Cooling Problem...Intermitten Heat

[tracyc]

I have a 2000 C280 Sport. I've noticed my heat wasn't producing the heat that it once did. I do get some heat but not as hot as it was. I just changed the thermostat and flush the coolent with all new G05. I'm still having the same problem except I do get heat then I would get burst of cold air, then back to heat (but not the same as before). Obviously, I think I have another problem. I did also purchased a coolant temperature sensor but haven't installed it yet. Wondering if this would solve my problem? or is there something else I'm missing. Needs alot of feed back soon because the temp here in Wisconsin is ready to drop to single digits in the next few days. Thanks in advance to all who reply.

[Vetruck]

Does anyone know if these cars have a diverter valve in the cooling system? I still do not know the cars that well but the symptoms you describe sound exactly like a faulty diverter valve on a GM car.

[hvmercy]

Facing the engine, left side next to the firewall.
Does anyone know if these cars have a diverter valve in the cooling system? I still do not know the cars that well but the symptoms you describe sound exactly like a faulty diverter valve on a GM car.

[Vetruck]

Well there you go TracyC. There is your culprit. WHat the divertor valve does is it closes off to keep the heat away from the blower motor when the AC is desired. Without it the hot water from the motor runs constantly through the heater core and the AC never blows really cold- thus alot of manufacturers have outfitted car with vacuum controled divertor valves in the heater hose lines to divert the hot water flow straight back to the radiator. If you valve is not working properly, it is not opening enough to send hot water to the heater core- thus no heat.

Also- I know GM cars very well, I am new to working on Mercedes Benz', but the principal of the cooling system is fairly universal in all cars. The GM divertor valves are made of ABS plastic and go bad very easy. THey are notorious for cracking. I removed the one I had in a Camaro I used to own and I ran that car like that here in Southern California for 15 years that way without a divvertor valve. The hot water just ran constantly into the heater core and my AC still blew cool enough- I perferred the reliability on not having the divertor valve to fail and leak, as opposed to have a little bit cooler AC- my AC still blew plenty cold. I would suggest if you live in a cold climate that you try and eliminate it like alot of people do in American cars.

Dean

[tracyc]

Thanks. I did a search on Ebay Motors for a Diverter Valves for my car (ranging from $99 used to $289 new). I attached a pic of the correct part (I think?). If this is what you are talking about, are there installation instructions anywhere? Is this complicated to swap out? Finally, I just found out there is a left or a right style. Am I to assume when I look at my firewall, if the Diverter is on the passanger side of the fire wall, I'll need a right diverter (per picture) or would it be the left?

[arar_hany]

Buddy I had the same problem with my 04 e320, I changed the Changeover/Heater Control Valve

[strictlyspeakin]

I don't know about that part but keep in mind I have a 94. You might want to look at a duo valve instead. Usually that is the part that needs maintenance when there are no heat issues. there are plenty of how to's already out there. Search duovalve
A quick search on eBay shows a part number 1147412078 that potentially fits your car.
I'm concerned by the sudden blast of cold air part. It sounds like a vacuum issue might be in play here. A broken line or leaky element causing the flap to open to the outside air.

[tracyc]

Diverter Valve or Duo Valve? That is the question...Anyone else who has experience my problem that would like to chime in? I just don't to change parts and keep guessing. I know there are alot smart people here who know alot more than myself. So, all the help I can get would be appreciated. Thanks!

[Vetruck]

It looks like they are the same thing- just a different name then the Chevrolet/GM ones. GM calls them diverter valves- sorry for the confusion. Here is a link I found, maybe this will help. It explains a little about how the valve functions

http://www.marcusfitzhugh.com/CLK/DIY/duovalve.html

[tracyc]

Thanks Vetruck. I'll get one ordered and replace the old one. Hopefully this will solve my problem.

[Sulaco]

Duo valve. Looks like 2 giant D cell batteries side by side on the left side firewall. You can experiment by banging on it with a wrench and seeing if it decides to pop open and let hot water move through.

Mine was frozen once and no matter how hot the engine got it wouldn't move to let the hot water through. I poured a pitcher of hot water on it slowly and tapped it once with a screw driver and heard it click. Heater began warming instantly.

[taz069]

On my 96 c280 the duo-valve was completely stuck. Being a do it yourselfer i took mine apart. Not complicated in the least. A little elbow grease with the disasembly of just a few screws my plunger/cylonids were stuck due to old corrosion over the years. Using some 400 grit sand paper and some cleaning solvent, freed mine up and still working like a charm. Keep in mind have no pressure on the radiator system when you take the piece apart from the hoses. You will lose a little bit of anti-freeze not a lot. Good luck hope this helps.

[tracyc]

Well, here is the update. I replaced the Heater Control Valve. Be fore I replaced it, my symptoms was that the passenger side vent and passenger side middle vent were blowing cold air when the heat was jacked all the way up. The driver side vent & driver side middle vent was blowing warm to hot air. NOW after the swap...all the vents are blowing cold air when I have the heat all the way up! What am I missing? Today was -5 in the morning anf got up to 25, tommorrow the same way. Please help!
Tracy

[strictlyspeakin]

Your original problem is why I was thinking that it was like a vacuum issue. Look at the part in this thread and see if you see any broken lines or cracks in the housing. You should find this part in the engine compartment passenger side near the firewall where a lot of the electronics are. The Duo valve was there as well.
http://www.club202.com/forums/showthread.php?15931-Vacuum-Valve-Block&highlight=vacuum
This link has an overall system design pic in it.
https://wiki.bentleypublishers.com/display/tech/Climate+Control+Description+and+Operation+Mercedes-Benz+C-Class+1994-2000+%28W202%29

Can you get any info from the sensors by following this thread?
http://www.club202.com/forums/showthread.php?15900-Mercedes-Engineering-Code&highlight=duovalve

Finally here is something about the duovalve.
http://www.benzworld.org/forums/w210-e-class/1350793-duovalve-removal-cleaning.html