Zetec cooling system

[Matth93]

I've had the car running properly now and it seems to push all the water out of the header tank. What I've found is that if I swap the header tank hose into the thermostat housing from the one on the right side to the one on the left it seems to stop doing it, is this right?

The rest of the system I've got the top rad hose to the thermostat housing and the bottom one to the water pump with the vent pipe on the thermostat housing to the top of the header tank

Have I gone wrong anywhere?

[Tony C]

Matt,

I've still got some notes/plumbing diagrams form my Zetec;

When the thermostat is closed, water flows through the small left hand outlet (when looking from the flywheel end), to the 'double-tee' at the front and back through the engine. It's only when the thermostat opens does the water flow through the top hose to the radiator.

Pipe No1 in the bottom picture would normally supply the heater matrix and is open all the time. I removed this and blanked off the outlet from the stat housing. From memory pipe No2 maintains flow through the head until the stat opens, something like that anyway!

You can block both small outlets from the stat housing, but what you get is the water pump trying to pump water through the system, but it has nowhere to go as the pipes are blocked up and the thermostat is closed. Thus the engine overheats. Eventually, the thermostat will get hot enough and open up and the engine gets a cold shock from the cold water in the radiator entering the engine which then closes the thermostat again etc. etc.

[Matth93]

Thanks Tony i'll redo them couple of hoses later then

[David T]

Mine's the same as Tony's Polo config., i.e. no heater matrix, but with pipe 3 from the bottom diagram from the bottom of rad to the header tank. Works perfectly. If you look inside the stat housing and figure out the way it operates with the stat you will see why other configs have so many issues.

[Matth93]

I've left it without a thermostat in for now and so without the bypass hose either, it seems to warm up ok but obviously once I use it a bit if it's not getting hot I'll put one in and add the bypass hose.

[Hammy]

Great help and advice here and a question I would probably have been asking soon as I've not done a Zetec with the standard Stat housing before. Hope it all works out Matt

[David T]

I tried initially without a stat, but the coolant would never get above 60-ish. Then tried a 3mm drilled stat, similar result. Then did it properly with the full complement of pipes!