Nissan Patrol 4x4 (Africa)

Can petrol boil in your tank with offraod driving in extremely high temperatures ?

With a quick search it seems like the boiling temperature for petrol is in the region of 80 Degrees C - I recon because the tank is under pressure that the boiling point will be higher ?

Why I pose these questions - when I was in the Northern parts of the Kgalagadi in March the daily temperatures varied between 33 Deg C (from around 9 am) up to 44 Deg C till around 6pm. Some of those days I drove for about 5 to 6 hours without any lengthy stop over dunes and stretches with heavy corrugation. And the sun/heat was just relentless. As far as I could gather my petrol consumption was not heavier than I would normally get in driving that type of terrain. After I stopped at the campsites/destinations I heard rumbling/bubbling noises coming from the tank, as if the petrol was boiling. I must just emphasize - it was really hot - even in the inside of the Patrol the floorboards was as hot as can be not even cooling down that much during the night.

Also taking into consideration the heat buildup and radiation from the sand, the exhaust etc I think these temperatures can sore to more than the boiling point of 80 Deg C ?

Mine also make that noise sometimes and I think it is only about the pressure that builds up while driving and when you stop the pressure will come down a bit.

I had the same problem last year in april driving up from Kutse to Deception the sound is asif the petrol is boiling.I opened the petrol
cap ever so slightly to allow the build up of gas to exit and this sorted the problem out straight away.
This was on a 10 hour slog through thick sand at high temps

Is it important under such conditions to equalise the pressure buolkding up in the tank? I.e. by opening the cap and closing it again.

Answer:

The precise boiling point will vary, due to the incredibly complex nature of ingredients that go into your average forecourt petrol, but around 95oC at a standard atmospheric pressure of 1 bar.

http://www.engineeringtoolbox.com/boili ... d_155.html

I see alcohol's boiling point is also in that region - I made sure its been kept cool all the time - so no boiling in that dept - just a couple of cold ones around the fire after a hot and hard day makes it all the worth while

Ja Jan,


Boiling point of a Gauteng driver is around 20 to 25 degrees these days. Seems itis getting lower and lower.

Well PV=nrT, so the pressure must be increasing! Lol

The petrol tank should not be under pressure. What you describe sounds like a blocked or partially blocked breather.

What happens is that as the temperature increases, the petrol expands. What you are hearing is the air in the tank escaping through the breather. If you remove the cap at this stage, you should hear a "woosh" as the air rushes out.

Even before changing the petrol filter, you must open the cap to release the pressure in the tank!

When we where on the Botswana Outreach and had the fuel pump connector problem - before I found the problem, I changed the filter and because I did not open the cap, the fuel burst out the pipe and burned my arm! I thought afterwards the petrol was so hot because of the connector problem that burned of halve the connector away.