some of you may remember i have had some issues with losing coolant (max to min in 150 miles ish) some times it doesnt use it sometimes it does, only really happend on a long distance drive, I changed the thermostat and it seemed to have sorted it but then it started to do it again!

before my drive home i decided to put the coolant resivour in a plastic bag, a nd low and behold the coolant lost matches the coolant in the bag.

this leads me to believe that the venting valve bit that goes down the left side is somehow failing, it has done nearly 200,000 miles all long distance stuff soo i would assume the spring valve is worn? i checked all pipes and they are all dry so it kinda has to be this!

I guess if i change the coolant bulb all should be ok?

has any one got a part number i searched but cant find anything!

cheers

Could there be a slight crack in the expansion tank? I like your way of finding the fault though

1J0121403B according to the paperwork for my car (18/10/2004). That was £8.04+vat back then!

Edited 1 March, 201115 yr by mbames

Lovely, cheers for that.

Well i did some fault finding checked all pipes and connections so it kinda had to be the expansion tank! when i lifted it up i could see some pink looking fluidon the metal below it (coolant) and lwo and behold a bag ful of coolant this monring!could well be a crack, ill get it replaced though and hopefully be the end of ym issues!

One would think that a very fine/hairline crack would create more of a misting affect when under pressure though and might leave some stains on its exit hole.

However as the coolant is gathering in a pool then maybe it is a larger hole. If you run the car and then undo the expansion tank cap do you get a hiss of air going in (ie. is the system still pressurised?)

Yep system still hishes when i undo it but not if i do it straight from cold if ive just checked it if you see what i mean. It only seems to lose it when its been under strain, i.e. long motorway journey which makes me think its a high pressure issue but yes i see what you meen about a crack in it, very possible, for the sake of £10 ill change the expansion tank and go form there do you think? it does seem obvious to me that it is that as the bag collected all of the fluid!

Bet it is more than £10 now :'(

But yes, seems the logical thing to change first. Run it for long enough and catch all the fluid in a bag and then you can just pour that back into the new tank (when fitted )

Does the tank price include the cap?

It could just be that the cap is lifting early and releasing pressure.

i was thinking the cap as thats the only part that has moving bits in it, any pressure that gets past the cap goes down the vent pipe away from your hand undoing the cap.

could be but the side dogleg sort of bit vent directly down to where the bag was where it was all collected!i think it could well be a crack but to be honest i might just replace both, dealer on the phone gave a rough price of 16 plus vat for both whether thats right or not we shall see

Heres my good used one for sale....

http://briskoda.net/forums/topic/192438-octavia-18t-vrs-coolant-bottle-and-cap/page__p__2293358#entry2293358

New they are £16.55 plus vat for the tank alone and about £10 for a cap.

think ive managed to sort one out but if tht falls through ill give you a pm Ollie!

No worries mate, its not going anywhere!