Coolant level question

[colnet]

Good luck with that Loely, in my experience an air lock on these cars is a nightmare, but like I say, thats my experience. The turbo engines do have a bleed screw on the bottom rad hose.

[960kg]

Air locks in the cooling system are serious and can be dangerous to the well being of the engine.

There should be NO airlocks at all. Air locks do not move with the coolant that is why they are called "locks" as it hampers the flow of coolant.

Of course water expands with heat but in the system it is not allowed to take up any more room because it is pressurised by the cap so the low and high water levels are incorrect they should remain constant.

The system is designed so that no air can be trapped in small places and when running the air lock if present will impede the flow of the coolant and so the interior heater will be cooler than normal but you will get hot spots around the cooling system depending where the air lock maybe. It can cause local overheating causing pinking and even blown head gaskets. Also the mpg can suffer.


On the `98 T4 model there was a cross valve in the large coolant pipe to release or bleed the air but on other models i failed to see this, i owned three at one time.

My 1.8 model pictured you can see that the top radiator hose is about the highest point in the system so therefore the best way to remove any air is to have a fast idle and gently loosen the jubilee clip when the thermostat has opened to circulate the coolant and the air will be expelled along with coolant past the hose. Take care not to let the hose come off the radiator because of any pressure and wear gloves so not to get burned by the hot coolant.

When the air stops do up the clip and return the fast idle to normal.

You will find this is the best way to properly bleed the system of air although not read in books.

You will know when the thermostat has opened as the top hose to the radiator will suddenly get warm which is the best time to bleed the air otherwise too much pressure and very hot coolant.

[NTG]

Just to let you know, when you boil water, the little bubbles is water in a gaseous state (vapour), not air.

[loely]

......There should be NO airlocks at all. Air locks do not move with the coolant that is why they are called "locks" as it hampers the flow of coolant.......
when the thermostat has opened to circulate the coolant and the air will be expelled along with coolant past the hose....

You can bet on it your gasket will blow with air inside the cooling circuit
The air will circulate when water pump give enough flow.Not at idlle.
Check level after warming up and cooling down;Thermostat must open but normal they have a little hole in the center to let pass a little flow of water or air so bubble can not stay at the thermostat,this one will not open when sitting in the airbubble,can't feel water t°.
If the airbubble still will not go round you can push a long ( 60cm) rubber tube in the filling gap(must be tight fit) and fill with water (put a funnel on top).Becouse the extra weight of the water you put a little more pressure on the circuit.
On older french cars had to use this,to much tube under the hood.


.......are incorrect they should remain constant.
Why do they mark level when hot on the tank if the level do not change?

[960kg]

Originally Posted by loely

......There should be NO airlocks at all. Air locks do not move with the coolant that is why they are called "locks" as it hampers the flow of coolant.......
when the thermostat has opened to circulate the coolant and the air will be expelled along with coolant past the hose....

You can bet on it your gasket will blow with air inside the cooling circuit
The air will circulate when water pump give enough flow.Not at idlle.
Check level after warming up and cooling down;Thermostat must open but normal they have a little hole in the center to let pass a little flow of water or air so bubble can not stay at the thermostat,this one will not open when sitting in the airbubble,can't feel water t°.
If the airbubble still will not go round you can push a long ( 60cm) rubber tube in the filling gap(must be tight fit) and fill with water (put a funnel on top).Becouse the extra weight of the water you put a little more pressure on the circuit.
On older french cars had to use this,to much tube under the hood.


.......are incorrect they should remain constant.
Why do they mark level when hot on the tank if the level do not change?

It does sound as though you have a blockage in the coolant system and should reverse flow with a hose pipe through the block and radiator?

Air LOCKS cannot move BUT air bubbles can as they are not locks.

There is only one mark on the reservoir as far as i know and that is the full level mark not hot or cold as they are the same because of a pressurised system.

Usually problems occur when the system is not filled the way manufacturers say so!

Steering systems have a cold and hot mark on the small dipstick.

[loely]

Sorry for airblocks -airbubbles confusion,my mistake but see uploaded pic.
It comes from a level indication from Opel . Is has clearly a mark "KALT" level.
So the level changes cold - hot I would think.
So i think I can say "we agree to disagree"
case closed for me.
cheers
Loely

[960kg]

I am only trying to help you so don`t really mind if you agree or not!

Opel is not Volvo.

On a Volvo reservoir you will get Max---Min written on it which is not Hot or Cold.

The Opel reservoir probably only has Cold written on it as you can`t top it up when hot because of the pressure??.......so therefore there is a level to maintain when cold......it will remain at that level when hot if all is healthy with the system.

On some aftermarket thermostats there is no small hole to bleed any coolant through which is why best to fit Volvo.

[bobthecabbage]

A 60C rise in temp of 6 litres of water (very roughly) equates to an increase in volume of 165ml based on this information.

http://www.engineeringtoolbox.com/vo...ion-d_315.html

As coolant is only 50% water then this figure will not be accurate. Also the expansion of water is not constant across the temperature range.

However this gives a good ball park figure that reflects what I see in my car.

The levels on the header tank are usually cold levels.

If your water level goes up and down a lot more than this then you have an air lock or the seal on the header tank lid is not working/the relief valve is knackered/your head gasket has gone etc etc.

Edit - Okay the system is pressurised but only when hot and the water has expanded. This may reduce the amount expanded slightly but in truth probably not very much. The pressure increases the boiling point of water but in order to stop the thermal expansion then you would need a huge pressure. You never see a system where water is heated without the facility for expansion. If you don't have an expansion vessel or relief valve then what you have is an explosion!

[clarkey1984]

Yes the coolant level in a header tank will be higher when fully up to temp than when cold, mine sits around an inch above the maximum when it's hot, and exactly on the maximum line when cold, I have never seen a car behave any differently, but that's because hot water takes up more more physical volume than cold water does, it's not a personal opinion, it's physics, and as such a fact, thus my hot and cold level point still stands, although agreed, not all makes have a marked level for hot.

[loely]

960kg,
I know opel is not volvo but the motor is still an combustion engine for both,so the same law goos for both.
The water does not go and read the brand on the hood to know what to do or how to beheave