Hi All. I've got an 06 R53. I've developed overheating issues that I can't figure out. I'm able to cruise at 60mph, no issues. but as soon as I floor it, the temp starts to climb above 220. Or, when I'm on the interstate with the cruise set at 70 MPH, the same thing happens. Here's the strange thing, I can flip my heat to max, and the temp will start dropping almost Everytime. IfIIf imruI'm running on the highway with the heat on, the car will overheat but it takes a lot more for it to overheat. Sometimes, I can drive the car 45 mins without an issue. I run scangauge and have it set to show me my coolant temps. I assumed this was the thermostat and replaced it (I wish I'd tested the old one). This did not fix the issue. I have an aluminum coolant tank and have had it installed for years without any issues but read where they can cause issues so I replaced it with the OEM Tank and Cap. I still have an issue. I felt that maybe exhaust gases are entering my cooling system so I performed a block test and did not show any issues (fluid remained blue). Here's my question, I've got 177,000 miles on the car and have owned it since it had 28k. Is it possible my supercharger is on its way out and maybe the water pump gears are partially stripped? The last time I changed the fluid, which was at 125k, i replaced the water pump just because I felt I may as well since there was overlapping labor.

Any ideas? No abnormal noise observed from the SC, I'm bleeding the system using the two bleeding ports....I'm at a loss here. No chocolate milk in the oil and no smoke coming from exhaust so I don't feel it is a head gasket. TIA

 

So, that's not strange with that turning the heat on helps the situation. That's standard operating procedure if you have a car that's over heating, because it helps pull heat away from the engine. Does it over heat faster in city driving/stop and go traffic? I'm kind of thinking that the fan might not be working, but it seems like at highway speeds that wouldn't cause it to over heat. Are you losing coolant at all?

 

Okay, I figured it was standard as I've learned this behavior from something I've owned in the past. No, the car does not overheat in city driving unless I start to kick the RPMs up (over 4k sustained outside of normal shifting). My fan is definitely coming on as I can hear it. When I flip the A/C on, the low speed runs or if it is really hit out, the high speed will run.

 

To answer the question about coolant loss. I am losing it out of the Cap once iII overheat. IfI that I have air in the system still but I've bled this countless times over the last few months. I have two other MINIs so I don't have to depend on this car but I would like to have it running properly.

 

In my opinion, those are the classic symptoms of a blocked radiator.
Try adding a generous dose of dish-washer powder for a few days, followed by a good pressure flush.
Be sure you get the air bubbles out when you refill it - MINIs are difficult.
If you consider a new radiator, my understanding is that those beginning with F are not that great.

 

I will try this. I've replaced the radiator a couple years ago but I will certainly try this. Thank you.

 

If the radiator is that new, it's unlikely to be blocked. Is it possible that two different anti-freeze fluids have been mixed? They can react to form a gel-like substance. Perhaps the dishwasher powder & a good flush will help.
But I think at this point I'd look at the water pump & thermostat.

 

This is one of 3 MINIS I have and I've got a ton of Coolant from MINI that I use (at the end of MTTTS 2016,they gave away all the spare coolant and oil they had carried on the support trucks and I walked away with quite a bit. Mixing wasn't an issue. The t-stat will come out next but I did replace this once already and am exhibiting the same issue.

 

What procedure did u use to bleed?

there are two bleed screws...

Sounds like air in system to my basic understanding

 

I know it does as I feel the same way. Here are the procedures I've used:

Cap off and bleed screws open, I fill the system and let the engine run with heat on high(fan low). Once I see coolant coming out of of the bleeders, I close and repeat once engine comes up to temp.

 

once u have fluid only from lower screw, close and keep closed.

focus on top bleed screw...until just water is coming from there, close and keep closed.

focus on fill tank, keep filling as it goes down...check for a few days as you drive it

that worked for me. Attached the Bentley notes

 

 

It really grinds my gears how zee Germans are always associated with "precision engineering" yet manage to screw up the simplest of things.

BMW coolant systems are notoriously crap but they haven't got the hint and continue with their poorly designed systems.

My Swedish engineered Saab was vastly superior to this German Scheisse.

When I first used the bleed screw on my R53 I both LOL'd and cried because it's such a painfully lousy design,
geez, talk about low effort. Splatters out everywhere and is just stupid.

I ended up modifying mine to have a proper bleeder and it makes life much easier.



Their choice of supplier is also laughable, from low quality castings from eastern Europe to just about everything else - factory coolant cap is another shiddy design and even brand new can be inoperative as GTT shows here and what I've personally experienced as well.

http://www.gtt.uk.com/gtts-cool-guid...ooling-system/



I ran a Volvo cap for a while which is a much better design but it's rated around 21 psi and I got paranoid about overpressurizing the system.



Worked well though as far as doing the job and never had any overflow splatter on my coolant tank.

 

All - I've re-read all the posts!
The radiator, expansion tank, thermostat & water pump are all fairly new; the head gasket is OK, so there aren't any obvious options left.
So, my thoughts - try an expansion tank cap off one of your other MINIs.
If you bleed it again, make sure the tank level doesn't drop so low as to let more air in - but don't over-fill it when you're done.
Is it possible that one of the many (older?) coolant hoses are being sucked flat at high RPMs & restricting flow? This seems illogical in a pressurized system & tricky to find, but is it possible? I saw it on a Renault4 some years back.
Unlikely, but could the water pump be 'cavitating'?
Just a note that the heater matrix is always hot in a MINI - the controls direct air through it (hot) or around it (cool) so I don't know why BMW wants it turned on while bleeding.
I'll be interested to hear the solution, as will others.
Speedwell - if you attach a vertical clear plastic tube to your modified bleeder, would it make any difference?

 

Thanks for re-reading the posts and pointing this out. Everything tells me it is either T-stat or air in the system and I'm boggled because I've bled the system before on my car and friends with great success as much of a PITA they can be.

You asked if I could use another cap. I cannot because my R52 is naturally Aspirated and my other MINI is a 3rd Gen. When I replaced my tank most recently, I did replace the cap as well. Something you said made me think....Is the water pump impeller shot and causing cavitation? This has crossed my mind. You do have an interesting theory on the hoses collapsing too. I think I will check this as well.

This week is a busy week working but I'll update the post on what I've done and what results I have. Thanks

 

​​​​​​Interesting modifications and I like it. Does the Volvo cap fit directly to the tank? I don't know that I want to go this route as I know that the system does function as it should. I Doo 300 miles a day, Baltimore/DC traffic and open roads, both of my Gen 1s have held up until now. The parts that I have replaced in the past was not because of part failure as much as it was something else that caused it or replacing out if precaution. With that said, I do get what you're saying with the quality and the cooling systems in general when it comes to BMW.

 

I agree, I have a S80 2.4T and I can verify this. I replaced it because the yellow looks ugly, was still the original factory fitted item with 200.000 miles on the clock.

 

So I'm not sure how helpful this is, but it sounds to me like your coolant is not circulating, or is not circulating well. I'm not sure if that's because you have a blockage in your system, a hose collapsing (unlikely) or there's a problem with your pump (or possibly supercharger)

 

A few days late, so you may have solved it, but +1 on this still sounds like air in the system. Just to be clear, you’re bleeding and bleeding coolant from the front valve until there are absolutely no air bubbles left, right? (Not just “until coolant comes out” like stated above).

When I bleed mine I probably end up emptying over a pint or more through the bleed valve until I get all the air out. I’ve found it also helps to close the valve, squeeze the top water hose with the system closed to force coolant (and any trapped bubbles) around a bit. You can see it forcing the expansion tank level to rise and fall. Then bleed it a little more. It sounds stupid, because it is. But it matches the stupid design of the system so..


A simple way to assess flow without pulling your water pump is to shine a flashlight into the (closed) expansion tank once the engine is up to temp. At idle, you should have a continuous stream coming from the thermostat return hose. Usually mine shoots across the top of the tank. If it’s intermittent, dribbling, or absent, you may have a blockage or pump impeller problem.

Another way I’ve checked flow through the radiator specifically, is to reach up from under the car and feel the radiator to thermostat water hose (bottom right, backside). At idle, It should be warm to hot when the engine is up to temp and coolant is flowing. If the top radiator hose is scorching and the bottom hose is cool or luke-warm, that can also be a sign coolant isn’t flowing across the radiator as it should.

good luck!