air filter box melted

[campervanbeethoven]

Hi knowledgable folks,
On a camping trip my 1984 T25 1.9 petrol , which has been running fine, smoke started coming out of the rear air vent.
The smouldering fire in the air box burnt out the air filter and melted out the bottom of the plastic air box. Luckily we had a fire extinguisher and were able to get a wet towel and a bucket of water on it. Any ideas of likely cause ?
Question is, are the plastic square box filter cases available to replace ?
New to buy or from a scrapper ?
Can the older style square one be directly replaced with a polo shaped round one (and is there any difference ?)
I think we got off lightly, engine still runs OK.

 

[davidoft1]

could be a build up of oil / dirt residue on the filter or a backfire , pretty sure i have a spare air box, happy to post can get some pictures

[silverbullet]

Possible causes: ciggy butt dropped in the vent (it happens) or a hot flake of rust from the exhaust/inlet air preheater.
Is LPG involved?

[campervanbeethoven]

Thanks but definately no LPG or cigs! I'm told that a build up of oil in the box and backfiring can be a cause. It was going up a hill slowly at higher revs at the time so that seems likely.

Anyone know if the later round filter case is a straight swap for the cube filter box ?
I am told both are for 1.9 DG  water cooled but square is before 1985 and round is after 1985, if that sounds right ?

[Aidan]

cigs can be deliberately or accidentally flicked into air vent by passing driver or blown up off the road by vehicle drafts

the air filter housings could be swapped but the connecting hose to the pancake over the carb and the pipework to the airbox also vary so you'd want a complete late set up ideally to fit

[Mocki]

Lack of maintenance….. oil soaked paper infused with petrol vapours , timing and or vac leak causing a backfire ?
Anyhow , stick with the square one there is nothing to gain by getting the later filter housing other than it wont actually fit in the mountings

[Stesaw]

I've got a complete box in Midlands if you need one.

[campervanbeethoven]

On further investigation of the air filter box I found a lot of charred nuts in the bottom !

[Stesaw]

Thats nuts!
Not quite the right way to roast them

[Mocki]

Ohhh squirrels …… but unless they were having a BBQ or a crafty fag they didnt start the fire

[Oldiebut goodie]

More likely to be mice, little barstewards filled up my glove box and air filter of my BMW. My fault for having hazels in the garden.