Cooling system query

[chesterak]

Simon,
The cooling system you describe can be split into three elements; the cooling water circulation system, header tank and expansion tank.
When you fill the cooling system its important that there are no air locks hence the use of a header tank that (usually) has a vent line from the highest point on the circulation system to the top of the header tank so providing a constant bleed. If an expansion tank is used it is (usually) located below the header tank and is connected by a second pipe to the top of the header tank (the connection on the expansion tank is at the bottom), HOWEVER, this second connection on the header tank is actually a syphon, that is, the connection extends inside the header tank to the bottom where it is usually always below the water level. When the cooling system heats up and expands at some point water will be pushed up the syphon pipe and into the expansion tank, when the system cools down and contracts (lowering pressure) the higher pressure in the expansion tank pushes water back into the header tank. The pressure cap on the header tank and/or the expansion tank is a one way valve - water out, no air in. Hope this helps.

Stan

It's life Jim, but not as we know it..:7

ps
I would welcum a spell chequer

[osgood]

Pete, I have to agree with Kev on this point, the spring and seal is designed to lift when excess presure relitive to whats printed on top of the cap is in the system, for what ever reason and let out water (over-flow).

I have seen it working as you say the other way, but this only takes place when the cap is knackered & some-one has got there system plumed in wrongly.

Contrary to popular belief the expansion tank is not rely a header tank, One sits above the water line & full; the other well below and genrally half full to allow for excess water to be pushed in from the water system when not required and vise-versa. Hope I have the spelling right this time!!:+ Eric.

[osgood]

Not all expansion tanks have pressure caps of the normal type, some are just flat with a seal & mine has some sort of valve fitted comes from a Frog car I think. You only need one pressure outlet in the system I guess.

I have noticed air bleeding back into the expansion tank in my car from the header; so it would appear to be a two way system although a very small pipe, so it does not implode the tank when water movement is back and forth from one tank to the other ultimately keeping the radiator full with no air locks.

I think I am right in saying, the higher the pressure in the system (cap poundage) the higher the water tempreture can move towards boiling without doing so. This also applies to large quantities of Antifreeze in your water system. Eric

[Dutch Paul]

< Sorry Paul, must be the Whisky chap!!! >

Eric

Absolutely no reason to apologize. I wasn`t getting at anybody personally.
It`s just that I moved over here from UK 6 years ago and 99% of everything I say now is in Dutch. I am now beginning to forget a lot of English words and grammar !! At least in this forum I can communicate with people in my own language. So it starts to get a bit confusing when I am thinking in Dutch and English while trying to read gobbledigook !!!

And as for the whisky you can probably imagine some of the English/Dutch gobbledigook I come out with when I`ve had a few !!x(

By the way "gobbledigook" - Is that spelt correctly? Is it English? And is it actually a word?

Reallity is an illusion created by a lack of alcohol

Just a thought

Paul

[gartrac]

[center]
I think you are all missing the point.

If you look carefully at the underside of the pressure cap, inside the rubber seal there is a small disc which can easily be lifted with your finger nail, should a situation occur when a negative pressure exists within the cooling system, as the engine cools down, this valve opens to equalise the pressure.

With the overflow pipe open to atmosphere air will be drawn in, with it connected to an expansion bottle, coolant will be drawn in

Have a good look I assure you it is there and works as described

Pete

[osgood]

I'll check that one out in my Chambers Dictionary Paul will get back to you. You are right of course a spell check would be usefull. Thank God for Microsoft spelling thingie!! All the best Eric.

[breskit]

Just wait 'til it gets double dutch! }(

As for expansion tanks, I think that not all are fitted with pressure release valves (just see modern cars with plastic tanks and placstic caps). When you see cars on the roadside with steam pouring from their bonnets, this is often due to a blow hose as there is no release valve on their systems.

Just an observation.

Tony B