A nice, simple, one this.....
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| Heater valve on a mid/ late 1960s car |
From the 1969 model year (so about September 1968), the valve to control the heater was mounted on top of the heater matrix and controlled by a lever and cable. Prior to that, the valve was mounted on the bulkhead below the dashboard and operated by a rotating knob. My car, being a 1968 model year car was one of the last to have the rotating knob.
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| Pallas-trim on the heater knob |
The styling around the knob, and of the knob itself, varied between ID/ DS and pallas spec models, but the function and valve are the same.
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| DS/ ID variant of the heater knob (photo copyright Mark Rueneuf) |
As well as looking retro and cool - especially as they were married to the 60s DS and ID 'gris rose' dashboards........
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| Heater knob in a 1968 DS (photo copyright French Classics) |
........the valves are a lot simpler. The later plastic valves tended to clog up easily and the bases would crack and they would leak. The bulkhead mounted valves were made from brass, had fewer moving parts, and were sturdier. Unfortunately they still clogged up and the valves jammed.
If yours is jammed, think very carefully before you apply brute force as the ends can, and do, snap off. The weak spot is the threaded part at the end.
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| Broken spindle.... (photo copyright Jonathan Palmer) |
If you need to service your valve, the other downside of these ones is that they are far less accessible than the ones on top of the heaters. They are tucked down at the back of the engine.
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| The valve is down the back behind the engine |
I'm reliably informed that you can remove the valve with the engine in situ. The first step to removal is to free-up the valve on the engine bay side. There is very little working room between the engine and bulkhead. Even less if your car has the extra aluminium heat shields. As such, it is virtually impossible to access and loosen hose clips - even more so if they are the original 'Mirex' buckle clips.
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| Hose clips on the valve body. Note that my hoses had been leaking! |
You might be tempted to cut the hose ends. This is fine: one of the hoses is a specific moulded 'S' shape, but both hoses are available as modern reproduction parts. The quality of the rubber may not be as good - but they will work.
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| Original hoses (top) and a reproduction (bottom) |
The best way to loosen the valve on the engine bay side is to tackle the other ends of its two hoses: one on the feed pipe from the cylinder head (behind the air cleaner) and one on the heater matrix itself.
With the hoses undone, the valve itself is removed by first either removing the rubber cover from the knob (if the car is a DS or ID) or by winkling out the stainless steel disc from the knob if the car has Pallas spec. trim.
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| Stainless steel capping disc on a Pallas knob |
In both cases this reveals a nut to remove the rest of the knob and temperature indicator.
The valve itself is them removed by undoing the two cheese-headed screws from within the cabin. These two screws also serve as the 'stops' for the rotation of the knob between hot and cold.
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| Screws holding the heater valve in place |
The valve spindle is a tight fit through the bulkhead, so needs to be pushed back through all the way before it can be angled and lowered down and out.
In theory, at least, there is another way. If you wanted to remove the valve from the bulkhead with the engine in situ, removing the rubber/ metal plate would leave a bigger hole in the bulkhead and provide more wiggle room. I removed mine, however (as the marks on the rubber in the photo show) that rubber plate sticks to the sound deadening on the bulkhead and was surprisingly hard to remove - even with the engine out. It was stuck so fast that at one point I wasn't even sure it COULD be removed.
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| Rubber seal and backing plate |
I vaguely recall, many years ago - back in the 1990s - that my valve got stuck and stopped turning. I took the opportunity while the engine was out to remove and free it up. I managed to find an 'O' ring that fitted and that was that. The car has since stood idle for decades and rubber doesn't last for ever so, given the passage of time, I felt I needed to go back and re-do that job.
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| Engine out - circa November 1998 |
Once I'd committed to removing my car's engine (again) in 2015, I always planned to service the heater valve (again).
I'd already removed the valve and the rubber/ metal back plate it fits to a year or so ago, as part of plans to repaint the engine bay.
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| Heater valve and backing plate |
The valve was unscrewed from the plate - just as you would do if the plate/ valve assembly was in situ on the bulkhead.
With the valve removed, the spindle (the part with the threaded end) should just pull out of the body - as it's only the rubber 'O' ring that's holding it in place. In my case, it's an 'O' ring I put in about 25 years ago. My spindle shows the battle scars from the mole grips I used to get it rotating back in the 1990s. At least I gripped around the main shaft and managed to avoid snapping the threaded part off.
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| Spindle removed from the valve body |
It's maybe worth noting at this point, the shape of the valve part of the spindle and in particular the cut out that gives varying levels flow as the knob is rotated. I'm not sure what the thin slot is for? Perhaps to absorb heat expansion? Perhaps to allow a small flow even when the valve is closed?
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| Note the thin slot |
Starting with the valve body, I used some emery cloth to gently clean the bore where the valve spindle sits. It's soft brass, so don't use anything too abrasive. I also used a small wire wheel on a Dremel to go up and down the bore to polish it a little.
With the 'O' ring removed, I lightly cleaned the spindle with wire wool. I used a file to dress the worst of the gnarled edges from the mole grips. I also cleaned up the threads on the screws. Yhese stick through into the bulkhead and their ends tend to rust. I decided to run all the parts though my ultrasonic cleaner. rather than fill the whole thing with cleaner, I just put the parts in a small jar of heated cleaning fluid and filled the rest of the ultrasonic cleaner with hot water.
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| Parts to go in the ultrasonic cleaner |
There is no point in dismantling and cleaning the valve if you are not going to fit a new 'O' ring. recently John Titus - another Citroen enthusiast - recommended a 'size 112' 'O' ring for this job. He also recommended one made from 'EDPM' rubber, as opposed to 'nitrile' or 'buna'. Nitrile rubber is used in marine (wet) applications but performs less well in hot conditions. The benefit of EDPM is that it more resistant to heat and can stand temperatures over 100 degrees. It's weakness is that it is not very resistant to petrol, oils and solvents. That isn't going to be a problem in the valve of a cooling system - provided you use the right lubricating grease. It's best to use silicone grease. Don't be tempted to use Vaseline (aka petroleum jelly). The clue is in the name. Plus it has a low melt temperature so is not suited to a hot water valve.
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| All ready for reassembly |
I greased the groove where the 'O' ring sits and reapplied a little grease after I had located it. While it's the 'O' ring on the spindle that seals in the bore, I also smeared a thin film of grease on the bore and spindle body to help reduce the risk of jamming. I was careful not to clog the thin slot - just in case it hampered heater performance.
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| New 'O' ring (note old mole grip marks!) |
The spindle just pushes into the body. There was a small pocket of trapped air at the end that initially prevented the spindle pushing home, but that soon cleared.The body seems to have a groove in the end of it as though there should be a second seal to cushion it on the backplate.
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| Groove for a second seal? |
Mine didn't have a second 'O' ring but I will investigate that further and can always fit one later. So in the meantime I refitted the backing plate to the bulkhead and then the valve to the plate. If you are also refitting the backing plate, note that it's easy to orientate it wrongly. It needs to be fitted so that the holes that hold the valve are at top and bottom (north and south).
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| Backing plate and valve refitted. |
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| It looks (and works) a lot better than it did |
If your engine is still in the car and you are trying to refit the valve, I've read a tip that supposedly make things easier. It's in the "Goddess" book by Charles Vyse. He suggests feeding a piece of string through the hole in the bulkhead where the valve spindle/ knob will fit, and then trailing the string down to the ground on the engine bay side. You then tie the string to the valve and tug it back into it's approximate position from inside the cabin.
It would make sense to be tying the string to the threaded tip. Partly for grip but also because it's a smaller dimension because of the flatted side. Also bear in mind that you will have/ should have two rubber hoses connected to the valve - which may make it heavier and harder to manoeuvre. Lastly, t's also worth noting that the valve assembly needs to be almost perpendicular to pass through the bulkhead hole - so some final fiddling and aligning on both sides of the bulkhead are probably called for.
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| The valve has to be turned through almost 90 degrees to locate it in the bulkhead |
That's about as far as I can go until I put all the carpets back in, but I can show you how it all goes back together. It really just the reverse of removal. The indicator plate is fitted over the carpeting.
The 'stop' is fitted on the spindle......
.....and then the indicator disc is fitted over the stop.
Next comes the knob. At this point, orientate the knob (and spindle) so that the stop only allows it to rotate between the 'hot' and 'cold' positions. When you are happy, refit the grip washer and nut and refit the cover (small disc or rubber knob) according to what model you have.
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