Are Head Bolt Heaters Still Made? Yes—here's Where to Buy

Yes—head bolt heaters are still made and still sold today. Brands like Kat's Heaters, Zerostart, and Kats-based lines under Tecumseh/Detroit Socket continue to manufacture the classic freeze-plug and head-bolt style heaters for cars, tractors, generators, and small engines, and they're widely available through Amazon, Summit Racing, NAPA, and farm supply stores.

If your equipment lives outside in freezing weather, this old-school technology is often the cheapest insurance you can buy. A warmed engine starts easier, pumps oil faster, and burns less battery on a -10°F morning.

This guide covers who still makes them, what they cost, how to install one without coolant leaks, and how to pick the right wattage for your engine displacement.

Are Head Bolt Heaters Still Made? The Short Answer

Yes, head bolt heaters are still in production. The category never died because the need never died: farmers, fleet operators, and anyone parking outdoors in cold climates still want a simple, cheap way to keep an engine warm overnight. Kat's Heaters (a long-standing U.S. brand) and Zerostart/Temperature Controls remain the most common names you'll see on shelves and listings, along with generic imports sold under various labels on Amazon and eBay.

You'll find them sold under a few related names, which causes confusion: head bolt heater, freeze plug heater, block heater, frost plug heater, and tank-style heater all describe heaters that warm the coolant inside the engine block. True head-bolt style units replace or clamp onto a head bolt, but most products sold today as "head bolt heaters" are actually freeze plug replacements or lower-core-plug heaters.

Typical retail runs roughly $20–$60 for a freeze plug style unit, depending on wattage and engine fit. Availability is best from late summer through winter; some sizes go out of stock during cold snaps, so buying in early fall is smart if you know your engine's spec.

What a Head Bolt Heater Actually Does to a Cold Engine

At freezing temperatures, oil thickens dramatically—straight-weight and even 5W-30 pour far slower at 0°F than at 70°F—batteries deliver less cranking current, and metal clearances tighten. A head bolt or freeze plug heater sits in direct contact with engine coolant (and in freeze plug designs, the water jacket itself), warming the block from the inside.

Warmer coolant means warmer cylinder walls and warmer oil sitting in the crankcase. That combination produces three measurable benefits:

• Easier starts: the starter spins the engine faster because thick oil isn't dragging on the bearings.
• Less battery drain: shorter cranking means less demand on a battery that's already at reduced output in the cold.
• Less engine wear: most cold-start wear happens in the first seconds before oil reaches full pressure; a pre-warmed engine reaches pressure faster.

There's also a comfort and emissions angle: heated engines produce heat for the cab sooner and reach closed-loop operation faster, which reduces rich cold-start fueling on carbureted and older fuel-injected engines alike.

Note the limits, though. These heaters warm the block and oil gradually—they don't warm the transmission, rear differential, or hydraulic fluid, which matters for tractors and equipment. (See Also: Are Hot Rivets Stronger Than Bolts)

Main Types of Engine Heaters Compared

Before buying, know that "head bolt heater" is one of several options. Each mounts differently and suits different engines. The right choice depends mostly on whether your engine has accessible freeze plugs, an available hose, or a dipstick tube.

For most people with a car or diesel pickup, a freeze plug style unit or a tank-style hose heater is the practical pick. For a portable generator or snow blower, a dipstick heater avoids any permanent modification. Tractor owners often favor lower core plug heaters because convection currents circulate warmed coolant through the whole block without a pump.

How to Install a Freeze Plug Style Head Bolt Heater

Installation is a moderate DIY job—most people finish in one to two hours. The important steps are draining coolant, removing the correct core plug, and seating the heater fully. Work on a cold engine only.

1. Verify fitment: match the heater to your engine's core plug diameter (common sizes are around 1-1/4" to 2" depending on the engine) using the manufacturer's application chart. Guessing by eyeball is how leaks happen.
2. Drain enough coolant to drop the level below the plug you're removing. A drain pan positioned under the block plug catches most of it.
3. Remove the core plug: tap one edge with a punch and hammer to pivot the plug, then pull it out with pliers. Clean the bore thoroughly—rust and scale prevent seating.
4. Insert the heater per instructions (some go dome-in, some dome-out depending on design), then tighten the clamp bolt until it expands and locks against the bore.
5. Route the cord away from exhaust manifolds and moving parts, and secure it with zip ties so a tug on the plug can't reach hot metal.
6. Refill coolant, run the engine to temperature, and check the plug area for leaks after it cools and again the next day.

One caution: never power the heater while the block is empty or the heater is out of the engine—it will burn out in seconds, and dry-firing is the most common way people kill a brand-new unit.

Choosing the Right Wattage and Fit

Wattage determines how fast the engine warms, and fit determines whether it leaks. Match both to your engine rather than buying the biggest number available.

• Small engines (under 1L displacement, generators, mowers): 100–300W dipstick heaters are usually adequate overnight.
• 4–6 cylinder cars and small tractors: 400–600W freeze plug heaters typically warm the block enough over 3–5 hours.
• Large V8s and diesel pickups: 750–1500W, and diesel owners in very cold regions often step up further or combine with an oil pan heater.

Check your circuit capacity too. A 1500W heater draws roughly 12.5 amps at 120V, so on a shared 15A garage circuit with a battery charger and lights, you can trip a breaker. Run it on a dedicated circuit or unplug other loads.

Fit verification beats part-number trust. Even with an application chart, physically measure your core plug opening and compare against the heater's listed diameter. Paint, rust, or a prior repair may have changed the plug size. If your engine has aluminum block areas or unusual plugs near the exhaust side, a tank-style hose heater sidesteps the problem entirely.

Also confirm cord length—extension cords in freezing weather should be a heavy gauge (12 AWG or thicker) and kept as short as practical to prevent voltage drop and heat buildup in the cord.

What to Expect: Warm-Up Times and Real Results

Set expectations honestly: a 600W heater won't make a -20°F engine feel warm to the touch in an hour. What it does is raise the block temperature gradually, and the benefit shows up as cranking speed and oil flow, not a warm cab immediately. (See Also: Are Head Bolts on Gm 3 0 Industrial Reusable)

As a practical planning guide:

Two rules of thumb follow from this. First, plugging in overnight is wasteful but harmless except for electricity cost—running a 600W heater 10 hours instead of 4 costs a few extra cents a night, which many people accept for convenience. Second, using a heavy-duty outdoor timer to switch the heater on 3–4 hours before departure gives most of the benefit at a fraction of the runtime.

In severe sub-zero climates, pair the block heater with an oil pan pad and a battery warmer; the combination reliably beats any single device.

Common Mistakes to Avoid

Most heater failures and coolant leaks trace back to a handful of avoidable errors. These are the ones that come up again and again:

• Dry-firing the element. Energizing the heater before coolant surrounds it destroys the element almost instantly. Always fill the cooling system before plugging in.
• Wrong plug diameter. Forcing an oversized or undersized unit into the bore guarantees a seep that shows up weeks later as a slow coolant loss you can't trace.
• Cord routed across the exhaust. Melted insulation on a live cord is a shock and fire hazard. Keep at least a couple of inches of clearance from manifolds and heat shields.
• Overlooking burping the system. After refilling, air pockets near the heater reduce contact and can cause localized overheating. Run the engine with the heater on and the cap off (cold) to purge air.
• Using a thin indoor extension cord. Cheap 16 AWG cords heat up under a 10+ amp load, especially when coiled. Use a short, heavy-gauge outdoor cord.
• Leaving the heater energized unattended for days. A low coolant level plus a working heater can cause localized boiling. Check coolant before extended plug-ins.

Avoiding these five or six issues covers nearly every problem report you'll read in product reviews.

Troubleshooting: Heater Doesn't Seem to Work

If the engine is still hard to start after a night on the heater, work through this sequence before blaming the unit:

1. Confirm power at the receptacle. Test the outlet with a lamp or multimeter—GFCI outlets in cold, damp garages trip more often than people expect.
2. Check the cord and connections. Wiggle the plug and feel the cord near the engine after 30 minutes of operation; a warm spot indicates a broken conductor inside the insulation.
3. Test the element. With the heater connected and powered, an ammeter or even a smart plug showing watts will tell you instantly whether it's drawing its rated load. Zero draw means a burned-out element or broken cord.
4. Feel the upper radiator hose after a few hours: it should be warm, not hot. Warm coolant means convection is working.
5. Verify coolant level. A low system leaves the element exposed to air, which both reduces heating and shortens element life.

If the heater draws power but the engine stays cold overnight, the likely culprit is a unit of inadequate wattage for the displacement, or extreme wind exposure stripping heat away. Moving the vehicle out of the wind or stepping up wattage usually solves it.

Common Questions About Head Bolt and Block Heaters

How Much Electricity Does a Block Heater Use?

Wattage rating divided by 1,000 gives kilowatts per hour. A 600W unit costs roughly 5–7 cents per hour in many U.S. markets, so an overnight run costs well under a dollar. Using a timer to limit it to 3–4 hours cuts that in half without losing much of the benefit.

Can I Leave a Head Bolt Heater Plugged in All Night?

Yes, and most people do—but it's not necessary beyond about four hours for typical wattages. All-night plug-in is safe if coolant is full and the cord is undamaged, though a heavy-duty timer saves electricity and reduces any risk from a marginal cord. (See Also: Are Gem Tipped Bolts Worth It)

Is a Head Bolt Heater the Same as a Block Heater?

Functionally, yes—both warm engine coolant inside the block. The original head bolt style clamped to a head bolt; today the term is used loosely for freeze plug style units, which are the dominant design sold. Check the product description to see which mounting style you're actually getting.

Will a Block Heater Hurt My Engine?

No—used correctly it reduces wear by improving oil flow at startup. Problems only arise from installation errors (leaks), dry-firing the element, or cords contacting hot exhaust parts. A properly installed unit is passive and safe.

What Temperature Should a Head Bolt Heater Reach?

A working heater typically brings coolant into roughly the 100–130°F range near the element after several hours, depending on wattage, ambient temperature, and wind. The block won't reach operating temperature (around 180–200°F) without the engine running—that's normal.

Do Diesel Engines Need a Bigger Heater?

Generally yes. Diesel compression ignition depends heavily on intake and block temperature, and larger displacements lose heat faster. Diesel owners commonly run 1000W+ heaters and add a battery warmer or intake heater in serious cold.

Can I Install One Myself, or Should a Shop Do It?

If you can drain coolant and swing a hammer on a punch, a freeze plug heater is within DIY reach. If the plug is hidden behind brackets, exhaust, or on a hard-to-access side of the block, a shop install usually costs modestly and saves frustration.

Verdict

Yes, head bolt heaters are still made—brands like Kat's Heaters and Zerostart continue to produce freeze plug, head bolt, and dipstick style units, and they remain easy to find online and at auto parts and farm supply stores for roughly $20–$60.

Pick the style that matches your engine: a freeze plug or lower core plug heater for cars, trucks, and tractors, or a simple dipstick heater for small engines and generators. Size the wattage to your displacement, install it with the coolant filled before it's ever plugged in, and route the cord clear of hot exhaust parts.

Fit applications vary by engine and year, so verify the exact plug diameter and heater spec against the manufacturer's application chart before buying. With the right unit installed correctly, a few hours on the timer makes cold mornings dramatically easier on both you and your engine.