Heater not working

My 1987 CL has developed a heater problem.  Heats up very well for the first ten minutes, then blows cold after about another three or four minutes. Water is circulating, new water pump, and new thermostat today. I have back-flushed the engine and the heater, with no apparent blockages. At working temp, first part of the inlet hose to heater is very hot, as is the inlet hose on the other side of the metal valve, the part of the hose that goes through the bulkhead. However, top part of return hose from the heater is only tepid (  only as far as the plastic valve - below that, the hose is hot again) . Strange, eh ?  When I had this problem on the wife's 306, I just flushed out the sludge from the heater with a hosepipe, which cured the problem, but I am baffled by this one. A mate suggested the metal valve may be jammed - Does anybody have any ideas, please ?   

If it's going through the bulk head hot then the problem could be with the matrix?  When you flushed it through and refilled did you make sure all the valves were open thus avoiding an airlock?

Is this on a MK2 Golf? If so wrong forum!

But we always like to help, the MK2 had a safetly recall in the early 90s to fit a valve in the engine bay to the heater matrix to cut the temp or pressure in the matrix as some had blown and dumped boiling hot water on the drivers/passengers feet. These valves are renown for packing up after a few years cutting the flow of hot water to the matrix. Either replace the safety valve with a stright thru pipe or renew it.

Early-1800 said

Is this on a MK2 Golf? If so wrong forum!

Aha!

I've had one of these let go in one one my mk2's and it bloody hurts!!  Your first warning signs are steamy windows :wink:

Try  www.vwgolfmk2.co.uk

I know its a mk2  and wrong forum but wouldn't want anyone gettign burnt legs.
ASAP replace the metal vavle in the engine bay, it is the one connected to the pipes going into the heater matrix, there is a plastic one also, so you know you've got teh correct area.
When there is a problem with the heating and water the valve will shut stopping hot water continuing to teh matrix i.e. no hot air in blowers, the valve was fitted as a safety device, it stops the matrix blowing and peeing hot water over the passngers legs.
VW were sued due to this in america when a women unfortuntaly had this happen to her.
My mk2 c reg did not have this modification when i bought it, but i fitted them asap.
It is defo the metal valve that is causing you your problems even thou better than burnt legs, change it asap with another bud and you heater will be back to normal.
Pete :wink:

Many thanks for the replies. I've been a classic bike man all my life, but can no longer manage the worst of the British weather, so have the Golf. Apologies for not realising it was a Mk II - shows what a four wheel numpty I am. However, I am grateful for your help . You would seem to have spotted my problem, particularly as I also have the "steamy windows " mentioned earlier. Much obliged.