W124 230TE - heater matrix

[adrianb]

Hi all,
Apologes for clogging up the boards, but I've just rejoined the Mercedes family with a W124 230TE auto and it has a few foibles that need sorting out, and I've split them into a few threads in an effort to make it all a bit more manageable - this one is for the no heat problem.

Heating
I've got no heat. I can't grumble, it was like that when I got it. It's a non-air conditioned model. I'm almost certain that it's down to a clogged heater matrix, as the previous owner has had a s/h duovalve / pump fitted in an effort to fix the problem, which while you can feel it making an effort to pump, doesn't quite manage to produce any heat in the car. I tried switching the fan off for a while, disconnecting the Duovalve plug (to make it "fail-over" to hot) and then switching the fan back on, and did get some warm air for a bit, though it very soon went cold again. This makes me think the matrix is clogged up.

From what I've read, it's a bit of a b***er to change the heater matrix - but I'm prepared to give it a go. What I need to know is how to do it. I've had a 123TE, and had the dash off - and back on - that without too much grief for a simlilar job. But I'm clueless as to where to start with a 124, trim removal, what order to remove stuff, the fixings I'll need to deal with etc. It doesn't have any air bags, so at least I don't have to worry about that. I'm more than happy to take some pics and write some text to show progress and provide a guide to others, though the job will have to wait until the weather dries out a bit, and I want to be really genned up before I start.
For starters, is there just the one heater matrix? Or is there a separate one for driver and passenger sides?

cheers for any info.

 

[television]

I can give you the Dash out papers on how to do this

 

[adrianb]

Thanks (again!) Malcolm, that would be very kind.

 

[The Crooner]

Isn't it worth a can of radflush for a few days, get it hot and see if the heater works, if so drain again and fill with water/cooling system fluid.

If not then you have to drain it anyway to get the matrix out.

Is it possible that the duo valve is seized in the closed position?

Can you bypass it temporarily to prove its working?

Tony

 

[television]

Thanks (again!) Malcolm, that would be very kind.

PM me with your Email address

 

[adrianb]

All true Tony. I'd feel happier trying this if it weren't such an old thing and I'd had more of a chance to get a feel for the car. I'm a bit worried about what else I might dislodge apart from the matrix sludge, but I guess it can't be more painful than a dash dissassembly/reassembly job.
I've got to admit I haven't yet tried by-passing the duovalve - every time I've had a chance to have a close look at the beast, the heavens have opened or some domestic emergency has cropped up. Of course if I don't try it, that's bound to be the problem isn't it! I'll try the rad flush - any recommendations as to brand?

 

[The Crooner]

It may be old, but it isn't fragile.

If the radflush (cant recommend a brand - try Holts) dislodges other things then you were only storing up problems for the future.

From experience the cooling/heating system has 4 areas of potential fail:

radiator

thermostat housing if its still plastic - the metal replacement is much more robust

hoses

duo valve

Others may add to the list.

Tony

ps

Is thwe auxilliary pump in front of the duo valve functional? you can feel it working if so.

Have you checked all of the fuses?

 

[Top Cat]

Adrian

I read recently on a 190 forum of a trick to descale and flush through the heater matrix in situ. I'm a bit snowed under right now but later today i'll find the info for you and copy it into here.

 

[adrianb]

Thanks Chris - if that can be done from the engine bay it'll be a whole lot easier.

 

[adrianb]

Can anyone give me pointers as to the coolant drain / refill procedure, bleed point / drain locations etc?
Cheers,
Adrian

 

[television]

There are non,, I would just take off the hose going in and out of the heater matrix and let it drain,,you do not need to drain more than that

 

[adrianb]

Thanks for that Malcolm, and for the drains info.
Adrian

 

[Zneb Sedecrem]

I have flushed a heater matrix on a 190 using the method as described on the 190 forum, however I had better luck with the following method which totally fixed the heater problem.

Disconnect the heater matrix hoses upstream of the duo valves and before the engine block on the other side.
Drain the matrix into a bowl or other place, save it if you can, saves buying more antifreeze!
Rig up a funnel and insert it in the pipe leading into the heater matrix. Either Side doesn't matter, as long as you can get to it to pour into it.
Now this is where you might think I'm nuts. But I tried the caustic solution method and this methid and this method works better.
Before you dismantle your car nip along to your nearest Supermarket and purchase either Citric Acid, some sell it in the home baking section, or find somewhere that does it (Google is your friend here). Or just do what I did and buy 12 bottles of pure lemon juice, the Jif Lemon type stuff NOT Squash.
Pour them all into the matrix, leave for 24-48 hours.
Now whereas the caustic solution needs to be flushed out quite quickly to prevent damaging the core of the heater matrix the lemon juice acid will only work on the deposits. My neighbour (an extremely clued up mechanic and ex Drag racer who built his own car from the ground up gave me this tip) and I was as skeptical as you may be right now but I figured there was no harm trying as I had done the caustic solution twice to no real benefit and was fairly committed to replacing the matrix, so if this knackered it then no harm.
Well, 24 hours later I flushed it out with a hosepipe attached to the matrix hose and the rubbish I got out I couldn't believe it. Obviously the lemon juice shouldn't be put on your pancakes afterwards!
I then reassembled, and filled with water/antifreeze mix and I got roasting hot air out of the car at idle speed. 5 days later I did a Coyote car rally round Europe in this 190 (bought of eBay for £410) and covered over 2500 miles all of it with perfectly warm feet!

Now if I can only solve the problem with my 230CE heating woes I would be very happy! Won't hijack this thread will start my own.

Hope the above helps for the cost of the lemon juice (I used Sainsburys own at 20p a bottle I think) it's worth giving a go.

 

[wireman]

I shudder to think what the lemon juice/caustic process has done to the inside surfaces of all the aluminum parts of your cooling system, corroded rad is easy, corroded matrix a good bit harder, corroded cylinderhead a nightmare.

At least you did the acid last which might have neutralised the caustic.

Is it realy worth a go?

 

[meanie]

Bicarbonate of soda works very well too.
If it still has a pukka merc radiator it will drain through the drain plug at the bottom.
No real trick to refilling - fill with the engine stopped, let it settle for 3 or 4 minutes, run the engine at idle for 5 minutes or so, then pick the revs up to 2500ish for a few seconds. job done.

 

[adrianb]

Plan of attack

Bear with me on this long post...

Thanks for all the handy hints fellas. I've not been able to set aside time to tackle the heating problem yet, which has meant scraping the ice off the inside of the windows (damp from the recent leaks/cargo window seals) in the mornings/evenings when it's been frosty - and that's meant quite a lot of scraping recently.

It does look like there will a rare coincidence of sun and an absence of offspring tomorrow morning, so if all goes to plan I'll have a few hours to play with the car.
Having had a bit of time to research and think about this some more, my plan of attack is as follows:

1 - I'll first try bypassing the duo-valves as per Tony's suggestion. Although these are supposed to like failing in "heat-on" mode, s*ds law says they may have chosen not to this time.

2 - I'll isolate the heater circuit with some hose clamps/bungs, and try the acid test or some variation of it, courtesy of messrs . My reasoning for this being an acceptable risk is as follows. If the heater matrix/circuit is blocked, my reading around suggests that the normal commercial car radiator flush treatments are not likely to be effective in this situation. In any case, I have a few concerns about the rest of the cooling system. The standard treatments all seem to require running the treatment through the entire system, with engine on. As far as I can tell, the rest of the cooling system seems to be doing it's job properly at the moment (as far as the engine cooling side is concerned), so I don't really want to scour it out and risk exposing additional problems unecessarily.

So, relying on more of Tony's advice, (though taking it of of context a bit - sorry Tony) I think the heater matrix / circuit components will be robust enough to take a weak acid for a few hours. My guess is that if the heater matrix is made of aluminium, there will be a bit of corrosion, and there may also be some minor effect on any rubber "o" rings or seals, but I think the overall effect likely to be very limited, as long as the acid is not too concentrated and only left in for a few hours(and then thoroughly flushed).

If the matrix/circuit does start to leak, I'll just have to isolate it again, and then wait for time when I can take the car apart (using Malcolms sheets) to replace the offending part. I won't be any colder (ok, but maybe wetter..).

My understanding (which could be wrong!) is that the way the acid works on the gunge is similar to the action of corrosion inhibiting compounds found in the newer coolant additives, so the effects are likely to be self limiting to quite a large extent.

Anyhow, the long and the short of it is, she's an old, cheap, and hopefully quite a tough car, that is my workhorse. I need to try and get the heater going, without much cost in time/money, so I reckon it's worth a go. We'll see what happens. I'll take pics.

 

[adrianb]

OK, well my plans for the weekend before last were blown out of the water. I ended up attempting this late on the Sunday afternoon - not the right time.

First drained the heater circuit. Detaching the heater circuit hose from the heater pump outlet drains coolant from the main circuit, but b****r all from the heater circuit. Probably, of course, because the heater matrix is completely bunged up.
Blocked off the heater pump outlet with a polythene glove and rubber band to prevent further coolant loss.
Detached the heater circuit return hose from the head, some coolant came out, but not as much as expected. Very thick layer of scale all over the head outlet. Tried blowing through the return hose and a bit of air seemed to go through, and a bit of heater circuit water seemed to come out from the duovalve side hoses, but that might have been wishful thinking.
Next tried detaching and blowing through the duovalve - no problem there, seemed clear enough and no resistance.

Blocking off the heater circuit, ahead of the duovalve, and on the return pipe, with the materials to hand and stopping the descaler getting into the rest of the system while still allowing use of the car wasn't going to work.
Now to get the descaler into the heater circuit.
As the duovalve seems to be quite a bit lower than the heater return outlet, I figured that the return side was the place to pour in the descaler, so as to allow gravity to help it into the blocked area (assuming there was going to be a bit of flow). So, holding up the detached the return hose from the head, used a funnel to feed in the descalent.
B****r all was going in. Seemed like just enough to fill the hose to the matrix outlet pipe at the bulkhead.
Nothing seemed to come out from the duovalve side. Fed the hose up by the rear of the bonnet over the bulkhead seal, so it was upright enough to keep the descalent in the hose, the end of which exited up by the windscreen. Carefully shut bonnet to first catch then left overnight to fester.

Sunrise Monday morning, back to the job. Attempted to flush - not a sausage. Time to go to work, so reattached all hoses and topped up system. Ran car up to temp, topped up again. No heat still. Checked level later after short run to work, and checked every stop all through the week.

Last weekend, tried again, but this time drained the entire coolant system. I think it's supposed to take 7.9 litres, but all I got out was about 4.5. Looked clean enough though.

Added a descaler to the system. Ran this from Monday to this morning. Only short runs 2-3 miles each way. Needed to top up three times. There is a bit of a weep via the header tank cap overflow, but not enough to account for the amount added (I've got the overflow feeding to a plastic bottle to monitor this one). No sign of a leak elsewhere.

This morning, checked level again - no problem. Started fine, but once underway for 3 or 4 mins coolant level light comes on. Stop and a top up. Get moving again for 3 /4 mins, just up to temp, starts to run roughly when stopped in gear, and revs are up to 11/1200 when in neutral.

Luckily I'm home today, so get back, bonnet up, let things cool for a bit. Check hoses - OK, but the top radiator hose is very hot, and the bottom one still just warm. This is a new problem. Carefully open the coolant header - glug glug, lose some hot coolant. Very murky looking too.

Leave to cool, check hoses - there seems to be coolant in all the pipes. Drain scaler. Notice dripping of coolant from crankshaft accessory belt pulley.

OK, so guess that there are probably three things that could be going on - as per Tony's post.

1 - thermostat is duff - tried to check the thermostat, but the head of first of the three bolts fell off when trying to remove. The others look pretty corroded as well. Are the thermostat cover (plastic) bolt holes threaded or can I just prise the cover off without destroying it? From what I can see of the bolt remains, it looks like the bolt thread runs up to the head.

2 - pump duff - possible - but rather it was the thermostat. Of course it could be both, as when draining, noticed a drip from the crank pulley, from the looks of it coolant, and coming from somewhere further up.
If the pump fails, is there some kind of breather hole where coolant can escape? If the pump is broke, are s/h pumps worth looking at?


3 - radiator blocked.

I've flushed the radiator again and some crud came out, though not alot. Tried flushing the heater circuit again and joy - after a pause, crud and water produced. Flushed from the duovalve side as well just to be sure, and all seems well.
So looks like heater circuit might be sorted. But before testing that, need to sort the thermostat/pump. Suspect/hope it's the thermostat, as two bolt heads have broken out of the three when trying to remove. The third was wet, and the bolt hole the same, and all pretty crusty round there.
Have attached pics of thermostat cover with broken bolts, a blanked off hose (what is that for), and the leak - which I now reckon is coming from the thermostat cover.

 

[adrianb]

Couple more pics: return hose connection from heater circuit to head, and bodge attempt at isolating heater circuit. Kept the glove on to save the original coolant which looks quite clean. Drained descaler looks a mess - very murkey.

 

[adrianb]

Have got a replacement thermostat. Attempts to remove the thermostat cover failed, and so it now needs a new one. £39 from dealer, including seals, a banjo bolt and fixing bolts.
Does anyone have any hints about the best way to remove the old thermostat cover? If the cover bolt holes are not threaded, then I should be able to prise it off without too much force - does anyone know if that is the case?

 

[The Crooner]

I'm 99.9% sure the cover bolt holes are not threaded - I remember changing my cover in MB Boston's car park, and I think, apart from loosing my best 10mm socket somewhere in the depths of the engine, it was easy.

Also from memory there is no gasket used on the metal cover, so its essential to get the mating surface nice and clean. (NOW DOUBTING MYSELF THANKS TO MURKYMERCS POST)

Tony

Tony