Or you could make the one I did and own it for $25.

http://www.peachparts.com/shopforum/diesel-discussion/382730-diy-$25-mercedes-coolant-pressurizer.html

Before spending money on anything, you need to know what exactly the problem is. If you have a blown head, you're wasting $200 on a radiator and won't be fixing the problem. Also, when you use a coolant pressurizer, the engine needs to be cold as in sitting overnight.

There's a ton of areas coolant could leak. Most of them are the hoses, but it could also be the radiator, water pump, heater core, etc. Figure out what the problem is FIRST and then spend money to fix it.

Dkr.

Radiator cap is #2.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

That is normal looking blowby for a diesel with some miles on it. It is the combustion gasses which get past the rings and pressurize the crankcase to a low level of pressure.

If you look down into the radiator do the tubes look clear or plugged?

Is there any water dripping from the water pump?

If your normal operating temp is 40 to 50C that indicates the thermostat is not working or you have a bubble in your coolant.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Well, its not always clear.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I want to step back a minute and ask about the procedure you're using to add coolant...are you filling it to the bottom of the neck? If so, you will have a "leak" every time you fill. This radiator is supposed to have an air cushion in the top tank. If you overfill, excess coolant will be pushed out the overflow tube as soon as the engine warms up. This is ok...the coolant will find it's level, and when the engine cools down there will be a proper air cushion in the tank. At that point, look in and that's the right level. If you then add more coolant above that level, it will just spew again.

I think that you want to explore the crud in the sealing ring of your filler neck. I can't tell from the photo if that's oxidized antifreeze or the remains of a failed gasket. But what you should see is all brass. So clean that up first. That alone could be the cause of your overheating condition, because it's keeping the cap from sealing. And replace the thermostat. I'm guessing that it's a latching thermostat, and is now stuck open.

Let's wait for the evidence before declaring catastrophe. The water pump and radiator are good, because the temps are low. The head probably isn't cracked. The valves seats probably aren't destroyed. The headgasket probably isn't leaking. In fact, the only place we know there is leakage is around the cap. So let's fix the obvious things first.

So I found a confirmed leak. I wiped the fan cover, radiator cap, hoses, etc down clean before I added coolant and drove home 30 miles in 100 degree heat. Got home, popped the hood, and I have wet coolant as pictured in the photos. At first I thought the coolant was left over from something the previous owner did like being sloppy and not so much a maintenance issue. I went through a gallon of coolant this week commuting 60 miles a day. I guess it makes sense since the coolant returns to the radiator cover and is getting blown through the neck of the cap. Or maybe I still have a more serious problem? I heard a head gasket pressurizes the system and can blow coolant. I guess it's worth $300 to find out though.

Looks like I'm changing a radiator and some hoses with the thermostat.

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Or ;

You could try to good advice given here instead of blindly throwing parts at it .

If you look down into the radiator there's a plastic thing with a ledge on it below the filer neck ~ this is the correct hot coolant level and adding more coolant will cause it to be forced out .

Some basics you've not yet covered :

? are you turning the heater full on when you refill the coolant ? .

? What color is the coolant ? .

? Have you yet properly drained, flushed and re filled the cooling system ? .

As 50° C is not even normal operating temperature I'd think there's maybe a gone missing (because you just bought this car) or stuck open thermostat .

Before to$$ing ca$h at it, do the proper basic maintenance like a careful, not rushed Citric Acid Flush .

When first I bought my '82 240D it ran over 100° C even in winter and looking down into the radiator I could see the crusty stuff around the tubes, this is called "Solder Bloom" plus the coolant would puke out at freeway speeds and it kept turning red/brown so I knew the faults were is lack of maintenance ~ I had to flush the beejeebers out of it repeatedly using powdered Citrc Acid (cheap on E-Bay) , leaving it in all day as I commuted 30 minutes each way to the heavy duty truck shop where I worked .

In time (or after several times) not only did the coolant remain translucent and new looking but the inside of the radiator (the tubes etc.) all looked like clean metal instead of crusty black crap .

The ball is in your court, Festina Lente here .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Not so bad. See the attached diagram. Replace the overflow hose and cap. Clean up the sealing surface. I think that should do it. But if it doesn't, the filler neck may be separating from the radiator tank, and the radiator may need to go.

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