About to tackle Head Gasket on my 2012 CT200h tomorrow

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Apr 2, 2020
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San Diego
Hello all,

Great threads out there. Couple questions.

1. What does this mean? "they were torque to yield bolts. 36 ft lbs + 90 deg + 45 deg is the torque spec." Torque to 36 ft lbs, then 90 degrees, then 45 degrees?

2. What is rotation direction when putting the crank at TDC? Counter or clockwise?

Thanks,
Leo
 
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Good luck! How many miles on it?

I dread this issue, and don't have suitable facilities to attack it myself (although I did successfully perform a head transplant on the much simpler engine of my Mazda).
 
Torque to yield is just as it sounds. The bolt is torqued to say 100 ft-lbs, then turned another 90 degrees, 45 degrees, or whatever is listed in the instructions. In your case it looks like it is torqued to 36 ft-lbs, then 90 degrees, then an additional 45 degrees. This is usually the case with stretch bolts, so I'd recommend replacing the head bolts. You will need one of these gauges to help with the degrees:

https://www.amazon.com/Performance-Tool-M205-Torque-Angle/dp/B004O7WCW4/ref=sr_1_2?dchild=1&keywords=degree+gauge+3%2F8&qid=1585877361&sr=8-2
 
all bolts tighten clockwise unless noted otherwise.
The TTY bolts are designed to be tightened to the point of 'elasticity' to cope with the head casting growth at operating temperature & subsequent contraction upon cooling.
 
I apologize in advance for this comment, but if you have to ask these questions you should not be performing this job yourself, for your sake and for the vehicle reliability. Do you even have any mechanical knowledge or ability?
 
Originally Posted by vw7674
all bolts tighten clockwise unless noted otherwise.
The TTY bolts are designed to be tightened to the point of 'elasticity' to cope with the head casting growth at operating temperature & subsequent contraction upon cooling.


I think he is asking which way the engine rotates so he can rotate it the same way to bring the cylinders up to TDC. I would think counter clockwise, but you would want to check any service manuals to be sure what the correct way they want you to rotate it being a hybrid. Be very careful working on this vehicle due to the hybrid system.
 
You're going to "tighten" the head bolts on three different and subsequent passes. You'll do all of them to 36 lb-ft (using the proper torquing sequence - usually inside to outside). Then you'll toss aside your torque wrench and rotate them all 90 degrees (again, proper sequence). Then again another 45 degrees (again, proper sequence).

Good luck and good on you for jumping in feet first. Even the most experienced person had a first time. Do your research, follow the FSM, take your time, and you'll be fine. It's not rocket surgery.
 
Torque to yield are one time use. BMW M 30 s used them. If you mark the flats, on the head bolts. and/or use a protractor.. Please dont try to re-use TTY, once they are stretched, they are too long. Kinda follows that would happen. Uhhmmn, the last head R+R was on a '99 CRV DOHC 4. No clue what your engine, the Honda rotated "wrong" would that be clock wise? I wouldn't attempt this without a manual or a PDF of a manual. An OHC timing chain and a belt has to turn 2 complete turns of the crankshaft and come back to the timing marks. Chains have to be wired in place around the crank gear or else you' have to pull the timing cover, which is a whole can of worms.
 
Originally Posted by jeepman3071
Torque to yield is just as it sounds. The bolt is torqued to say 100 ft-lbs, then turned another 90 degrees, 45 degrees, or whatever is listed in the instructions. In your case it looks like it is torqued to 36 ft-lbs, then 90 degrees, then an additional 45 degrees. This is usually the case with stretch bolts, so I'd recommend replacing the head bolts. You will need one of these gauges to help with the degrees:

https://www.amazon.com/Performance-Tool-M205-Torque-Angle/dp/B004O7WCW4/ref=sr_1_2?dchild=1&keywords=degree+gauge+3%2F8&qid=1585877361&sr=8-2


Yes, I have a digital torque wrench. Just needed to verify the statement. Never heard of this type of procedure. Thanks for the confirmation.
 
Originally Posted by vw7674
all bolts tighten clockwise unless noted otherwise.
The TTY bolts are designed to be tightened to the point of 'elasticity' to cope with the head casting growth at operating temperature & subsequent contraction upon cooling.


Thank you.
 
Originally Posted by mattd
I apologize in advance for this comment, but if you have to ask these questions you should not be performing this job yourself, for your sake and for the vehicle reliability. Do you even have any mechanical knowledge or ability?


No worries. I'm 53 and have worked on cars, motorcycles, atv's and boats since I was 16. I just didn't understand the torque to yield instructions. Anything I've worked on is torque to a specific lb and that's it, never heard of torque then turn 90, then 45, in it's pattern of course.
 
Originally Posted by jeepman3071
Originally Posted by vw7674
all bolts tighten clockwise unless noted otherwise.
The TTY bolts are designed to be tightened to the point of 'elasticity' to cope with the head casting growth at operating temperature & subsequent contraction upon cooling.


I think he is asking which way the engine rotates so he can rotate it the same way to bring the cylinders up to TDC. I would think counter clockwise, but you would want to check any service manuals to be sure what the correct way they want you to rotate it being a hybrid. Be very careful working on this vehicle due to the hybrid system.


Yup, exactly. I'll rotate the crank counter to get it to TDC.
 
Originally Posted by cpayne5
You're going to "tighten" the head bolts on three different and subsequent passes. You'll do all of them to 36 lb-ft (using the proper torquing sequence - usually inside to outside). Then you'll toss aside your torque wrench and rotate them all 90 degrees (again, proper sequence). Then again another 45 degrees (again, proper sequence).

Good luck and good on you for jumping in feet first. Even the most experienced person had a first time. Do your research, follow the FSM, take your time, and you'll be fine. It's not rocket surgery.


Roger that, thank you sir.
 
Originally Posted by andyd
Torque to yield are one time use. BMW M 30 s used them. If you mark the flats, on the head bolts. and/or use a protractor.. Please dont try to re-use TTY, once they are stretched, they are too long. Kinda follows that would happen. Uhhmmn, the last head R+R was on a '99 CRV DOHC 4. No clue what your engine, the Honda rotated "wrong" would that be clock wise? I wouldn't attempt this without a manual or a PDF of a manual. An OHC timing chain and a belt has to turn 2 complete turns of the crankshaft and come back to the timing marks. Chains have to be wired in place around the crank gear or else you' have to pull the timing cover, which is a whole can of worms.


Yes sir. Got brand new head bolts (10) and a head gasket kit. Timing cover has to already be removed before pulling the head. I know of those can of worms. Had to re-time my Polaris RZR 1000 last month and the chain fell off the crank gear, had to remove the stator cover and stator to put it back on the gear. Not fun.
 
Here is the head bolt sequence and timing marks if anyone finds this thread and needs to do the same.

[Linked Image]

[Linked Image]
 
Originally Posted by CR94
Good luck! How many miles on it?

I dread this issue, and don't have suitable facilities to attack it myself (although I did successfully perform a head transplant on the much simpler engine of my Mazda).


148k. Apparently a known issue on this model Prius/Lexus engine. Hybrid especially since it starts and stops multiple times. Done a few head gaskets in my days, just never on a newer hybrid. My first head gasket was on my 1st car when I was 16. 1976 Triumph TR7, it was always blowing head gaskets. A lot easier to work with a carbureted engine.
 
Originally Posted by MPDano
Went to Oreillys to get the proper head bolt tools. $14 total

[Linked Image]

[Linked Image]


Technically, those are not the correct sockets but they will usually work.

Crankshaft rotates CLOCKWISE on this engine, not CCW.

You will need another person to help you with reinstalling the timing cover, so I would plan on having someone around for that part of the process. Make sure the surfaces are surgically clean with zero debris remaining before applying RTV. The RTV needs to be applied in a bead (3mm thickness is what I target). Use FIPG Black.

Also, leave the exhaust manifold bolted to the head. Disconnect the manifold at the donut. It is much easier to do it this way than to unbolt the exhaust manifold in-car.
 
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