Rick's Free Auto Repair Advice

Does head gasket sealer work?

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

Most of the time it doesn’t. And even it if does, it’s rarely a permanent fix. Whether it works on your engine depends on how the head gasket failed. If your head gasket leak appeared after your engine overheated, give it up, head gasket sealer is not going to work. However, if your car didn’t overheat AND the leak is between the cylinder and the cooling system, you might have a chance. Read on to find out how this stuff works and when it works.

What causes a head gasket leak?

Head gaskets can fail between the between the cylinder and the cooling jacket, between the cooling jacket and the oil passages or between a cooling or oil passage the exterior of the engine.

Leaking head gasket symptoms:

Head gasket failure between the cylinder and the cooling jacket

Engine overheats quickly because air/fuel/exhaust gasses are being pushed into the cooling system. Those gases are very hot and that’s why the engine overheats so quickly

Coolant overflows out of the coolant reservoir. See above. Plus, all that extra gas/exhaust pushes the coolant out of the engine.

Upper and lower radiator hoses become very hard when engine is running or detach from the engine completely. The gas/exhaust gasses raise pressure in the cooling system.

White smoke comes from the tailpipe because coolant leaks into the combustion chamber, is burned and exists the exhaust as steam.

Coolant reservoir empty because the coolant is being burned

Head gasket failure between the cooling jacket and oil passage

Coolant in the oil that turns the oil into a chocolate milkshake color, OR oil in the coolant.

Head gasket failure between the cooling jacket and oil passage and the exterior

An oil or coolant leak from the head gasket to the exterior will usually cause oil stains on your garage floor or driveway.

Oil and coolant levels will be low even after your refil

Coolant reservoir will be low or empty.

, the symptomsaround 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.

How does head gasket sealer work?

Plugging head gasket sealers

Head gasket sealers can work in two ways: One type plugs the leak with wood pulp, pepper, ginger root, etc; like a finger in the dike.  The other, more modern types, patch the gap with a heat sensitive liquid glass.

The finger in the dike products are the oldest and cheapest method. They sometimes work to stop a cooling system leak in a radiator or heater core where the pressure is less than 15-psi. But they don’t work very well for head gasket leaks because the pressure can easily run up to 200-psi.

Nano liquid glass style head gasket sealers

Bars Leaks HG1 or CRC’s KW FiberLock sealer are just two of 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 plugging sealant that forms a “finger in the dike” patch. Next, the temperature sensitive chemicals attach to the plug material and melt out of suspension to form a longer lasting. Most sealers of this type use sodium silicate, or liquid glass. The “glass” in Sodium silicate actives from high heat, the kind found around the steel ring at the top of the cylinder. The nano particles form a patch along the hottest areas of the head gasket and continue to build until the breach is sealed.

Sodium silicate sealers don’t work inside a radiator or heater core because there’s not enough heat to melt the glass out of suspension.

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

If you’ve overheated your engine and warped the head, you’re kidding yourself if you think either of these types of head gasket sealers will fix the problem. When a cylinder head warps, you wind up with a gap that expands and contracts during the normal  heating and cooling cycles. No sealer is going to work in those cases.

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 poor design, 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.

Do the more expensive head gasket sealers work better?

No. The all work with the same technologies. The expensive ones use hype and guarantees to lure you in. If you like being scammed, payed for a sucker or just plain screwed, spend the $100 and buy the expensive sealers.

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.

Here’s the thing about head gasket sealers; many of the cheap head gasket sealers (the products costing less than $30) aren’t compatible 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 you have to flush the radiator, heater core, and block (pulling the block plugs) have to completely drained and refilled. Then you pour in the stuff with water 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. Only after you’ve done that can you fill with coolant.

These sealers rarely work. They’re a lot of work for such a lousy payback. And, as with most head gasket sealers, the leak must be small enough to allow you to run the engine long enough without leaking for the sealer to work. 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 forum will tell you they plug up the radiator and heater core. Well—they can, but only because the user didn’t follow the directions. Because these sealers contain a plugging agent, you can’t “over dose” the system. If you add too much, the plugging agents settle out of the liquid and clog the small fin tubes in the heater core and radiator. This is a case where more is NOT better.

© 2012 Rick Muscoplat

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Posted on by Rick Muscoplat



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