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Vicious Cycle Overheat Scenario


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10 replies to this topic

#1 6 Star

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Posted 30 September 2012 - 05:24 PM

One day I was sitting in traffic in my Brat.
(ea81 with oem craptachi, deleted asv's and aav)
Its kinda hot out, high 80's to low 90's.
I notice my engine temp begin to creep up from its normal operating temp location.
When the temp goes up, so does the idle speed. :eek:
Now that the idle speed is increasing, the engine is working harder and I'm not going anywhere (stuck in traffic) so the temp creeps up more, and the idle speed goes higher.
This system of events keeps going on until I finally break out of traffic and get to cool the engine down.
I'm guessing that had I not gotten out of traffic I would have overheated.
This is the first time that this has happened, and I'm guessing it is related to the hotter weather.
What could I do to remedy this from happening in the future?
Bigger cooling fan/s?

#2 Idasho

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Posted 30 September 2012 - 05:26 PM

Just sounds like the fan(s) did not kick on.

#3 6 Star

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Posted 30 September 2012 - 05:29 PM

Just sounds like the fan(s) did not kick on.


It did kick on, I checked that after I got to my destination.
Never had a problem with the thermostat or fan before... :confused:

#4 coxy

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Posted 30 September 2012 - 05:32 PM

Plus 1 on the electric fan not cutting in,they do so so rarely that when what you experienced is generally the first sign of trouble.
You can manually triger the fan to make sure it's OK and thus come to the thermo switch in the radiator being the issue,Simply run a power wire ti the fan relay to trigger the system if that works then the thermo switch is the problem which is the most likely problem.

#5 Idasho

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Posted 30 September 2012 - 05:35 PM

If it cooled down once you started rolling, then you have a lack of airflow through the radiator when stopped.

Simple as that.

Just because the fans were working when you got to where you were going tells me that it is intermittent. That tells me that it electrical. Overheating due to a bad radiator isnt intermittent. Nor is overheating due to a bad water pump of coolant blockage.

#6 coxy

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Posted 30 September 2012 - 05:43 PM

Are you sure the electric fan did work as the mechanical one runs all the time anyway,The thermo switch can still be the issue as in it switches in too late or the radiator may simply be getting tired and need a flush or recore is another possibility,Fine when enough airflow is available but marginal when stuck in traffic ewspecially at those outside temps.

#7 6 Star

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Posted 30 September 2012 - 05:46 PM

Plus 1 on the electric fan not cutting in,they do so so rarely that when what you experienced is generally the first sign of trouble.
You can manually triger the fan to make sure it's OK and thus come to the thermo switch in the radiator being the issue,Simply run a power wire ti the fan relay to trigger the system if that works then the thermo switch is the problem which is the most likely problem.


I remember replacing the thermo sensor on the intake manifold when I did my rebuild. I know that sensor only controls the dash gauge. The thermo switch in the radiator worked and seemed ok, it might be starting to bug out huh? Might be worth just replacing to be safe.




If it cooled down once you started rolling, then you have a lack of airflow through the radiator when stopped.

Simple as that.

Just because the fans were working when you got to where you were going tells me that it is intermittent. That tells me that it electrical. Overheating due to a bad radiator isnt intermittent. Nor is overheating due to a bad water pump of coolant blockage.


I have a new waterpump on, but my radiator has seen better days. It has a lot of little rocks from the road stuck in it and a few mushed fins here and there.

#8 6 Star

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Posted 30 September 2012 - 05:47 PM

Are you sure the electric fan did work as the mechanical one runs all the time anyway,The thermo switch can still be the issue as in it switches in too late or the radiator may simply be getting tired and need a flush or recore is another possibility,Fine when enough airflow is available but marginal when stuck in traffic ewspecially at those outside temps.


I don't have a mechanical fan. It could very well be that the radiator needs a flush.

#9 coxy

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Posted 30 September 2012 - 05:51 PM

Brumby's (Brats) out here run a small mechanical fan on the idler pulley not the water pump and a larger single electric one on the right side looking forward,what does the Brat use twin thermos,I like our setup better more reliable

#10 6 Star

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Posted 30 September 2012 - 05:57 PM

Brumby's (Brats) out here run a small mechanical fan on the idler pulley not the water pump and a larger single electric one on the right side looking forward,what does the Brat use twin thermos,I like our setup better more reliable


Hmm kinda like the a/c fan that comes on ea82's.
After I check the radiator flow and replace the thermo switch I'll look into a electric fan upgrade.

#11 coxy

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Posted 30 September 2012 - 06:06 PM

If you go aftermarket it will possibly give you the option of an adjustable switching point as well so the electric fan can be adjusted to come in earlier.
Many later engines are set to run very hot ex factory so much so I think the thermo cuts in after the overheat scenario occurs.
I reprogram Triumph motorcycles and Ducati's and BMW's because I have the software to change the cut in and out points for the thermos makes a big difference,No point in cutting thermo fans in at 106 degrees celcius(roughly 225 degrees farenheight) like they do on modern engines for emmisions reasons better the cut in around 85 degrees farenheight before they get too hot easier to control temps that way.




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