Can a "mechanic in a can" really fix your head gasket? Maybe.

[Hagerty]

An old saying in the mechanical and construction trades runs: "If you don't have the time to do it right the first time, when are you going to have the time to do it the second time?"
https://www.hagerty.com/media/maintenance-and-tech/can-a-mechanic-in-a-can-really-fix-your-head-gask...

[hyperv6]

Generally no!

Most cases head gaskets are often more damaged than these things will fix. A small leak may last longer and a larger leak will fail sooner.

Consider this fix a flat for the engine. It may get you to civilization but don’t rely on it.

[audiocage]

Eiw.

[Bavarian]

We had a 2001 325i that had a cracked head from new. I serviced it , after warranty for a few years. we changed the coolant, one service visit , and the car would misfire on cyl #5, on cold starts, until warm.
We found the head cracked, and wound up using Blue Devil. It worked at once. I sold it to a friend a year later, with full disclosure. It is still working. The clerk at the Auto Zone store who checked me out, added, " This **bleep** works!'

[CentauroRider]

Like radiator stop leak stuff, its temporary at best. You might get a way with it in some cases but the many "rebuild your engine" in a bottle is far from anything that I'd put my faith in. It does make you wonder how many used cars were given a "fix" and sold with fingers crossed that it doesn't come back?? Caveat Emptor as they say!

[DGMechanic]

My friend had a Toyota Land Cruiser with a v-6 that developed an internal coolant leak. The auto mechanic quotes for head gaskets was quite high. So, we flushed the thing out with NAPA coolant flush and used KW sealant. I did pressurize the cooling system during the cooldown stage just to make sure the stuff went in the hole. His wife drove it for 5 years before it was traded off for a new car. Never lost a drop of coolant and I never saw anymore gases in the radiator.

[pyrobirk]

I can confirm that these work in some cases if you follow the directions to the letter. We've put about 15k miles on our 2011 Traverse in the 14 months since I used one of these, and we've seen zero signs of head gasket problems since then.

[DUB6]

Awww, just throw a few bananas in the crankcase and maybe some oatmeal in the tranny and diff...

You can drink some Maalox to settle the burn, but the ulcer is probably still there!  I'm with @hyperv6 - use it to limp home, then line out a way to do the long-term proper fix.

[hyperv6]

I had a co worker that stripped a plug in an Omni. It was not worth the parts to tear down. So he JB welded it in. He did get two more years out of it. 

Many products in a can are often temporarily fixes to a terminal problem. Your results may vary.

Now one thing that does work is Marvel Mystery Oil. The old timers turned me on to this and it really works. 

I had a 65 Corvair with a locked up engine. We got it free. The valves were sticking so we put more in the gas and oil and it freed up the engine.

The car was crashed in 67 with 9,000 miles. It sat for 30 years. Once we got it back on the road it is still going today. 

The Marvel cleaned up the engine and it never was an issuer. 

[Oldroad1]

I sealed a water cross hole for a temp gauge fitting on an old 289 Torquer using the JB Weld method 20 years ago and that repair is still lasting. As for Marvel Mystery Oil, I'm also a believer. Had a 68 Dodge Super Bee after sitting for 40 years was bending push rods due to multiple valves sticking in the guides. Drained the oil, removed the rocker covers, and drenched the valve train with the oil with a squirter. Let it penetrate for couple of days with several more squirts then wound the engine by hand and no more sticky valves. Replaced the engine oil and filter and it ran beautifully. 2 OZ of this product is great for gas tanks and the rest of the fuel system before fill ups.

[hyperv6]

In the old days it was common to see a cracked radiator,  head or block in racing and teams would use JB Weld to seal the leak.  We also would dump a Coke on the clutch to make it sticky to finish a race too. 

[Oldroad1]

Coke on a hot clutch? Bet that was a taisty smell!

[drjim]

Yep. Been using MMO for about 50 years now. GREAT stuff!

- Jim

[Oldroad1]

Tried some Blue Devil oil leak sealer on my Honda Odyssey which suffered from several oil micro-leaks. I steamed the engine clean and have been driving it for over a year without any drips. I was and am still amazed.

[JSievers]

I've used original formula pelletized Bars Leaks in many cars over the years with consistently great results. It costs almost nothing to try, and even if it doesn't work you are no worse off than when you started.

[Vairnut1967]

Gladly I don't need any of these products for my air-cooled Corvair.

[61Rampy]

Same here! However, Corvairs can and do blow head gaskets, but it's usually 60-64 engines with the narrower head gaskets, or if a head stud pulls out of the block.

[Pitt2500]

Had a Mercury Sable with that 6 cylinder known for blowing gaskets.
Put a sealant in it and ran fine for months until we traded it off for Suburban.
Not sure what you have to lose especially if NOT planning on keeping it for a long time after you discover head gasket issue.

[Oldroad1]

What about the poor sap you sold it to?

[miata93]

I do not recommend doing this, neither does Lucas Oil Products Inc. However, I am about to tell you what I believe is a great "Hail Mary" play regarding "mechanic in a can" automotive chemicals. My '06 Toyota Prius developed a trans-axle bearing seal leak at about 20K miles. Rather than face a $600 repair bill for the installation of a $6 part I chose to try the chemical route first. So I bought a bottle of Lucas Oil Transmission Fix. When I brought it home I noticed in the fine print that it is not compatible with CVT transmissions and their respective fluids. I decided to try it anyway. The Prius only holds 4 quarts of the CVT fluid, so I drained 1/2 a quart and replaced it with the Lucas. Immediately I noticed a completely different feel in the "shift" characteristics. Pronounced slippage resulted, I presumed due to the different friction characteristics of the fluid. I decided to drive it gently for the next 150 miles. Then I drained it completely and refreshed the trans-axle with 4 quarts of the OEM fluid. The leak had sealed and stayed that way for 10 years and 90K miles. It was fine when I traded it in. I have also had a good experience with Lucas oil leak sealer on a leaky oil pan gasket. When using this, I loosen the oil pan bolts just slightly to temporarily increase the leak. I run the stop leak just before the oil change, then torque the bolts up to factory specs. I also have positive anecdotes regarding Marvel Mystery Oil for its anti-varnish and anti-gum properties.

[timb0]

In 1997, while my wife and I were exploring the U.S., I left the lift-up pressure release on my Subaru radiator cap off. I slept as she drove. The coolant all left and she kept driving. The heads were white when I raised the hood. Exhaust blew into the radiator, and 2 mechanics told us the car was junk. We had 1000 mi to home in Calif. I drove it anyway after filling with water, and bought 2 cans of KD Block Seal and 50 gallons of drinking water at Wal Mart. We drove on, stopping and filling radiator until we no longer had to. We made it home from Rock Springs Wyoming to Cotati Cal with no more problems. I still have the car.

[miata93]

A great story! This reminds me of the time that I was driving to my first real job in Boston. I blew my radiator on the Ohio Turnpike around Cleveland. I was able to nurse my car into Erie PA by keeping the cap off and pulling off to refill the radiator at gas stations. At least once I had to take a wastepaper can down to a culvert beside the road and refill the cooling system with swap water. LMAO !

[RallyeRalph]

The Taurus/Sable/Continental 3.8 V6 had a strong propensity for head gasket leaks. We used SteelSeal (expensive and you have to follow the directions to the letter) on numerous cars and it worked every time,. Not just to get it over the curb but way down the road. When my mechanic used it on his own Continental and retired 6 years later, he still had not needed to make any further repairs. and it ran fine. Being a second generation used car dealer, I've heard of a few temporary fixes. My father told me of water-glass to repair cracked blocks in Model A's, bananas in differentials to quiet them down (it worked but the combination of smell of rotten bananas and hypoid oil after several months when the noise came back? Whew!), one time he had an old Chevy 6 with the chronic bottom-end rattle and he soaked a leather belt in neatsfoot oil, cut it into sections, dropped the pan and rod caps and put the strips in over the rod bearings and torqued it down. Worked for months.
But they didn't always work. One time he needed to grind the valves on a Model A, which involves removing the flat head. He removed the head bolts but the head was frozen /rusted to the block and would not separate. So he put the plugs back in and started it to let the compression loosen the head. It sat there for an hour and ran with the same miss as before but a still tight head. So he got the bright idea to remove the plugs and put a little gunpowder down each cylinder and literally blow the had loose. He started it and it blew a piston into the pan but the head stayed tight. The prvious owner must have used some 'mechanic in a can' on the head gasket.

[61Rampy]

GUNPOWDER??????? OMG!!!

[MustangJim]

I had a bad head gasket in my 1984 Plymouth Reliant K, I think it was the 2.3 4cyl. A trusted mechanic told me that if I was going to try to pour in sealant the by pass the heater core first, otherwise it would clog the heater core. I did'nt listen, the heater core went and this was in the middle of winter , and it was my winter car. I wanted to park it and restore someday but didn't have the room if I was going to replace the "winter" car so this was the end to my K car that I wish I still had. I was NOT going to bring it to a shop and pay for a new heater core and head gasket. 

[AsaJay]

The video was probably the best I've seen on a topic like this. He really went into explaining every aspect, caveat, right thing and wrong thing to do. I have really enjoyed Chris' videos and they just seem to get better all the time.

[SAG]

A good 'Head shop / Machine shop',
is the only way.

?_a fix-it in a can. People will buy anything, thinking_
who knows their thought process.

[DUB6]

@SAG - I'm not even from Haight-Ashbury, but most everyone I know has an entirely different definition of Head Shop than I think you do... 😄