Really stange heater PART 2 HELP

[mk3miniturbo]

I have put new resistors on my heater after loosing speeds one and two. 
I lubricated the fan and all seemed good.
I was out the other day and it made a quick squeel and blew the week old £25 resistors.  So I have to replace the resistors and fan (not happy).

Anyway the problem comes when the car is fully up to temp and it is ticking over.  Within 1.5 mins it has gone cold.
Water is topped up.
I have tried to remove air locks 3 times.  Vehicle has run up to temp so fan comes on.  I have needed all the water pipes and some air was released.

If I hold the revs above 2.500-3.000 it keeps warm but if it ticks over it goes cold?

Is it the by-pass valve that is foo*ked or something else?

Please anyone any help would be OH SO APPRECIATED??

Thanks

[Judderi]

I would replace the bypass valve with a bit of pipe and see if that makes any difference 1st.

[Mk2Kezza]

Sounds like the bypass valves are knackered. They work by diverting some of the water of the cooling system away from the heater matrix and back into the system (bypassing the Matrix). I think they are also temperature dependant as when the cooling system is warm, the pressure increases and the valve allows even less heated coolent to the matrix. When you are revving your engine the pressure maybe forcing coolant into the matrix therefore having heat.

As Mk2GTI2.016v has said, stick a piece of pipe in as a replacement and see what happens. I bought hose from my local Motor factor for 80p, cut to length and popped it on - hey presto Sahara temps again!

[mk3miniturbo]

Thankyou for the help squire, I will try the above fix later on this week.
If it is the heater by-pass valve any idea where I could get one?
Dont think our lass would be too happy if she got the remains of my heater matrix on her legs?

Thanks for the help

[Judderi]

Dont worry. They dont exactly explode and go everywhere. More like a hole develops and you start getting a misty window and damp foot well. If that happens then its time to upgrade to a mk3 one. Jobs a good un!

Plus you can no longer buy new valves. So your only chance is second hand ones which will probably be nackered too!

[Organisys]

I would replace the bypass valve with a bit of pipe and see if that makes any difference 1st.

YES! DO IT!

While you are there, flush the matrix through using a hose pipe.

[martinb]

i,ve got a similar problem, just had a new matrix, when driving along i get lovely toastie air, when i stop or am just ticking over it goes almost cold again. Do you reckon this would be the same problem/solution??

cheers

[rubjonny]

If its had a new matrix and the coolant is topped up, the only things it can be are buggered bypass valves or a worn waterpump.  GSF sell replacement heater matrix feed & return hoses for £8 each + VAT

[Organisys]

i,ve got a similar problem, just had a new matrix, when driving along i get lovely toastie air, when i stop or am just ticking over it goes almost cold again. Do you reckon this would be the same problem/solution??

cheers

You will I suppose get a bit less water passing through the matrix, because the water pump won't be spinning as fast (pumping so much). But check your system for airlocks.