is it safe to use cellulose thinners through these brushes the stuff i've using is ment for cars but I'm assuming that its the same stuff as humrol sell reason being in the past my aztek melted inside now i'm not sure if this was down to the cellulose or using pure turps to
mix the enamels with any ideas?

Mikeli,

I do not recommend using cellulose thinner for airbrushing. Cellulose thinner is very agressive to plastic, and as you indicated, it eats the rubber/plastic seals inside the airbrush.
I've had problems in the past too, now I use White Spirit or synthetic thinner when working with enamel paints....