Haha. I hope the title grabbed your attention.

I had a bit of a mysterious incident earlier on today. I had just been on a 20 mile run round the doors this morning and, just as I pulled up at the side of the road, I heard a sound rather like someone blipping a power hose.

At first I thought it was coming from outside but then realised there was steam/mist(not smoke) coming from under the bonnet. I turned the engine off, jumped out the car and popped the bonnet open to try see where it was coming from.

It cleared fairly quickly so, after about 5 minutes, started it up again and nothing wrong. I've driven another 100 miles since then and nowts the matter. Anyone got any ideas what it could be?

Where was it coming from? If you were on a passionate run you could have overheated the water a little bit and it could have blown through slight gaps in the head gasket. If the radiator isn't working right, this could cause a bit of overheating.

Edited 1 September, 201015 yr by devonutopia

If you were on a passionate run

off topic I know sorry - but this is the best phrase I've ever heard for giving it some stick - LOL

Must be Devon speak

Where was it coming from? If you were on a passionate run you could have overheated the water a little bit and it could have blown through slight gaps in the head gasket. If the radiator isn't working right, this could cause a bit of overheating.

I'm actually a driving instructor and, although I'm not a stranger to a "passionate run" I was actually on a lesson at the time, tootling about far too slow for anybody elses liking. The temp gauge was normal and when I opened the bonnet it cleared in about 10 seconds so I couldn't find out where it was coming from. Puzzled I am

Could be the pressure cap on the coolant reservoir.

Could be the pressure cap on the coolant reservoir.

My next line of thought, if the car was not being driven in an enthusiastic way.

Could have been a bit of steam coming out the top of the bottle if the cap wasn't fully screwed on. Not 100% but I think the bottle also has an escape valve type thing which might have been activated.

Could be the pressure cap on the coolant reservoir.

Would this be the sign of a fault?(I'm no mechanic)

a bit of a head scratcher,

I might be barking up the wrong tree but two theories and things I would check.

1. possibly over filled with water and this causing excess pressure in the water system causing the pressure release cap to be utilised.

2. possibly the first signs of a head gasket problem. E.G the compression of the cylinder being released into a water gallery and then causing the water system to be over pressurised, again blowing the release on the pressure cap. see if you can get the engine pressure tested, all of the cylinders should be pretty much equal in pressure.

either way first check the pressure release cap looks ok and is seated correctly (tight).

hope this helps.

Steve.

It could be a faulty cap (yes it does have a pressure relief valve).

It could be a failing water pump. You can check this by taking the cap off the expansion reservoir and checking that a steady stream of coolant is coming out of the return hose.

Another possibility is a bad thermostat or a blockage somewhere.

And of course it could be a head gasket.

Edited 1 September, 201015 yr by rwbaldwin