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Fiesta 1.25 Wierd Overheat Problem

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Hi and Merry Christmas to all,

Wondering if anyone has a clue what's going on with my Fiesta. This has happened twice now.

A few weeks back I set off for work on a very cold morning. A couple of miles in I noticed I was still getting freezing cold air from the blower, even though the temp gauge was about half way, which is normal. Then the gauge started creeping up. I pulled over and turned the engine off before it hit the red. After a few minutes I headed back home but had to stop twice as it was still getting high. I hadn't owned the car long so I drained the coolant and replaced it with a new mix of antifreeze, about 35% which apparently protects to -17, which we never get in Surrey!! It was fine after that but it happened again today!

So the engine gets hotter than usual but blower is blowing freezing cold air. There is no heater control unit at the moment, I noticed this after I bought the car. The two pipes from the engine are linked to the two in the bulkhead by small copper pipes and hose clips! Don't know if that makes any difference but can't imagine it will.

Thanks in advance for any tips/solutions/help.


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Hi, first thing to do is change the thermostat. On this engine it's usually a two-stage thermostat so you shouldn't just remove it or you'll affect the coolant flow through the head. Next, get a new heater valve, available off eBay or amazon for £15 or so. System needs pressure testing to check for leaks. A sniffer test should tell if the head gasket is leaking, hope u get it sorted

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Thanks Philip,

What do you mean about the thermostat being two stage and that I shouldn't just change it? I've done Thermostats on several other makes and it was just a straight swap. How do I do this one?

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If you were to remove the thermostat completely you could either remove a designed restriction in the system that causes water to circulate too quickly and get cooled properly in the radiator, or if the cooling system has a bypass circuit when the 'stat is removed that stays open and prevents the water flowing through to the radiator.

My last bike worked this way - it was modified for track only so the thermostat was stripped down but the main part with seal on it left in place. But you also had to blank off other cooling pipes or water would just flow back to the waterpump.

Think Phillip didn't say don't change it, but don't remove it completely - for the reasons above.

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Sorry Sean, I've probably complicated a simple answer. The thermostat is usually all in 1 piece, and you remove/replace it all as 1 assembly.

In my case I removed all the workings/valve to improve flow of cooling system leaving just it's circular housing in place plus the rubber seal around it. This was for a track bike where the job of the simple old thermostat is replaced by the high-tech process of adding/removing duct tape from the radiator :rolleyes:

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