How good is head gasket sealer?

I have a blown head gasket on my 2005 ford e250 4.6L - i have been watching a few videos how people are talking about that they use head gasket sealer and it works. If it does, how many kms does it last? I have heard that it lasts people around 50k, what's your experience on it?

Any help is appreciated.

I would not trust any form of sealer.

If you get a failed head gasket fixed as soon as it's discovered, the actual damage to the engine can be minimal to none.

If it's run for any length of time with a failed gasket, combustion gasses erode the failed area and can damage the head and / or block beyond repair.

Don't take any chances.

Good (bad…) example photo here:
http://www.autoservicesdoncaster.com/engine-services-2/engine-reconditioning/bad-fueling/

If the system will hold coolant for at least 45 minutes without leaking into the crankcase or leaking onto your driveway, then you have a 50/50 chance that it'll work. If it leaks out sooner, don't even bother.

Here's one I've used and it works----sometimes. It's the best stuff out there without all the hype and extra money.

http://ricksfreeautorepairadvice.com/head-gasket-leak-sealer/

Personally, I'd say that you might aswell get the proper gasket. You might aswell do it correctly the first time, so you don't have to strip it back down again incase something goes wrong or the sealant doesn't seal in a certain place etc.

Best advice… Get it fixed properly.

Fix it right - there's no other way

The best thing you can do there's change the gasket! But if your money is tight and you want it to last a little longer until you get some money scraped up then get a bottle of Bars leak!