All,

Building a Velocity and we drained the coolant system down to fit an in-line probe type thermo-switch for the fan ( brought from kit car solutions ).

Once everything was filled up again, we ran the car up to temperuature to set the fan switch. One thing we noticed was that once up to 100 on the gauge ( a bit high i know ) the hoses started to collapse.

The hose from the rad to the water pump collapsed, and so did the hose out of the thermostat.

These are all brand new hoses. Engine is a Zetec. Rad is an Escort MKII rad.

Any ideas?

is this as the engine cooled down?if so its the water contracting and causing a vacume,if not looks like too much pressure or dodgy hoses

I know thw 2 litre zetec needs an 1800 water pump to work properly,not sure if this would cause the problem if still using a 2 litre pump though cos its going the wrong way.

nope. its a 1.8 with the 1.8 water pump.

they collapsed while the engine was running, and expanded again once we took the rad cap off.

could this be a naff cap?

weird try it again and see if the same happens,could have been an air lock.
also run it up without the cap on,does the water dissapear?have you got a cap on the rad and an expansion tank?.
if so put a plain cap on the rad with overflow going to the expansion tank

Did it do that before you fitted the thermostat unit??

Very strange. It sounds like the pump is drawing the water but there is a blockage from the rad (ie no water flowing into the pipe). Cant think why that would happen tho unless the thermostat is causing a constriction and limiting the flow. Maybe this is why the temp is so high - not enough flow.

Have you tried loosening the cap when the pipes are being sucked in - of course be VERY careful - hot water and pressure etc. (Disclaimer time - I take no responsibility for scalding / personal damage howsoever caused etc etc).

Im not sure if the pump is supposed to be sucking from the rad or pushing water into the rad?? If all was well before fitting the sensor then this is where i would commence investigation.

Water Pumps

Not sure if this is relevant to the problem but as I understand it the water pump needs to be from an Escort configured Zetec. A 1.8 Modeo pump will be rotating the wrong way.
Easy way to tell which type you have, the inlet/outlet? pipe is at 90 degtees to the cranckshaft centre line if it's an Escort one, inclined towards the rear if a Mondeo one.

Mick

all seemed well until we had to take the bottom hose off to fit the tempswitch probe. Does it sound like an air lock?

I t must be a massive air lock,i run mine with cap off the header tank and fill as it heats.