Simple; your cooling system is not correctly filled, the expansion bottle is there to collect any excess coolant which is expelled, it then sucks this back into the engine as required.
Firstly, drain the cooling system, put in a good system cleaner and follow the instructions, ensure the heater control valve is in the hot position to ensure the cleaner gets through it, and to prevent any air locks when refilling. drain the coolant and raise the front of the vehicle slightly, refill with pure water, run the engine to full temperature and drain this, repeat until the system is clean.
Raise the front of the vehicle, and mix the anti freeze and water in a watering can, fill the cooling system SLOWLY, massage the radiator hoses periodically to expel any air. Fill the radiator to the top and then fill the expansion bottle to the correct level, if the problem persists, it is either a water leak, internal or external, or the radiator cap is faulty.
BEFORE STARTING THIS, ENSURE THE TEMPERATURE CONTROL INSIDE THE VEHICLE IS SET TO THE HOT POSITION, IF IT IS NOT, THE HEATER WILL NOT FILL AND CAUSE AN AIR LOCK.
If there is no sign of a leak from any connection then I suspect the coolant could be going out the exhaust pipe. When the engine runs coolant gets sucked into a cylinder and mixed with the fuel. Coolant is syphoned from the overflow to take the place of coolant lost from the engine block.I would suspect a cylinder head gasket problem.
You might find water in the oil but not always. Dont rely on finding signs of water/brownish slime on either the dip stick or mouth of the oil filler cap. The head gasket could be blown from a waterway and passing coolant directly into a cylinder.
When at full operating temp, try holding a dry cloth over the exhaust outlet. Does the cloth get wet?
If a head gasket fault is suspected, it can be checked by getting a 'compression test.'
The principal of the expansion bottle is to collect excessive system water from the radiator via the cap relase pressure valve when the engine is hot and then it syphons back water when the coolant cools.
I would check the temperature guage as if you are boiling water withing the engine it is most likely to be via the cylinder head gasket. I assume with the engine hot the bottle becomes empty and you topp it up and it dissappears again, so it has to be going somewhere. You either have a leak in the ststem which should be fairly visible by spray staining or drips or if it is into the cylinder then you will have excessive steam from the exhaust and oil contamination in the sump. This is identifiable as "Salad Cream" usually in the rocker cover and on the oil filler cap. You will also notice a greying of your oil and if left overnight the water will rise to the top.
If the cylinder head gasket is blown you should notice a drop off of power and a consderable temperature rise as super heated exhaust gases get into the wateras well as the water dissappearing.
A compression test on each cylinder should identify the culprit but obviosly the gasket will need to be changed. With the head off, check both mating surfaces for squareness and cracks which will need to be rectified before the head is replaced with the new gasket otherwise you will have the problem again.
Bottled
Simple; your cooling system is not correctly filled, the expansion bottle is there to collect any excess coolant which is expelled, it then sucks this back into the engine as required.
Firstly, drain the cooling system, put in a good system cleaner and follow the instructions, ensure the heater control valve is in the hot position to ensure the cleaner gets through it, and to prevent any air locks when refilling. drain the coolant and raise the front of the vehicle slightly, refill with pure water, run the engine to full temperature and drain this, repeat until the system is clean.
Raise the front of the vehicle, and mix the anti freeze and water in a watering can, fill the cooling system SLOWLY, massage the radiator hoses periodically to expel any air. Fill the radiator to the top and then fill the expansion bottle to the correct level, if the problem persists, it is either a water leak, internal or external, or the radiator cap is faulty.
BEFORE STARTING THIS, ENSURE THE TEMPERATURE CONTROL INSIDE THE VEHICLE IS SET TO THE HOT POSITION, IF IT IS NOT, THE HEATER WILL NOT FILL AND CAUSE AN AIR LOCK.
Out the exhaust?
If there is no sign of a leak from any connection then I suspect the coolant could be going out the exhaust pipe. When the engine runs coolant gets sucked into a cylinder and mixed with the fuel. Coolant is syphoned from the overflow to take the place of coolant lost from the engine block.I would suspect a cylinder head gasket problem.
You might find water in the oil but not always. Dont rely on finding signs of water/brownish slime on either the dip stick or mouth of the oil filler cap. The head gasket could be blown from a waterway and passing coolant directly into a cylinder.
When at full operating temp, try holding a dry cloth over the exhaust outlet. Does the cloth get wet?
If a head gasket fault is suspected, it can be checked by getting a 'compression test.'
Expansion Bottle
The principal of the expansion bottle is to collect excessive system water from the radiator via the cap relase pressure valve when the engine is hot and then it syphons back water when the coolant cools.
I would check the temperature guage as if you are boiling water withing the engine it is most likely to be via the cylinder head gasket. I assume with the engine hot the bottle becomes empty and you topp it up and it dissappears again, so it has to be going somewhere. You either have a leak in the ststem which should be fairly visible by spray staining or drips or if it is into the cylinder then you will have excessive steam from the exhaust and oil contamination in the sump. This is identifiable as "Salad Cream" usually in the rocker cover and on the oil filler cap. You will also notice a greying of your oil and if left overnight the water will rise to the top.
If the cylinder head gasket is blown you should notice a drop off of power and a consderable temperature rise as super heated exhaust gases get into the wateras well as the water dissappearing.
A compression test on each cylinder should identify the culprit but obviosly the gasket will need to be changed. With the head off, check both mating surfaces for squareness and cracks which will need to be rectified before the head is replaced with the new gasket otherwise you will have the problem again.
GOD LUCK
OLDMINIMAN
M J Young