Do you need to bleed cooling system after replacing car expansion tank ?

[FastLife91]

I replaced my expansion tank and cap as old tank was leaking.
I put the brand new tank and cap on but noticed that when checking the coolant every day or 2, the water level seems slightly lower each time

Can't see any visible leaks, no sign of HG failure.

I do notice that the black pipe (overflow pipe I think) loos as though has air bubbles flowing in it going to coolant tank so I guess it is air.
also the water in the tank does not seem to expand when hot

I was wondering, should the cooling system be bled after replacing coolant tank ?

If so, how do I bleed it, do I just remove rad cap , set heat to max and let it idle for a while ?

cheers

 

[TCJBOLDIE]

You need to "burp" the radiator.
For those confused this is how I do it.
I cut the bottom off a drink bottle and seal the neck onto the radiator filler inlet with silicone and clamp off the hose to the overflow bottle and TURN THE HEATER ON FULL start the motor and the fluid will expand upwards into the bottle as it heats up then I squeeze the bottom hose a number of times at intervals to force any trapped air out and adding more fluid to keep the water level well above the top of the radiator and let it cool down fully WHILE ENSURING THAT THE WATER LEVEL STAYS ABOVE THE TOP OF THE FILLER before removing the drink bottle and the overflow/return hose clamp.

NOTE BE EXTREMELY CAREFUL WHEN SQUEEZING THE HOSE AS ONE DOES NOT WANT TO LOSE/INJURE FINGERS ETC BY COMING IN CONTACT WITH EITHER THE FAN OR VARIOUS BELTS !!!!

 

[FastLife91]

You need to "burp" the radiator.
For those confused this is how I do it.
I cut the bottom off a drink bottle and seal the neck onto the radiator filler inlet with silicone and clamp off the hose to the overflow bottle and TURN THE HEATER ON FULL start the motor and the fluid will expand upwards into the bottle as it heats up then I squeeze the bottom hose a number of times at intervals to force any trapped air out and adding more fluid to keep the water level well above the top of the radiator and let it cool down fully WHILE ENSURING THAT THE WATER LEVEL STAYS ABOVE THE TOP OF THE FILLER before removing the drink bottle and the overflow/return hose clamp.

NOTE BE EXTREMELY CAREFUL WHEN SQUEEZING THE HOSE AS ONE DOES NOT WANT TO LOSE/INJURE FINGERS ETC BY COMING IN CONTACT WITH EITHER THE FAN OR VARIOUS BELTS !!!!

Do I just take the rad cap off and let engine idle and refill when water gets near minimum, till it gets to 90 degrees ?

My fan not working at the moment.


Quick question, is it normal for water to travel through overflow pipe into expansion tank ?

 

[herb]

Most modern engines don't need bleeding anything really after 2000 period. But I still like to leave the cap of the expansion tank and give each pipe a good squeeze with the engine running.
Also the overflow your referring to is probably the inlet into the expansion tank from the flow of the coolant

 

[FastLife91]

Most modern engines don't need bleeding anything really after 2000 period. But I still like to leave the cap of the expansion tank and give each pipe a good squeeze with the engine running.
Also the overflow your referring to is probably the inlet into the expansion tank from the flow of the coolant

So are you saying that modern cars don't get airlock in the cooling system ?

I mean the pipe that is Clipped onto the expansion tank, is it normal for water to run through it and into the expansion tank ?

 

[HDi fun]

THere's nothing to lose by opening the top parts of the system during warm up and losing air/steam.

 

[FastLife91]

THere's nothing to lose by opening the top parts of the system during warm up and losing air/steam.

So do you think by replacing expansion tank that air has got in the cooling system?

Also, is it normal for water to flow through overflow pipe and into expansion tank ?

 

[HDi fun]

Cooling arrangements vary widely. If the expansion vessel is simply joined to the top of the water rad then possibly not.

There are full flow systems such as BMW uses to facilitate the residual heat arrangements in the car. These don't need any bleeding at all.

If the car is driving well and coolant temperature gauge is stable then I think you've no problems at all.

 

[FastLife91]

Cooling arrangements vary widely. If the expansion vessel is simply joined to the top of the water rad then possibly not.

There are full flow systems such as BMW uses to facilitate the residual heat arrangements in the car. These don't need any bleeding at all.

If the car is driving well and coolant temperature gauge is stable then I think you've no problems at all.

I notice after putting new expansion bottle on that water level seems to drop very slightly every day or 2, It has a new cap too

I was told to bleed it by removing rad cap and put heat on full blast until it reaches operating temp of 90


I have a question, the 2 hoses that attach to the expansion bottle, the top hose (overflow) has water running through it that spills out into expansion tank, is this normal ?

thank you

 

[HDi fun]

Without knowledge of your car specifically if there is flow through the expansion tank then I think it's fair to assume it's normal for your car.

 

[FastLife91]

Without knowledge of your car specifically if there is flow through the expansion tank then I think it's fair to assume it's normal for your car.

thank you, I really appreciate you trying to help me


Yes, the top overflow pipe that is connected to the expansion tank, it has water that flows through it and into the coolant tank. some air bubbles in there too, I guess it's from airlock

 

[TCJBOLDIE]

Do I just take the rad cap off and let engine idle and refill when water gets near minimum, till it gets to 90 degrees ?

My fan not working at the moment.


Quick question, is it normal for water to travel through overflow pipe into expansion tank ?

IF you leave the cap off then the water will overflow when it heats up and will require topping up when cold.

Water/coolant should only flow to the expansion tank if it overheats or boils OR if the cap is faulty.

 

[Yugguy]

On mine I remember reading that it was worth filling the expansion tank slowly to prevent airlocks.

This is a handy resource for Focus:

http://www.fordwiki.co.uk/index.php?title=Category:Focus_Mk1

 

[FastLife91]

IF you leave the cap off then the water will overflow when it heats up and will require topping up when cold.

Water/coolant should only flow to the expansion tank if it overheats or boils OR if the cap is faulty.

I just got home

I removed rad cap and waited for over an hour, instead of water level dropping it rose slightly. Took ages for temp to reach 90 degrees, then it dropped straight back to around 30

Was this right or should the water have kept dropping with cap off instead of rising ?

 

[TCJBOLDIE]

I am not familiar with your car and my expansion tank has 2 hoses but only 1 feeds the overflow from the cap filler neck into the expansion tank and the other hose is to drain off excess fluid from the expansion tank to the ground.The expansion tank should have fill level markings and should never be full to the brim when everything is cold as any fluid that is sent to the tank when things are at operating temps can only overflow to the ground/road.

IF you remove the cap WHEN THE MOTOR IS COLD and the radiator is full then it can only overflow ONTO THE GROUND when the motor heats up to the correct operating temps PROVIDED THAT YOU CLAMPED THE HOSE TO THE OVERFLOW TANK TO STOP FLUID FLOWING INTO THE EXPANSION TANK.

If the thermostat is functioning properly it should only take a few minutes of idling before the water level begins to rise.

 

[HDi fun]

I am not familiar with your car and my expansion tank has 2 hoses but only 1 feeds the overflow from the cap filler neck into the expansion tank and the other hose is to drain off excess fluid from the expansion tank to the ground.The expansion tank should have fill level markings and should never be full to the brim when everything is cold as any fluid that is sent to the tank when things are at operating temps can only overflow to the ground/road.

IF you remove the cap WHEN THE MOTOR IS COLD and the radiator is full then it can only overflow ONTO THE GROUND when the motor heats up to the correct operating temps PROVIDED THAT YOU CLAMPED THE HOSE TO THE OVERFLOW TANK TO STOP FLUID FLOWING INTO THE EXPANSION TANK.

If the thermostat is functioning properly it should only take a few minutes of idling before the water level begins to rise.

Common rail diesel engines don't waste much heat. In some cases the coolant temperature gauge won't move at all from cold start.

 

[TCJBOLDIE]

FWIW I simply tried my best to explain exactly what I do to remove any trapped air from the cooling system on my cars to someone who needs help but has little practical knowledge/experience around motors.