every time i bleed and top up the radiator and cjeafter a run the level always drops down by the same amount (about a cupful). I have no apparent leaks and i cant help think the cap isnt letting the excess water be drawn back into the rad as the system cools even though i have replaced the cap and checked the expansion tank hose and level

 

Im pretty sure the rad should always be full.

 

anyone else got a similar issue? or is it normal?

 

cheers,

when the engine is cold the water level will be around 1>2 from the top cap there abouts ..

when the engine is hot should be to the point it over flows a little .. as there is build up heat pressure makes the water expand a little

cheers mark, do you mean 1-2 inches?

 

as the engine cools, it 'should' draw back from the expansion tank through the cap (under the disc on the sealing washer) to the radiator again but if the level im getting is 'normal' then im not too bothered.

i did wonder if the lugs being worn on the radiator neck were stopping the top seal on the cap from seating properly.

Yeah sorry 1 to 2 inch

As for it drawing water bk in no it dosent its there to stop air entering the system when it builds to much pressure and releasing to the bottel

And tbh it shouldnt be doing that anyways

Under normal driving conditions

 

If the level of water in rad when cold is the same from day to day

Nothing to panic about

im pretty sure it should draw back in as it cools, but the expansion tank is so low that the head of liquid is too large for it to syphon back. i'l try pressure testing the system again and see if theres a small weep somewhere.

 

http://auto.howstuffworks.com/cooling-system7.htm

if you look at other posts about it on here you will see that it isn't an expansion tank.

its an over flow tank, expansion tanks are also pressurised.

a few on here have done away with it...

yep ... overflow tank .. and me and others dont have it at all ..

im pretty sure it should draw back in as it cools, but the expansion tank is so low that the head of liquid is too large for it to syphon back. i'l try pressure testing the system again and see if theres a small weep somewhere.

 

http://auto.howstuffworks.com/cooling-system7.htm

 

You're right mate - it does.... I remember JeffTT mentioning it in an earlier thread somewhere.... As the engine cools down, coolant is sucked back from the expansion tank to restore the equilibrium in the radiator - but it can take some time. So best test the level after the car has stood cold for a few hours mate!

 

As for the coolant level, it should be just below the rad filler neck when cold - and about half way up the dipstick in the expansion tank....

 

One tip I got from Jamie at Zedworld was not to turn the rad cap to its fully closed position - apparently over time the filler neck can get a little worn where the rad cap sits at fully closed; hence coolant can seep past it under pressure. So he suggested I leave the cap about 5mm to the left of fully closed..... :wink:

 

Richard:cool2:

yep ... overflow tank .. and me and others dont have it at all ..

 

Sorry, yes - it is an overflow tank and not a pressurised expansion tank (my mistake above); but the explanation Fraser linked to also referred to it as an overflow tank....:wink:

Yeah sorry 1 to 2 inch

As for it drawing water bk in no it dosent its there to stop air entering the system when it builds to much pressure and releasing to the bottel

And tbh it shouldnt be doing that anyways

Under normal driving conditions

 

If the level of water in rad when cold is the same from day to day

Nothing to panic about

 

Mark your wrong bud...when its hot it vents into the bottle then as it cools the rad forms a vacume which bleeds (sucks) the water back up from the bottle into the rad.:winkiss:

when i go and pick up me zed from cold cas i have of at the mo the arch wheel linners ill mark it with a black marker and see were the level is the overfill expansion tank is when i get home watch this space

Iff you had an expansion tank that held 100 gallons the rad would still push and pull the same amount each hot/cold cycle...the expansion bottle on a zed has a tube that sits above the bottom of the bottle on the inside and comes out near the body of which the pipe fixes to.The importance is making sure the coolant level never drops below this inside pipe.