Pressure!

[Gilb666]

Hi folks

Noticed i had steam escaping from the pressure cap on the expansion tank after it had been into the garage

Topped up with water as i figured they may have had to drain it, and forgot to refill

All was fine for a couple of days, but after stopping in traffic (talk about bad timing, taking my sister to her wedding!) a load of steam started coming out of the bonet

Found a leak in the plastic connection on the right hand side of the head, so can get that bit sorted easily enough, but just worried that if it was coming out of the expansion tank the preasure is too high in the system and caused the connection to fail?

Interestingly, i've taken the same connector off another engine i've got, and it seems to have failed in the same place, common problem?

[ianaudia4]

The flange on the right hand side of the block (looking at it) is still available from VW, about £5. It is quite common for the gasket to crack and break, cheap fix. The header tank cap may be worth replacing as well for a few quid (£4 ish).

[the edmundator]

The coolant system isn't inherently pressurised, pressure builds up as a result of expansionof the fluid in a closed system as temperature increases. If you overfill the system, the expansion tank won't be able to do its job and a leak is almost inevitable. In a fully functional system the only other time you'd get steam escaping is if the engine is overheating and causing excessive coolant temperature.

Perished hoses and gaskets, and failed expansion tank caps would be likely sources for a leak.

[Nate]

for peace of mind, i think i'd be wanting a sniff test on this just to make sure the problem isn't anything more sinister

[Gilb666]

Thanks for the quick responses on this one guys, it is very much appreciated!

The coolant system isn't inherently pressurised, pressure builds up as a result of expansionof the fluid in a closed system as temperature increases. If you overfill the system, the expansion tank won't be able to do its job and a leak is almost inevitable. In a fully functional system the only other time you'd get steam escaping is if the engine is overheating and causing excessive coolant temperature.

Perished hoses and gaskets, and failed expansion tank caps would be likely sources for a leak.

After the first time , i filled it up with the motor running, and it seemed to level off around the right mark, squeezed the pipes and they didn't feel empty. tbh was a bit dark so may have slightly overfilled

for peace of mind, i think i'd be wanting a sniff test on this just to make sure the problem isn't anything more sinister

sniff test? water has always smelt a bit funny, but its been like this for the 3 years i've owned it, and it has had a complete new motor fitted about 2 years ago which didn't change this - i also seem to remember something similar in my old golf so though that was just how it was. what kind if smell should i be looking out for?

[PeteGLi]

I don't think Nate means a human nasal sniff test More like a block test - look on

http://www.frost.co.uk

and search for Block Tester

[Gilb666]

That does make more sense!

Never even herd of one of those before, but as it costs more than an hours labour at my garage, i think i'll replace the broken bit, and see if they've got one if that doesn't work

[ianaudia4]

more than an hour to carry out a test?

[Nate]

there are 2 ways of doing a sniff test. one is to stick a thingy in the top of the expansion tank that bubbles any escaping gas thru a liquid that changes colour with the presence of hydrocarbons (like the block tester on frosts website - cheaper versions available on the bay) the other is just to hold the exhaust gas tester used for the mot in there, which will indicate hydrocarbons present.

many garages will charge you an hour labour for doing this, as their minimum labour charge is 1 hour. pay cash and don't need a reciept and you'll probably find an independant that will do it for 5 or 10 quid

[Whitescala89]

What is the inside measurement for the coolant pipe tank to the rad?

[Gilb666]

What is the inside measurement for the coolant pipe tank to the rad?

Sorry dude, just finished putting it all back together, haven't been on today so didn't see this!

Think i found the cause of the problem - seems when my garage changed the clutch, they unplugged the power to the rad fan, and forgot to plug it back in again.

replaced the broken part and the expansion tank lid, drove home and it seems fine now, yay!