Heater trouble on 190E 2.0 (MY1989) PLEASE HELP!

[television]

You are correct Nick and I am wrong in the other post, as the valve is vacuum operated

 

[AMH]

Hi all! I have a 190E 2.0 litre saloon which has covered 140,000 miles and never missed a beat. Just recently I noticed that the heater wasn't performing up to scratch (No air conditioning). I had a look at the expansion tank and noticed that the water level was down a bit - maybe low enough to draw some air onto the system. (She's not using any water - I have to admit that due to the reliability of the car, I (Foolishly) rarely check the water level). I filled it up and "bled" the system by squeezing top and bottom hoses - as per Haynes manual. This did nothing. Went to my independent and he said that the matrix would probably be full of c**p and that I would have to replace it. He also said that he had the same problem and that he had tried Bars flush with no result - and that he'd left it in the system for the last six months!
Ok: I'm now convinced that this must be that dark grey coloured round shaped valve which sits on the off-side of centre near the bulkhead. I'm told that this is what controls the heating by "sucking" a ball up using a vacuum so that the hot water can circulate. (I've tried putting a tiny bit a spit on the end of the vacuum pipe and it seems to suck it in)
She's not using any water or oil and there's no evidence of head trouble. I did get it to work once whilst left idling on the drive. She got really hot and the heater got hot too just before the fans kicked in.
My next task is to replace the valve (I've no idea how much these are) but do I need to do this? Am I missing something really obvious here? I've run out of ideas other than replacing the valve - so any input from you would be much appreciated. I'm freezing in the car! (It does work slightly, so it's not that bad - but nowhere near it's usual furnace quality!!)
Thanks for your time. Adrian.

 

[Aussie Nick]

I think that the whole system is clogged up. You need to have the radiator out and cleaned professionally. You probably need to flush through witha chemical cleaner a couple of times after radiator clean. Also when the radiator is off try running a hose nozzle under high pressure through the heater pipes to get the gung out. This will mean you have to disconnect both in and out and connect the nozzle up to the in or out. You will get wet so wear a raincoat but it should work.

 

[television]

Malcolm. Which other thread are you referring to? I can't find it?! Adrian.

I posted on the valve, but I was incorrect so I removed it

All of the heater is here in the links

http://www.detali.ru/cat/oem_mb1.as...990&GA=722.417&GM=717.404&CT=F&Cat=15F&SID=83


can you bye pass the valve with a piece of pipe to test

 

[AMH]

Yup! Tried all that, Nick! I've even stuck a lose through the matrix inlet AND outlet hoses - no sign of any gunk at all. I also took the liberty of flushing the system with caustic soda. Yes, not a typo; caustic soda. The water just came out clear. What next? Sulphuric acid? The main radiator is almost new and running clear also! .......So: could it be that valve?

 

[AMH]

Malcolm. Which other thread are you referring to? I can't find it?! Adrian.

 

[Aussie Nick]

Sorry it didnt help. If the coolant is running free it has to be a restriction of the hot water inlet somewhere in the system which leads us to the valve. Before you go and buy a new one try bypassing as Malcolm has suggested.