Going to try BlueDevil Head gasket sealant, your tips/advice

I have a 03’ Honda Civic with about 140k miles on it. Have had a blown head gasket for about a year or so just haven’t had the money to fix it. So every so often I’ll have to refill the antifreeze. Yes, I’ve had it tested it’s the head gasket, with a pinhole leak. Everything else in the cooling-system has been tested functional, all signs point to the head. I’ve heard mixed reviews about these sealants, the vast majority say they it works but there are always the smaller percentage saying it doesn’t work or it’s just a temporary fix. I’d love some input on this. I need to have this car fixed…this car has been the bane of my existence. I want to make sure I have all my ducks in a row and have the directions specifically down/correct.

Here are the directions I found online:

I want to must make sure I have this correctly.
When It states that the cooling system must be clean and free flowing this is to say that I must have the thermostat and radiator cap removed? and that by clean I must do a radiator flush with a flushing agent and then water?

I’ve never removed a thermostat, I am guessing it’s not that difficult.
Similarly I’ve never flushed a cooling system before either I don’t know where the bottom radiator hose is, what might this entail?
The flushing agent I’ve chosen is: Prestone super flush.

What does it mean by flush then fill. If I am flushing with water after prestone isn’t also filling the cooling-sysem with water, or is that to say I must close up the system somehow beforehand.
Also how do I determine how much is enough water to put it so that there is enough for 32oz of blue devil?

The rest seems pretty simple to follow along it’s just 2,3 and 4 that have me a bit confused.

Excuse the vast car ignorance

A simpler solution, which may or may not work, is to pick up a small bottle of the stop leak that Subaru uses. Just add it to the existing coolant without having to drain, flush, etc. It’s less than $5 a bottle and is routinely added whenever the coolant is changed.

I recall something maybe similar to what jdmere describes that I was shown years ago at a good parts place frequented by professionals and with a machine shop. The counter man said GM put it in routinely in new cars. I think it was a vial of small particles, smaller than sand, maybe about 4 oz. volume.

Regarding step 5: Be sure to have the heater set on hot (the fan doesn’t need to be on.) I would let it idle with the cap of for a few minutes while watching for air bubbles to emerge from the rad cap (the coolant level will drop and you would then top it up with water.) Once it remains filled, cap the system and let it run as per instructions.

That said, I think you are right to be cautious about how to deal with the problem.

Such products offer some hope for as a last ditch effort at getting a few more miles from an engine. I have seen several cars run for many trouble free miles on such snake oils but wouldn’t recommend taking any long trips depending on the leak being reliably stopped. It’s a cheap roll of the dice. You might be a winner.

I think that cooling system stop leak products don’t come close to head gasket sealers @jdmere.

@RodKnox Well I’ll roll the dice. It seems the majority have good luck with it and the ones that don’t either are not following the directions or the leak is just too large to seal. I just want to make sure I am following the directions right so that no mishaps arise.

If you’re going to keep the car I’d bite the bullet and get the head gasket done properly. A sealant like this will probably fix your pinhole leak but it probably will seal other parts of your cooling system as well . . radiator, heater core, thermostat, small coolant passages in the engine, and whatever. I’ve seen this happen personally, the stuff does work, but sometimes works too well. Good luck! Rocketman

Before you spend the money for that stop-leak product, try adding a teaspoon of ground black pepper to the cooling system.

The dehydrated pepper will absorb the coolant and soften while flowing thru the cooling system. Then when the pepper finds the leak it will accumulate at the leak and when exposed to the air dehydrates again stopping the leak.

I had a vehicle with an external head gasket leak, and the pepper stopped the leak for over a year. That was until the head gasket deteriorated to the point where it had to be replaced.

If the black pepper doesn’t work, I have a much cheaper method to stop the leak that can be obtained from a pharmacy.

But try the pepper first and let us know if it works.


@Tester‌ interesting never heard of this method before. But it’s got me wondering if I should try it. So I would add the black pepper into radiator hole? and let it circulate throughout the engine. Is this a permanent fix? sounds like it would breakdown pretty easily.

What does everyone else think of this idea?

You just add the pepper to the radiator and drive the vehicle.

No. It’s not a permanent fix. Be neither is the stuff you pay $60.00 for that claims to do the same thing.


I have worked on countless cars after folks use whatever snake oil they’re sold on to try to fix their leaking head gasket. Unfortunately by that time I’m replacing the water pump, radiator and heater core along with the head gasket due to them being so plugged up with “fix in a bottle”.

I’m working on a car now after running K & W Chemical FiberLock® Head Gasket & Block Repair

It’s not the same stuff but, I’m telling you from experience it didn’t turn out good for me. The car started overheating even more quicker.

I decide that I was going to keep the car so I took the engine out and ran with 0.020" oversize pistons. I dropped my engine block, cylinder heads, crankshaft and camshaft off at the Machine Shop. The guy called me and told me I had warped my heads and he had to shave them 0.008" and my valve’s were pitted.

I’m not telling not to run stop leak but, I just want you to be aware just in case it doesn’t work as expected. People always talk down on head gasket sealants but, I didn’t listen.

ksteed94, I’m with you on this. I believe that using something to generally block or seal small holes and cracks will do exactly that . . . block small holes and cracks where it finds them, often times making things worse like your case. If you’re still reading these posts OP, consider what you’re doing with this sealant. You are sealing stuff well beyond the pinhole leak you’re trying to fix. Replacing a head gasket is (mostly) labor but ruining other parts by clogging them up and warping the head when you overheat this engine will cost a whole lot more than the head gasket. Good luck, keep us informed and I hope it works out for you! Rocketman

BTW, you can google “Blue Devil Head Gasket Sealant” and watch the video of how to do this, and in the one I watched . . it worked! I couldn’t find a You Tube video where someone posted a failure. Rocketman

my only tip should you chose to go the Blue Devil route is. Be sure you have alternate transportation.

Jim, I’m a Honda guy and I eagerly await your report on the outcome. One thing that I don’t see on the instructions is to replace the water/sealant with 50/50 antifreeze as the last step.

Additives are a crutch and last ditch effort. It may be worth a shot but I wouldn’t plan on any cross country trips in the car.

Sixty bucks for Blue Devil? No thank you.

I have an '03 Civic ES with 159k miles. I decided against any of the chemical stop leaks. After replacing the head gasket the problem is fixed and the motor runs great. Bought this car new, and I decided to keep it going for another 5+ years. If you intend to keep the car for a year or less, go with the chemical. But, if you want to keep it for one + years find a way to fund a proper repair.

My daughter in law has an '04 Civic, 140k miles, we tried Blue Devil and it did not work. We had the head gasket replaced (timing belt and water pump too) and it has been fine since. The mechanic said they saw where the blue devil ran out, but the breach was too big for the stuff to seal it.

Additives are worth trying if the goal is to squeeze some extra life out of a worn out beater.

Additives are NOT a way of permanently repairing a problem, and often “the fix is worse than the cure”.

The exception to this may be fuel additives designed to clean out contaminated fuel systems. They can work in some specific instances, like systems gummed up due to lack of regular use.

It worked for me. Honda 2000 accord. Not this brand but same concept