2003 Ford Ka overheating

[BillyMarson]

Hello everyone
I have a 2003 Ford Ka which is overheating regularly and building pressure in the cooling system
I've spoken to my dad who tends to know his stuff, he reckons it isn't the head gasket due to how well the engine runs other than this.
Basically the coolant seems to be bypassing the radiator, so whether this is an issue with the rad I don't know, we used the garden hose with a nozzle on it to make it faster flowing, and flushed through the rad both ways through the top and bottom hose, same with the stat housing and with the filler tank, the flow was good and this led us to believe that the issue had been solved, lo and behold it overheated, pressurised and steamed everywhere.
I've found a rad online for a tenner, I'm just wondering if anyone else has any suggestions on what it could be, possibly to avoid spending money on a rad I don't need if it's not necessary.

Thanks very much

Bill

[GreenV8S]

BillyMarson said:

Basically the coolant seems to be bypassing the radiator

The thermostat is what controls how much flow through the radiator. If the stat has failed, would usually fail partially open but could also fail fully open or closed. If the radiator is staying cold, that would be the first thing I'd check. The simplest way to test is to remove it from the vehicle and drop it in a pan of boiling water. It should open fully, and then close as the water cools down.

Id the radiator is getting hot and the engine is still overheating, check the fan is working. If the radiator is hot and the fan is working properly and it is still overheating, you probably have a silted up radiator.

[S0 What]

Check the small bore return hose to the header tank, if these block you will get overheating on most fords of this period ? worth a check, failing that get the coolant sniff tested for ex gasses

[BillyMarson]

After taking a look inside the stat housing, there's no thermostat in it, presumably taken out by someone looking for a quick fix to this very issue.

By the small bore hose do you mean the one from the filler tank to the top of the thermostat housing? My dad called it the return but he sometimes uses old terminology I'm not familiar with.

Thanks a lot for your input so far chaps

[SebringMan]

S0 What said:

Check the small bore return hose to the header tank, if these block you will get overheating on most fords of this period ? worth a check, failing that get the coolant sniff tested for ex gasses

This. I always called them the bleed off/return pipes as they are almost essential for the system to self bleed air out of itself.

Most Fords IME tend to have two:

-One going from the Header Tank to the Thermostat Housing
-Another going from the Header Tank to the top of the radiator.

If both of these are blocked the car will be unable to remove the airlock. This would cause overheating.

Which engine is in the Ka? The Endura-E (a rebaged Crossflow/HCS engine from the 80s or pre Crossflow Kent way before that) or is it the Duratec RoCam engine (the Brazillian engine fitted at some point after 2003)? Fords IME tend to have a foot on the thermostat to circumvent the radiator when the engine is cold. This speeds up warm up times. Without this foot the bypass hose/passage on the engine will allow uncooled coolant to go back into the engine without it ever seeing the radiator.

While this may not cause the overheating it would not help matters. I know the 1.8 and 2.0 Duratec HEs in addition to the Duratec V6s have this foot but I don't know about the KA engines. I'd be checking for that myself.