About those spark plugs...

It's not that hard to get out, it might feel tight but it'll come out.

 

The problem isn't unique to the Prius -- most modern cars can suffer from this. You have an aluminum head and steel spark plugs. Dissimilar metals tend to cause galvanic corrosion. It's compounded by the use of extended-life plugs. Not that there's anything wrong with extended-life plugs, just that they stay in service longer, so have more of an opportunity to corrode. With our iridium plugs, they stay installed for 100+K miles -- in some cases, owners let them go much longer than the recommended service interval.
If anti-seize was properly applied when the plugs were installed, there shouldn't be a problem.

Care should always be taken when removing a steel fastener (spark plug, bolt, stud, etc.) from aluminum -- actually this applies to all materials, but aluminum is particularly important since it's so soft. Once the spark plug breaks free and begins to back out, pay close attention to the resistance. If you feel the resistance increase, STOP. Corrosive material is binding up in the threads. Reverse the direction of the ratchet and tighten the plug until it bottoms out -- this helps clean the threads a little. Now loosen again until you feel the resistance increase, then stop. (you should notice it's gone 1/4 to 1/2 a revolution further than the first time. Continue this loosen-tighten dance until the plug is removed. If you find it reaches a point where it will no longer progress, try dousing the threads with penetrating fluid when it's at the max loosened position. Then as you tighten, the threads help deliver the penetrating fluid to the problem area where the binding is occurring. Patience and a light hand are the key to success.

Having said all that, when I changed the plugs on my Prius (at 100K miles), they came out as if they had been installed the day before. Once they were easily broken free, I could hand-loosen them with my socket & extension.

One more common mistake when changing plugs: overtightening. Don't over-torque them! The torque spec is 13 lb ft. If you don't have a torque wrench, don't sweat it... it's hand tight, then sugged up a bit with your elbows bent. Don't lean into it.

 

^ Wow, thanks for this.

Still, I'd use a decent torque wrench, but that's me. Any thoughts on anti-seize compounds?

 

Just make sure the engine is cold. The Prius G2 has been pretty forgiving have not read alot of posts about stripped plugs but your way past when you should have pulled them.

Normal procedure would be get a mirror and flashlight and look in the spark plug well and see how bad its corroded down there. Then with compressed air blow out the well hole.

If I'm concerned about pulling them I usually go cryogenic that really helps. I get a long paper towel cardboard roll or rolled up craft paper and wrap it over the spark plug and spray freeze spray down the tube and freeze the plug. Freeze it good. The plug shrinks in the hole and usually comes right out.

Other way is using an impact driver in reverse I impact the plug real soft for a while....bang..bang..bang. That constant soft impacting in reverse really helps.

The expensive part is at your miles taking the ignitor boot off. It will be stuck on there and once the boot is removed it will never make a good seal again because the rubber is now hard especially if it looks burnt on the ends. Clean the boot off with rubber conditioner (I like Black Magic Protectant) and pull on it and see if it has pin holes or the boot is to hard to now make a seal. Hold the boot edges up to the sun and look for pin holes. Many poster reporting misfires after plug replacement.

When I pull the plugs its getting 4 new ignitors too. Not going back in there again.

 

1. You might be able to find the last time your plugs were replaced through the Toyota owners portal. I bought two Prii used. One had an excellent maintenance history through Toyota. The previous owner brought it in every 5k miles like clockwork and did EVERYTHING the techs suggested. The other Prius was brought into Toyota only a handful of times over 140k. You never know. Toyota Owners Official Web Site

Just create an account and input the VIN of the vehicle. Any maintenance done at Toyota dealerships will show up.

2. From what I know, the greater danger upon removal is breaking the plug, not stripping it (unless you're talking about stripping the hex, not the threads). Stripping usually happens when you put the plug in. In either case, I suppose it's possible. tvpierce and edthefox have some great suggestions. It shouldn't take much force to get a spark plug out. If it does, make sure your engine is cold. If it's still hard, try either an impact wrench (take it easy with it, of course) or try to cool the plug even further (like with freeze spray as edthefox suggests). They're supposed to go in without much torque at all (generally around 15 ft-lbs, and I think it's 13 ft-lbs for our Prii, as previously stated). That's basically hand-tight plus a tiny bit of extra oomph. Not much at all. Unless they've been in there for ages and rusted/seized, it's not going to be that hard to get the plugs out.

3. Lastly, it CAN hurt to replace your spark plugs (not really as a direct result of the plugs, but really some other issues that can arise from the disturbance). Edthefox touched on a couple of issues that can come up as a result of spark plug replacement. It shouldn't scare you away from doing it, but before you jump in an go for the replacement, I would finish step 1 and see if you can get lucky and find out your plugs were replaced recently.

 

Never heard about stripped threads on Gen2 Prius, a least for the first replacement.
Gen2 blessing is plugs pretty easy to reach.
Mine were (at 135k) grungy and came out hard but slowly with Sears ratchet and a spark plug socket.

Don't forget to use the correct type for Prius iridium tipped etc.

 

Late in the day, but taking the plugs out halfway through their life, clean them with carb cleaner and an old toothbrush (avoid abrasives), and re-installing with a very thin application of anti-seize, works for me.

 

On the Toyota owners site I also use it to keep track of my own maintenance. It helps. So there's nothing but dealer recall visits and my maintenance on the site.
Only drawback is alot of times after I have imputed some data the next day I get a robo call from my dealer about maintenance due on my car.

 

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