Ignore all the heat related issues for the time being. You can drive yourself crazy.

"EC" stands for "economy". The CCU will attempt to maintain the temperature set on the control wheel but it will not engage the compressor to do so.

Tomorrow morning, check the expansion tank. It will probably be low. Add coolant up to the "cold" mark, not above.

Drive it again.

Repeat.

See if the coolant finally stabilizes in the tank and the temperature on the gauge finally achieves a stable level at cruise.

Then, we'll go from there.

My problem is gone - my upper hose is now firm as is the lower. Temps still the same 82 or so. Early on in this post I mention my symtoms were similar to 83mercedes after I installed water pump, belts, hoses and a thermostat. My hoses were always hard before I performed the work, so I was thinking air in the system also - even though my temps have been OK.

Well guess what I did - went to the parts store and bought a brand new radiator cap My system is now pressurized. Seems odd though, as the system was always pressurized prior to the work I did. My tip off was that I always had a tiny trickle of coolant out the drain tube after shut off - with the hose soft. So I thought maybe......

__________________
'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

Excellent.

Sometimes the simplest of things..............................................

OK, so after days of driving with the "heat" (I say this since it still comes on only for short intervals, even on defroster, as mentioned in an earlier post) on the water level has not dropped and the temp is still running @ 100C.

So, the next step is to use an IR thermometer, so could someone tell me where I can get my hands on one of these?

I am replacing the radiator shortly, I will update on how that goes, how much coolant I am able to put in, etc, etc.

The lines are squishy because of a bad reservoir cap or a reservoir leak I believe. I am going to get a new one and try it out, and search extensively for a leak.

So far, the following have been ruled out as the problem: air pocket which can be removed other than by an act of God, thermostat, and water pump (unless my new one is not functioning, which isn't possible since it's such a simple design...it either turns or it doesn't).

I plan to replace the fan clutch since there is some play and I figure I'll tackle cooling problems all at once. Radiator also, reservoir cap, and maybe get an expert to figure out my climate control problems if they do not go away if I ever get rid of this temp. problem.

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)

If you disconnect the electrical plug on the top of your monovalve, you should have full heat at all times. If you don't get heat then, you will know that the problem lies with the engine cooling system, not the automatic climate control system.
Sears sells an IR thermometer.

Don't mean to sound like an idiot, but what and where is the monovalve?

I haven't really done any work on the climate control system and since it is apparently very complex I don't really plan to (other than this I suppose). Thanks for the help!

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)

It is on the firewall, passenger side, in the engine compartment. It is "L" shaped, usually brown plastic, has a heater hose attached at the bottom and left side. There is an electrical connector at the top. The valve is electrically closed, blocking coolant flow through the heater core. When power is removed, it opens and allows maximum coolant flow, therefore max heat. Disconnecting it takes the ACC out of the picture, as far as heat regulation is concerned.
Picture: http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1EH0TL2AI1HW1DJPDR&year=1983&make=MB&model=300-CDT-001&category=R&part=ACC+Mono+Valve
My thinking is if you don't get max heat with the monovalve disconnected, you must have a problem with coolant flow or level. That aside, I will not be surprised if a new coolant bottle cap solves your problem.

I think your best bet for an infrared thermometer is on e-bay.

I found this one pretty quick at a reasonable price:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50974&item=7506611104&rd=1

There are quite a few others in the category "infrared thermometer".

Of course, you can also verify the situation if you simply remove the thermostat.

If the temp drops back to 75°C. or so, then the thermostat is probably doing the proper job and the gauge simply reads a bit high.

Thanks for the advice on both the IR gun and the monovalve.

I wasn't sure if the cap would make that much of a difference...I know it cools somewhat better when pressurized, but hey, that would be great if it could dramatically change things.

If still running hot after monovalve disconnect, radiator replacement, cap replacement, certainly will get thermometer and make sure gauge is accurate.

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)

So I took out my thermostat and did the test where I run it and see what the gauge reads. I took it out for a 25-30 minute drive and drove at about 55-65 mph. The temp rose to 60C and stayed there basically irregardless of my speed (slight fluctuations of a few degrees, but nothing major).

So does that mean that both my thermostats are bad??? The odds of that seem astronomical.
Is 60C what it's supposed to run at sans a thermostat, or is my gauge reading high?

I guess I'll do the test in a pot of water, but I need to get a thermometer...

In the meantime I'm going to keep using the car without thermostat for the sake of the engine, unless anyone can think of a reason not to do this. Really what would prevent one doing this all the time (in summer, of course, and I know it would hurt diesel mileage)? Wouldn't it be better to run the engine colder anyways?

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)

There really is no good reason to run it with the thermostat in the summer months, however, fuel economy will be slightly off due to the colder coolant drawing heat away from combustion.

Dr. Bert makes some compelling arguments to run these engines colder, especially in warm climates. Do a search on his name and read all about it.

Your issue is either the gauge or the thermostats. Nothing else can be the culprit.

I don't want to knock the sage advise by Dr. Bert, but if your talking about driving a diesel (OM617) on short trips with a cold (or no) thermostat this is not going to give the same performance (meaning acceleration) as an engine that has the proper thermostat and allows the engine to reach around 80C quickly.

Precombustion chambers need to get hot and the head needs to warm up to allow that in short trips a cold diesel is a sluggish diesel (compared to a hot one).
Is it reasonable to say that a cooler running engine will reduce some of the thermal breakdown in oil over a long period of time? Show me the data.
I advise against running without a thermostat unless for testing purposes.
BTW, wasn't herr Doktor referencing gas engines that had some high mileage figures, not diesels?

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

[QUOTE=83mercedes]

Also I could try putting in a different thermo if that one is bad, I actually happen to have one, but the one in now is a behr, not likely defective.

[QUOTE]


Take the thermostat out and test it the old fashioned way, on the stove. Get you a cheapy cooking thermometer and measure at what temp the thermostat opens. Or if you're lazy remember water boils at 100C, you want it wide open before that.

Also, I went through 3 bad ones from the dealer before finding one at Autozone that worked, so don't think "oh so and so made it, it must be good".

-Alan


EDIT: If this was already suggested, then kindly look over this. I just noticed there's more than one page to the thread

__________________
2005 Audi A4 1.8T CVT -Silver/Black "Siegfried"

1982 300D - Silver/Blue "Ralph" -For Sale:
http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/119226-1982-300d-sale.html#post852260

1989 VW Diesel Jetta Blue/Blue "Bodo" RIP

Yeah, I may try getting a new one, but I would take the sacrifice in power if it means my enginge will last longer. I've got some other issues I need to worry about before rebuilding the engine.

The only thing is, would this cause a greater buildup in engine deposits because of unburnt combustion byproducts, or would this be acceptable?

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)

Reid, he had a special set of circumstances whereby the diesel would have increased durability without sacrificing any other issues.

First, he is in a warm climate. The time to get the engine up to 60°C. is not exceptionally long, even without the thermostat.

Second, he does not run it on short trips. His commute is something like one-half hour IIRC, so the engine reaches its operating temperature, about 65°C. and remains there.

I'm not convinced that there will be a performance loss when an engine running at 65°C. is compared to an engine running at 90°C. Remember, the exhuast gas and charge air temperatures will be slightly cooler. This could result in slightly more available power.

He is quite convinced that engine wear is severely reduced when running cooler temperatures, either gasoline or diesel. I don't have the data, but, I've got no reason to doubt him.