Even though I have a two car garage, I park my Corolla outside, with Jan-Feb temperatures typically around 15 to 30 F (-10 to 0 C). To help improve fuel efficiency, reduce smog emissions, improve comfort, and reduce engine wear, I’ve installed an OEM freeze-plug-type engine block heater.

Before I get into the DIY writeup, there are some easier things I should mention that you can do to improve your warmup:

  • If at all possible, park under cover. Somehow my weight set, bicycle rack, and table saw managed to kick my car out into the cold. So if like me you “have to” park outside:
  • Use windsheild snow covers overnight so your glass won’t be as cold, or require as much scraping. On clear nights, the radiant temperature of the sky is always much colder than the air, so without covers the glass ends up extra cold. That attracts fog to the glass, even after you scrape it off.
  • If you shower in the morning, put a cooler in there with you to catch some of the hot water and keep it hot. Right before you head out, transfer it to a pitcher and pour it over your windshield, then clear it off with the wipers. This warms up the glass so it will stay frost free while your engine is cold and not idling.
  • Apply an anti-fog coating to the inside of the glass. (Well, maybe not. I learned it isn’t like RainX, it evaporates.)
  • The goal is to idle as little as possible during warmup, even at stoplights. Preferably no idling at all.

I’m doing this today having tried everything else I could think of and having convinced myself that a block heater is going to rock.

MetroMPG has a nice section on block heater types and more info.

This took me about 3.5 hours to complete, not including time spent planning and gathering parts. A garage quoted me $100 labor for this installation. So if your time is precious, money is not so precious, or if you don’t already have the right tools on hand, it’s not crazy to pay someone to do this job.

I would even say next time I’d consider a recirculating coolant heater instead, assuming I can find one that fits my next vehicles.

Now on to DIY!


If you don’t have a 4A-F Toyota engine like me, your OEM or aftermarket block heater may install in a very different location. So the first thing to do is to find out how dissimilar your installation will be.

I got my heater from a Toyota dealer for about $40, and the guy was nice enough to find a schematic that showed the location of the correct plug. More recently I noticed Amazon.com carries Kats block heaters, and you can lookup the correct heater by vehicle make, model, and trim. Kats came up with the correct heater for my car for only $18. I don’t know how you would figure out which plug to install it in, short of asking a dealer for help. My Haynes manual doesn’t cover the topic.

If you’re doing a freeze-plug type heater like this one, another important step, before you take anything apart, is to get some calipers and verify that you’ve purchased the correct size. I was sold a 35mm heater but I had a 40mm plug. I figured that out with my calipers before I started and was able to exchange it for the correct heater.

Parts and supplies:

  • Freeze-plug engine block heater (mine is a 40mm diameter 400W version - $40 IIRC from Toyota, $18 from Kats)
  • Exhaust manifold gasket ($19, optional, I would say)
  • Exhaust pipe gasket ($3, not optional)
  • Zip ties


  • Impact wrench (and air supply) or breaker bar
  • 3/8” metric sockets, wrench and extensions
  • 1/2” impact sockets and extensions
  • Torque wrench
  • Short stubby flatheat screwdriver and hammer - very important
  • Channellock pliers
  • Hex keys
  • Wire brush, sandpaper

Step 1

Jack up vehicle and remove engine pans. SAFETY: there’s a right way and a wrong way to use jacks for working under a vehicle. Use jackstands, and know which parts of the underside are strong enough.

Step 2

From underneath the car, remove the exhaust pipe nuts with an impact wrench and extension. (Breaker bar might have worked. I love my impact wrench.) Also remove the exhaust manifold bracket bolt (there is a socket resting on it in this pic).

Remove exhaust pipe nuts

From under the hood, remove 5 screws holding the warm air intake. (This is a 4A-F feature for improving warm-up time, I think.)

Remove warm air intake

Remove the 3 nuts and 2 bolts holding the exhaust manifold. Remove the exhaust manifold.

Remove exhaust manifold

Step 3

My car was past due for a coolant drain and refill.

Put a catch pan under, and open the radiator stopcock, located on the driver’s side of the radiator, or take off the lower radiator hose. Open the radiator cap.

Drain radiator

OOPS! I’m about to make a mess, because the engine is cold and the thermostat is closed, which is the safe way to drain coolant, but the engine block will not drain all the way through the radiator. I should have also drained from the engine block drain plug. I never did find that. Without the engine block drain plug, I could have also 1) covered the open exhaust pipe with saran wrap to prevent coolant from entering the exhaust (potentially poisoning the catalytic converter later on), 2) waited for the radiator to completely drain and move the catch-pan under the freeze-plug area before I punch it out.

Step 4:

Punch the freeze plug at the bottom, hoping to make it turn sideways. I used a short stubby flathead screwdriver and a sledge hammer. The shortness of the screwdriver is important because I need clearance to swing the hammer and I don’t want to have to remove the radiator just to get more clearance. The sledge hammer can be turned sideways, making it easier to get maximum impact in a short range.

Hammer the freeze plug

You can see coolant is coming out here, that was my last warning. I waited until the flow stopped, thinking that meant the coolant level in the engine was below the plug. Not true! Somehow I forgot to take pictures of holding the hammer over the leak to keep it out of the exhaust while looking around frantically for a better way to contain the mess, which I never found.

Oh no! My freeze plug went into the engine instead of turning sideways like all the videos I watched showing how to do this. This is the part of the plan that always gave me chills. The car cannot be driven until this is resolved.

Freeze plug sideways

But it was nothing a pair of needle-nose pliers couldn’t solve. I got the plug where I could grab it with channellocks and apply a lot more force.

Freeze plug removal

Wiggle it around, apply a lot of force, and then:

Successfully removed

Success! Sort of. No pictures of the mess on the floor. It’s amazing how rubbery the stuff smelled, like tire air. New coolant didn’t smell rubbery. It must be the effect of recirculating for years in a closed system with rubber hoses. It also looked and felt a bit like engine oil, which was really disturbing (maybe not surprising, with 223k miles on the engine), but there was hardly any oil floating on top of my catch-pan. Is oil miscible in coolant?

After tightening the heater plug’s claw, it still didn’t sit snug. I can wiggle it around, but it’s in no danger of falling out. Maybe that’s okay. I’m not sure why this happened. Maybe it’s because Toyota stopped making the block heaters for this car and the dealer traded me a generic brand when I came back to get the right size (4 years after my initial purchase, they were being nice to me).

Heater not completely tight

Step 5:

I found a location I can zip tie the power cable to. This required some thought; the cable must never touch any parts of the exhaust, lest the insulation burn away and short to the block, nor must it interfere with any moving parts. To the driver’s side I had the clutch drive cylinder (which moves around a little) and nothing I liked for zip-tying, so I went to the passenger side but avoided the serpentine belt area.

Also, it’s important to replace the gaskets. Maybe I could have got away with keeping the manifold gasket (at the top of the picture), but the exhaust pipe gasket definitely needed to go.

Wire routing and new gaskets

Also, the old exhaust pipe gasket, in falling apart, left material stuck to the manifold. I managed to get it about 80% cleaned up with the wire brush, sandpaper, and a little bit of chiseling with a screwdriver.

Cleanup failed gasket

Step 6:

Reinstall the manifold, warm air intake, and engine pans. Note that the bolts that compress the gaskets have torque specs that ensure these hard metal gaskets make a seal. I didn’t have my Haynes repair manual handy so I didn’t know the torque spec, so I went on instinct, which I sometimes rely on even when I have a torque spec handy.

Fill with fresh coolant.

Every tutorial I read on replacing coolant required burping the engine, which involves idling until it reaches temperature and the thermostat opens. I thought this would be necessary since otherwise the engine might have a big air pocket that wouldn’t be filled, so I did it, although it took more than 10 minutes of idling which pains me deeply, particularly since I have a block heater now, but I figured the block heater might not be submerged prior to burping and therefore would burn up if I tried to use it to approach opperating temperature.

I know I warmed up enough to open the thermostat since I could see coolant flowing with the radiator cap open. Somehow it never took much additional coolant though. Since I had a sizeable spill, I don’t know if the volume in matches the volume out, so there might still be an air bubble in there somewhere. If so hopefully it’ll work it’s way out and it’ll just draw more coolant from the reservoir.

In any case, I’m tempted to say that, looking at the coolant hose arrangement in my engine, that filling the radiator would most likely fill the engine block, and you can most likely drive it normally without idling and burping, just pay attention to your temperature gauges and coolant reservoir level, and don’t blame me if something gets damaged. After all, it’s just a suggestion, and I certainly don’t know how it will turn out since I didn’t try it that way. (Someone let me know if you try that and damage something.)