Another compost worm farm question

I have a drum with holes drilled in it and a tap in the bottom, I'm not sure what to call it really, it has tiger worms in it though and I'm pretty sure they're still alive. The liquid that comes out is black and quite thick like engine oil and smells real bad is it still OK for the garden?

Meant to add that vege scraps and leaves get put in it it is full of fruit Flys and partly shaded so not very hot

The liquid is okay for the garden. But dilute it 1:20 before using, to be safe for the plants.
If the liquid smells really bad, there's something rotting in the liquid catchment area. And it's rotting anaerobically - that means that bit has run out of oxygen. Usually worm farms have the liquid collection area separated from the rest of the bin by a mesh or drip tray, so there is air above the liquid. If your bin has the "solids" soaking directly in the worm liquid, it will quickly run out of air, and the rotting process starts to release smelly stuff like sulphur.
In the short term, add lime into the drum and flush through with water. I use a 10L watering can. Flush until the discharge doesn't smell as strong. You can use the waste liquid as fertiliser - just remember to dilute. In the longer term, you need to make sure the bottom of your bin is getting aerated properly.

EDIT: Also, I wouldn't use the smelly liquid to water salad veges that you usually eat raw. Might give you food poisoning. Anything cooked before eating should be fine.

Thanks for that, there is mesh separating the areas though

Hm. Do the flushing step. Then try mixing in a sprinkle of lime and maybe shredded newspaper every time you add stuff to the worm farm in the future. Lime can help with smells too because it speeds up composting, and the shredded paper absorbs the free nitrogen that turns into ammonia. Less smells also means less flies.

Eventually, after a year or so, it also helps to dig out the old stuff and restart the worm bin. I do this once a year.

how do you take out the old stuff without disturbing the worms though?

If your worm bin was doing well, you could push the uneaten stuff off to one side, and slowly scrape out the worm poos underneath. As you do that, the worms will flee away from the area being scraped. This is the slow and kind (to worms) way.
I've tried this. It takes forever!
What I do now is have a second, identical bin ready to set up like a fresh worm bin. You need the compost (with no chemicals) or coir fibre on top of the drip mesh, about 10cm deep.
Then drain your existing bin of liquid. Scoop out all the uneaten stuff and pile it onto the centre of the new bin. Tip the old bin over onto a tarp or some plastic or even a large piece of plywood. Start scraping off layers of worm poos into a bucket. When you reach live worms, move to the other side and repeat. The worms will naturally migrate to the centre of the pile. If you pick out any healthy worms, toss them into the new bin. Discard unhealthy looking worms.
Eventually, you will have a pile of worm poos with minimal worms, and a pile of worms with minimal worm poos. I tip half the worms back into the bin. and the rest go free into my garden or go to the chickens.

You should weigh down the lid of the new bin for a while. Worms hate being moved and will try to escape the new bin.

Wash out the old, empty bin with soapy water. Really scrub and spray it out so it's clean. This is your spare bin for next time you need to do a clean out. I use two sets of the $40 square black worm bins from the Warehouse.
Alternatively, if you don't want to have two bins, then you have to clear out the existing bin, scrub it out well, and set up again for the worms.