Bubbling Coolant

[Steve Payne]

Fitting a switch in the top hose wont work. What is the point of switching the fans on before the water goes through the radiator?

For some reason a lot of manufacturers recommend this. If your doing 70mph the chances are your fans will be and there is no need.

If you want the fans on earlier fit a rad switch that is set at a lower temp or even adjustable to get the desired temperature.


Steve

[Richie]

I thought of fitting a lower temp switch too...and still might ...the existing switch came from one of our reputable suppliers...but the location of the switch - being below the bottom hose its not even in the flow of the coolant - seems daft to me...
If the car is moving, my fans don't need to come on. Like most, it's only when in traffic etc that they're needed. Would it not be sensible to have them turned on sooner by putting the switch where the water is hottest ... not after it has passed through a cooling radiator?

Though at 95 degrees at the switch, at the same time the water was at 105 in the top hose. Applying very unscientific thought...if the fans are triggered at 95 in the top hose instead of the bottom hose, by the time the coolant goes back into the engine, it would be at around say 85 not 95...?

[Steve Payne]

Just fit a lower temp switch at the bottom.

Top hose is wrong, there is a lot of heat generated while driving at high speed but because of the airflow the radiator cools it.

If you fit it one in the top hose it will bring the fans on while driving fast.

Steve

[AH1951]

It used to be that cars in the UK were equipped with either a 'summer' or 'winter' thermostat.
In your case, fit a summer thermostat, so that it opens at a lower temperature, that is, unless you already have the summer type installed.
This might help. It could give you the temperature operating margin you need to avoid heat-soak boiling.
It's a very cheap thing to do, so give it a try.

[Chris_R]

The original specifications were:
Thermostat opening temperature - 81c (178f)
Thermostat fully open - 93c (200f)
Fan cut-in temperature - 87c (188f)
Fan cut-out temperature - 78c (172f)
The otter switch for the fans should be below the outlet hose connection. Because it is a cross-flow radiator you will get coolant flow across the switch.
The temperature at which the fans cut in is affected by the input temperature at the top. You should be checking the temperature of the cut-in on the outlet hose connection.

[Richie]

Cheers all - much appreciated.

Well, at the outlet, my fans are cutting in regularly at 95 degrees

I guess that as has been suggested above, the easiest way to address this is to simply fit a correct 'otter switch' that comes on at 87 degrees...

[nick2004]

Did you replace or check the caps so that the system can pressurise ok?

[Richie]

Oops! The impending arrival of a baby has meant that I've not done anything and this had slipped right off my radar...
My thoughts are that a lot of this is down to the switch operating at 95 degrees as opposed to 85...hopefully a simple fix...I'll keep you posted and thanks for the reminder

[Richie]

Big thanks to Steve Payne... I now have one of the adjustable switches fitted. Despite being stuck in serious traffic on Tuesday, the temperature didn't get above 200 Fahrenheit / 95 centigrade at the top hose ... I know this is on the warm side but that's ok.
The blooping in the top hose remained however. Clearly, it's not boiling so I'm guessing that some air must be in there somehow... Any ideas anyone?

[Ian Roberts]

Hi Ritchie

Well you have preempted me by fitting the adjustable rad switch that you can get from Steve and was what I was going to suggest. I have one and the car has never overheated ever since I fitted one. The next thing is to consider upgrading the alternator and fitting bigger fans which is my next task. However I also had the apparent boiling sound with my car just recently and discovered that it was indeed a faulty expansion tank cap. The spring was not giving the right pressure and the seal was faulty. Swapped it out and problem has gone away.