Collapsing Radiator Hose - Mazda 323

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Mon 18 Sep 2006 18:50
Collapsing Radiator Hose - Mazda 323 - stunorthants
The bottom hose on my radiator colapses when the engine is cold - any ideas why?

I had the actual pipe replaced a month ago and discovered that it had perished quite badly, but changing the pipe hasnt made any difference and it still collapses when cold. Once the car has been running a few minutes it fills out normally.

The car doesnt overheat and as far as im aware, has no cooling issues, so its a bit of a curiosity as to why this is happening.

Car is a 1986 Mazda 323. {Added to subject header where people will see it without necessarily having to open your post first - DD}

Thanks in advance!
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Mon 18 Sep 2006 19:07
Collapsing Radiator Hose - 659FBE
This is most likely due to a stuck vacuum release valve in the radiator cap. All caps have a valve (usually in the centre underside) which opens when the cooling system pressure becomes lower than atmospheric. This happens as the system cools, and the hoses will collapse unless this valve is working.

You might be able to free it off - try giving the underside of the cap a good scrub with a brush under a running tap, then try to operate the valve manually. Otherwise, try a new cap.

659.
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Tue 19 Sep 2006 02:08
Collapsing Radiator Hose - Pete M
The other thing that can happen is that the pipe to the overflow bottle can be blocked or the vent in the overflow bottle blocked. In either case, when the motor cools and tries to suck the coolant back in, it can't do it. The radiator cap vent may be ok.
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