Unfathomable heater problem

[Zneb Sedecrem]

Year: 1992
Make: Mercedes-Benz
Model: W124 - 230 CE
Engine: 2.3L
Air Con: None

At the mo I have intermittent/no heat. Here's the problem. If I set the control wheels to the warmest setting (fully red) and switch the fan on full the air gradually gets colder and colder.
If I blow it onto the screen it starts out quite hot then stays luke warm for a bit but eventually gets very cold.
If I select floor that starts out lukewarm and then gets colder quicker and eventually all the vents end up blowing just cold air.
If I leave the fan on position one I get a trickle of warm-ish air almost all the time. The inlet/outlet pipes into the matrix are too hot to touch as is the metal pipe running behind the dash.
The sensor vacuum pump behind the glove box is spinning but doesn't seem to be drawing in any air as it won't hold a bit of tissue on the other end of the pipe (I removed the light and pulled the vacuum pipe off and did the tissue test).
With the car running if I move the control wheels I can't see the flap control level arm move at all on the air distribution box.
Duovalves are hot up/down stream and their bodies are too.
Any ideas how to fix this?
I'm just cold!

 

[rpe2]

If not the duovalve, then suspect the circulation pump.

 

[The Hooded Claw]

Go to the local Plumbers merchant & get some Central Heating Flusher ( About a fiver) disconnect the hoses to the matrix & pour it in..... leave for a couple of hours & drain


SORTED!!!!!!!!!!!!!!!

 

[turbopete]

i didnt realise that stuff worked in cars. thought it might be too harsh for the rubber hoses. i must remember that. cheers

 

[wireman]

Try radflush its made for cars.

The circulation pump is effective only at low engine speeds, without it the heater works but only gets hot while on the move. With it the heater will continue to give out heat for a good 20 minutes after engine switch off.
You can see the impeller in the little elctric pump, if the ignition is on you can see it rotating.

From your description it seems to me that you have a choked matrix, this could be on the air side with leaves etc blocking the matrix but is most likely that some (most) of the matrix water ways are choked with gunge from the cooling system.

I have never been sucessful clearing a matrix by chemical means, the total water tube area is too great and any cleaning materials are bypassed from where they are needed by one or two of the tubes which are not blocked.

Pulling the plug from your duovalve will open it fully and you should get full heat wether you want it or not, there is a good duovalve post in DIY.

 

[meanie]

Or bicarbonate of soda.

 

[Zneb Sedecrem]

Turns out this was probably being caused by oil in my water, as I partially drained the system and the header tank and upstream of duo valves was fiull of brown sludge (like very runny, light brown mayonnaise) so guessing head gasket has gone and oil is getting into the water, being sirculated and then silting/sludging up the matrix. So now I need to get the head gasket sorted.

I reckon once the major problem is sorted, flushing the system with any of the methods described will at least sort 75% of the heating problem and the circulation will return and I'll be warm.
So now I just need to find someone in/near Guildford who can do the head gasket. Anyone?

 

[The Hooded Claw]

Turns out this was probably being caused by oil in my water, as I partially drained the system and the header tank and upstream of duo valves was fiull of brown sludge (like very runny, light brown mayonnaise) so guessing head gasket has gone and oil is getting into the water, being sirculated and then silting/sludging up the matrix. So now I need to get the head gasket sorted.

I reckon once the major problem is sorted, flushing the system with any of the methods described will at least sort 75% of the heating problem and the circulation will return and I'll be warm.
So now I just need to find someone in/near Guildford who can do the head gasket. Anyone?

TBH.... If its never overheated or lost coolant (Alot) ... you may well be better just throwing in some "Block Sealer" or even a bit of Rad weld ........( I wouldn't normally say that ( Its ALWAYS BEST to DO THE JOB RIGHT) but if you didn't even KNOW yer HG had gone then it aint MUCH of a problem .....

 

[The Hooded Claw]

i didnt realise that stuff worked in cars. thought it might be too harsh for the rubber hoses. i must remember that. cheers

Pete, in years gone by, you would have SERIOUSLY SCREWED UP yer engine if you had put that stuff in.... Many Moons ago most Central Heating boiler were made of Cast Iron....with Gallons of water content.


Smaller now the Wall hung versions are made from Aluminium & Copper with only a couple of pints of water in them............ Hence the "Flushers" have changed into stuff that LIKES Ali & Copper .... & won't eat them like glue on a Poly ceiling tile....... they are a tad more aggressive than "Proper" car flushers but do get the "Hard Deposits" shifted ect.

 

[mattkh]

..... so guessing head gasket has gone

Hi
Any other signs pointint to this ? I would do a compression check first.