Golf Driver Heater problems

Dear All

The heater on my 1990 Golf 1.6 Driver is threatening to put me into a mental home .
The heater only blows mildy warm air on the slowest speed and if I turn it up it turns freezing cold.
There is adequate anti-freeze in the system (50/50) and there are no leaks.
However yesterday I drove over 95 miles at an average speed of 65 mph and the temperature of the coolant wasn't very hot at all. In fact when I removed the expansion bottle cap there was very little pressure.
Could it be that the thermostat is jammed open and the coolant is never reaching the required temperature thereby sending luke warm water to the heater matrix which is then further cooled by the blower.
Please help me because one of two things is going to happen, I will end up with a coat that fastens up the back or my wife will get hypothermia.

In anticipation
Many Thanks

Tom

If the temp gauge isn't getting above half way then I'd try a thermostat. If the engine is getting up to temp then worry about the flaps inside the air distribution box.

Thanks for the reply

I took the precaution of fitting a brand new thermostat and the problem is much the same.
Today I was out in the Golf and I noticed that the top radiator hose gets warm but the bottom one is cold.
Is the air distribution box separate from the heat exchanger box and how easy is it to get to. I only have a Haynes manual and it is a little on the sparse side with regards to the heater matrix.

Thanks again for your reply.

Tom

What's going on with the temp guage when this is happening? Will the motor warm up and blow good heat at idle, and will the cooling fan cycle?

Yes, it could be a heat exchanger flap, or cable adjustment. I think it's the one on the bottom. Also, could be a heater core.

Thanks for the reply, it is appreciated.

The temperature gauge under normal running shows the needle in the middle of the gauge and the top hose to the radiator is warm as is both hoses going through the bulkhead to the heater core.
Even at idle the heat is never really hot and if I switch on the blower it starts to cool down which would suggest a problem with the control flaps.
Is it neccesary to drain the entire system to get at the flaps because I have just changed the anti-freeze when I put in a new thermostat.
Any help would be most grateful becuase I have to do a 220 mile journey in four days and the temperature here in the north of England is down to 7 degrees celsius.

Thanks

Tom

I'm familiar with the American Golfs so maybe all this won't apply to right hand drive vehicles...

But one way to test to see if the temp flap was working. Move the temp control each way, till it stops, full hot then full cold. If you can heart a slight "clunk" sound at full hot, then at full cold, it usually means that the temp door is working properly. It is controlled by a cable that clips on down at the bottom of the heat exchanger. One other note, in the US they had a recall on the heater core that covered 1985 - 1992. I've replaced hundreds of them and even got to the point where I could do them in an hour and a half, even with factory AC.

BTW, did this car ever have good heat since you've owned it?

Occasionally I would fill an engine from the top radiator hose first when I would have trouble bleeding a cooling system.

Have you ever noticed little pieces of black foam coming out of the vents?

Thanks to everyone so far.

I have seen nothing coming out of the vents but then I have only had the car for two weeks,
Today I had to fit some new seat covers and I left the engine running until the radiator fan came on and the heater got the hottest it has ever been but after five minutes with the blower on the temperature dropped back to luke-warm.
I am topping up the expansion bottle a little every time I let the engine cool down which would suggest I have an airlock because there are no leaks anywhere on the system.
Any help would be appreciated because my wife is now starting to nag me.

Thanks again

Tom

Since you've already tried the thermostat it's time to look at the heater controls & air box. There are several sources online that show how to do an A2 heater core as this was a very common failure. the first thing to check is the heater control cable that runs from the dash control to the flap arm at the bottom of the air box. If that is okay then you will probably need to pull out the air box with heater core and investigate. I've seen new cores last less than a month & as the cars get older the foam padding on the flap doors falls off & results in the symptoms you describe.

A heartfelt thanks to all who replied to my plea for help.
I will now have to wait for a warmish day (I have no garage) to try and sort these flaps out.

Once again thanks and I'll let you know how I get on.

Tom