Saw my mechanic squeezing coolant hoses?

[Gawri20]

He was squeezing one of the coolant hoses going to the radiator, and looking at the coolant tank watching the water bop up and down, what is he looking for by doing this? What does it show or indicate ? Thanks. Gawri

[geeks]

Depends on the car, the temp etc but i would say he was looking for air in the system!

[Brigand]

Yeah, its a good way of getting air out of the system, as your forcing the air around the hoses etc and expelling it out the radiator cap or coolant bottle by putting that pressure on.

[Clivew]

Gawri20 said:

He was squeezing one of the coolant hoses going to the radiator, and looking at the coolant tank watching the water bop up and down, what is he looking for by doing this? What does it show or indicate ? Thanks. Gawri

Why didn't you ask him?

[HustleRussell]

Squeezing the hoses is also a good way to check the cooling system is pressurising as it should, and checking that the 'stat opens.

[Getragdogleg]

On cars with a header tank you have a big feed hose out the bottom and a little airbleed/water flow return in the top.
Some older cars have problems with the little top hose getting blocked up and that can mean the system is clogged up or some muppet has put two buckets of radweld in it.
A quick squeeze or two of the larger hoses ought to make a small jet of water come out of the small header tank hose into the tank.

Obviously, if no water is seen to circulate then the mechanic will take a closer look.