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Discussion Starter · #1 ·
Hi, looking for some help!

Mondeo Mk4 2.0 tdci 58 plate titanium x….
Engine temperature on the gauge fluctuates and mostly runs cool. Floor it up a hill and it will be bang in the middle, ease off or sit at 50 on a motorway through roadworks and it drops right down to nearly bottom of gauge. Looking at temps in diagnostic mode on convers+ it’s giving never more than 75degC, often 60-65 with steady driving.

I changed the coolant temp sensor a while back (that clips into the thermostat housing), didn’t solve the issue, symptoms persist.

got round to changing the stat today (pig of a job!!!)…….symptoms persist!! Arghhhhh. New stat had another new temp sensor.

any other ideas???
Ta!
 

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Super Moderator
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Tested the thermostat? Sometimes new parts can be faulty.

Does the thermostat open at the correct temperature?
 

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Discussion Starter · #3 ·
I didn’t test the new one as I was working on the logic that a new one would just work! It’s a ECP Circoli thermostat which has replace the original Ford stat.

Seems odd that the problem is exactly the same after changing the stat

Before I whip it back off, is there anything else that could be the cause? Given I’m now on coolant temp sensor number 3 I’m going to rule that one out too. Airlock? Dodgy water pump?

In the mean time I’ll give the old one a test….
 

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You could get an OBDII reader and check the temperature given by the dash is the same
as the reader.

They may all look the same but some work better than others, worth spending a bit extra on
a tested one (£20 ish). (TunnelRat Electronics)

If you buy something else make sure its got live data not one the cheap 2 button readers
that only show a fault code.
 

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i thought this was a problem on mine as there are low temps also, just got it 4 days ago, but i did get it to 90 degrees on racing up motorway took some doing but around the doors will stay at around 70 for ages. i have the error code 244c-00 - i await forscan dongle
 

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So that rules out the dash voltage issues. Likely the engine really is running cool.

Was the sealing ring as thick as the original? Common issue with the MK3 Diesel was that the
original sealing ring 6mm + thick where the replacements were under 4mm so the new stat was a
loose fit in the housing allowing coolant to bypass it.
 

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Discussion Starter · #8 ·
The thermostat is integral to the housing and cannot be replaced separately. It’s the PSA 2ltr with the housing bolted on the rhs of the engine block (looking from the front of the car)
 
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