Dumb@ss Cooling Question . . .

[silvtr1000]

Can someone out there help me learn something new?

In an engine cooling system, there's an engine, an expansion bottle, a radiator, a thermostat, a fan, a pump and some hoses?

Do both liquids flow through ALL of these components?

As I understand it, the rad gets topped up with just water, and the expansion bottle gets a mix of water/coolant?

If both liquids flow through the same components, why can't both rad and exp bottle be filled with the same liquid?

If both liquids don't flow through the same components, how does the liquid get cooled and go on to cool the engine?

Can a rad be full, but an expansion bottle be empty, and vice versa?

Not embarrassed to ask, grateful for answers.


Mark

[Guest]

Can someone out there help me learn something new?

In an engine cooling system, there's an engine, an expansion bottle, a radiator, a thermostat, a fan, a pump and some hoses?

Do both liquids flow through ALL of these components?

As I understand it, the rad gets topped up with just water, and the expansion bottle gets a mix of water/coolant?

If both liquids flow through the same components, why can't both rad and exp bottle be filled with the same liquid?

If both liquids don't flow through the same components, how does the liquid get cooled and go on to cool the engine?

Can a rad be full, but an expansion bottle be empty, and vice versa?

Not embarrassed to ask, grateful for answers.


Mark

Mark.

In actual fact, moth the radiator and the expansion bottle should be topped up with water/antifreeze mix.

In actual fact apart from a very small amount you should only really top up through the radiator cap on the Surf.

On later fully sealed systems you only top up through the expansion bottle but the Surf is a semi sealed type and you top up through the radiator cap. If you just top up with water you will dilute the antifreeze over time.

And yes the water and antifreeze mix and flow through the engine together.

A quick explanation of the expansion bottle.

When the engine gets hot, the coolant gets hot, Water expands as it gets hot and creates pressure in the system, eventually this pressure will rise above the radiator caps rating (0.9 Bar - about 13 psi) and forces the rad cap rub internals open, this allows coolant through the overflow pipe into the expansion bottle. As the water cools later when the engine has stopped or after the engine is under less stress, the coolant contracts and sucks back the water through a bypass in the radiator cap and into the engine.

In theory in this way the cooling system should not need topping up as the expansion tank fills and empties according to need an dthe temperatire of the engine. Older cars without an expansion tank used to just dump the coolant out onto the floor through the overflow pipe and so consequently needed topping up frequently.

However on a semi sealed system like the surf, if there is a problem, the expansion bottle can overfill and then dump water out onto the floor through it's own overflow pipe. This is why you get overheating when the head cracks, water is forced out past the radiator cap because of high combustion pressures getting into the cooling system. This forces far to much coolant into the expansion bottle which then overflows. Over time (maybe 5 minutes maybe an hour) the cooling system gradually empties because there is less and less coolant available as it has overflowed from the expansion bottle, and the engine overheats because there is no coolant left to cool the engine.

Cheers

[silvtr1000]

My question was prompted by a situation with my 1.5 petrol Corolla, not my Surf.

The Corolla overheated big time on the way home last Tuesday. There was plenty of dirty sludge in the empty expansion bottle and the rad was empty. I changed the oil & oil filter, air filter, sparkplugs and topped up the rad (with water) and the expansion bottle (with water/coolant). There wasn't even 2 litres of oil in it...

Everything was fine after this, but I checked all the fluids last night (maybe 4 hours after I switched off the car) and the expansion bottle was empty again (but with less crud in the bottom), but the rad was still full. I filled the expansion bottle again.

Should I have left it empty? Is it supposed to be empty when lying still? Where does the fluid go?

Thanks for the reply Andy.


Mark

[Morr]

My question was prompted by a situation with my 1.5 petrol Corolla, not my Surf.

The Corolla overheated big time on the way home last Tuesday. There was plenty of dirty sludge in the empty expansion bottle and the rad was empty. I changed the oil & oil filter, air filter, sparkplugs and topped up the rad (with water) and the expansion bottle (with water/coolant). There wasn't even 2 litres of oil in it...

Everything was fine after this, but I checked all the fluids last night (maybe 4 hours after I switched off the car) and the expansion bottle was empty again (but with less crud in the bottom), but the rad was still full. I filled the expansion bottle again.

Should I have left it empty? Is it supposed to be empty when lying still? Where does the fluid go?

Thanks for the reply Andy.


Mark

Its possible there were air pockets in the system when you refilled it before, in which case as these worked there was out (thru the expansion bottle tube), the system would have drawn in the water from the expansion bottle thus emptying the bottle again, this assumes that the system is leak free. Its also possible that the expansion bottle itself may have developed a leak, either way top up again and check frequently till you determine if there are any leaks present.


Look for a level mark on the expansion bottle, these are often hard to see with the accumulation of dirt and crud over the years, but should be there. If you reckon all is well in over the next few days ie don't lose anymore water or overheat, you should then drain and flush the system as you would with the surf and refill with correct coolant mixture. Procedures should be broadly similar to those found on here for the surf.

[silvtr1000]

Cheers guys.