Coolant reservoir

[l1ncs]

I have just bought a MK2 golf and have heard that the plastic reservoir http://www.jwhubbers.nl/ring/trip47/img/ring47-3958.jpg Like the one here, doesnt hold the pressure properly. Is this correct and is it worth changing. I have had overheating problems with my car (thermostat) and the water seems to boil off very quickly, could this have anything to the reservoir? Also does anyone have a suitable replacement for sale if indeed they are worth changing?

[eightvalve]

chances are there's nothing wrong with your reservoir. do u have a water leak anywhere else? Or maybe a headgasket blown? Check the oil under the rocker cover for brown sludge. when you say "boiling off"..have you seen steam....if so, where from?
Explain the overheating problem?
Is it when stuck in traffic? Normal driving?....where's your water temp gauge pointing and whats your oil temp reading when it overheats"

[Uruk Hai]

The two Golfs I've had have been fitted with both types of expansion tank and the round one (the one you have) has been the best by far.

[eightvalve]

..by the way, I dont think you have a prob with your thermostat.  Any probs with the thermostat tend to go the other way, i.e., it will stick open and it takes ages to warm the engine up.wouldn't ususlly cause an over heating problem

[monzablue16v]

Quite possible that the header tank cap has gone which stops the water pressurising and it will then boil over. Go get a new one from volkswagen if there is water around there.

[mattneck(Beavis)]

Blue expansion cap, £6ish from VW 

[rubjonny]

The round tanks are a better design to the early ones, so fit a new blue cap and look elsewhere for leaks

That being said, if its a pattern one they tend to be rubbish so genuine VW is the way to go.

[T_J_G]

refill the coolant with peoper stuff. mine boiled over easily found out some dipsh!t had used just water/a very weak mix.

[l1ncs]

The overheating probelm is when im in traffic. It is fine when im moving but it quickly overheats as soon as its left standing. I was told the thermostat was stuck open and this is what is causing the problem? Is this wrong? Im not sure at what temperature the oil is at but when the water temp creeps up to about half way round i can start to see steam. The steam seems to be coming from the left side of the bonnet above where the reservoir is.

What could it be casuing the overheating if not the thermostat? Im starting to get a bit worried now as i was hoping for a relatively easy fix.

[l1ncs]

I have also checked the oil filler cap and there is no gunk or anything around it. I happened to check the oil temp when i had been driving around for a while (water temp was at the higher end of the solid white bit) and it was reading 80.