Heater tap restoration

Much has been written about the issue of leaking heater taps on spridgets, so possibly I will not say nothing new except just sharing my experience.

Since the first day I started to run the car before summer, I noticed a small amount of coolant liquid was always present on the heater tap shaft, no matter it was open or closed.

I read at the mg-experience forum that some people where successful in restoring it just changing an internal o-ring, but many other had  no luck.

First let me say that based on Seth's webpage where you can find a very comprehensive description of the problem, there are 2 kind of hater valves: the lets say first generation that can be disassembles, and the second late generation wich are sealed and not possible to open.

It is interesting to notice that at least on the first generation type valve, different designs exist, as Seth's valve can be opened in just 2 parts, whether my valve is opened in 3 parts.

But lets start from the beginning.....

The first step was of course to drain the coolant liquid if the system, not all, but just the necessary so when I removed the heater hose I will not cover all the engine bay with liquid. So I just opened the small radiator tap and drained about 2 liter in a plastic container that I kept to refill later.

Next I wrapped all the surroundings of the heater tap with some paper to absorb any present liquid and unscrew the only 2 nuts that holds it in place.

Once I had the heater tap in my hand, it was just a matter of removing parts, first the tap knob, then the top part, and finally the middle body part.

On the upper part of the middle body I discovered the problem. Although the o-ring was present, it was full dry, normal as it was possibly the original one nearly 50 years old. I removed it with some small files. The photo shows the origin which had taken all the shape of the thread and the dirty shaft!!!

I hold the shaft on the lathe and cleaned it with some 400 grit paper to a very soft finish. The shaft is the most important finish, and is dirty and with a rough surface, any new o-ring will not seal properly. The 3 body parts where cleaned with the sand blast machine and then some metal polish was used.

The came the hard work: finding the correct o-ring. Taking measures, I had that the shaft dia was about 7.5mm, and the upper body inside dia was 11.5. So the most logic measure to look was an o-ring with 7 m inside and 12mm outside. I went to many hardware stores, and had no luck... I was starting to get pretty upset because I wanted to use the car and couldn’t and I would possibly had to buy a new tap.

But fortunately I located a hardware store specialized in bearing, o-rings, seals, etc where they had all possible combinations of different dimensions. I got 2 different o-rings: 12x7x2,5mm and 12x6x3mm

I finally decided to use the 3mm thick oring as it would be the tightest one. I used some vaseline and push the o-ring in its place. I had to flatten the tap base against a flat surface with some sanding paper to give a good flat surface and used some special gasket paper to cout the correct new gasket. The last touch would be painting the tap knob in red which gave a great look. 

Finally the shaft was very tight but easy to turn. After some 100km with the valve opened and closed, no sight of leaking, so looks like a success.

By the way, I had to buy a plastic bag of 20 o-rings (3mm thick size) so now I have 19 spare ones that I dont need. If anyone has difficulty to find locally the correct one, just send me an email and I will see who I can help.