Bongo Fury

hijimhere wrote:Not to sure about what temps that thermostat open/close - my experience suggests that thermostats are fully opened @ 98 degree and boiling point with a good 50/50 mixture is 106/107 degrees. Maybe it was a stuck thermostat. Has it happened again?

It shouldn't boil at 106 in the engine, surely the pressure pushes the boiling point further up again?

I have seen 104 on my Tm2 just after cresting a considerable mountain in Spain and it went straight back down again. if I had stopped at that point it might well have gone on to overheat dueto heat soak (IMO). Mine has had a new head a couple of years ago and also new rad, pump, stat., etc. IMO I wouldn't push a Bongo that hard that had an original head gasket and radiator and was 18 years old.

My sensor is on the back of the head as recommended by Haydn.

Instructions in TM2 say to set Alarm 5-10 degrees hotter than the point at which the fan cuts in. Could it be that my monitored temp of 87-90 normal running isn't hot enough to bring the fan in, therefore could I up the alarm from 96 to, say, 104? Is it true that boiling point is more than 100 due to the system being under pressure, and if so, what is the actual 'boiling' temp in the system?

We didn't actually boil at 102, we were just starting to lose coolant from header overflow pipe at that reading.

Maybe I'm being too cautious?

Derek

50/50 no pressure boils around 106c

but under pressure it should be abour 15c more again

According to this: http://www.absoluteradiator.com/Radcap.htm running at 1.1 bar (when the header cap will blow) will increase boiling point to 260F which is just over 126C. It does not state if that is using tap water or coolant, but the latter would be expected to increase the boiling point.

If it hasn't been pruned there is a thread on here somewhere that gives all the parameters orf the cooling system, thermostat control range temperatures and fan cut in temp as well as animated circulation diagrams etc. I think Widowson put a lot of work into it among others.

Velocette wrote:If it hasn't been pruned there is a thread on here somewhere that gives all the parameters orf the cooling system, thermostat control range temperatures and fan cut in temp as well as animated circulation diagrams etc. I think Widowson put a lot of work into it among others.

There is no harm in having the alarm set a little low because you want to be keeping an eye on it once it gets into three figures. I think mine is set at 105 but I have one eye on it almost all the time!

106/107 is the boiling point - for a shift of +15 C to 121/122 C you would need a pressure akin to 2/3 bar (56/84 psi aprox) pressure - if the rad/reservoir caps are rated lower than that - your coolant would be spilling out of both caps before you got anywhere near 121/122 C. the leakage you experienced suggested a small amount coming out of the overflow pipe which would support the suggestion that the coolant had only just pressurised to overcome the header tank pressure cap.
be worth checking to see if you have the correct rad and header tank caps. I have a Sykes pressure testing kit which can test caps and pressurise the system. Don't have a the 2.5TD adaptor though so if any one has could you tell me where you sourced it/them!

hijimhere wrote:106/107 is the boiling point - for a shift of +15 C to 121/122 C you would need a pressure akin to 2/3 bar (56/84 psi aprox) pressure

It looks like you have miscalculated bar and psi.
The cap raises the pressure to 1.1bar above atmospheric so the boiling point should be around 122 Celsius when the cap is forced open.