Hello.I will be replacing a head gasket on a 12HT.The truck has 230000 KM.The manual states 83 FTLBS .Do the bolts need to be replaced or can they be reused?
Thanx
Thanx
12HT Head bolts (1 Viewer)
- Thread starter Bigfootheli
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It's always good practice to replace head bolts, that being said i haven't always done so and rebuilt a Case 188D with the same bolts no problems yet as of 5 years.
Head bolts are still available from Toyota. 90910-02070
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Old post being brought back to life... it came up when I was looking for something else.
The 12HT and 2H head bolts are not TTY head bolts, and as such, if they are in good condition - free of any rust or pitting - can be cleaned and re-used.
Note it is very important on these engines to measure the bolt hole depths of each bolt hole to ensure there is enough room for the bolts in the event that the head or block has had material removed.
To do this, find your longest bolt out of the set.
Clean out all the bolt holes carefully.
Hand tighten the longest bolt , very lightly oiled, into all of the holes and then carefully measure from the block surface to the underside of the bolt. Record the stick-out length on a piece of paper or write it on the block with a sharpie or paint marker.
Next, measure the thickness of your old, compressed, head gasket.
Then, measure the depth of the bolt holes in the cylinder head from the top to the face of the head where it meets the block.
You should now have 26 depth measurements, and a "stack height" for the compressed gasket and head.
Compare the stack heights to the bolt hole depths and see if any of them are either not deep enough, or are very close to your stack height.
You do need a few mm extra of hole depth to allow for the tiny amount of bolt stretch during the torque sequence.
If any of your bolts are too long or close to being too long for the bolt depth, then carefully trim the bolts and clean up the start thread at the end of the bolt. A proper re-thread / thread chaser is a good tool to use for this job.
When installing your bolts, make sure you follow the proper torque sequence, the proper torque, and use an appropriate lubricant. ARP Ultra Torque is the current favorite for this job.
Once, and only once, you can re-torque your head bolts after a complete warm up and cool down cycle of the engine. Repeating a re-torque on a composite gasket will continue to crush it and lead to failure.
If you are running a high boost engine, my own practice has been to add 10 ft lbs of torque to the re-torque of each head bolt after the back-off and then bring back to my new setting. Note that I am running the MLS gaskets that I had designed for this application back in 2014, and not a composite gasket.
Hope this help prevent a few gasket failures in the future.
~John
The 12HT and 2H head bolts are not TTY head bolts, and as such, if they are in good condition - free of any rust or pitting - can be cleaned and re-used.
Note it is very important on these engines to measure the bolt hole depths of each bolt hole to ensure there is enough room for the bolts in the event that the head or block has had material removed.
To do this, find your longest bolt out of the set.
Clean out all the bolt holes carefully.
Hand tighten the longest bolt , very lightly oiled, into all of the holes and then carefully measure from the block surface to the underside of the bolt. Record the stick-out length on a piece of paper or write it on the block with a sharpie or paint marker.
Next, measure the thickness of your old, compressed, head gasket.
Then, measure the depth of the bolt holes in the cylinder head from the top to the face of the head where it meets the block.
You should now have 26 depth measurements, and a "stack height" for the compressed gasket and head.
Compare the stack heights to the bolt hole depths and see if any of them are either not deep enough, or are very close to your stack height.
You do need a few mm extra of hole depth to allow for the tiny amount of bolt stretch during the torque sequence.
If any of your bolts are too long or close to being too long for the bolt depth, then carefully trim the bolts and clean up the start thread at the end of the bolt. A proper re-thread / thread chaser is a good tool to use for this job.
When installing your bolts, make sure you follow the proper torque sequence, the proper torque, and use an appropriate lubricant. ARP Ultra Torque is the current favorite for this job.
Once, and only once, you can re-torque your head bolts after a complete warm up and cool down cycle of the engine. Repeating a re-torque on a composite gasket will continue to crush it and lead to failure.
If you are running a high boost engine, my own practice has been to add 10 ft lbs of torque to the re-torque of each head bolt after the back-off and then bring back to my new setting. Note that I am running the MLS gaskets that I had designed for this application back in 2014, and not a composite gasket.
Hope this help prevent a few gasket failures in the future.
~John
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