Author Topic: Hot under bonnet after Driving  (Read 5791 times)

Annastesia

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Hot under bonnet after Driving
« on: October 22, 2023, 08:56:05 PM »
Hello,

I've noticed that there is still heat coming from under my car bonnet an hour after driving (around 30-40 miles).

It isn't boiling, but there is still a warmth being given off from the parts.
The overheating icon has never appeared.

Is this common or would it be best to investigate?

My coolant level is just above the minimum level so I'm wondering if this may be having an effect on the engine etc cooling down afterwards   ::)

Henryge

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Re: Hot under bonnet after Driving
« Reply #1 on: October 22, 2023, 11:56:13 PM »
Hi There, What you have to remember is that a car engine takes time to get up to operating temperture.
               So 30 to 40 miles so your car engine is well warmed up (metal Parts) engine coolant engine oil.
               They have factored all this in so when driving, heat is being generated and expelled at the
               same time. So when you stop in a traffic jam the engine bay will get hotter but it will still
               take awhile for axuillery fan to come on. Then when you park up all that heat is released from
               the engine parts solid and liquid whch take time to reach open air temperture. So yes this normal.         

ColinS

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Re: Hot under bonnet after Driving
« Reply #2 on: October 23, 2023, 07:25:12 AM »
This is normal, so no need to worry.

embee

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Re: Hot under bonnet after Driving
« Reply #3 on: October 23, 2023, 10:58:00 AM »
The bulk of the engine apart from the exhaust runs at typically about 90C. It takes a while to warm up to this when starting from cold and similarly takes quite a while to cool down again especially if you park somewhere out of the wind.
Check the coolant level regularly,  keep it between the max and min lines when cold. It shouldn't really lose any worth mentioning, don't worry if it settles slightly below the max line after a while. I haven't topped mine up in 3 years.
Don't confuse coolant and screenwash, I know some folk who have. ::)

Annastesia

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Re: Hot under bonnet after Driving
« Reply #4 on: October 23, 2023, 11:59:24 AM »
Wow, thank you all so much for putting my mind at ease! I was googling it and there was some sites saying it could be due to issues so I panicked, but its good to know its normal and nothing for me to worry about.
Thanks you all again :)

Westy36

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Re: Hot under bonnet after Driving
« Reply #5 on: October 23, 2023, 12:04:09 PM »
Yeah, it's suprising how hot they remain quite a while after parking up. As others have said, all very normal.

I think part of the issue, is the compact engine bay. Years ago cars had loads of air and space around the engine bay and didn't have undertrays fitted, so they probably cooled a fair bit quicker.

Lord Voltermore

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Re: Hot under bonnet after Driving
« Reply #6 on: October 26, 2023, 07:38:07 AM »
The engine  is a big lump of metal  and can retain heat quite a long time ,like an oil filled storage heater.
If your level is just above minimum and never drops further  everything is probably fine.

General discussion on line will tend to be cautious because  if you are indeed leaking engine coolant and its ignored the consequences can be expensive.        Its a good idea to check your coolant level occasionally anyway. It should stay the same. Check its when its cold before a trip, as the level may change as coolant temperature rises and falls.    You shouldnt actually 'consume' coolant , like you might with engine oil, except maybe a tiny amount over many years .But it can deteriorate so service plans normally recommend draining and refilling  coolant occasionally.     If you dont know when it was last changed and your car is of an age and mileage when it might be due, consider including it when your next service is due. It might be included  as part of a bigger service needed at that interval, or it might be an extra cost option.   

-   But check what is the correct level in the owners handbook.   The correct level sometimes looks to be lower than you might expect.It needs some space to expand when it gets hot.   People sometimes top it up  and overfill it.  But this excess may be vented out onto the road when the system gets hot  ,and the level again drops to the correct level.  This may be mistaken for a leak, and they top it up again, and again.     

 
« Last Edit: October 26, 2023, 08:10:02 AM by Lord Voltermore »
  I will fix that dripping tap.  No need to keep reminding me every 3 months.

coldstart

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Re: Hot under bonnet after Driving
« Reply #7 on: October 31, 2023, 07:18:56 PM »
Yeah, it's suprising how hot they remain quite a while after parking up. As others have said, all very normal.
The "meter maids" in Switzerland are using this to determine if you have overstayed your welcome in the blue zones (good luck with EVs on this one)  ;D

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