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Solving MINI Cooling Problems..........

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  • Solving MINI Cooling Problems..........

    Coolant should be replaced every 4 years on a MINI?

    'Jasper Oxford' on MINI2 (link below) recommends more often than that, say once a year:

    The cooling system on these engines is not particularly reliable. They have a reputation for boiling up.

    I have an 01 Cooper which is about to have a new head. After a great deal of time looking at the MINI cooling system, I concluded it can indeed fail where others would be tolerant. This gen MINI uses a Chrysler PT cruiser 1.6 engine, basically. It's ok in that car, but in the MINI it's a lot of engine crammed into a small box. If the cooling system starts playing-up, it'll quickly overheat.

    Usual causes:

    Air locks in top of head......this engine is inclined rearwards, heater matrix take off is at lower section of head. Hence air must be bled out via the thermostat's bleed valve, but here's the crunch....this valve can, and often does close while there is still air in the head.

    Coolant properties 'worn out', causing the coolant to boil at a lower temperature, i.e. liberate gases...which are not necessarily expelled through the stat's bleed valve......hot spots = more gases trapped, etc. Coolant in these engines must not be allowed to 'bubble', since the system will not always bleed by itself. Degraded coolant WILL begin to gas-out in a really hot engine, ignore BMW's 4 year advice........change it once a year 50-50 mix.

    I have followed an old remedy with my 01 Cooper: it has a thermostat with a hole in. At one time people used to drill a small hole in the stat, not large enough to over cool, but just large enough to make sure there is always some flow past the stat.........doing this on the MINI means it bleeds itself, works perfectly.

    However, the MINI's stat has a (unreliable) bleed valve, or jiggle pin.....you simply get a pair of cutters & castrate the thing, leaving a hole which will be about 3mm, this is ok in hot climates, but in the UK it should be about 1.5 - 2mm. I have a 2mm reducer on mine.

    Jiggle pins only really work properly when the stat is mounted vertically, which on a MINI the are'nt. Horizontal stats really require a slight but constant bleed, otherwise their bleed pins can slam shut while there is still air in the system.

    Check also the stage 1 cooling fan dropper resistor hasn't gone open circuit, if it has, you won't get stage 1 fan cool down....and it'll boil up without it. Stage 2 i.e. full fan speed I've never seen come on, and I don't know anyone that has either. I can only assume stage 2 is to stop it bursting into flames. The stage 1 dropper resistors are notoriosly weak.

    That's esentially why so many of these MINI's go down with head gasket failure. In any case, if you boiled it, chances are you've done the head gasket too. Hope action was taken quick enough so you don't have a warped head.

    ('Snip' the jiggle pin.....a constant bleed hole stops this happening again.)

    More tips for early MINI overheating problems:

    First, establish that the water pump is circulating coolant....if the interior heater is working this indicates the water pump is working. I don't think you need to pay further attention to the pump at this point.

    Filling & bleeding.....check you're not running the engine on low coolant.

    Now an important point:........the temperature gauge on some Coopers (mine included) is controlled by the ECU...and does not necessarily tell you when the engine is overheating. When the engine is started from cold the ECU will push the gauge up in unison with the coolant temp, HOWEVER!.....when the gauge reaches 'N' or midway the ECU holds the gauge at that reading REGARDLESS OF ENGINE TEMP. It is what's commonly referred to as a phoney gauge. Lot's of cars these days have such gauges, some new cars don't have a gauge at all.

    BMW's philosophy is, basically: "we don't want the owner to know how hot the engine is, we'll decide what is normal".

    Now, you have obviously done some testing of the radiator fan circuits. You say the engine reaches boil without there being any stage1 fan operation. You also say you are unable to jumper a stage 1 fan. I think you are on the right track....you must now suspect the voltage dropper resistor as having gone open circuit, i.e. 'burned out'

    There are actually two components to this, a large dropper resistor, and a smaller thermistor in series with it. These components are located within the plastic fan mounting assembly.......they are accessible but you have to remove the radiator to get at them.

    The dropper resistor has a resistance of about 0.5 ohm. It's wattage is generally reckoned to be underrated, they frequently burn out. There's also an issue with it's electrical connections.....it isn't soldered in place, it's 'tack welded'....the welds corrode & go open circuit.

    You have to consider: you've got no stage 1. The engine boils but only if you turn the heater off. The water pump is ok and doing it's job.

    Loss of stage 1 fan is the culprit. (even if the thermostat were stuck closed, stage 1 will still cut in).

    You'll need to replace the radiator fan assembly, resistors are'nt sold separately. I suggest you remove the assembly, gain access to the resistor & check it. My money is on you finding an open circuit resistor.

    I had the same problem on mine, but refused to pay BMW money for a weak replacement so I made my own resistor & wired that in.

    and more tips including the importence of using the correct coolant/antifreeze:

    Ok, if the A/C calls for, and initiates rad fan, that would indeed suggest 'some' cooling fan function.........but be careful to ensure this is actually stage 1 fan you are getting, and not stage 2.

    Sounds like you have a can 'o worms problem.

    The thing about these engines is they can throw so many 'red herrings' at you for the simplest of faults.

    I believe you would be wise to methodically remove and inspect the systems associated with the fault.

    1) Go over the wiring harnesses, paying particular attention to the connectors. start at the fan connector and work your way back as far as possible. Make sure all the connectors are good.

    2) Check relays.......this is important!.....the aircon probably on your model uses it's own separate relay to switch in stage 1 fan, which might account for why aircon puts the fan on. The ECU signal for stage 1 fan will go via it's own dedicated relay.....this could be duff, which might be why engine temp doesn't switch the fan on, but aircon does. You need to make sure these relays are good, purely as a matter of procedure if nothing else.

    3) Make absolutely sure for certain the fan voltage dropper resistor circuit is ok. Do not 'assume' that aircon is giving you stage 1, it might be giving you stage 2 full speed....which bypasses the resistor entirely.

    4) Is your water pump working?......run the engine, verify hot air comes out of the internal blower....if it's cold......the water pump is knackered. If it's hot, the water pump is circulating coolant and is probably ok.

    5) Are you sure the thermostat is opening?....for the sake of 20 bucks do this test: get a new thermostat....take a reasonably heavy pair of cutters and crop out the jiggle valve (the wiggly little pin) just leaving a hole. Fit that thermostat. Refill and run the engine. The cylinder head will now bleed itself, and continue to do so. IF everything else is ok and is verified......your engine will not have trapped gas pockets and shouldn't boil over.

    6) Coolant system pressure cap, which on an 'S' I believe is on the expansion tank.....if this cap is opening too early because it's worn out, you'll get boil over, simply because the coolant is not being held at a high enough pressure and will therefore liberate gas at a lower temp....leading to gas pockets in the head and subsequent hot spots which liberate more gas, and so it goes. The pressure cap is often overlooked, but actually is a vitally important component.

    Note: the three vitally important things you MUST FIRST verify are; water pump, thermostat, and radiator fan electrical circuits which includes coolant temp sensor.

    I assume you are filling with a 50/50 antifreeze - water mix, and not just plain water?

    Do not ever under any circumstances fill with plain water......trust me plain water in these engines WILL BOIL.

    You are trying to fix one of the most cantankerous engines ever put into something that bears the MINI name.......it is going to fight you every step of the way...rise above it, at least keep yourself cool even if the engine doesn't.....being methodical and not rushing is what will beat this.

    http://www.mini2.com/forum/first-gen...ml#post3767761

    http://www.mini2.com/forum/first-gen...-boils-up.html





    Bleeding cooling system:
    http://www.mini2.com/forum/maintenan...ml#post3794294

    http://www.mini2.com/forum/maintenan...screw-plz.html

    http://www.mini2.com/forum/first-gen...-radiator.html

    DIY: How to change the coolant
    http://www.mini2.com/forum/first-gen...e-coolant.html

    http://www.pelicanparts.com/techarti...ant_Change.htm


    Bleed Valve locations:
    http://www.mini2.com/forum/maintenan...screw-plz.html
    Last edited by mab01; 06-05-14, 10:54 PM.

  • #2
    R53 Cooper S - Supercharger
    A thing also worth checking if your MCS is having overheating problems is the supercharger water pump drive gears.
    When they start to wear they don't drive the water pump properly this will cause overheating due to bad flow rates, and it's quite a hard fault to detect.

    R53 MCS Water Pump:
    "In the case of the R53 MINI Cooper S, the water pump is driven off the end of the supercharger. This setup is a bit different than most cars (and R50 One/Cooper) where the water pump is driven off the engine belts. When a water pump begins to fail, you’ll notice that the car tends to overheat at low engine speed, such as sitting at a stoplight. When you accelerate, the engine temperature will drop. Now, this is not always indicative of a water pump, but a good starting point. You may also want to try squeezing the top radiator hose with the engine warmed up and running. You should feel pressure build up on the back of the hose and surge once it is released. If you feel no pressure, it’s a fair bet that the water pump is failing."
    Pelican Technical Article: MINI Cooper - R53 Water Pump Replacement

    Pressure Cap
    2001 Mini One - we bought for my daughter. First afternoon of using it after collecting it from the dealer got home to hear the water 'boiling' in the header tank and immediately thought the worst - head gasket.
    The Mini One/Cooper doesn't have a pressurised header tank (unlike Cooper S), the pressure cap is on the engine fill point, looking at the pressure cap there was evidence of coolant leakage so I suspected this might be the cause, the cap releases the pressure so the water boils. When I took the cap off the seal was in pretty poor shape and just twisting it caused it to split so as a temporary fix I made two rubber seals out of a bicycle inner tube to match the thickness of the original and refitted the cap, job done, no more loss of coolant or boiling.

    I bought a new cap from the local Mini dealer for around 11 which is now fitted.
    http://www.mini2.com/forum/first-gen...ml#post3818920

    NOTE: Most MINI's without air-conditioning only have a single speed radiator cooling fan.

    Low Speed Fan Problems:
    If you click the air con on make sure the fan kicks in, it should, if it doesn't check all the fuses in the engine bay fuse box.

    More on checking you have both fan speeds working:
    The Radiator Fan has 2 speeds, sometimes low speed fails.......so engine gets hotter until High speed fan cuts in at the higher temperature:

    Low Speed Fan Resistor - we need solution - North American Motoring

    Quotes from the NAM thread above:
    "The cooling fan first stage speed is like a base point to provide a constant regulation of temperature while 2nd stage fan is for peak temperatures reached when car is stationery or under load, it quickly brings the temperature back to the regulation zone.
    At 105C the low speed should be on
    At 112C the low and high speed should be on together
    OR if the refrigerant pressure from the A/C compressor is good and Air Con is on then the fan should also be on."

    "In a perfect Mini cooling system, the low-speed fan will come on (and stay on) when you turn on the A/Con - always. If the fan does not come on (low-speed) when you turn on the A/C, but then comes on at high-speed after a few minutes (you'll know it's on high - very loud), those are the symptoms of a burned-out resistor."

    "I decided to spend some time observing the fan in my garage and after a while of having the car on and the fan still, I decided to turn on the A/C and the fan did turn on. I turned the A/C off and the fan remained on. Waited some time and it stayed on at the same speed. So I got back in the car, turned the A/C back on and rev'd it for a while and then... high speed came in.
    So in short, I was able to determine that my fan does indeed work at low speed and high speed."

    Gen 1 Fan Relay Kit
    "If you are having problems with your low speed fan on your first generation MINI, then you need this relay kit to fix the bad diode. This will work for both fan units, the one wire harness, or the two wire harness. You just need to wire it in a bit different than the directions show, see the photo! Very simple and easy to install and saves you from having to buy a whole new fan assembly at a cost of 290.00 dollars! The only way to truly test the fan is with a one of several special programs on the market. You hook up to the car, like a code reader, then you can turn the fan speeds on one at a time to make sure they both work. With out this program, turn the air conditioning on and let the car idle. The fan will run in low speed few a few seconds, every 60 seconds.
    Give us a call if you have any questions, but we have installed a few of these kits, and they work great."
    More:
    http://www.detroittuned.com/shop/?productID=530

    Ebay Relay Kit:
    http://www.ebay.com/itm/For-2003-200...-/360719141283







    Problem: Engine Fan Stays On:
    Had a similar problem to some others here - the fan quit and the mini overheated. Tracked it down to a fault in the relay, as mentioned on previous posts. Mini (BMW) don't sell the relay on it's own - just the whole thermo fan unit. I did the following...
    Checked the fuse for the Fan - all good. swapped the relay for the identical Battery Fan relay in the fuse box - no change, and switched it back. Used a motorbike indicator to verify that power was getting as far as the plug connection, on the front left of the car, very near the hood release lever. All good.
    This is serious now...
    http://www.mini2.com/forum/first-gen...n-stays-2.html

    Fan Wiring Connections:
    The two connectors for the fan wiring are for the power to the fan (the big connector) and the low speed relay coil (the small connector). The big connector should have three wires, two red/blue, which are the power to the high speed and the power to the low speed, and a brown which is the earth connection. The small connector should have a green/red wire, which is power to the relay coil, and a brown, which is the relay coil return (earth).
    The red/blue on pin 4 of the big connector is power for the high speed. This should be always at 12V as the power is switched through the relay, when it is turned on by power applied to the green/red wire of the small connector by the DME control module. The red/blue on pin 2 of the big connector is powered by the DME by turning on a relay in the fuse box. The power is fed to the motor through a resistor that is mounted on the fan assembly to give the low speed.
    The Fuse box side of Pin 4 in the big connector will always measure 12V to ground, the fan side will read open circuit to ground as the relay contacts are open. With 12v applied to the small connector green/red wire the relay is turned on and the high speed fan should run.
    The Fuse box side of Pin 2 in the big connector will only read 12V when the DME calls for the low speed fan to run. Measuring the resistance to ground on this pin on the fan side of the connector should read the resistance of the motor plus the low speed resistor.
    Typical failures are the relay sticking, which will prevent the high speed fan from running, and the resistor going open circuit, which will prevent the low speed fan from running.
    The pins (and sockets) within the connector are numbered. The big connector has four pins, but only three are used. If you can't see the numbers (they will be very small) then go by the wiring colours. You will have to determine which of the red/blue wires is for the high speed (12V always) and which is the low speed (only 12V when the fan is on).
    (Thanks to XRV848 on MINI2.com)
    http://www.mini2.com/forum/first-gen...nt-system.html

    MINI Temperature Gauge
    As with many modern cars the MINI temp gauge doesn't show the correct water temp. It just sits in the middle regardless until the water temp goes through the roof then decides to move to the red at which time you've posibly already overheated.

    Their is a way to get your computer to show actual water temp on the digital display:

    With the key in the ignition, but in the off position, press and hold down the odometer reset button, while holding the button down, switch the key in the ignition to position 1.
    The screen will say 'Test' and a number.
    Scroll through, (pressing reset button) through to test 19 and wait a moment.
    Wait and the message will say "log i-off" then "log i-on" and back to "log i-off" again. When "log i-off" appears, press again.
    Now you can press reset to get to 7.0 and this is your water temp in Centigrade.

    I recommend doing this to save overheating for the time being whilst you don't have complete faith in your cars cooling system!
    This is great for fault diagnosis. You will be able to see the thermostat controlling the temp as you drive and when stationary you can check the fan comes on at low speed at around 106C.
    http://www.mini2.com/forum/first-gen...ml#post3828926

    Lukewarm Heater Matrix problem:
    http://www.mini2.com/forum/first-gen...rm-heater.html
    Last edited by mab01; 06-05-14, 10:52 PM.

    Comment


    • #3
      Antifreeze Update for winter motoring
      For MINI's like most modern cars you need to use the correct coolant all year round but not always convenient to go to a MINI Dealer.....Halfords sell a suitable antifreeze coolant below:
      Halfords | Comma XStream G48 Antifreeze Concentrate 5 Litres

      The Comma XStream G48 Anti Freeze Concentrate is suitable for BMW, Mercedes Benz, Volvo & pre-1996 VW group cars.
      This is also approved for MINI just follow the mix ratio.
      http://www.halfords.com/wcsstore/lib...ma-xstream.pdf

      Thermostat Replacement:
      http://forum.minicooper.org/showthread.php?t=14560

      R50 Cooper/One Water Pump Fault
      "Took the pump off and it seemed very loose,as if the impeller wasn`t turning with the shaft,fitted a new pump and all was well with the system and the heater."
      http://www.mini2.com/forum/first-gen...nightmare.html
      Last edited by mab01; 27-12-12, 08:25 PM.

      Comment


      • #4
        This gen MINI uses a Chrysler PT cruiser 1.6 engine, basically. It's ok in that car, but in the MINI it's a lot of engine crammed into a small box. If the cooling system starts playing-up, it'll quickly overheat.
        I suppose saying it originates from a PT Cruiser makes it sound better than originating from a Chrysler Neon.

        Like saying the 1.8 K-Series came from an MGF rather than a Rover 218.

        Comment


        • #5
          i,m blown away by the info there mab most impressive....,blimey !! but if its that cantankerous an engine boy am i glad ill stick to an original A.....very good read though i must say....!

          Comment


          • #6
            Originally posted by hawaiianblue View Post
            Like saying the 1.8 K-Series came from an MGF rather than a Rover 218.
            You mean the Lotus Elise engine?

            Comment


            • #7
              Do not ever under any circumstances fill with plain water......trust me plain water in these engines WILL BOIL.
              Strange because antifreeze doesn't increase the boiling point of water, in fact many racers use plain water because it cools more effectively than antifreeze mix. However if you did run plain water for prolonged periods the lack of an anticorrosion additive would probably eventually cause the system to clog up with sludge, resulting in overheat.

              Comment


              • #8
                Originally posted by hawaiianblue View Post
                I suppose saying it originates from a PT Cruiser makes it sound better than originating from a Chrysler Neon.
                PT Cruiser was never a favourite of mine but I suppose it sold reasonably well and lasted for 10 years in production:
                http://www.insideline.com/chrysler/p...-10-years.html

                Comment


                • #9
                  Originally posted by hawaiianblue View Post
                  Strange because antifreeze doesn't increase the boiling point of water, in fact many racers use plain water because it cools more effectively than antifreeze mix. However if you did run plain water for prolonged periods the lack of an anticorrosion additive would probably eventually cause the system to clog up with sludge, resulting in overheat.
                  I know pressurising the cooling system definitely raises the boiling point of water but so does antifreeze according to this:

                  "The fluid that most cars use is a mixture of water and ethylene glycol (C2H6O2), also known as antifreeze. By adding ethylene glycol to water, the boiling and freezing points are improved significantly. Even with ethylene glycol added, these temperatures (in a car cooling system) would boil the coolant, so something additional must be done to raise its boiling point."

                  "The cooling system uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of water is higher in a pressure cooker, the boiling temperature of coolant is higher if you pressurize the system. Most cars have a pressure limit of 14 to 15 pounds per square inch (psi), which raises the boiling point another 45 F (25 C) so the coolant can withstand the high temperatures."
                  http://auto.howstuffworks.com/cooling-system3.htm
                  Last edited by mab01; 28-10-12, 08:11 PM.

                  Comment


                  • #10
                    Originally posted by foxy52 View Post
                    i,m blown away by the info there mab most impressive....,blimey !! but if its that cantankerous an engine boy am i glad ill stick to an original A.....very good read though i must say....!
                    Some say the early Mk1 MINI Chrysler Tritec engine sounds a bit like the A-series.....it is a pretty tough engine as well if not totally neglected, as they often are by modern motorists who rarely if ever check any fluid levels between what can be a 2 year service interval!

                    Comment


                    • #11
                      Originally posted by mab01 View Post

                      Filling & bleeding.....check you're not running the engine on low coolant.

                      Now an important point:........the temperature gauge on some Coopers (mine included) is controlled by the ECU...and does not necessarily tell you when the engine is overheating. When the engine is started from cold the ECU will push the gauge up in unison with the coolant temp, HOWEVER!.....when the gauge reaches 'N' or midway the ECU holds the gauge at that reading REGARDLESS OF ENGINE TEMP. It is what's commonly referred to as a phoney gauge. Lot's of cars these days have such gauges, some new cars don't have a gauge at all.

                      BMW's philosophy is, basically: "we don't want the owner to know how hot the engine is, we'll decide what is normal".
                      The temperature gauge is something I was not aware of until a few months ago. I think BMWs philosphy is flawed. I would like to know if my car is running slighty warmer than normal, so I know to back off a bit and let it cool slightly.

                      On the filling and bleeding, when I had the rad on my R50 replaced by a local speciallist I noticed the sound of trickling water coming from behind the dash. I guessed it was the flow going through the heater matrix. I checked the level in teh expansion tank, but all appeared OK, so I opened the bleeds and low and behold some air came out. It took another couple of drives and bleeding sessions to get all the air out of the system and stop teh trickling sound coming from the heater.

                      I'll vouch for the Chrysler engine being tough, I've had my R50 for almost 7 years now and the milage has just passed 130,000. My car has had quite a hard life thrashing up and down the country, but it still pulls well and doesn't burn much oil, around 0.5 litres between the 14,000 mile oil changes.

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