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Ross, Diagnostic and repair technician
Category: Car
Satisfied Customers: 1183
Experience:  Licensed diagnostic and repair technician
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My ford mondeo ran low on coolant today and dial showed it

Customer Question

My ford mondeo ran low on coolant today and dial showed it overheated but no warning light came on now fan is running for few minutes after i switch engine off after topping up coolant
Submitted: 2 years ago.
Category: Car
Expert:  Ross replied 2 years ago.
Hi my name is***** am a diagnostic technician and look forward to working with you.There are a few possibilities as to what has happened, Firstly before we look into the problem at hand the fact the coolant was low in the first place is a concern. Were there any obvious leaks? and roughly how much coolant did it require to get it back to the maximum. Thanks. Ross.
Customer: replied 2 years ago.

It wasnt completly empty it took about just under a litre i could still see coolant in resevoir bur it was low havent noticed ant leake.

Customer: replied 2 years ago.

It keeps on overheating now and loosing power

Expert:  Ross replied 2 years ago.
Many thanks, Sorry for all of the questions, Does your model have a key lock in the rear hatch as well as operating on central locking? This is often mechanical problem with the links for the release.
Expert:  Ross replied 2 years ago.
Sorry, that wasn't for you.Ok, it's not a huge amount by any means, I suspect the low coolant may be due to the engine running hot and releasing steam, this is normal under these conditions.Clearly the fan is running, which is a good sign, Ideally now the car needs to be left to cool if not already and started and left to idle, the temp gauge will gradually rise to the normal position, at this point the thermostat beings to open to bleed coolant to the radiator and the fan will cycle on and off as necessary.There are a few possibilities as to what may have gone wrong, the most common is simply a sticking thermostat. When the car is left running and reaches the normal half way point, turn the interior cabin heater on full HOT. See if this keeps the temp gauge in a normal position, If it does I suspect the thermostat is faultyIf not, either the water pump, radiator or temp sensor could be at fault, but the thermostat should be ruled out first.Please follow these steps below and report back1. Start engine from cold (or 1 hour after last used)2. Monitor temp gauge, just before half way point turn blowers to full HOT4. Monitor temp gauge - If it rises well above normal and into the red, switch off and allow to cool5. If it stays at a normal temp (around half way) the thermostat is the suspect6. Let me know what happens - If you need any further help doing this test just reply to me
Customer: replied 2 years ago.

Hi it rose above normal after a while and would not drive kept cutting out.

Expert:  Ross replied 2 years ago.
Ok, I suspect this is the thermostat, these also suffer with faulty coolant bottle caps which allow the coolant to escape as steam at low temps. The cap allows the system to pressurize which increases the boiling point to approx 125c if this is leaking it doesn't help matters so its worth replacing this, they are around £8The thermostat is the most likely cause, again these are usually around £10 and should be changed before going any further.