Howto: Duovalve maintainance

[rodisi]

I don't know if I missed something, somewhere, but should the voltage readings be taken when the car is at normal operating temperature? I took my readings in a cold car and have the impression that that may be wrong.

 

[rodisi]

I am sure you will find that all the LHD Mercedes W210 CDI cars have turbos as well - I am suggesting you are wrong,

It's very possible that I am wrong. I'm only saying it because the car does not have the oomph of a turbo.

How keen are you at automotive DIY?
It seems from your questions that your are quite unfamiliar, but still keen to get involved.

I have rarely taken a car in to a garage for fixing, however I've never had a car as "technically advanced" as this.

I appreciate all the help given by all on this forum and hope my questions will slowly evolve from the stupid stage.

 

[television]

I don't know if I missed something, somewhere, but should the voltage readings be taken when the car is at normal operating temperature? I took my readings in a cold car and have the impression that that may be wrong.

To test the voltage from the controller the control have to be set to MAX cold, then that should be no voltage on pins 1 and 3.

 

[rodisi]

Why me? Why can't my life be as easy as the photos show? I've finally got down to opening the duovalve but have stopped at PoD's 2nd posting. The valve does not want to split. Arrowed in my photo are the two plungers, pistons (whatever) - they do not want to budge. The metal plate moves up but these two appear to be stuck to something underneath. From what I understand they are only connected to the valves so if they were stuck together, the valves should come up with the plate. I don't want to exert too much force as I don't know what will happen. Anyone have this problem?

BTW, I tested the solenoids and both are 15 Ohms so luckily I can forget the discussion on 1,000 copper wire turns.

 

[television]

They have stuck in, you may be lucky with a pair of pliers and give them a twist, but only do it from the end sticking up, if they will come out then a light sand and they should be fine, never oil them.

 

[rodisi]

They have stuck in, you may be lucky with a pair of pliers and give them a twist, but only do it from the end sticking up, if they will come out then a light sand and they should be fine, never oil them.

I don't think I gave enough detail above. The two shafts arrowed below, in green

I can push down about 5mm and then they spring back up and I can twist them easily with my fingers but I cannot pull them up. I'm thinking that they are stuck onto the valves below and I'm afraid to pull too hard.

If I try to lift the whole plate as shown by the purple arrows, the shafts (green arrows) stay where they are and the plate moves up about 5mm to meet them and stops.

Thanks for your patience.

 

[television]

They should come out, put a thin knife between the metal plate and the base and lift it all out, and you can possibly free off the stuck valve , they are fragile and break easily, once you have the plate off where the green arrows are maybe you can ease them out by turning them by hand.

Watch the clip
http://www.youtube.com/watch?v=8jhPEfLI45s

 

[rodisi]

Again thanks, yesterday and today, I have watched that video several times and have re-read this thread and the one in the other forum as well as the Pelican instructions, in the hope that I'm missing something. In fact, I've just stopped working on the car and have come up to watch the video once more. At 2min 17 where he removes the coil and cover assembly, he's worried about not pulling up the plungers - in my case, they will not budge. I've tried lifting up the whole metal plate but the plungers stay where they are like they are stuck on something and I'm pulling up against the springs.

It's just not logical. Even more illogical is the fact that I have put a piece of metal down the centre of the plunger until it has reached the valve below it. I then push the plunger down and the metal I've inserted does not move, telling me that the plunger is not stuck to the valve - I've done this to both sides, no difference.

I've made a drawing to try to make things clearer but it just shows me that I must be mad. I can push the plungers down, I can twist them easily with my fingers BUT I can't pull them out - how crazy is that?

 

[television]

Your problem is the the two bronze pointed valves at the bottom of your drawing have corroded into the main plunger, the bronze pointed valve is too large to come up through the hole in the plate its mounted on.


With the plate off the car you have got to free off the bronze pointed part from the main plunger, they break so easily, heat may not help as the bronze will expand more than the steel, it might break the corrosion though and free them off.

 

[rodisi]

With the plate off the car you have got to .....

That is my problem, I can't pull the plungers up and I can't lift the plate. When I try, the plungers stay in their place and won't lift off - that's what's so annoying. Even more annoying is the fact that I can push the plungers down against the springs and they pop up again but stop as if there's a snap ring preventing them from coming up any further.

I'm at the point of giving up - it's so illogical.

 

[television]

Being honest the bronze valves are stuck in, I think that you will have to replace it, at least you know what the problem is.

You have nothing to loose by trying to lever the plungers out.

 

[Alex Crow]

At the risk of repeating myself, I would suggest removing the complete upper half of the assembly, and working on it on the bench.

Your valve will not allow the plungers to be removed like that, but even if they did, it would not really help you.
Have a look here at the pictures in post #2 and you can see why... http://www.peachparts.com/shopforum/tech-help/242566-how-i-fixed-my-duovalve-w210-got-my-heat-back-saved-myself-$250.html

 

[television]

Well the plunger shafts are still stuck to the bronze valve in the bottom, what ever way you look at it, the diameter of the bronze valve is larger than the hole the plunger is in, that why they will not come out.

 

[rodisi]

I can see what you're saying, however, why can't I pick the whole lot up with the metal plate? I mean if the plungers and valves are stuck together, then the whole lot should lift out when I pick up the metal plate.

I've made a short video here that can explain more than my words.
https://vimeo.com/87458609

 

[television]

Thats a good video and a mystery to me now there are only the bronze valves in the bottom

 

[Alex Crow]

And why is the valve even being taken apart?

We need to see 0v on your 'pin3' with hot air in the car before we have reason to doubt the valve - it may well be fine.

If the control panel back lighting fails to light up with the headlights, but the lighting does flicker, this suggests a dry joint on the circuit board - a common fault with the W202.

I know you feel you have read it all on the internet, but please do have a look here, the pictures show how the conical valves are pressed onto the plunger shafts...
http://www.peachparts.com/shopforum/tech-help/242566-how-i-fixed-my-duovalve-w210-got-my-heat-back-saved-myself-$250.html

 

[television]

And why is the valve even being taken apart?

We need to see 0v on your 'pin3' with hot air in the car before we have reason to doubt the valve - it may well be fine.

If the control panel back lighting fails to light up with the headlights, but the lighting does flicker, this suggests a dry joint on the circuit board - a common fault with the W202.

I know you feel you have read it all on the internet, but please do have a look here, the pictures show how the conical valves are pressed onto the plunger shafts...
http://www.peachparts.com/shopforum/tech-help/242566-how-i-fixed-my-duovalve-w210-got-my-heat-back-saved-myself-$250.html

Thats interesting if they are pressed in, I have done 124 duo valves and 140 duo valves, one these the bronze part was just loose, same on the 210.

The bronze valve in the bottom just stays down, the shape of it allows the water to lift it and pass under in the hot mode, when you turn the heat down the solenoid just reduces the amount it can open.

The one in the DIY has loose valves.

 

[rodisi]

Thats a good video and a mystery to me now there are only the bronze valves in the bottom

So I got fed up with this story and decided to go to a junk yard and see if i can find my duovalve. I did. I was lucky that it was in the car and it gave me the opportunity to see how to take the whole thing out.

I decided right there to check it out (wasn't going to pay for a duff one). Well lo and behold, exactly the same problem as mine. It wasn't at all a waste of time because it showed me a different way of opening it up. This showed me that i was wrong in the drawing that I had made and that you, Malcolm, were right. There is another bronze valve on each plunger and this one points upwards and this is what's corroded onto the plunger and prevents its lifting.

The first photo below shows the upward pointing valve, the second shows it with the downward facing valve and third is my modified drawing.
Solution which I shall try when I can now get to it again - remove the upper hose and lift the upper half of the body and not just the metal plate, as shown in the photos.

When watching the video on the tube, I believed it when he said that there are various models of the duovalve but basically the same - no they're not.

I shall update when I get the chance. Thanks again

 

[television]

Thank you, I am pleased I was right on this, those bronze valves just float.

 

[Alex Crow]

The 'upper bronze valves' are not corroded to the plungers, but press fitted onto them.
Follow my link, read the thread and look at the pictures please.

Also, why as the valve being stripped when we have not seen 0v at the outer pins?