still got problems please help could it be the thermostat???

ive got a hissing nosie coming from the cap on my header tank  its  a 1.8 gti  i think im losing coolant  maybe steam from said cap ??  really dont no  help please

sounds like head gasket or snakes

i was going up the m4 last week the temp went right up  never done this before i looked  and there was water spray on the passenger side strut and on the bonett under neath   so topped up with water got home  checked everything   just in case   i changed the header tank for brand new one filled it up  with coolant   went for a drive  temp gauge was fine just under half all the way  did 80 miles all fine   checked under the bonnet no leaks but hissing from the bottle / cap waited then opened  to find the bottle was half empty   any help please   ??

beat me to it .

watch out for snakes  :wink:

The water bottle cap is designed to remove the excess pressure. You could have a faulty cap, sticking thermostat or a blown cylinder head gasket.

its a new head gasket could it be just air because i refilled  the coolant ??? there donesnt seem to be any leaks standing still   just after ive driven it and then the hissing

Did you have the head skimmed and checked ?

i'd guess faulty cap, or system not bled right. who did the head gasket ?

the head gasket was done prperly where can i get a header tank cap  from   i think thats  the fault  because i changed the bottle and just topped it up and drove it   then when i got home the bottle was hissing and it was half full off coolant  ????

Had a similar problem, new cap solved it. Euro Car Parts, German and Swedish or VW dealer should have one.

Cheers

thank you everyone really really helpfull

also when refilling coolent make sure the heater slider is all the way across to hot, ie fully open. slowly fill through the header tank with the engine running. then put the top back on when your happy with the level.

developments on the hissing noise  i went for a 50 mile trip today checked the coolent before i left and it was fine   drove and stoped after 25 miles or so checked the hissing noise still there fans coming on  and temp gadge  says half ish  so drove home parked up checked again  still hissing left the car for about 8 hours  went out and checked half hour ago and it was sort of ticking  from the cap   so i removed the cap and HISS for bout 1 second then nothing now getting really worryed  now   could it be a faulty therostat ?????? help please thank you guys