NADA Ranco Valve Leaking

[keynsham1]

So the inevitable has finally happened. After my trip back from the NEC Classic car show, and the first time I have used the heater in years, a small puddle of coolant has appeared on the garage floor and for those with a NADA car, you will not be surprised to hear it is the Ranco heater valve that is the culprit. Some years ago, I was lucky enough to find a second hand one which I needed when my original decided to leak the entire contents of the coolant system on the floor. So, the replacement has also given up now, so I need to replace it.

My question is if I replace it with the usual option of the Jensen one, or the one in the picture, which don't have the capillary, then I assume it will all work fine except for the climate 'control' function which is supposed to keep the cabin at a constant temperature? TO be honest, this function did seem to be hopeless in reality as when driving back the car seemed to be nice and warm and then become quite cold. I am not really interested in the control part; I just want the heater to work and the coolant to stay in the engine!!

Interestingly, Martin Robey sells the Interceptor replacement and comment on the lack of capillary attachment in their advert! Also, in their advert it shows a picture from the Interceptor parts book which shows the valve looks very much like the original Rover valve!!Lastly, the same make part is only £23 on Amazon!!!

 

[sdibbers]

Excellent find!

 

[keynsham1]

So I have removed the dreaded heater valve and decided to take it apart to see what really goes in in these things.




So first job was to peel back the swaged edge. No mean fet as the metal is thick and so hard to bend and you have to lever it against the plastic backplate!



Having done that and got the two pieces out, I was presented with a perfectly intact rubber diaphragm!



To cut what could be a long story short, The leak doesn't come from the diaphragm. In fact no water gets near it. It has atmospheric air on one side and either the same or a vacuum on the other, depending on whether the heater is switched on or not.

Further dismantling revealed the valve that allows water past.



The actual valve is at the top of the picture. It is held closed by a spring on the other side of the main diaphragm, the diaphragm itself being attached to the end of the pin at the top. The black rubber bit in the middle is a rubber bellows. Somehow, and I haven't quite worked out how, when a vacuum is applied to the diaphragm, it pulls on the pin, squashing the rubber bellows and allowing the valve to move and let hot water into the heater. When the vacuum is removes (heater off) the spring pushed it all back in place and seals off water flow. All good so far??

It is actually the rubber seal around the top of the bellows, or possibly the bellow itself, where the leak is. This allows water to get into the vented side of the diaphragm chamber and leak all over the floor! It also rusts the housing....



The capillary is interesting. It actually just sits in contact with the pin at the top of the valve via another small rod and so can only measure the temperature of the water entering the heater. As this will always be either hot when the heater is on and water is flowing, or cold when the heater is off, it would seem to be just a sort of on/off signal and I cannot see how the heater can use this input for adjusting the temperature in the car.

I am intrigued though so I am going to scratch my head a little longer!

Mean time my replacement no capillary valve is winging its way to me from America as we speak!!

 

[keynsham1]

Update! The capillary tube doesn't contact the pin at all. It seems to be a sealed pipe, I am guessing with fluid in. It sits in front of the heater matrix and can somehow balance the water supply to the heater. If the air through the heater matrix is too hot for the setting in the cabin, it expands the fluid in the capillary which in turn closes the water valve to reduce the flow and if it is too cold the fluid would contract, and the valve would open to let more hot water through. I am guessing still but either way I will be doing without it from now on!!!

 

[colnerov]

You could fit one of these for less than a tenner.

 

[keynsham1]

Last comment on this subject from me!! I have just worked out that all the capillary does is adjust the flow of water around the heater matrix based on the temperature of the coolant. (That may have been obvious to some!)

I always assumed that somehow it controlled the temperature of the air inside the car, but it can't. Basically, if you sit in traffic and the engine gets hotter, the air through the heater matrix will get hotter, heat the capillary, (which is coiled just after the heater matrix in the airflow), which in turn closes the flow valve a bit to reduce flow so the car doesn't get hotter inside. And of course, when you pull away and the engine temperature drops back down to normal, the capillary shrinks and allows the flow valve to open more to let more of the now cooler coolant through thus constantly maintaining the temperature of the air flowing from the heater into the car.

Not having this facility on the replacement valve is probably going to go unnoticed!!