E300D - no heat from heater

[crt]

Now, I've stripped the duovalves down and they appear to be working - the pistons run freely and, when turned upside down (pistons sticking up) and reconnected to the power, they pulse up and down depending on hot/cold settings.

I then flushed out the heating circuit by connecting a garden hose to the hot feed from the engine block. Finding the right pipe took a couple of goes - there is a y branch just after the block, with one side going to what I think must be the matrix and the other going to what I said in my last post was a bypass returning to the duovalve/recirculating pump.

When connected to the matrix pipe, gungy water gushed out of each duo-valve aperture, and then shortly after ran clear.

I reassembled everything (predictably breaking one of the coarse thread screws that others have warned about) and, lo, I had heat once the engine heated up.

However, it went cold again after I topped up the reservoir. At time of writing it remains cold but I am going to tinker some more.

If anyone has any further thoughts it will be appreciated.

 

[television]

I think that a flush or reverse flush might solve all of your problems

 

[crt]

How do I do a flush or a reverse flush (in addition to the flush of what I think was the heater sub-circuit)?

 

[television]

You need to do the whole system including the rad.

To reverse flow it the hose would have to go into the bottom hose on the rad and just pack it out with rags or something

You should be able to do the same on the heater matrix, the water flows from the duo valve,, try a hose in from the other side

http://www.detali.ru/cat/oem_mb2.as...GM=717.433&CT=F&cat=44R&SID=83&SGR=180&SGN=04

Any of those pipes would do

 

[47p2]

Try to flush in the opposite direction to the 'normal' water flow

 

[crt]

This continues to vex me.

I've had the duovalve off a couple of times now. (A 4mmx50mm Spax woodscrew is a good substitute for the original self-tapping screws - only the slightest torque snaps them.)

I've flushed the heating circuit twice.

Still only cold air (last week's burst of heat proved to be temporary).

What I've deduced is this. At around 80 degrees on the gauge I have heat coming out of the engine and into the heater feed loop on the passenger as it disappears behind the bulkhead.

With the top of the duovalve off, and revving the engine, water is pumped out of the duovalve (both sides). But...it is cold.

Where is the heat going? It's certainly not in the cabin. I've noticed that when I take the cap of the main water reservoir when the engine is hot I don't have any pressure. Could this be connected to my heating problems (e.g. thermostat defective)?

Can anyone explain the circuit from the hot engine side to the duovalve?

 

[crt]

I was wondering whether anyone reading this thread a few months on might be able to cast any light on my problem with my W124 95 E300D? (The car has effectively been off the road for some time due to an unfortunate incident involving the bonnet).

To summarise, I get no heat from the heater.

The duo valves and associated electric pump seem to be working.

The thermostat is opening and closing and the engine maintains a steady 80 degrees when warmed up.

I've by-passed the duovalves completely with a homemade assembly of 15mm copper pipes.

What this shows is:

- there is hot water at the point at which the heating circuit leaves the cylinder head;

- there is no water (let alone heat) coming through at the point at which the two pipes from the heating circuit would join the duovalves; and

- there is hot water coming through the bypass hose which Ts off the heater circuit by the cylinder head and joins again at the duovalves.

Now this would suggest that the heater matrix is blocked, BUT:

1. when I attach a garden hose to either end of the heater circuit, water comes through freely (at 2 bar pressure); and

2. for a (lengthy) period I did have heat while the copper pipes were attached but this has now stopped (yet water from the garden hose still flows through freely). (I lost this heat when I drained down the entire system, used Holts rad flush and refilled).

This suggests there might be an intermittent blockage and one that cannot resist 2 bar pressure (from the mains) but can resist pressure at engine water pump pressure.

Does this sound plausible?

Anyone have any other ideas?

Thanks as usual in anticipation.

crt

 

[dieselman]

This suggests there might be an intermittent blockage and one that cannot resist 2 bar pressure (from the mains) but can resist pressure at engine water pump pressure.

Does this sound plausible?

Not really. It sounds more like an air lock problem. When filling the engine run it at idle and keep squeezing the bottom hose. Trapped air will be forced out but this can take quite a while.

 

[crt]

So....is the airlock likely to be in the heater circuit (I suspected air there but the free flow from the external source suggests not) or the engine circuit? If the heater circuit, do you mean squeezing the bottom hose at the radiator/thermostat or one of the heater circuit hoses?

Thanks.

 

[turbopete]

i had an escort years ago that did something similar. bleed the system, heater would come good, run the car for a couple of weeks and the heater would go cold. the car used very little water, but the fault was a head gasket allowing the combustion pressures into the waterways causing air locks. bleed them out and the heater worked again! unlikely to be the cause of your problem, but another idea for the thoughts bin

 

[crt]

So, five years on I've now fixed this. What the ultimate cause was I don't know, since I think some of the problems were exacerbated with the effluxion of time. Since 2009/10 I've been running the car sparingly in the winter months when I had no heat, but it got to the stage where everyone else refused to get in it, so finding some time a couple of weeks ago I did the following:

1. dash out and replaced the heat exchanger/matrix. Dash out ('95 with passenger airbag) surprisingly easy, though time consuming and nerve-wracking (lots of instructions on the forums on getting the dash out but I couldn't find one that dealt with the passenger air bag: once it is out, there is a yellow metal rectangular frame that has to come out and then the dash follows). I couldn't see how to get the heater box out to extract the matrix in the recommended way so, once the dash was out, I took the top of the box off and wriggled the matrix out, springing open (and damaging one of) the sides. Getting the new one (MB original, c£130) in was difficult, and as the heater box was still in situ was only possible by cutting the metal feed pipe just after the bend and rejoining with heater hose (the join is right behind the air bag so accessible if need be).

2. But, still no heat. Bleeding the air and backflushing through the duovalve made no difference.

3. Taking out the Chinese cap valve pins from inside the duovalve did get heat though. I had done this four years ago and it made no difference so perhaps the matrix was at fault and this was a new problem.

4. Further examination and testing revealed that the duovalves were no longer working electrically (when they were four years ago). No power getting to the pins, was this due to the heater controls? Out again with the centre console (getting quick at this now), no power, but fuse 7 intact. However, as with all the W124 fuses, though intact, it was not actually making a good electrical connection, a clean up sorted that, so got power through the controls, duovalves working but still no heat with the Chinese cap pins in.

5. This post:

http://www.peachparts.com/shopforum/tech-help/242566-how-i-fixed-my-duovalve-w210-got-my-heat-back-saved-myself-$250-2.html

gave me some hope, and out with the duovalves again. My seals very badly swollen as shown in the link. Changed the top seals (using drilled out tap washers as suggested), thinking that might be enough. No heat. Levered out and replaced the bottom seals (using slightly smaller washers to sit inside the tubes). No heat.

6. All this happening at the same time as doing coolant change. So another back flush and sat the thing facing uphill to bleed it out and...eventually controllable heat on both sides.

What is my conclusion? I suspect I may have had a blocked matrix, but I am not sure, though I do have a shiny new one now. I think the duovalves may have been ok five years ago but they may not. However, the swollen seals I think operate to compress the internal moving valve pin (Chinese hat) so that it is pushed down from the top and meets the swollen seal at the bottom so that whatever the electrical position, the valve is always closed. Replacing the swollen seals with new flat washers means the pin can move up and down again. (And saved £100 for a secondhand valve or £400 for a new one).

The other thing I have learned is that once air gets into the system it will mask and confuse other symptoms. And if the duovalves are blocked it is difficult to get the air out.

Hope this is helpful for anyone else struggling with a W124 heating system.

 

[television]

Thanks for posting back after all this time, yes the heater matrix just like a rad can block up, the duo valve normally fail in the hot mode.