Ive got a problem of the expansion tank overflowing from the spout (the cap is on)at the top of the bottle when the engine is idling .when the car is running no problem but as soon after stopping with the engine still running the coolant can be seen rising up the spout of the bottle untill it starts to come out of the spout .any ideas as to why ???
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Yes, it is important to include the overflow tank or bottle as integral with the radiator and coolant system as a whole. They all intermix. Actually, the level in the overflow tank is a true measure of the correct amount to keep your coolant at. There are two marks on the overflow: full hot and full cold. The coolant system on all modern cars is a sealed system and therefore should never require adding, save a very small amount through evaporation within the overflow tank- the only part that is open to atmosphere.
So once you get all the air out of the system that is possible, both in the engine and in the radiator, you have a full level everywhere, including the overflow tank where it should always remain somewhere between the full hot and full cold marks.
You are right that the overflow collects the heated radiator coolant. But it is due to the expansive properties of coolant-or water- that it expands when heated, (but not boiling-that is very bad news of a different sort). Your radiator cap is designed to open at a specific pressure, just enough to allow coolant to flow into the overflow. As the engine and coolant cools, it contracts, the level drops in the radiator, and a natural vacuum there will siphon the overflow tank back into the radiator until it is full again. That is why you have the full hot and full cold marks.
I will shut off the lecture now. I hope you have liked my answer. If not, I give you permission to kill me now- if I may so jest.
do they go bad, that part is easy, entropy happens , throughout the universe. cars, x10000 (a mechanic is born, for this task)
my guess, is the car is boiling over, right? post all symptoms and what size engine.
if boiling over. try a new cap, on the radiator. the overflow tank is for normal AF coolant expansion. and the reverse actions. cooling and contraction.
over heating has only 2 causes, in the macro. engine makes too much heat. cooling system failures. the mechanic has tools and tests that find out which one it is. if not a hand on person, take it to any ASE rated shop.
Water expands with heat if you completely topped up the reservoir cold it should overflow. Actually the biggest problem is when breathers block on reservoir caps and the water vapour pressure cracks the bottle. The reservoir allows you cooling system to run full and take in account the volume (expansion ) increase when engine gets to running temperature.
If the coolant was hot when you noticed water coming out the radiator, that is normal from the heat expansion of the coolant. That is why there are coolant overflow tanks-also called coolant expansion tanks. When refilling coolant, always top up the radiator, and fill the overflow tank to at least the cold mark level (about half-way up on the tank). With cap off, run engine till the thermostat opens- upper radiator hose will become hot-then shut off engine, add coolant to radiator as needed, replace cap. This method of filling will help to expel any trapped air in the system. Oh, and remember to set your heater controls on high when filling coolant, so the heater core and lines also circulate and expel air. Check the seal on the radiator cap that it is still good. The cap seal is important to seal the coolant system, as it is a closed system under about 15 psi of pressure. The reason to pressurize the system is that the pressure will raise the boiling point of the coolant by about 10 degrees- important when you consider how hot the coolant has to be when running. OK, enough tutorial-I don't think you have a problem with the water pump! G'd luck, reeve.
You still have a lot of air in the cooling system and you have to speed up the water pump to get any coolant to flow through the heater. Let the engine cool off, then open the radiator cap and top off the radiator. Pour the coolant in at a rate slow enough to let the air bubble up without splashing the coolant back out. Once you get the coolant level up to the top overflow hose, the remaining air will be pushed out by expansion through the overflow tank once the engine gets hot, and will be replaced by coolant from the tank on cool-down.
It should bleed out by itself as there is an overflow tank mounted under the hood. This tank (plastic Usually), is an expansion tank that allows the hot fluid to force itself into this expansion/overflow tank, allowing the air to escape. If this tank is not about half full (there is a fill line marked on it), when you end driving. The fluid when it gets cold will be sucked back into the radiator, then you need to add fluid to the cold fill line after it cools down. If the vehicle is over heating then your pressure cap may be kaput or your radiator is being blocked or cooling fans not operating.
radiator coolant level and overflow tank low
fill overflow tank to max
remove radiator cap top off coolant level, start car and let it warm up for 5 or 10 minutes, if fluid level drops top off radiator with coolant again
check for heat output if OK replace cap DONE else
have someone increase engine RPMs (around 3500rpm) top off coolant level (there was air in system) replace radiator cap
When you top off the radiator you fill it to the neck where the cap goes. When the engine heats up the antifreeze eventually will distribute and the excess will go into the overflow bottle.
After the car cools, it will draw the antifreeze from the overflow tank into the radiator. Then check the level line on the overflow bottle(tank) for the normal amount of antifreeze per marks on the bottle.
You should have your radiator cap checked for its pressure rating. Use the type of cap which allows for an overflow system. The older caps would not let the antifreeze flow both ways.
Before removing the overflow tank check:-
1) the pressure cap is of correct specification and serviceable,
2) the overflow tank is not over-filled- space most be allowed for normal expansion of coolant.
The overflow tank should not be difficult to remove if it is necessary.