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280CE 1984
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175 Posts
Discussion Starter #1
Hi, I have noticed that I am fairly regulary topping up water into the radiator - say once or twice a month..? How often is "normal" for topping it up, does some evaporate away normally anyway..?. I can't see any leaks at all - the only thing I saw is coolant coming out down the (overflow..?) hose that runs down from the filler cap to the bottom of the radiator - this was following a very short run just up the road literally at the weekend. I am wondering if the pressure parmater of the cap may be wrong causing coolant to come out when it shouldn't...?? I am planning on flushing the coolant as it is very very weak with anti-freeze now and re-filling with proper amount of MB coolant which I have just bought. Before I waste this VERY expensive solution, I was wondering if I need to change the cap itself, do they go wrong, and could that be the cause maybe of small fluid loss. Many Thanks, Martyn.
280CE, 1984, M110 Engine
 

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77 240d, 02 Ford F250 V10 (7mpg), 05 GMC Denali (The Baby Hauler), 2000 BMW 323CI (was my Bros car)
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817 Posts
Caps can go bad. If they can't hold the pressure or the seal fails it will bypass coolant into the recovery tank (if applicable) or drain on the ground. I would change the cap. It's a cheap fix.
It normally won't evaporate in my opinion because it's a closed system.
 

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1979 280CE
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6,118 Posts
280CE's don't have a recovery tank. Replace the cap.
 

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1979 280CE
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6,118 Posts
What are your running temps? Do you have any white smoke from the exhaust?
 

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Premium Member
280CE 1984
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175 Posts
Discussion Starter #6
I will check....

I haven't noticed any white smoke coming from exhaust, running temp is right in the middle, I have never had issues with temperature - I just top up with water when necessary.
 

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'82 300D
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1,279 Posts
You can also install an aftermarket coolant recovery tank. Keep it filled to the proper hot/cold level and the radiator will keep itself at the proper level.
 

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1979 280CE
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6,118 Posts
Yes
 

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81 mercedes-benz 240D 400k (in portugal),97 Mercedes-Benz E36 Amg (dad's car)
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330 Posts
Hi, I have noticed that I am fairly regulary topping up water into the radiator - say once or twice a month..? How often is "normal" for topping it up, does some evaporate away normally anyway..?. I can't see any leaks at all - the only thing I saw is coolant coming out down the (overflow..?) hose that runs down from the filler cap to the bottom of the radiator - this was following a very short run just up the road literally at the weekend. I am wondering if the pressure parmater of the cap may be wrong causing coolant to come out when it shouldn't...?? I am planning on flushing the coolant as it is very very weak with anti-freeze now and re-filling with proper amount of MB coolant which I have just bought. Before I waste this VERY expensive solution, I was wondering if I need to change the cap itself, do they go wrong, and could that be the cause maybe of small fluid loss. Many Thanks, Martyn.
280CE, 1984, M110 Engine
hey my 240D had the same problem not has bad as yours but bad enought that my grandad had a 4l botle of water in the trunk before i bought it, and this easter what happend was that one of the tubes that conect the radiator to the engine the tube mount in the radiator had rusted out and broken and it was lossing preasure from there until it actually didn't hold any more and the tube fell off. needless to say the next was a white smoke coming from the car lol my solution at the time was to replace the radiator with a new one (150 euros) because the mounts were messed up. now i believe that it doesn't losse any water to my knowledge how ever if you never had your radiator changed id advice you to check that, you probably have the same has me the good new's is that one mine it didn't damage the car :) :)
 

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money pits of various forms
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5,885 Posts
How does your heater smell? I would look for leaks particularly in the heater core and or servo unit.
 

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Premium Member
280CE 1984
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175 Posts
Discussion Starter #14
Nearly There

Hi Guys, thanks for the help so far on this.

Yesterday, I started to drain and flush the engine coolant - I have bought new engine coolant, a new radiatior cap and thermostat 'o' ring from MB dealer (after reading the Haynes manual)

I drained all the coolant by taking out the drain plug at the bottom of the radiator and the plug on the engine block - as advised in Haynes manual. But I stopped short at taking off the thermostat housing to enable me to flush the engine bit with the hose pipe as I could see that there is gasket sealer paste or equiv on the housing where it mates with the fitting on mine currently.

I don't have gasket paste, should there actually be a gasket there..? If I had kown this I could have got one from the dealer before I started...?

For info, the water that came out was really brown and things were pretty well lined with brown gunk from what I could see. I flushed a lot of water through and things are much better than before. As I didn't know whether I am taking the thermostat housing off yet, I just filled her back up with neat water for now.

Questions:

1. How much engine coolant do I add..? The Haynes book says the total capacity of the coolant is 10 Litres but not how much coolant to add..? In another book I think I may have read that the strength should be around 33%...? (The MB coolant instructions just says measure strength with a measuring device) I don't have measuring device so is this right - 3 Litres of coolant and 7 litres of water...? It sounds a lot to me..?

2. The old radiator cap was certainly not the correct one - The new one says 120 on it and the old one says 110 - Could this just be why she has been losing a bit of coolant..?

3. Should there be a gasket on the thermostat housing....? Is there actually going to be a benefit from me flushing that part now - as I have run it following flushng everywhere else - so my theory is that it will have helped to clean and reduce the concentration overall...? Perhaps a quick flush again without taking off the stat housing and refill with correct amount of coolant. Or should I persevere and do the job properly.....?

Thanks again, Martyn.
M110, 280CE, 1984
 
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