I know it is not advised to drive a vehicle with a blown head gasket but if no choice was there then how long could you before major damage occurs?

I been chasing some issues for quite some time and now got evidence that my HG could be shot. It has been minor for a couple of months but this past week it got worse and I can visibly see some type of fluid soaked into the carbon buildup on piston #3.

I just had new cats installed three weeks ago so I am concerned about those.

Could also be leaking valve guide, stuck valve, leaking piston o-ring, faulty injector, spark or coil.. Have you done a compression test?

My engine had a cracked head and I drove it for ~10 months / ~10k miles before fixing it. I definitely do not recommend delaying getting it fixed though. If I had known my head was cracked all along then I would’ve fixed it much sooner. My symptoms were minor though, it would misfire for ~3 seconds only during a cold start, then run completely normal after that and I had to top off my coolant overflow once every 8 weeks or so.

If you see any signs of your coolant and oil mixing then I would not drive it at all and get it fixed as soon as possible. If you are only losing coolant (as was the case with my engine) then you could probably get away with driving it easy as long as you watch your engine temperature closely and make sure your coolant overflow is never below the LOW line.

That question is pretty hard to answer. I’d say imo since it noticeably got worse I’d restrain from driving it if possible.. I don’t think anyone will really be able to give you a for sure answer on this, we can only guess. Could be a day could be a week could be a year. I will say if you do drive it be very gentle, more throttle you give more chance you have of doing damage imo.

About 3 years ago my wife was driving our 96 Tacoma, 3.4 with about 225K miles when the radiator cracked and she didn't see the gauge climb until it was too late. #6 cylinder had virtually no compression. I was told I could try this Blue Devil gasket sealer.
https://shop.advanceautoparts.com/p/...E&gclsrc=aw.ds

It worked for 20K miles until my step son drove it with no water in the radiator and it blew the head gasket again! So at this point 245K and it's a spare vehicle that I don't really feel like messing with at the moment, what do i do? You got it, I tried it again! And yes Virginia there IS a Santa Claus, and he gave the Tacoma 3.4 a third chance to rule the world!

Sounds like what mine is doing too except mine misfires for a good 20 secs to a minute followed by smoke, and then is fine. I have been losing coolant at a pretty fast rate. I would say i have to fill the jug every 2 to 3 weeks.

The shop that did the cats also did a compression test and said numbers were good. i did a block test and it was also good. He recommended new injectors, thinking one or two were leaking so I replaced them and the issue remains. What is odd, or just pure coincidence, is that it started misfiring worse after I used synthetic oil by mistake. I know synthetic oil is thinner and more prone to seeping past bad seals. Probably just coincidence.