K-Seal ST3501 Pour & Go Head Gasket Sealer, 16 oz – Repairs Blown Head Gaskets, Cracked Heads & Engine Blocks

Jeep Wrangler 4.0 Inline 6. Had an issue with a piston and suffered a catastrophic failure. Disassembled engine, and replaced piston, then reassembled with a fresh head gasket. Did not plane block or head, just put it back together. Engine ran fine, but I noticed lack of coolant system pressurizing, and I was refilling the radiator daily. I found a pressure leak near number 1 cylinder, which was causing significant coolant loss when engine was operating. My head was either damaged or I nicked the gasket when putting it back together by myself. Which is possible, that head is heavy and awkward. Anyway, after a lot of reviews and research, I selected K-seal. I followed instructions and added it directly to radiator. It has small copper looking flakes in it, and at first I thought it was a waste of time, because after pouring it in, and going for a drive I saw the same small flakes on the inner fender where the steam from the leak was coming from. Then after a few more days, I noticed that my cooling system was fully pressurized when hot, and the coolant was not disappearing every day. It has been about three weeks and several hundred miles, and it is solid as a rock. No coolant leak, smell or refill needed. Very impressed, this really worked.

Had bad coolant blowing out the exhaust on my 1989 Chevy 5.7 K1500 111k miles. Not just steam but coolant as well. Used K Seal and it did not work. So pulled heads sent to machine shop that checked them and said no faults found. Heads milled, inspected cylinders, nothing found. In fact old cylinder head gaskets and intake gaskets were okay. Re-assembly did not touch the exhaust. Just as bad. I again used K Seal. Forget the 3-5 minute idle, did not work. So allowed it to cold soak overnight. Next day ran it on the road with it blowing steam all the way. Let it cold soak overnight. Next day leak was gone. Went for drive and no smoke. Mind you this was just day one, but given the severity of the leak, this looks promising. Still not sure why it worked on the second can and not the first. I lost a lot of coolant when I pulled the heads, but it is possible enough residue of the first can of K Seal remained. My current thinking is that the problem may be a crack in the intake manifold and not the block. This is because the engine did not blow coolant before I changed the intake manifold gaskets a few weeks prior just as routine maintenance. The manifold EGR passage was totally clogged with carbon which I removed. It is possible this carbon may have sealed the crack in the manifold. Chevy manifolds have massive exhaust and coolant passages that run parallel to each other and a defective EGR system could generate excessive heat that cracks the manifold internally. This would allow coolant to get into the exhaust.

It took about two weeks but it finally sealed the Head Gasket on my daughters 1998 3.8 liter Mustang. It did not damage the heater core or thermostat. I kept in contact with the manufacturer on the proper way to repair this head gasket. I was also told that I can flush the cooling system if I so choose and that it would not affect the repair. Money well spent!

I used K Seal in my 2015 F150 that had a bad head gasket at around 150k miles. I drive this truck hard and pull a lot of trailers, so it definitely gets worked. So far, the K Seal has held up for a few weeks now, which honestly surprised me given the condition of the truck and how I use it. No overheating and no obvious signs of coolant loss since adding it. Is it a permanent fix? Probably not — but for the price, it’s a solid budget alternative to try before spending thousands on a full head gasket repair. If you’re in a pinch or just want to see if a sealant will buy you some time, this is worth a shot. Would recommend as a temporary or first-try solution.

Stay away from this stuff. Will cause your thermostat to stick closed. I followed instructions exactly and flushed system after installing three times and bought a new thermostat and it caused the new one to stick also

Didn’t work in my situation

This stuff really works. First try . Thanks .

Added this to our Pacifica with the dreaded head gasket issue on the pentastar. There was a slight leak on cylinder 6 causing coolant to fill the cylinder over night. Ran this through one cycle and came out next morning to a smooth running engine no check engine light and no puff of coolant vapor on startup. I had nothing to lose as with the car having 170k miles in it didn't feel like a 5000 repair was worth it. If this didn't work it would have went to the junkyard anyhow. I ran this with the cap off and no heat on as I did not have any issues with a heater core leak left cap off during cooldown over night to allow the pressure to possibly vent out of the expansion tank rather than pushing the sealant out. Time will tell how long it lasts but just gained myself a new fishing vehicle! As I said this was a very slight leak that wasn't noticeable really only at startup so your results may vary.

Trovavo olio nella vaschetta del raffreddamento. Con k-seal ho risolto

Très bon produit. Très efficace.

Iba a llevar mi coche al desguace y gracias a este producto funciona perfectamente, ideal para roturas de junta de culata leves

das Zeug hat in nullkommanix das Thermostat abgedichtet. Immerhin... Ich glaube, dass so Zeug unter optimalen Bedingungen funktionieren kann, ich habe es sicherheitshalber bei einem alten Auto angewendet, bei dem der Wechsel der ZKD nicht wirtschaftlich gewesen wäre, also ohne wirtschaftliches Risiko. Dass das Thermostat allerdings sofort verstopft, hatte ich nicht erwartet, das dürfte der ZKD - und damit dem Auto - dann den Rest gegeben haben. Friede seiner Asche. Ich werde es nicht noch mal kaufen.

Bit of my background. I'm an ex-Honda technician of 24 years. But I quit the dealership over 10 years ago. I feel I'm quite experienced with cars. Honda's at least.I still drive a 1996 Honda Odyssey, here in Aug 2025. Beginning of this year, I noticed a mysterious coolant loss. Maybe a 1/4 liter every 2 -3 weeks. Also some intermittent stumbling or misfiring when engine is started, but clears up within 2-3 seconds of starting. Also noticing excessive pressure being relieved when opening the rad cap. Typical head gasket symptoms. Then I noticed a few drops of coolant on the ground. That ended up only being a leaky radiator. Found a cheap new radiator on Rockauto and replaced it, hoping that fixes all coolant loss issues. No luck. I continue to just drive it and topping up coolant. July comes around and the misfiring after start up is getting worse. At times, taking up to 20-25 seconds to clear up, and now it feels like it's multiple cylinders misfiring. The new radiator is leaking as well. I assume the excessive pressure from exhaust in coolant is the cause. Given the van's age, 500,000 km's and host of other issues it's had in the past year or 2, it's not worth the time and energy to fix a head gasket. I fear this is the end of the van. My wife is thrilled and ecstatic, she really wants a new or newer vehicle.I've never been one to believe in any of this "quick fix in a can". But at this point, its worth a shot as there's nothing left to lose. Bought a bottle of this K-Seal Head Gasket repair here on Amazon.Just after driving the van, the engine is hot. I opened the rad cap slowly and noticed the coolant was low. I didn't bother draining any more coolant as I hoped it was low enough to fit the whole bottle. I was wrong, only managed to pour in just over half the bottle. I started up the engine and ran for 40 mins. Shut off and cooled for 3 hours. Reached under the radiator and opened the drain just enough to pour in the remainder of the bottle. Started engine, no misfiring. Perhaps just a coincidence. Ran for another 40 mins then shut off for the night. Next morning, I started it up, still no misfiring or stumbling. Drove to work just fine. started up after work, again no stumbling. It's now been a week and a half of regular driving and I finally checked the coolant level. It was full, no top up needed. New radiator stopped leaking too. Still early, but so far the results are extremely positive. I'm thrilled and ecstatic. Wife is not. I will update if it shows signs of leakage again