Radiator hoses deforming when revving engine.

[squench2002]

Hi folks,

i have noticed that when you rev the engine on my W163 the large bore hose that runs along the top of the radiator deforms and gets sucked in.
Replaced the hoses but it's still happening.
Any ideas?
Thermostat is new this year and temp is perfect.

cheers
Ian.

 

[tony jr]

Hi Ian,

I am sure someone else posted a similar issue a while back. I remember the post but not what caused the issue.

Worth doing a search

Tony

Sent from my SM-T310 using Tapatalk

 

[toby1]

Is it causing an issue? Does your car drive ok?

 

[Roxie]

they all do it

 

[John Laidlaw]

yip they all do it - the reason is that revving will cause a postive delivery pressure through the hose, followed when you lift off by a drop in positive pressure, effectively inflating the hose wall followed by a somewhat negative pressure, therefore the hose wall deforms, as there is only a textile reinforcement built in and nothing to resist the 'sucking in' you are seeing.
some manufacturers use a helical wire in the hose wall which resists the suction, but with these engines there is no need

 

[Frontstep]

My lungs do it too

 

[oigle]

It should only happen when engine is cold and thermostat is closed. Once engine is at operating temp, the system should have a positive pressure of about 12psi in it and no deformation should occur. If you are still getting it, your pressure cap needs replacing.

 

[JML270]

^1 pressure cap.
Make sure it's fitted with at least 3 clicks as per instruction label on fuse box cover.