hissing header tank after gasket change

C5dan · Post by **C5dan** » 12 Apr 2010, 23:04

Hi folks
bought a c5 2.0hdi 115000 miles. First day found hissing expansion tank and coolant spilling. Garage had checked and payed someone they use to replace gasket and skim. All was well for a couple of weeks. Now suddenly have hissing from tank again. Could there be some other causes apart from gasket. Temp guage sits in the right place after warming- doesnt overheat. No real coolant loss yet, just that hiss. Planning to buy new cap to rule that out, but any other suggestions?

Dommo · Post by **Dommo** » 13 Apr 2010, 00:05

This may sound daft but my 306 was missing a little rubber seal around the end of the header tank cap causing it to hiss, I never really thought much of it until I saw another 306 with a rubber seal, fitted one to the 306 (which my dad now drives) and it's never hissed since.

C5dan · Post by **C5dan** » 13 Apr 2010, 00:26

That's definitely present. I will get a new cap though, Dommo, to make sure. It's the root of the pressurisation that I'd like to get to. Where else might the air be entering?

Post by **RichardW** » 13 Apr 2010, 07:57

If it's overpressuring to the point of hissing past thepressure cap, then it's either head gasket, cracked head, or cracked block. I'd be tempted to ask for my money back....

citronut · Post by **citronut** » 13 Apr 2010, 08:28

if the garage that got the work??? done is were the car was bought from it is possible they just had it bodged, or had minimul work done for head gasket replacement (did not do the job properly)

regards malcolm

rmunns · Post by **rmunns** » 14 Apr 2010, 19:21

I expect there will be some tut-tuts for saying this.

I've had over 50 cars, mostly several years old with lots of miles and previous owners. So naturally I've had my fair share of coolant problems - head gaskets, radiator leaks, split hoses.......................

On several occasions I've got home by leaving the radiator cap off , thus avoiding the high pressure build-up.

As long as it's not too-hot weather and the car is not thrashed then I reckon it isn't a problem.

Post by **Peter.N.** » 14 Apr 2010, 21:52

The head gasket started leaking and blowing the water out of my XM about 6,000 miles ago, I have since left the filler cap loose and have hardly put any water in it since.

C5dan · Post by **C5dan** » 17 Apr 2010, 00:42

Guys
I love to hear the sunny outlook. I'll be back with an update shortly....