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Car Forum / MINI / November 2004Should I cry or lol? overheating mini
Not too sure that i should be posting this, but here goes as it may stop someone else from also embarrassing themselves. Order of events. engine overheating. changed radiator cap. still overheating. changed thermostat. still overheating. remove radiator and send for servicing(1). still overheating. remove radiator and send for checkup(2).Demonstrated no leak in pressure bath. changed sender unit. same reading. i then decided to adjust the timing as it was erratic at times especially when driving and noticed that the distributor cap clip at the bottom was not clipped on! attached clip. stopped overheating and obviously performs better. I do know that timing effects the heat generated but did not expect it to make such a difference. Therefore decided to set the timing after I resolved the overheating problem. I'm a big boy and ready for all the insults. ;) Angelo (1983 1275HLE Clubman) Well Angelo,,,,,,,,,( piece of mind),,,, you know your radiator and sender unit are both ok ;-) one consolation is,, that if it happened to me,, I would be up to my elbows in cylinder head by now, Fitzy > Not too sure that i should be posting this, but here goes as it may > stop someone else from also embarrassing themselves. [quoted text clipped - 21 lines] > > Angelo (1983 1275HLE Clubman) <"Fitzy" <....... one consolation is,, that if it happened to me,, I would be up to my elbows > in cylinder head by now,......> Cylinder head was to be my next step, I'd already decided that the head gasket was blown. Angelo (1983 1275HLE Clubman) > <"Fitzy" <....... one consolation is,, that if it happened to me,, I > would be up to my elbows [quoted text clipped - 3 lines] > > Angelo (1983 1275HLE Clubman) If it makes you feel any better, there was one the occasion that my mini overheated to the point where the engine didn't stop when I turned it off (via the key), so I pulled all the ignition leads off the spark plugs, and it still carried on running - it must have been VERY hot! I ended up putting it in gear with the handbrake on, and stalling it. I didn't know any better at the time, but my dad kindly informed me that the head gasket must have gone, so I spent the best part of a weekend replacing it (i've done several times since, and can now do it in about an hour, not a whole weekend!). Anyway, the old gasket looked fine to me, but I fitted the new one anyway. Took the car for a test drive, and it started overheating shortly after setting off. ..... it turned out to be the thermostat - a 5 minute job to replace! Doh! Ben. > If it makes you feel any better, there was one the occasion that my mini > overheated to the point where the engine didn't stop when I turned it off > (via the key), so I pulled all the ignition leads off the spark plugs, and > it still carried on running - it must have been VERY hot! How was pulling the plug leads going to change anything once the ignition was off? 8-) > I ended up putting > it in gear with the handbrake on, and stalling it. Some of the last carburettored cars such as early 1980s Mazda 323s actually had an anti-diesel valve which dumped fresh air into the inlet manifold below the carby when you turn the ignition off, ensurign they can't run on. One of our occasional Aussie posters fitted one to his highly strung 1275 Moke which completely cured his running on problem. > > If it makes you feel any better, there was one the occasion that my mini > > overheated to the point where the engine didn't stop when I turned it off [quoted text clipped - 12 lines] > can't run on. One of our occasional Aussie posters fitted one to his > highly strung 1275 Moke which completely cured his running on problem. Hi, That anti-run on valve was fitted to Metros. Keith > I do know that timing effects the heat generated but did not expect it > to make such a difference. It's not immediately obvious how big the effect will be, but have a think about it: The amount of air and fuel going through the engine is pretty much fixed by the engine speed and the carburettor settings, no matter what happens to it once it's inside the engine. If you change the timing so that you get less power, all that fuel still gets burnt. Where has your power gone? Into the cooling system! And then you put your foot down further to get the missing power, so even MORE heat goes into the cooling system. For example, lets assume that at a steady 35mph in top gear your motor is normally 30% efficient. It burns 100 units of fuel and produces 30 units of power and 70 units of heat. Now change the timing so it's only 25% efficient. If you don't change your throttle position, it burns 100 units of fuel and produces 25 units of power and 75 units of heat. Just 7% more heat, right? But wait, you're slowing down! You apply more foot to get more power! At just 25% efficiency you burn 120 units of fuel to get the 30 units of power you need - and you make 90 units of heat. Your efficiency only dropped by 16% (1/6) from 30% to 25%, but your fuel consumption went up 20% from 100 to 120 and your heat load went up 28% from 70 to 90! Yes, ignition timing affects cooling. Phew !!! ................. Thanks for the explanation Graham,,,,,,,,, I am impressed Fitzy >> I do know that timing effects the heat generated but did not expect it >> to make such a difference. [quoted text clipped - 29 lines] > > Yes, ignition timing affects cooling. > Phew !!! ................. > Thanks for the explanation Graham,,,,,,,,, I am impressed I'm an engineer. I can't help it. The numbers, they call me, like sirens, I cannot resist! 8-) >>>I do know that timing effects the heat generated but did not expect it >>>to make such a difference. [quoted text clipped - 29 lines] >> >>Yes, ignition timing affects cooling. Thanks Graham! Now I have the theory to go with the practice. :) This is one lesson I won't forget in a hurry. -Angelo Thank you Graham for the scientific approach. I think you just answered a question I've had for many years. Back in the 70's I was driving a '66 Austin Cooper S (1275) from New York to California and when I got as far as Colorado I started overheating. I pulled into a service station to check the radiator water level.....and of course had to wait for the engine to cool down before removing the radiator cap. The station attendant, having never seen a Mini was curious and came over and ask what the problem was. I told him about the overheating problem and he told me to retard the timing 4-6 degrees and that should take care of it. He explained that because we were at 6000 feet above sea level the rarified air would have an effect on the engine performance......he was right. JimBob >> I do know that timing effects the heat generated but did not expect it >> to make such a difference. [quoted text clipped - 29 lines] > > Yes, ignition timing affects cooling. |
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