And I would never add that crap to seal anything. I would do the work with new seals.

 

Did a little experiment: after the truck was warmed, I shut it down and immediately unscrewed the expansion tank cap to relieve all the pressure in the cooling system. After about 2 hours I started the car back up. Where it would usually misfire, it was super smooth and quiet. I'm guessing that relieving the pressure prevented coolant from being sucked back into the cylinder, causing it to misfire. I'm pretty much convinced there's a crack on cylinder 4 and plan on K Seal-ing, driving for maybe 400 miles and then doing a flush on the coolant system.

For the flush, if I have access to a pressure tester can I use that to ensure I get out ALL of the old coolant? Like will it push out all the coolant from the block if I'm pressuring the system?

 

I'm not confident that K-Seal will be a long-term solution for you. I'd give it less bad odds for a head gasket repair than for a cracked block repair, but who knows?!

However, having K-Seal in your emergency road kit makes sense because it has somewhat of a reputation for a temp fix and that might get you home or at least out of the woods some day:




Be sure to dilute before adding if you do have a critical road emergency where you have to repair via bottle in the field:




*no matter how you use a product like K-Seal, expect it to reduce your cooling capacity. Expect higher engine temps forever forward. Expect shorter waterpump life, etc. Basically expect it to gum up more than just the crack. ...and there's not a strong chance that it will even fix the crack. Maybe 25% chance of temporary success?


I used it once on a $1,000 300ZX twin turbo that I picked up cheap because it had a "blown motor" and figured I had nothing to lose because it was going to be a parts car. Dang thing ran from Alabama to Las Vegas before the K-Seal "fix" on it failed.

 

I'm not confident it will be a long-term solution, either! I have it in the car...to be honest, I might just keep on burning coolant for now. Once it's up to highway speeds it doesn't drink a ton...I can drive a hundred miles or so and only maybe 1/8 of the expansion tank. Which is not good, it shouldn't lose any, but I'm confident if I set out on a trip with a full tank of coolant that I won't run it all down and overheat.

I wonder how bad it will gunk things up if I K-Seal it and then do a flush a couple hundred miles later. You think if I use something like Super Flush it will still leave residual K-Seal behind?

 

You are going to gunk things up and a flush isn't going to solve that. You could put a junk yard leaky radiator on instead of your good radiator and then do a flush and then reinstall your good radiator to mitigate *some* of what you are going to gunk up.

 

Welp, may have screwed the pooch last night. After checking the coolant level to find it once again quite low after filling it only a day earlier, I got frustrated and used the K-Seal. I poured about half the container into a half-gallon of 50/50 mix. Shook it vigorously, and added it to the expansion tank. Got it up to temp and drove home...and watched as the temps kept rising. Got to be about 212 at idle. Which is about 11 degrees more than it was even with the leak. Hooooo boy. I parked it and it sat at 208 for a bit before I turned it off.

I drained a good amount of coolant out and will fill with regular 50/50, and I'm going to do a full with multiple backflushing, etc as soon as I have time. But, I have to drive about 100 miles tomorrow.

I don't think I'm fully clogged anywhere since the temp does go down with acceleration, but it's just overall higher. Any chance that will go down? I feel pretty dumb.

 

Update time: flushed the coolant system with Irontite Thoroflush and installed (finally) a geniune low-temp thermostat, and engine temps are lower than they've ever been.

While flushing I made sure the flow in the heater core and radiator was smooth and clog-free, and it seems like I've gotten any remnants of K-Seal out. The old Motorad thermostat looked clean as well. That Thoroflush stuff is no joke... Anyway, highway temps between 179 - 188 with round-town temps maxing at 195 after a 100 mile trip. Feeling good. Gonna just pretend that it's fixed and make sure the coolant is topped up. When it's warm I'll replace the coil packs, wires, and plugs. Hopefully that fixes the misfire and the chemical test will be proven wrong. Stranger things have happened, right?...?