Dalek caps and pressure release

[ghost123uk]

OK Martin & Mike, I get that

So a T25 operating in a very hot country and working hard can be expected to exceed the capacity of the cooling system (Rad & Fan) to keep the temperature at the optimum value, set by the manufacturer (by fitting a 80 something degree stat). I am SURE they know what they are doing, but I still find it odd that a system that is designed to run at an optimum temperature is also designed to regularly exceed that optimum

By the way, just playing devils advocate here for the purpose of the discussion

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Aside = My cap has been faulty for I don't know how long, so I have been running around with no pressure and all has been fine, gauge dead centre, no water loss, heater fine etc. All a bit confusing

I will fit the new cap at the weekend, and will report back if the pressure generated blows any sad pipes (or my rad ) I bought 1 hose from Brickwerks at the same time as I know that one looks poor !

[Plasticman]

He he, well it was designed ok I reckon, but did they (vw) allow for the hi-tops fitted, the 1/2 ton of important rubbish we carry etc. also antifreeze effects boiling point of system, all in all with everything set up and as it should be I dont have any probs with overheating except where I have knowingly abused things.
Mike

[Red Westie]

OK Martin & Mike, I get that

So a T25 operating in a very hot country and working hard can be expected to exceed the capacity of the cooling system (Rad & Fan) to keep the temperature at the optimum value, set by the manufacturer (by fitting a 80 something degree stat). I am SURE they know what they are doing, but I still find it odd that a system that is designed to run at an optimum temperature is also designed to regularly exceed that optimum

By the way, just playing devils advocate here for the purpose of the discussion

~~~~~~~~~~~~~

Aside = My cap has been faulty for I don't know how long, so I have been running around with no pressure and all has been fine, gauge dead centre, no water loss, heater fine etc. All a bit confusing

I will fit the new cap at the weekend, and will report back if the pressure generated blows any sad pipes (or my rad ) I bought 1 hose from Brickwerks at the same time as I know that one looks poor !

Well the optimum range is fairly broad say anything from 85C to late 90's C and that is why the added head room provided by pressuring the coolant is vital (from memory, 1 bar over atmospheric pressure increases the boiling point to around 112C)
However, there are lots of variables in all of this and as you have found out it is possible (under temperate low load and non stressed situations ) to get away with a non pressurized system BUT! you are sailing close to the wind because at the first signs of heavy load, decreased coolant circulation and reduced air flow the fluid may reach boiling point and form pockets of gas in areas of critical heat transfer ie cylinder heads and upper combustion chamber area and gas is a very poor conductor of heat so localized hot spots occur causing seizing/warping and failure of gaskets and seals.
Other factors to consider are reduced boiling temperatures with altitude and barametric pressure (going up a mountain for instance) Where pressurized , sealed cooling systems are essential to protect against boiling and loss of coolant.

If the cooling system has been designed correctly in theory at least, the heat generated by the engine should never exceed the cooling capabilities of the radiator and cooling system even under the most extreme conditions (Sahara desert etc) but as the ambient temperatures increase (air temp) the radiator becomes less efficient at imparting it's heat energy to the air going through it. If you research vehicle specifications you will often find manufacturers listing bigger radiators and larger cooling fans for vehicles supplied to hot countries ie: Australia/Africa etc
Infact the major difference when travelling to a hotter country is that the electric fan/viscous coupling (on some cars) comes on a lot more and plays much more of a factor in keeping your engine within this optimum temperature range

Martin

[ghost123uk]

More good info there Martin

[ghost123uk]

Put the new cap on yesterday and decided I would change 1 hose I knew looked dodgy, the short one below the alternator. What a pig to get at

Anyway it's done now and the now "pressurised" system does not appear to have developed any leaks, fingers crossed it stays that way