Rick's Free Auto Repair Advice

Does head gasket sealer work?

Can you really fix a head leak with liquid head gasket sealer?

If you’re constantly topping off your coolant and can’t find any trace of an exterior leak, you may have a blown head gasket. Or, if your engine overheats and you’ve checked the radiator, fans, and water pump, you may have a head gasket leak. Either way, you may be considering a head gasket sealer. Everyone wants to know if they work.Here’s the answer:

Some head gasket sealers work—sometimes

Some head gasket sealers work. Others don’t. And the price has nothing to do with their success rate. I’ll give you the whole truth about head gasket sealers. Or, if you want to skip the lesson and get right the to the heart of the matter, scroll down to head gasket sealers.

What causes a head gasket leak?

Head gaskets can fail in many ways. First, the gasket can fail around the coolant ports between the block and the cylinder head, allowing coolant to enter the crankcase. The coolant turns your oil milky-white like a milk shake and that destroys your entire engine. What causes the gasket to leak in the first place? Sometimes it’s just a poor gasket design. But most often it’s because of owner neglect by not changing coolant according the manufacturer’s schedule. Coolant contains anti-corrosive additives and when they’re exhausted, corrosion build up and degrades the metal surfaces in the cylinder head and head gasket. To check for that kind of leak, just pull the oil dipstick and examine the oil. If it looks like a milk-shake, you’ve found the problem.

The second way a head gasket fails is by leaking oil to enter the cooling system. That happens because oil pressure (up to 60-psi.) is greater than cooling system pressure (15-psi. Max), so the oil forces its way into the coolant. To check that, yank the cap off your radiator or coolant reservoir bottle and look for an oily film floating on the top. Again, owner neglect is the #1 cause due to lack of oil changes. But there are a few engine styles that fail in this manner even when they’re properly maintained.

The third way head gaskets can leak is to allow coolant into the combustion chamber where it’s burned. That’s much harder to diagnose. The coolant simply disappears in the exhaust. On the way out, it damages the oxygen sensors and can destroy the catalytic converter. Some people say you can see white smoke coming from the tail pipe. But that’s not always noticeable. It all depends on how hot the catalytic converter is at the time. The best way to diagnose a heat gasket that’s leaking coolant into the combustion chamber is to conduct a compression test and a cylinder leakdown test. You can also perform a combustion gas test.

Once you’ve determined that the head gasket is leaking, you’ve got a few choices. Replacing the gasket is the most permanent fix, but it’s going to be expensive (at least $1,000). So you may be tempted to try one of the liquid head gasket leak stoppers on the market. Well, ok, let’s talk about those.

How does head gasket sealer work?

Head gasket sealers work in two ways: One type plugs the leak with wood pulp, pepper, etc., like a finger in the dike.  The other, more modern type, forms a bridge between the gap with nano particles. Obviously, the finger in the dike is the oldest and cheapest method. Those stop leak products  may work in a cooling system where the pressure is less than 15-psi., but they don’t work very well in holding back cylinder pressure that easily runs up to 200-psi.

So the first thing you should understand is that you can forget about using cheap head gasket sealers (the products costing less than $30). First off, most of those sealers are incompatible with coolant. So you have to drain the entire (and I do mean the entire) cooling system and refill the engine and radiator with plain water.

That means radiator, heater core, and block (pulling the block plugs) have to completely drained and refilled. Then you pour in the stuff and run the engine for the specified time. Then you have to drain the system again and leave it open to the air for 24-hours. Then you can refill with coolant. These sealers work way less than 50% of the time. They’re a lot of work for such a lousy payback. And, as with most head gasket sealer, the leak must be small enough to allow you to run the engine for the specified period of time. If you have a large leak that’s rapidly pumping coolant into the crankcase, you’re not a candidate for ANY head gasket sealer (no matter WHAT the manufacturer’s guarantee says).

Next, you have to be very careful with plug type sealers. Everyone online will tell you they plug up the radiator and heater core. Well—they can, but only if you don’t follow directions. Keep in mind that the fin tubes on heater cores are VERY small. If you overdose any cooling system with a plug type sealer, it will clog the fin tubes. In this case, more is NOT better.

Then there are the next generation head gasket sealers

Bars Leaks HG1 or CRC’s KW FiberLock sealer are the newer nano-technology sealers. Bars head gasket sealer, Bars leaks, head gasket leak
Head gasket sealer, Fiberlock, Bars leaks CRC These work with a 1-2 punch. First, they contain a plug sealant that forms a “finger in the dike” patch. Next, the temperature sensitive chemicals attach to the plug material and melt to form a “permanent” seal. The nano particles form a patch along the hottest areas of the head gasket and continue to build until the breach is sealed.

Nano particles don’t work inside a radiator or heater core—there’s not enough heat there. If your engine is a candidate (see below), these products work 80-90% of the time. Just pour them directly into the radiator (not into the coolant reservoir). You may have to disconnect the upper radiator hose and siphon out some coolant to do this.

Which engines aren’t good candidates for head gasket sealer?

READ THIS: If you’ve overheated your engine and warped the head, you’re deluding yourself into thinking that a head gasket sealer will fix the problem. With a gap between the head and block and expansion and contraction during normal heating and cooling cycles, no sealer is going to stick. Then again, you’ve got very little to lose by trying either of these products. Just realize up front that you’re most likely going to end up paying for a head machining and a new gasket.

Now let’s talk about the real candidates for head gasket sealer

If your engine will run for at least 20 minutes without overheating or losing most of its coolant, the KW and Bar’s products MIGHT work for you. If the cylinder head isn’t warped due to overheating, but the head gasket has deteriorated due to pre-ignition or corrosion (not overheating) then you can give it a shot. For these engines it’s worth a shot and the sealers often have an 80% success rate.

How about the more expensive head gasket sealers—the ones that cost almost $100?
Well, how do you feel about being taken to the cleaners? Scammed? Played for a sucker? Screwed? Get my point? You don’t need to spend that kind of money on a head gasket sealer. If a sealer is going to work, either of the two products above will do the job just fine.

If the sealer stops the leak, you’re done. You do not have to add additional sealer down the road when you change coolant.

© 2012 Rick Muscoplat

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Posted on by Rick Muscoplat


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