#overheating
13 posts in Car Diagnostics blog about "overheating" — OBD-II diagnostics, DTC codes, repair. ← All posts
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P0691 and P0692: cooling fan 1 control circuit low and high
On a variable-speed fan there is no relay to swap. The control is a module and a signal, which changes both the symptoms and the diagnosis.
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P0217: engine over-temperature condition — the code after the damage starts
Most codes warn you. This one records that the engine already exceeded its safe temperature, which makes it a damage-assessment code as much as a diagnostic one.
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P0480 and P0481: cooling fan relay control circuit
A cooling fan that does not run produces a very specific pattern: fine on the motorway, overheating in traffic. That pattern is the diagnosis.
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Steam from under the bonnet: stop or drive on?
The decision has to be made in about ten seconds, and getting it wrong turns a cheap hose into a cylinder head. Here is how to read the situation from the driver seat.
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Temperature gauge going up and down: thermostat or air lock
A needle that will not settle is telling you coolant flow is intermittent. Whether that is a lazy thermostat, trapped air or a failing pump is decided by when it happens.
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Transmission overheating warning: causes and immediate actions
Heat is what kills automatic gearboxes, and the relationship is brutal: every 10 °C above normal roughly halves fluid life. What you do in the next five minutes matters.
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The thermostat: two ways to fail and two very different consequences
Stuck open, a thermostat never lets the engine warm; stuck closed, it destroys it. The signs of each and what diagnostics shows.
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Mountains: how not to burn the brakes descending or cook the engine climbing
A mountain road loads a car unlike a motorway. Engine braking, overheating, and what to check before you go.
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The cooling fan will not run: where to look
The fan is the last line of defence against overheating. How to test it in two minutes and why the fan itself is usually innocent.
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The water pump: the signs that appear before the engine boils
A water pump rarely fails suddenly — it weeps and whines in advance. The warning signs and why it is replaced with the timing belt.
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Burning smell in a car: eight sources and how to tell them apart by scent
Burning wiring, a slipping clutch, oil on the manifold, and overheated pads all smell different. Diagnosis by the character of the smell, when it appears, and what diagnostics shows alongside.
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Engine overheating: what to do in the first two minutes, and why the gauge lies
Overheating is one of the few cases where stopping correctly matters more than diagnosing correctly. The action sequence, six causes, and why the dashboard needle should not be trusted.
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Summer heat: why cars overheat in traffic specifically, and what to do beforehand
Cooling systems are designed with margin, but that margin is eaten away over years: a clogged radiator, old coolant, a fan that engages late. What to check in May so you are not on the hard shoulder in July.