Steam or smoke from side vent

Hello
I need help on this I have a 55 td6 150000 miles full service history, the issue I have is I was parked up picking my daughter up from school with car in park and idling but then noticed it vibrating and looked up and drivers side wing vent was slightly steaming or smoking I turned it off waited for my daughter and started it back up and the car was fine idling smoothly this has only happened a couple of times but worried to what it could be I'm not sure if it's relater to the heater being on. I'm hoping someone out there has advice thanks.
Mel

Whats's the coolant level doing, static?
I'm positive you know that steam = water loss or drip n sizzle

I would check the scuttle drains for debris but I doubt this is your issue.

Only Transit Vans leak scuttle water onto the engine, right, right?

The coolant level seems fine, what are the side vents connected too ? Or are they for show ? But why would the engine run a little rough for a few seconds when it happens I'm going to try some diesel fuel system cleaner see if this sorts the problem, what do you think ?

could it possibly be a leak at the leak off pipes, causing rough running and the leaking fuel dripping on an exhaust manifold? It's just a guess as I don't know how this engine is laid out

Hi
I'm not sure what a leak off pipe is or even looks like lol it doesn't smell like diesel under the bonnet is leaking and I've lifted the bonnet while it runs and can't see anything out of the usual but if I had a leak wouldn't it happen all the time instead of occasionally? Thanks for your thoughts

Does a 55 plate have the diesel fired heater in the front wing somewhere, just a thought.

Hi mine does have the heater that you can set the time to come at, is that housed in that area of the car?

The aux heater I believe is on the passenger side (UK).
Odd re. vibration?? I wonder if it's something to do with gbox cooler lines.
Does the gbox perform normally?

It could indeed be the FBH (Fuel Burning Heater) exhaust or steam from water/rain getting to the FBH exhaust.

The side vents are not just for show, they allow air flow through the engine bay for the hotter running V8's (operating temp is 105degC).

I must admit I had just jet washed it and the weather was spitting but the next time it did it the weather had been raining but had cleared up