Radiator Top Hose Problem - Mercedes ML 270 cdi Auto 2002

13enzy

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Mercedes Benz ML 270 cdi Auto W163 2002
Hi
I have recently posted threads where I have encountered in-cabin heater problems, the blower was working fine but no heat.....
So I decided to Flush the Engine/Radiator cooling system, Flushed the Heater Core/Matrix, Replaced the Thermostat, Renewed the Antifreeze, Changed the Electric Auxiliary Coolant Pump and then "extensively" Bled the whole Cooling System to eliminate any Airlocks etc.
The heating "problem" was eventually solved....but NOT, by any of the above.....
So as a last resort.....I embarked on changing the Heater Flap Actuator on the fan blower motor, and as i started to remove the front fascia "heater control" panel, I noticed one of the connector was not properly inserted and had become loose, soon as it was connected....Hey Presto! ....we now had Heat .... Problem Solved !!!!.....
But, I have now come across another quite "worrying" problem, The Top Radiator Hose becomes "FLAT" (collapses) when I rev the car up. I have never noticed this before, and wanted to know from you guys if this is normal?....to me it looks horrendous and "scary" to say the least, it is as though it is trying to "suck" water, but it is not getting anything and the effort of this suction is making the "round" pipe (top hose) go totally "FLAT" ????.....
That is the reason why I have explained in detail of all the work I have carried out on the cooling system, and I thought maybe I have done something wrong, which is causing the top hose (pipe) to collapse when the car is revved.....can anyone shed any light on this problem ?
PS. The replaced Thermostat was a brand new Febi make, with a new Sensor and a rubber Seal etc.
 

Arzaam

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W203 2002 c180
No expert but normally when radiator hose collapses that means they are worn from the inside and need to be changed, if the reservoir cap is original its largely responsible for maintaining pressure in the system.
 

oigle

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Currently 2003 ML270. 2012 Nissan Maxima 250SL.
I would ask whether the engine is hot or cold when the hose flattens. If hot, the hose should be replaced. If cold, its a good chance the reservoir pressure cap is not venting properly and the system is vacuuming. Try it with the cap removed and see if the hose still flattens.

Ian.
 

John Laidlaw

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BMW 530d X Drive Tourer M Sports
No expert but normally when radiator hose collapses that means they are worn from the inside and need to be changed, if the reservoir cap is original its largely responsible for maintaining pressure in the system.
Often. Problem with rubber vulcanised products is that when presented with steam/very hot water they change still- they are pretty much a ‘live’ thing, so continuous revulcanising of a sort is happening. They won’t have a finite life as eventually that process will lead to delamination and in the cases where it’s a non wire bound hose and only with a fabric reinforcing scrim in the wall it’s not suitable for vacuum application.
 

Frontstep

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I suppose it depends on how much it collapses, you could just have air still in the system.
The top hose might be tired, they used to have springs in them to deal with all that sucking.
There is a lot of sucking going on.
I suppose a new one wouldn't hurt especially if it feels wrong.
My old gems top hose goes in and out when I rev it.
 

Taffy7hfa

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2004 ML350 Inspiration .2002 ML270 CDI .2016 Hyundai i30 1.6crdi.2014 Peugeot 308 1.6 HDI.
My tope hose often flattens overnight then resumes its normal shape once the engine is started,I assume its because its probably the original hose which is now 15 years old and needs replacing, there are no obvious signs of deterioration. The Cap seems ok, I have read other posts on here that have talked about the top hose flattening out on the ML 270.
 

Frontstep

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I forgot I replaced my pressure cap.
 


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