Photo Essay - How To Replace Prius Spark Plugs

I bought a 2007 Toyota Prius a couple of months ago that will most likely be converted into a taxi. Until then, it’s been used occasionally as a personal car.

The Malfunction Indicator Lamp (ie MIL - the orange engine warning light) came on a few weeks ago. I checked for diagnostic codes at the time and got codes that related to spark plugs, so wasn’t excessively fussed about it at the time.

Tonight I decided to fit new spark plugs. I went looking for Denso SK16R11 plugs but the only supply was a nearby Toyota dealership. They quoted me $A24 per spark plug, and even when I asked about a taxi trade price it only dropped to $A22 each (I should be paying around $A14 each). I went elsewhere and bought NGK IFR5T11 spark plugs for $A10.80 each instead.

I started the night by checking for codes again. I got the following:
P0300
P0302
P0304
U0073
U0121
C2318

The P030X codes relate to spark plugs, which is why I knew that it was time to change them. I also want to do any maintenance possible on the car now, as once it becomes a taxi I will have limited access to it.

The C2318 code relates to a low charge in the 12v battery, but the car hadn’t been driven for a couple of weeks. I’m not yet familiar with the U0073 and U0121 codes.





I bought this car at auction, and although the user manual has all the required stamps, there were no invoices for previous maintenance (ie meaning that I don’t know what’s been done on the car in recent years). The car currently has 147,688km on it (ie around 91,769 miles).



This is the engine bay area. I replaced the air filter on the day that I bought the car. To access the spark plug area I started with removing the relay box.



There are two bolts holding the relay box in place. I removed them both with a 10mm socket.



Once the relay box has been moved to one side the four coils can be seen (ie one per spark plug).

The coil with the white lettering was only put on recently. When I got the car it had another, incorrect coil there. The car ran, but the coil was taller than the others. I bought a secondhand coil and put it in.



Each coil has a bolt holding it in place. These bolts also have a 10mm head.



Once each bolt is removed the coils can be lifted out. On top of each coil is a rubber seal to keep moisture out of the spark plug cavity.



I started removing the spark plugs. I used a 1/4” drive ratchet, a 150mm extension bar, a universal joint and then a spark plug socket.



As I couldn’t find Denso SK16R11 spark plugs for an acceptable price I bought NGK IFR5T11 plugs instead.



There is considerable debate about whether or not to put anti-seize on spark plugs. Until tonight I have never put anti-seize on a spark plug in my life, but I’m going to start to. Right now I have another taxi that is well overdue for replacement spark plugs, but the existing ones are seized in. I can’t get them out, and nor can a mechanic that I referred the car to. We’re stumped.

I didn’t put the spark plugs in that car, but considering the difficulty it is currently creating I’m going to start putting anti-seize on spark plugs from now on. And remove then at least every 50,000km to make sure that they’ll come loose.

I bought this bottle of Loctite 38650 copper-based anti-seize a while ago and never used it until now.



The spark plug socket that I use is a Bikeservice BS9133 16mm Thin Walled Socket. I bought this to fit a KTM enduro motorbike as normal 16mm spark plug sockets don’t fit in the head cavity. The thin walls on the Bikeservice socket give the socket a thinner diameter than other sockets.

That socket has a 3/8” drive but I used 1/4” stuff when changing spark plugs so have a 3/8” to 1/4” adaptor plugged into it.



This photo shows the thin walls of the socket, and now this makes the socket thinner than other 16mm sockets.



When removing sockets I remove the rubber part inside the socket as it makes it difficult to tighten sockets (ie the rubber tends to stay behind, on the socket). I use the socket to loosen each spark plug, and then poke a telescopic extendable magnet down to remove each spark plug.

Or, you can retrieve each spark plug by poking a coil down and retrieving it (ie the spark plug will plug into the coil).



The telescopic extendable magnet is also useful for retrieving nuts and bolts from distant corners after dropping them, which I sometimes manage to do.



Toyota specifies 18Nm for the spark plugs (we use metric here in Australia) but subtract 20-30% when using anti-seize. I figured that I’d tighten them to 15Nm with my Snap-On TECH2FR100 digital torque wrench, but it was feeling too tight and I wimped out at 12.3Nm. I gave up on using the torque wrench and put it away for the night.

The Snap-On digital torque wrenches vibrate as they approach the preset figure and then beep when they reach that figure.

There is a smaller version, the TECH1FR240, which would have been much better suited for this. If I ever see a new-near one go cheap enough on eBay then I’ll buy it (as I did with this one).



I then loosened the spark plug and retightened it with a 1/4” ratchet.



As with the anti-seize, there is debate about whether or not to put dielectric grease in the coil ends. On another car that I have as a taxi (Ford Falcon) the coil rubber tends to stick to the spark plug, making the coil extremely difficult to remove. Using dielectric grease has helped with that, so I’m going to do the same with my Toyotas.



The coil for cylinder 2 had some moisture on it, which would explain the misfiring when the car is cold.

As mentioned, the car had an incorrect coil for number 2 when I bought the car. This meant that there was no seal at the top of the spark plug cavity.

I like to keep my engine bays clean, so washed it on the day that I bought the car. Not knowing about the lack of seal on coil number 2, water would have gone down that cavity.



I set the car to idle and left it running for around half an hour. I then removed the four coils and left the car as it was for another hour or so, to let any remaining moisture evaporate away.



I then put the spark plugs, coils and relay box back in place.

I put the spark plugs at the base of the windscreen, in matching order of which cylinder each one came from.



Once I was finished with the engine bay, I took the spark plugs into my shed and had a look at them. Number 2 was darker than the others, presumably from misfiring as a result of moisture. The other three all looked the same as each other.



The spark plugs that came out are NGK PFR5B-11. Although they did the job, they’re not considered to be the ideal spark plug for the Prius.



Spark plug number 2 had corrosion from previous moisture.



Whereas the other three spark plugs had no signs of any corrosion.



I recently bought a Midtronics HYB-1000 Hybrid Battery System Analyzer. I still don’t know if it’s going to be of any long-term use, but at least it checks for diagnostic codes. I checked and there were no codes. I’ll drive the car around town for a couple of days and then check again.



I checked on the display and saw that the 12v battery was showing 14.1v, which is fine. After the earlier C2318 code I was expecting to have to replace that battery, although I possibly still will anyway.



I also have a Midtronics MDX-P300 battery tester, so decided to use that to test the 12v battery.

My previous taxis have been Ford Falcons, and I use a SuperCharge MF50 battery in them. That battery is rated at 650CCA and 107RC. I find that once the battery gets below 600CCA it’s time to replace it as then I have problems with the onboard taxi equipment (ie it resets and stuffs up when the car starts because of the starter motor using all the power).



The 12v battery in the Prius is rated at 325CCA, and tested at 384CCA (ie as good as new). I like how the Midtronics tester can print out the results. I write the date on each bit of paper and put it in the bag with the tester. Over time I can monitor the gradual wear of a battery, and replace the battery before it leaves a car stranded somewhere.



And that was it. I’m still quite new to the Toyota world but it was late at night, I was doing this in the driveway and it started to rain. Later on I’ll tinker with, and maintain, a few other items in the engine bay.

 

Ford stopped making the Falcon in September last year. It was a fairly large, 5 seat car that was made in sedan, station wagon and ute form. There was once a panel van version as well.

The Ford Falcon was made in 6 cylinder and V8 versions. There was also a turbo version of the 6 cylinder motor, and that one was actually quicker than the V8s.

For decades, almost all taxis in Australia were Falcons. In recent years there has been a move toward Toyota hybrids as they are cheaper on fuel.

I used to drive my Falcon taxi but pulled the pin on that a year ago. Uber has wiped out the taxi game here, and it's all about poverty for taxi drivers now. My car was a station wagon, and I used to belt it around pretty hard. I even put Brembo brakes on it (repeated stops of a 2,000kg car results in heat fade on standard calipers).





In the whole Holden (ie our version of General Motors) vs Ford thing I was always a Holden person, but as I developed mechanical skills and familiarity with the Falcon platform I bought a Ford Performance Vehicles (ie FPV) ute. That one has a turbo 6 and produces 270kW at the engine:



It will soon be replaced with another one that was modified by a previous owner to produce 353kW (473hp) at the rear wheels:

 

I spent a bunch of time last night Google searching and reading through various different car forums. There were all sorts of opinions about whether or not to use anti-seize, and if so, what sort to use.

There were numerous posts recommending to use copper anti-seize, and Loctite's official info on it recommends that particular one for use on spark plugs. I went with a majority vote and decided to use the copper stuff that I've already got (ie it was after midnight, so there wasn't an option to go shopping).

Loctite's info: "A premium quality copper anti-seize and thread lubricant that may be used to prevent seizing, corrosion and galling where high temperature conditions exist. Temperature range: -30 F to 1800 F. Provides good electrical conductivity. Typical applications include spark plug threads installed in aluminum, exhaust manifold bolts, engine bolts, oxygen sensors, knock sensors, thermostat housing bolts, fuel filter fittings and battery cable connections."

I actually removed the spark plugs from this car a week ago and put them back. They were quite difficult to initially loosen, which motivated me to put anti-seize on spark plugs for the first time in my life.

 

In other news, here’s what a blocked Prius catalytic converter looks like (from another car):

 

That's on the list of things to learn and do.

On previous cars (ie Ford Falcons), I used to flush the brake fluid every six months.

I paid way too much for a Wurth brake fluid tester a few years ago. Useful, but I should have bought a cheaper generic one.



I bought and used Speed Bleeders to replace the brake fluid nipples. They have a one-way valve inside them, which meant that I could flush the brake fluid on my own late at night.

Speed Bleeders: Australian Ford Forums



I'll be doing the same with the Toyotas... but I need to study it a bit and learn how to do it without stuffing up the ABS unit.

Australian Ford Forums

Speed Bleeders: Speed Bleeder Bleeding Brakes Bleeding Motorcycle Brakes Automotive Bleeder Screw Brake Bleeder