On newer (GM) vehicles, you are suppose to use new head bolts every time you remove the cylinder heads. I understand they are suppose to stretch, but why can't you reuse them? If they stretch past their elastic limit (or whatever it is called) wouldn't they be no good even when new?
What happens if you reuse cylinder head bolts?
- Thread starter Loobed
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If they are TTY (Torque To Yield) bolts, then I believe they eventually stretch to a maximum point upon cooling/heating of the engine (with cycles.) As to reusing.. No real way to know if they hold up their strength, I suppose.
The only issue I ran into with cylinder head bolts was on an old car that I did not put each specific bolt back in each specific hole. Engine never worked right after that and the car got junked. Fortunately, it was junk to begin with.
The only issue I ran into with cylinder head bolts was on an old car that I did not put each specific bolt back in each specific hole. Engine never worked right after that and the car got junked. Fortunately, it was junk to begin with.
Why wouldn't be they good when new? You have a bolt that's perfectly good, stretch it beyond it's limit, and THEN it's no good anymore. Torque to yield bolts are designed to permanently stretch when installed and do not return to the state they were in before.
Only use torque to yield once - Other wise they will be torque to fail.
^ This. Best description ever!
Agreed, his best reply ever.
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They say you can re use them once, but at the chance of being under the hood again because you cut corners it will be better to get new ones and sleep better.
Nothing like doing it all over again because you wanted to save a little time and 30 bucks on new bolts, lol.
Nothing like doing it all over again because you wanted to save a little time and 30 bucks on new bolts, lol.
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"What happens if you reuse cylinder head bolts? "
Possible blown head gaskets and warped heads, that's all.
Possible blown head gaskets and warped heads, that's all.
Kestas
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No, it was not the best reply ever. TTY bolts may be reused if the bolts are under the manufacturer specified max reuse length. If no such specification exists, then new bolts must be used.
Nine years ago I reused the TTY bolts in my 95 Mercedes E320 with no ill effects to this day. They were well within reuse limits.
Nine years ago I reused the TTY bolts in my 95 Mercedes E320 with no ill effects to this day. They were well within reuse limits.
I've re-used them for many years without trouble of any sort. Even on highly boosted turbo cars and, yes, some diesels.
I've never had one "not achieve" rated torque properly and normally.
However, I did have one "new" rod bolt fail to stretch to the proper length within the proper torque specs. No matter how much I tried, it would not stretch. I purchased another.
Aircraft engines use stretch studs to hold the cylinders down. They are regularly re-used.
I've never had one "not achieve" rated torque properly and normally.
However, I did have one "new" rod bolt fail to stretch to the proper length within the proper torque specs. No matter how much I tried, it would not stretch. I purchased another.
Aircraft engines use stretch studs to hold the cylinders down. They are regularly re-used.
Originally Posted By: Kestas
No, it was not the best reply ever. TTY bolts may be reused if the bolts are under the manufacturer specified max reuse length. If no such specification exists, then new bolts must be used.
Nine years ago I reused the TTY bolts in my 95 Mercedes E320 with no ill effects to this day. They were well within reuse limits.
^^^What he said.
Do a search, as this, and the science behind re-using them has been discussed to death...and quite well...before.
No, it was not the best reply ever. TTY bolts may be reused if the bolts are under the manufacturer specified max reuse length. If no such specification exists, then new bolts must be used.
Nine years ago I reused the TTY bolts in my 95 Mercedes E320 with no ill effects to this day. They were well within reuse limits.
^^^What he said.
Do a search, as this, and the science behind re-using them has been discussed to death...and quite well...before.
If they are true TTY bolts they shouldn't be used again...thing is to find if they are really TTY or not. Just because they have a degree torque setting doesn't mean they are TTY. Some bolts on Mercedes are one use only, but they give a stretch limit for head bolts.
i wouldn't do it. bolts are cheap enough to buy new and feel better about it. my guess is it depends on the vehicle.
I have reused them with 'down and dirty' head jobs.
But there are too many variables to call this a correct procedure.
All sorts of things can stack up wrong.
TTY bolts are elastic, and are springs. They have limits.
I have had success with reusing them, but can not recommend it.
But there are too many variables to call this a correct procedure.
All sorts of things can stack up wrong.
TTY bolts are elastic, and are springs. They have limits.
I have had success with reusing them, but can not recommend it.
They are actually operating in their plastic range, and when relaxed, follow an elastic line parallael to their original elastic line, but with the offset due to the permanenet elongation (that must exist, as they have yielded).
Depending on the material, the process can be repeated a number of times safely...some none, some a few.
Depending on the material, the process can be repeated a number of times safely...some none, some a few.
Stretch bolts are designed to be elastic, the closer they get to the limit of elastic stretch, gradually more permanent stretch occurs (I don't know the exact relationship); each time they permanently stretch they reduce the maximum clamping force possible (before failure) as the structure weakens each time permanent stretching occurs.
Also there can be issues with damaging threads on aluminium blocks.
Also there can be issues with damaging threads on aluminium blocks.
Don't know about GM but I'm reusing the ones on the Focus. Granted they were new and only used for a couple hours runtime before it sucked in another piece of valve seat. Used some copper gasket coating on the headgasket. We'll see what happens... I didn't reuse the factory bolts the replacements was cheap.
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