31 replies to this topic

[roblightbody]

Hi,

 

I have a really simple question.

 

Here's my understand of how it works :-

 

If the Mini's engine gets hot enough, the thermostat will open, allowing water to circulate through the radiator and be cooled.  The thermostat regulates this so the car stays at normal working temperature.

 

If the engine is not hot enough, the thermostat won't open, so water won't be moved through the radiator.

 

Therefore, it doesn't matter how awesome your radiator is, because the thermostat will control how much cooling it does.

 

So my question is - what bit of the above is wrong?  How can an engine get over-cooled by a radiator that is "too good" for it?  Why does the thermostat not just shut more?

 

I have a mildly warmed up 1990 Cooper, which overheats on a hot day or when driven at high speed for a while.  I'm contemplating upgrading the radiator but worried about over-cooling.

 

Thanks,

 

- Rob L

[Minigman]

A lot of minis overheat in traffic or continuous high revs. Every mini I buy with or without overheating issues, I always fit a new performance rad, an 82 degree stat and new heater matrix. Put on a new high flow water pump whilst fitting this lot and flush the block thoroughly - you'd be surprised how much crud gets washed out. I've never had an overheating issue after this no matter what stage of tune.

[Wim Fournier]

That's right. As long as the bulge of the thermostat is not leaking its wax it goes on opening and closing as far as is needed to keep the engine temperatur close to the right hight. If the remaining capacity of the radiator is too little to cope with temperatur on hot days and driving full speed uphill than the thermostat is out off reach to control engine temp.

May be you do good to rinse the radiator inside, first with 'household acid' and than again with soda. For that, take the radiator out of the car. Put it upside down and fill it with boiling household acid through the outlet opening. Plug the opening and shake the radiator. And when your arms get tired from shaking, take out the plug and turn the radiator upside up and drain it.

Boil the soda water and fill the radiator again, plug, shake and when you have had it, drain it.

Take the filler lid off and rinse with clear water for a long time. Put the waterhose in the neck.

Perhaps you won't need a new radiator now.

So, if you really want to buy a new shiny aluminum radiator, don't rinse the old one. Just go and permit yourself to buy a brand new one.

[Anthony30]

If the thermostat sticks open, it can cause the engine to run too cold, or overheat. A radiator can't cool the cooant too much, only not enough in higher performance engines/ cars that live in a hotter climate. 

 

 

 

[Spider]

Your theory is pretty bang on, but if taken to an extreme level, and the radiator is, let's say 'infinite' then the coolant being admitted to the engine block will be 'stone cold'. This 'stone cold' coolant then has to make it's way up from the water pump, through the block and head, finally to the Thermostat before it will close off or down to regulate the engine temp correctly.

 

So, that's in theory, however, I doubt there's a practical radiator you could buy that would fit a Mini that would cool that much. As an experiment once, i had two radiators fitted up (one front mount), effectively doubling the cooling capacity, however I found that apart from taking longer to warm up, it all worked normal.

Edited by Moke Spider, 01 January 2017 - 07:07 PM.

[roblightbody]

If the thermostat sticks open, it can cause the engine to run too cold, or overheat. A radiator can't cool the cooant too much, only not enough in higher performance engines/ cars that live in a hotter climate. 

 

 

 

 

Thank you.  Over and over I see over-cooling mentioned, "never run your engine too cool" and I keep thinking how is that possible? Mini Spares have this on various radiator listings such as - http://www.minispare...P2000.aspx?0704

 

So we're saying regardless of the performance of the radiator, if the thermostat is the correct one and working correctly, the car will end up at the right temperature, but might take slightly longer to warm up if the radiator is super effective?

[roblightbody]

That's right. As long as the bulge of the thermostat is not leaking its wax it goes on opening and closing as far as is needed to keep the engine temperatur close to the right hight. If the remaining capacity of the radiator is too little to cope with temperatur on hot days and driving full speed uphill than the thermostat is out off reach to control engine temp.

May be you do good to rinse the radiator inside, first with 'household acid' and than again with soda. For that, take the radiator out of the car. Put it upside down and fill it with boiling household acid through the outlet opening. Plug the opening and shake the radiator. And when your arms get tired from shaking, take out the plug and turn the radiator upside up and drain it.

Boil the soda water and fill the radiator again, plug, shake and when you have had it, drain it.

Take the filler lid off and rinse with clear water for a long time. Put the waterhose in the neck.

Perhaps you won't need a new radiator now.

So, if you really want to buy a new shiny aluminum radiator, don't rinse the old one. Just go and permit yourself to buy a brand new one.

 

Thanks for your tips and suggestions.  Because it is only 2 years since the engine was rebuilt, and its done a limited mileage since then, I can't think its too clogged up .... plus it did the "slowly overheating at speed" within months of the rebuild.  Prior to my 1990 Cooper I had a 1994 SPI and it never did the same thing.

[Anthony30]

 

If the thermostat sticks open, it can cause the engine to run too cold, or overheat. A radiator can't cool the cooant too much, only not enough in higher performance engines/ cars that live in a hotter climate. 

 

 

 

 

Thank you.  Over and over I see over-cooling mentioned, "never run your engine too cool" and I keep thinking how is that possible? Mini Spares have this on various radiator listings such as - http://www.minispare...P2000.aspx?0704

 

So we're saying regardless of the performance of the radiator, if the thermostat is the correct one and working correctly, the car will end up at the right temperature, but might take slightly longer to warm up if the radiator is super effective?

 

Assuming everything else is as it should be, the thermostat should regulate the temp, and the rad should cool the water. A minispares 2 core 82 degree thermostat should be more than enough in this country, under normal road conditions. Currently the set-up I've got. 

[Anthony30]

 

That's right. As long as the bulge of the thermostat is not leaking its wax it goes on opening and closing as far as is needed to keep the engine temperatur close to the right hight. If the remaining capacity of the radiator is too little to cope with temperatur on hot days and driving full speed uphill than the thermostat is out off reach to control engine temp.

May be you do good to rinse the radiator inside, first with 'household acid' and than again with soda. For that, take the radiator out of the car. Put it upside down and fill it with boiling household acid through the outlet opening. Plug the opening and shake the radiator. And when your arms get tired from shaking, take out the plug and turn the radiator upside up and drain it.

Boil the soda water and fill the radiator again, plug, shake and when you have had it, drain it.

Take the filler lid off and rinse with clear water for a long time. Put the waterhose in the neck.

Perhaps you won't need a new radiator now.

So, if you really want to buy a new shiny aluminum radiator, don't rinse the old one. Just go and permit yourself to buy a brand new one.

 

Thanks for your tips and suggestions.  Because it is only 2 years since the engine was rebuilt, and its done a limited mileage since then, I can't think its too clogged up .... plus it did the "slowly overheating at speed" within months of the rebuild.  Prior to my 1990 Cooper I had a 1994 SPI and it never did the same thing.

 

Tried replacing the thermostat? Might be a cheap inferior part. That's where I would start anyhoo. 

[Anthony30]

Your theory is pretty bang on, but if taken to an extreme level, and the radiator is, let's say 'infinite' then the coolant being admitted to the engine block will be 'stone cold'. This 'stone cold' coolant then has to make it's way up from the water pump, through the block and head, finally to the Thermostat before it will close off or down to regulate the engine temp correctly.

 

So, that's in theory, however, I doubt there's a practical radiator you could buy that would fit a Mini that would cool that much. As an experiment once, i had two radiators fitted up (one front mount), effectively doubling the cooling capacity, however I found that apart from taking longer to warm up, it all worked normal.

I don't think any car has a radiator that good to be honest. Just one that adequately cools the water enough to stop the car from overheating, under most engine load/speed conditions.  I suppose if they wanted to you could run A/C pipes on a specially designed rad of some description. But that's just me thinking out loud, and easier ways of getting around the problem.  

[roblightbody]

I've found this whole topic really helpful in boosting my understanding, thanks so much guys.  All points have been absorbed and noted!

[carbon]

Rob, the suggestion of fitting a 82C thermostat is a good one. Also incorrect ignition timing will likely cause engine to run hot, as it's off the optimum (most efficient) point.

 

The other thing to consider is how sure are you that the temperature gauge is reading correctly? If the head has been changed it is possible that the temperature sender and the gauge are not matched, and then won't read accurately.

[Magneto]

I think you guys might be missing his point, my car runs right on the "N" under hot temp conditions (it gets much hotter and much colder where I live than in England) with it's new aluminum radiator, however in cold weather it simply does not get up to normal temp. This is a puzzle to me because I thought exactly as you guys did, that the thermostat will stay closed till the engine heat opens it up and it will run at normal temps, but take longer to get there....and opening the heater valve to get heat in the car cools it off even further...this in comparison to modern cars that warm up quickly and never go a drop over or under normal temp, no matter the outside temps. So, how come?????

[Spider]

I think you guys might be missing his point, my car runs right on the "N" under hot temp conditions (it gets much hotter and much colder where I live than in England) with it's new aluminum radiator, however in cold weather it simply does not get up to normal temp. This is a puzzle to me because I thought exactly as you guys did, that the thermostat will stay closed till the engine heat opens it up and it will run at normal temps, but take longer to get there....and opening the heater valve to get heat in the car cools it off even further...this in comparison to modern cars that warm up quickly and never go a drop over or under normal temp, no matter the outside temps. So, how come?????

 

Try blocking off the bypass hose so the thermostat can actually do it's job.

[nicklouse]

Ahhhhh the comparison to modern car temp gauge readings. Sorry you can not do that.

A modern car will read normal and not move as long as the temp is within a given temp range. That is to say it does not change as readily as a true temp gauge.