Overflow of antifreeze w124

Bean

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I was wondering if anyone could help. We have driven our w124 e280 estate 1995 from the uk to the centre of France (Loire valley, Sancerre). The last couple of days when we have returned from a drive the coolant overflows and the temperature gets to above 90, but when we're driving around the temperature seems fine, around 85-90. The car was checked by a local garage and they couldn't see any obvious issues i.e. Worn pipes or worn radiator cap. On Saturday we're planning on driving just north of Paris and then onto Dunkirk to take the ferry across on Tuesday. Is it safe to drive the car and fill up with water when needed or would it be better to call the RAC breakdown before driving any further?
 

grober

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Obvious candidates to check would be the thermostat and your cooling fans--- the engine one- viscous coupling and the one /two electric fans for the air con [ if fitted] at the front of the radiator. Any malfunction of these aformentioned would possibly cause your problem if driving hard [ long motorway miles at high speed] in hot conditions with the air con on making extra demands on the cars cooling system.

You could try to continue lower speed driving in short bursts keeping a wary eye on the temperature gauge. If coolant overflows and requires topping up you must wait till the engine cools down before adding more coolant- adding cold coolant to a hot engine is asking for trouble.

If covered by RAC recovery/breakdown I would seek a second opinion from someone on the spot- better in a hotel /camsite /public car park than on the hard shoulder of the motorway.
 
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zipdip

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You should have no trouble getting home,just keep topping up the water when you have stopped for a while be careful of taking the expansion tank cap off while the engine is still hot.
 

Dec

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How much coolant are you losing from the bottle?

Dec
 

rorf

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Should get to 100 deg C without the coolant overflowing - I would suspect the coolant container pressure cap is faulty. Are you running with good quality Mercedes coolant which is changed every 3 years?

But it could be faulty thermostat, fans not activating when needed, blocked dirty radiator, corrosion of internal coolant passage ways etc etc.

Most common vehicle breakdown is due to overheating!
 

brucemillar

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Agree with everything above. One point to make here: Are you sure you are not overfilling in the excitement to to ensure that you are not overheating? Any overfill in the system will be pushed out the overflow as the coolant expands. If the cap is bad it will also push out through there. When cold check that the level is up to the "min" line on the header tank. When hot it should be at the "Max" line. Anything above max will be pushed out onto the road.
 
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Bean

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Thank you all for your replies. Currently losing most of the bottle. Not using coolant, just water. When I top up, I haven't been overfilling, just to the minimum level. It's odd because today for instance, drove 50 miles, stopped a couple times, temperature was fluctuating between 85-95 no lose of coolant (water) but as soon as we get back to the hotel, which is on top of a hill, the temperature rises to about 100 and water is pushed out through the overflow. I changed the cap in 2014 but maybe it needs changing again?
 

pembssurf

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Make sure you are adding enough coolant as using and topping up with just water will give you exactly the same symptoms. You need to raise the boiling level with a good quality coolant!
 
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Bean

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Sorry, I'm not very technical. Since this started, 2 days ago, I've only used water and not coolant when I top up. Should I use coolant even though it may just overflow?
 

grober

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Sorry, I'm not very technical. Since this started, 2 days ago, I've only used water and not coolant when I top up. Should I use coolant even though it may just overflow?
No you shouldn't worry too much. A 50/50 mix antifreeze/water is not going to have a much higher boiling point than 100% pure water.




Its the antifreezing and anti corrosion properties that are more important so as a temporary measure clean water is fine. It should be noted however that pressure is much more important in raising the boiling point so any leaks of pressure anywhere in the system are not good.

see

Things you should know about coolant | hellafunctional
 

Dec

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It would best to take it for a spin to get it up to temperature then run the engine with the bonnet open to recreate the fault and watch what’s happening to see if the water is leaking somewhere else on the engine.

Dec
 

WDB124066

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Switching points on the cooling system, may shed some light - attached. In the past I have written the various temps down on a small piece of paper and taped it to the dash to give me a greater understanding what should be occurring when.

I must say if you are spitting fluid out of the tank with only 100 deg C on the gauge it does sound like the rad cap is lifting too early, there simply isn't enough pressure in the system @100 DegC to achieve this normally without other factors coming into play like a serious blockage.

Did you buy a Genuine MB cap or some aftermarket one.....?

More thought on this [while sitting here reading Corrosion and listening to "In the grip of a tyre fitters hand", I suspect a split plastic header tank, the one that the rad cap fits on, and I suspect what you think is the cap lifting may well be the tank split opening up and passing fluid that way....?? A pressure test should help id this but don't go above 1 bar without looking very closely at the waterpump for leaks. You will see a puddle on the mounting bracket if it is. Not an entirely cheap fix if the pump lets go unfortunately. But start with a good inspection of the tank.
 
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rorf

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your vehicle is an E280 inline 6 so I would also suspect that the head gasket is leaking, thus forcing water out of the system.
 
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Bean

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Again thank you all for the posts. I've inspected the tank it seems fine - no splits. The cap was a genenuine MB one and whilst it's only 2 years old the inside is very rusty. When I get back to the uk I will order a new one though. When the coolant does overflow it overflows through the pipe at the top of the header tank.
 

trapperjohn

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Have not read the whole thread but the easy start point for your problem is changing the expansion tank cap, again for a genuine MB one. This sorted the exact same problem I had on a 220TE I had once up on a time.
 

WDB124066

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If it is the head gasket you can test for this by looking for combustion products in the water, ask your mech to do this if things don't improve after the [cheap] cap change.
 

hotrodder

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Seems a bit 'glass half empty' to be jumping to head gasket problems... common failure mode for the m104 is external oil leaks rather than the gasket fire ring(s) letting go allowing combustion gases to escape into the cooling system

The header tank overflow is supposed to feed into a 'recovery tank' hidden in the innerwing (scroll down to 20-4540) 20 Cooling System - M104
In theory any coolant puked out of the header tank should be drawn back in as the system cools down. Obviously if the overflow/recovery tank or the hose feeding it is split this won't happen. A dodgy rad cap (or leak somewhere else) would also stop this happening by preventing the system from building pressure as the coolant warms up and expands. There's a vacuum valve in the rad cap (red blob in the pic)

badradcapseal.jpg

which'd stop coolant being syphoned back into the header tank if it's blocked/mullered etc. Green arrow is pointing at the seal for the pressure stage and obviously there's another seal for the top of the filler neck

If a genuine cap is going rusty within 2 years it suggests that the coolant was well past it's useful life before further diluting it? As said i wouldn't worry too much about that in the short term (freezing temps are months away, pressure is more responisble for raising the boiling point that antifreeze etc) but i'd get the coolant changed as soon as you're back if it doesn't need draining to fix the problem anyway
 

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