Overheating issue

[FST4RD]

Not a toyota but thought you guys could help.
Took the mechanical fan off the mini and replaced it with a 10" electric fan. With the radiator being side mount the mechanical fan is obviously on the engine side of the radiator. I mounted the electric fan on the other side between the radiator and the wheel well.
Now it's spinning the right way blowing air through the radiator and into the engine bay.
The only thing is that when your idleing its fine, temp guage sits bout half or a little below, when you driving it goes right up and I pull over before it gets to red point on the guage to let it cool down.
Normally if most cars are idling they overheat not the other way round right???
So anyone have any suggestions as to what might be the problem??
Maybe a air lock somewhere??
Thanks

[postfach]

try mounting the fan on the side of the radiator where the original fan was, now reverse the polarity on the fan so that it sucks air through the radiator instead of blowing onto it. unless you drained all the water out to put the fan on its unlikely theres air in there if there wasn't before.

[FST4RD]

Yeah thought bout that, but there aint that much room, might be a real squeeze.....

[postfach]

im trying to picture a mini's engine bay, the mech. fan is normally mounted on a pulley correct? can that pulley come off?

[FST4RD]

No it can't it drives the water pump.......
I thought where it is would be fine, sucking cold air from out side and pusing it in. Just seems really weird that it cools right down when it's idling.....

[postfach]

yeah it does seem weird, the only explanation i can think of is that whilst the car isn't moving the air around the fan isn't being disturbed, but when its moving there is a low pressure zone or something sucking air away from the fan and its not able to actually blow anything through to the radiator

perhaps even the moving air is causing the fan to slow down by forcing it in the opposite direction, meaning lower flow through the fan

[Crucible]

So is this why you initially changed to a thermofan? Did it have this problem prior to fitting the thermofan? With it up to op temp check both hoses they should be hot!! or pretty close to each other anyways. If the lower hose is a fair bit colder then you have a flow problem.

Process of elimination

1/ Remove the thermostat and try - still the same?
2/ Remove the radiator and get it rodded, backflush the block through the thermostat housing, reassemble and test - still the same?
3/ check & replace the waterpump, Pump Impellers corrode and stop moving coolant!

Hope this helps

[Leon]

Now it's spinning the right way blowing air through the radiator and into the engine bay.

As best I recall, the mini pulls air from the engine bay, through the radiator, and into the low air pressure zone of the wheel well ... so if my very long ago memory of Mini's serves me right, you've got the fan running the wrong way for a Mini. But, for crying out loud, go check somebody with a Mini before you take my word for it!

[FST4RD]

Everything was working fine. Reason i took it of was the noise, if you been in a mini you'll know they're not the quietist things.
Also coming back from the g/f's place put the car in neutral and rolled down the hill (quite a long decent) and it didn't over heat, get to the bottom and driving home and the temp starts rising......
I'm kinda at a loss here, everything i've learnt bout cars is kinda going out the window at the moment!!!

Oh and when I wired it up in the first place it was sucking air from the engine bay..... but made no real difference....
might try that again though

[postfach]

As best I recall, the mini pulls air from the engine bay, through the radiator, and into the low air pressure zone of the wheel well ... so if my very long ago memory of Mini's serves me right, you've got the fan running the wrong way for a Mini. But, for crying out loud, go check somebody with a Mini before you take my word for it!

well all he has to do is start the car and look at which way the pulley spins and then which way the fan blades are angled. if the original fan used to blow air from the engine bay into the wheel well then the problem is definitely as you say, the air is trying to go the wrong way

I'm kinda at a loss here, everything i've learnt bout cars is kinda going out the window at the moment!!!

don't worry sometimes a problem can be something real simple and you've just overlooked it cos it never seemed important, been there done that

[Crucible]

Did it have this problem prior to fitting the thermofan?

[FST4RD]

Ok gone out and checked the original fanand it did push air from the engine bay on to the radiator.
So i reversed the fan so it's now sucking from the radiator to the wheel well.
Can't be bothered going for a drive to see if it works, will try tomorrow.

Oh yeah both the top and the bottom hoses were the same temp.

[Ae92typeX]

how many blade fan was the mechanical one? they came out with several, some being more quite than others (16 blade for example). Really, in the minis Ive had over the years, the fan is not the cause of noise- more the chain simplex setup and just typical ohv noise. The fan on mine is not loud at all. I recently did the time chain and its running very quiet.

As suggested above. check which way the mechanical fan blows/sucks. I cant recall tonight, but am happy to check. Also flush out the radiator and make sure the fanbelt is still at the correct tension for the waterpump. Ive heard of some people in the past saying that the small electric fans were not as effective as the mechanical ones. Its hard to say really, but one must remember, without the airflow from the front, the fan plays a more crutial role than on your typical front mount radiator with a fan.
If you remove the thermostat (not a good idea really) than get a blanking plate or your cylinders will burn uneven.

edit: bah, slow distracted typing lol.

[Crucible]

If you remove the thermostat (not a good idea really) than get a blanking plate or your cylinders will burn uneven.

Was just suggesting that to find out quickly if that was the fault! Yes like suggested dont run permantely without one

[FST4RD]

Hmmm never thought bout the fan belt slipping, might have to check that tomorrow, but in saying that both hoses in and out of the radiator were of a decent temp, bout the same to....
Did a radiator flush not that long ago with the stuff you pour into the radiator and run it for a while and drain....

[FST4RD]

well drove to work this morning after changing so the fan sucks through the radiator and double checked that the radiator was full......
And it didn't over heat, it didn't even reach half up the gauge, probably a little over a third up.....
Now i'm just wondering is this to cold???
How do you know if the thermostat is opening???

[Stealer Of Souls]

Take it out and plop the sucker in some boiled water...
Get a good thermometer and watch it like a hawk...
Watch for when the thermostat closes. If you've got it in a pot heat it up and watch for when it opens. Record the temperatures and check against the factory specs.
Alternatively, you may find when you pull it out that it's already open... If so it's buggered...

Oh. All this assumes is an opens when hot sort.

[FST4RD]

I take it that the thermostat is the brass plug thing on the front of the motor with a spade terminal and a wire attached to the front of it???
SOrry bout my ignorance in this field of subject.
How do you know when it's opened??

[Ae92typeX]

To get to the themostat on your mini, you have to unbolt the three nuts on the thermostat housing, where the top radiator hose goes.
Be careful when removing- they can get a little fixed in place and need GENTLE prying- to hard and the housing will break- they get weak over the years.
The thermostat is the round thing under that. Do a google and you should see what it looks like. They are only about $15 new, so I tend to replace mine when its suspect anyway- as yours appears to be.
If you do choose to test in pot of hot water, tie it to a string so it sits above the bottom of the pan. You will also want a new gasket for the housing when putting it back together. I usually make my own out of gasket or cork sheet, but you can buy them also.

[Ae92typeX]

oh, and that thing with the terminal is the temp sensor for the gauge.

did you drain the system when fitting the new fan?- its possible the thermostat has been the issue all the time- first sticking closed, not stuck open. just a thought anyway.