Heater MK1 golf

Hi Guys Ive been for a really good run today…at one stage of the journey i was very hot but turning the heater to cold didnt really do much  is this the design as when its turned to hot boy its hot.

Its not 'air blend' system like newer cars which direct air over the heater or not giving instant hot or cold. It takes a while for the ambient air from outside to cool the hot water in the heater matrix.

The other problem may be that the cable is not cutting off the supply at the valve, check when you move the lever the valve under the bonnet is moving correctly.  

Early-1800 said

The other problem may be that the cable is not cutting off the supply at the valve, check when you move the lever the valve under the bonnet is moving correctly.  

Yep, I would go with that. or your valve is knackered… just don't go back with oem, use a non-vacuum valve off a 944 Porsche.

Thanks guys.

Where about is this under the bonnet ?

Not sure what i'm looking for

thanks guys i can confirm its operating as it should …well  thats on the outside, do these fail internally ?

They usually leak, but suppose they could still allow hot water to pass if fkd internally.

Turn off before starting engine, feel both hoses that run into the bulk head. Run car, do the hoses get warmer/hotter/hot?

The answer is yes they can fail internally i have had the Screw strip and the mech stayed closed and didn't heat the car so I replaced it….. about 6 months later it exploded apart as I was driving down the road…No indication it was leaking at all prior.

The new ones can explode off the car.

Here is what they look like assembled.


Here is the Guts of the thing after the ultrasonic weld gave up on a drive,… I rapidly lost coolant wonder why?



Here is one that was only hours old, and leaking like a sieve.




Lay a good bead of JB=Weld Full strength around and in to the seam using a Syringe, then allow to fully cure for a day, you have to mix it 50-50 be exact, I use a scale and disposable plastic lids from coffee tins.



Which is why I am now recommending using the Porsche valve as I haven't heard of them blowing apart, or having weak heat sealing, as I had 2 brand new ones from different sources leak in the same area…

OEM on my 81 never failed, and never leaked in the 20 years I drove my bunny.



Porsche 944 valve.


Easier to adjust your heat/cooling, and is easier on the mechanism….(heater control sliders).