Non reusable bolts
Discussion
So, just been changing the timing belt on the car, what lovely weather to do it in!
To do the job, you need to remove the engine mountings on one side. Haynes says that you need new bolts when you refit (only read that part today, when the car was in bits
). The dealer isnt open to wednesday (fair enough) and would guess it wont be untill friday when they get the bits in. My (sensible) head says to wait, but I thought I would put it to the PH masses to see if it neccisary.
Oh, they are done up by getting to a specified tourque and then turning by 45deg. if that makes any difference. Would guess they are stretch bolts?
To do the job, you need to remove the engine mountings on one side. Haynes says that you need new bolts when you refit (only read that part today, when the car was in bits
). The dealer isnt open to wednesday (fair enough) and would guess it wont be untill friday when they get the bits in. My (sensible) head says to wait, but I thought I would put it to the PH masses to see if it neccisary.Oh, they are done up by getting to a specified tourque and then turning by 45deg. if that makes any difference. Would guess they are stretch bolts?
TheLurker said:
So, just been changing the timing belt on the car, what lovely weather to do it in!
To do the job, you need to remove the engine mountings on one side. Haynes says that you need new bolts when you refit (only read that part today, when the car was in bits ). The dealer isnt open to wednesday (fair enough) and would guess it wont be untill friday when they get the bits in. My (sensible) head says to wait, but I thought I would put it to the PH masses to see if it neccisary.
Oh, they are done up by getting to a specified tourque and then turning by 45deg. if that makes any difference. Would guess they are stretch bolts?
Never heard of Stretch Bolts being used for engine mountings, but it is a while since I have been at the sharp end....To do the job, you need to remove the engine mountings on one side. Haynes says that you need new bolts when you refit (only read that part today, when the car was in bits
). The dealer isnt open to wednesday (fair enough) and would guess it wont be untill friday when they get the bits in. My (sensible) head says to wait, but I thought I would put it to the PH masses to see if it neccisary.Oh, they are done up by getting to a specified tourque and then turning by 45deg. if that makes any difference. Would guess they are stretch bolts?
If this is correct though, please wait on the new bolts arriving, it will possibly end badly if you use the old ones.
750turbo said:
TheLurker said:
So, just been changing the timing belt on the car, what lovely weather to do it in!
To do the job, you need to remove the engine mountings on one side. Haynes says that you need new bolts when you refit (only read that part today, when the car was in bits ). The dealer isnt open to wednesday (fair enough) and would guess it wont be untill friday when they get the bits in. My (sensible) head says to wait, but I thought I would put it to the PH masses to see if it neccisary.
Oh, they are done up by getting to a specified tourque and then turning by 45deg. if that makes any difference. Would guess they are stretch bolts?
Never heard of Stretch Bolts being used for engine mountings, but it is a while since I have been at the sharp end....To do the job, you need to remove the engine mountings on one side. Haynes says that you need new bolts when you refit (only read that part today, when the car was in bits
). The dealer isnt open to wednesday (fair enough) and would guess it wont be untill friday when they get the bits in. My (sensible) head says to wait, but I thought I would put it to the PH masses to see if it neccisary.Oh, they are done up by getting to a specified tourque and then turning by 45deg. if that makes any difference. Would guess they are stretch bolts?
If this is correct though, please wait on the new bolts arriving, it will possibly end badly if you use the old ones.
ETA, actualy, I think I remember somthing about them being designed to shear off in an accident so have a built in weakness?
All bolts will stretch when a significant torque is applied. The additional 45degrees of turn will add significantly to the applied torque and take the bolts well beyond the point at which they will elastically return to length.
Replace them. As a general rule, replace any bolts that you use a torque wrench on.
Replace them. As a general rule, replace any bolts that you use a torque wrench on.
Dr Doofenshmirtz said:
Well, if it was me I'd use the old bolts. I'm sure the car will be fine to drive - if it bothers you just order some new bolts and pop them in at your convenience.
Thats what I'm going to do. I only asked as I thought some of the bolts that need replacing are inaccesable once reassembled, but that is not the case. Apparently Seat (the manufacturer) dealers dont change them when they do the job.Edited by Dr Doofenshmirtz on Monday 27th December 22:45
They are torqued to 30Nm then by 45deg. so not a massive torque.
Thanks for your help guys.
If they are for the engine mount, you should be OK to re-use them but changing them out once you get new ones probably isn't a bad idea.
If they were cylinder head bolts then re-using them would be a bad idea.
Any fastener that is specified to be turned X degrees after being torqued is usually not a reusable one.
If they were cylinder head bolts then re-using them would be a bad idea.
Any fastener that is specified to be turned X degrees after being torqued is usually not a reusable one.
Haynes manuals do have a habit of telling you to buy new bolts/fasteners for virtually everything.
I'm sure they will be OK, as others have said 30nm is hardly very tight!
I'm not sure about the veracity of renewing all bolts you use a torque wrench on - as a matter of fact, it sounds incorrect to me. Manufacturers specify a torque setting for pretty much every fastener on a car - they certainly don't all need renewing every time they are removed.
Not all head bolts are stretch bolts, and even then some are re-usable (as long as they are still within spec)
I'm sure they will be OK, as others have said 30nm is hardly very tight!
I'm not sure about the veracity of renewing all bolts you use a torque wrench on - as a matter of fact, it sounds incorrect to me. Manufacturers specify a torque setting for pretty much every fastener on a car - they certainly don't all need renewing every time they are removed.
Not all head bolts are stretch bolts, and even then some are re-usable (as long as they are still within spec)
It's hogwash. There are plenty of reasons why the tightness of a bolt would be specified that have nothing to do with the bolt itself - you might want to:
- crush something (e.g. a crushable washer)
- not crush something (e.g. an aluminium timing cover)
- avoid stripping the threads out of a soft component (one made of aluminium or plastic)
- tension something (e.g. a belt)
- slightly deform something (e.g. an exhaust olive)
- adjust something (e.g. a wheel bearing)
Starfighter said:
All bolts will stretch when a significant torque is applied. The additional 45degrees of turn will add significantly to the applied torque and take the bolts well beyond the point at which they will elastically return to length.
Replace them. As a general rule, replace any bolts that you use a torque wrench on.
Whilst i agree with the first part of your postReplace them. As a general rule, replace any bolts that you use a torque wrench on.
the second part well sorry but b
ks if that were the case you wouldneed to replace half the fasteners in your engine bay!
not to mention wheel studs
ONLY certain apps use "stretch bolts" like (some) cylinder head bolts.
and some types of brake callipers. which should be replaced after
a stated number of removal/re-torque cycles
e.g. landrover 2&300 TDi cylinder head bolts can be reused IIRC 3 times
then they MUST be replaced.
to the OP: if the book says replace them then do so as another poster said
in this specific model the bolt may be designed to sheer in an impact
and is thus a safety device you probably "could" use a normal bolt
but i would not advise it.
If it's set to a preload and then angle tightened it is probably a stretch-to-yeild type bolt in an automotive type application.
Which means the bolt will have deformed, so you run the risk of:
a) Not having as much clamping force when you retorque them, and:
b) A good chance of snapping the weakened fastener if you're not careful, hence the limited re-uses specified in the above posters example.
Which means the bolt will have deformed, so you run the risk of:
a) Not having as much clamping force when you retorque them, and:
b) A good chance of snapping the weakened fastener if you're not careful, hence the limited re-uses specified in the above posters example.
Edited by PhillipM on Tuesday 28th December 02:10
There are two reasons why bolts cannot be reused:
1. As stated by previous posters; bolts that are torqued and then have a further angle applied are often stretched to near the yeild point, and therefore should not be re used.
2. If there is a patch on the bolt it is possible that it may only be used once. (The patch is there to stop it loosening, act as a seal or is a friction modifyer which will affect the final torque of the tightened bolt if re used.)
Be careful, bolts are often overlooked, remember that they hold everything togather and are safety critical.
1. As stated by previous posters; bolts that are torqued and then have a further angle applied are often stretched to near the yeild point, and therefore should not be re used.
2. If there is a patch on the bolt it is possible that it may only be used once. (The patch is there to stop it loosening, act as a seal or is a friction modifyer which will affect the final torque of the tightened bolt if re used.)
Be careful, bolts are often overlooked, remember that they hold everything togather and are safety critical.
DAVEVO9 said:
Starfighter said:
Replace them. As a general rule, replace any bolts that you use a torque wrench on.
You wouldn't replace wheel studs/bolts every time you change wheels? My first post used the word "significant" for this reason. Had I antisipated selective quoting I would have included this in the second line also.
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