Engine overheating

Tiny
TROTEN123
  • MEMBER
  • 2006 RENAULT LAGUNA
  • 3.0L
  • V6
  • 2WD
  • AUTOMATIC
  • 174,000 MILES
Water temperature goes up after say 30 minutes of driving. No coolant is being lost through leaks or into the oil etc.

1. Bled coolant system with heater fully on.
2. Let car idle in driveway with heater on for 20 minutes, no overheating.
3. Drive car locally. Initially no overheating then suddenly car system indicates water temperature is rising and advises stopping.
4. Get car home. No coolant loss. Turn engine off for 10 minutes. Start engine – temperature normal. Allow to idle for 20 minutes with heater on, no overheating. Turn heater off temperature starts to rise.
Saturday, April 4th, 2020 AT 8:02 PM

2 Replies

Tiny
HARRY P
  • MECHANIC
  • 2,293 POSTS
Hello. A few questions, in no particular order.

Is your car's heat working well when the car is overheating? If not, then there's an issue with coolant flow. We'd have to investigate further. Could be a bad thermostat, clogged radiator, failing water pump, etc.

Are the cooling fan(s) coming on? If you don't hear them running then I would suspect a problem with the engine coolant temperature sensor which is what a car's computer will use to judge when to run those fans.

Also, have you tried changing the thermostat? It's possible that your thermostat could be only partially opening, which will cause increasing that won't be immediate.

Are there any aftermarket modifications that could be causing this. Some example would be a custom grille on it, lowered ride height, a transmission cooler etc.

Let us know.
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Saturday, April 4th, 2020 AT 8:12 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,192 POSTS
Hi,

It sounds like the temperature sensor could be sending a false signal. When it indicates overheating, do you ever see steam or hear bubbling in the engine / cooling system?

Also, have you ever noticed bubbles in the coolant overflow bottle? Did you replace the thermostat? Please keep in mind, there could be a head gasket issue even though you are not seeing coolant mixing or coolant loss. Here is a link that you may find of interest. It discusses what to check for. It will indicate oil/coolant mixing, but there are other indicators.

https://www.2carpros.com/articles/head-gasket-blown-test

What would be interesting to check is if the coolant is the actual temp the gauge indicates. The sensor could be bad. I don't know if you own or know someone that owns an infrared thermometer, but if it indicates overheating, you could simply point the thermometer at the radiator and see what it says.

Take a look through the link I included and let me know if you noticed any of the symptoms indicated. Also, let me know if the thermostat was replaced.

Take care,
Joe
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Saturday, April 4th, 2020 AT 8:21 PM

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