down their length. I can't see they connect to, so I cant see a leak directly - are these heater hoses? They are maybe 1 inch OD.

I'm going to do the service mode, bumper removal to try and pinpoint leak. If I fail from that point, I'll be seeking a professional- only mini independent near Portland seems to be in Freeport?

 

I had a VERY similar problem when I first purchased my mini. Unfortunately it was the water pump. I was not able to see any coolant leaking either. If I were you I would change the thermostat and the thermostat housing which is another common thing to let go in mini's it's also relatively easy to fix and it's cheap-ish. If that doesn't fix the issue I would say it's definitely the water pump, the part isn't too expensive but it's very labor intensive :( but like others said fix it ASAP if coolant isn't mixing with the oil you're lucky but it could be on borrowed time...

 

Thank you for your reply!

May I ask if you mean you couldn't see where the coolant was leaking from or there wasn't a leak visible? My Mini is very wet underneath now. The coolant seems to be accumulating quite quickly into the bottom of the engine region- originating from that corner.

I have a water pump on hand, perhaps Ill order a thermostat and replace as preventative.

 

No problem! And basically I would park my mini in a garage and saw 0 fluid on the ground the only place I noticed any coolant was on the water pump hose but not much... I think the coolant was hitting some sort of hot component and evaporating but it can't hurt to do the thermostat housing, I would rather do that any day of the week than that damn water pump

 

You may also want to check out the coolant reservoir I know they are prone to getting small cracks! Can't hurt and could be a really cheap fix! 👍

 

Thermostat is an hour or so. Water pump is a day (have to remove the SC, no?)
Start with the easy stuff.
To me the big red flag is that the coolant is going *somewhere*. If you're seeing it on the hoses, that's a good thing (well, better than going into the combustion chambers.)
If you see no evidence at the thermostat (and there WILL be evidence) at the least you'll get a better look at the coolant hoses. Best case scenario, it's just leaking from one of the connections.
I definitely wouldn't let it be until Spring. The only thing worse than a broken car is a broken car covered in ice!

 

So, the MINI was out of commission for a week while it was up on jack stands in my garage.


With the help of this forum, Girl's Guide, Mod MINI on Youtube, and Pelican Parts Write-ups, I was able to get the confidence to tear the face off the MINI and address this overheating issue.

Turns out the gasket on the water pump had failed, and coolant was gushing forth, and going down the block. The supercharger was sucking some in, and it was also mixing with an oil leak from a failed o-ring on the CPS. Everything was was R&R'd.

But it turns out I was wrong, I don't seem to have a low speed fan, so the resistor must have failed. I found the 3-prong connector in the engine bay, which is connected to a harness with two wires. I spliced the two positive wires together on the 3-wire side, hoping that the fan would just run on high all the time until I can get a resistor. This didn't work? It still seems to only run the High Speed mode just before it gets WAY too hot again. Did I jumper it incorrectly for this purpose, or does this mean a relay is dead?

I really don't understand how it's wired. How does the car send the relay signal to that harness to differentiate between the two fan speed stages?