Torque setting - Gearbox oil drain/fill plug
Discussion
Background: I DIY most of the car jobs, but anything big goes to the garage. I've gone my entire life so far without a torque wrench or even thinking much about torque - other than 'seems tight enough'. However I've now discovered the Internet with lots of conflicting approaches...
I want to just change the oil on what I think is an MMT6 gearbox (2014 mk4.5 mondeo 1.6 diesel). Simple job!
How worried should I be about the torque of the drain/fill plugs on re-fit?
1) just tighten to a sensible level, wait a bit, then check and nip up? Wait a bit longer and recheck. (this would be my default approach - and how I've done multiple gearboxes and hundreds of engine oil changes - although latter usually have some type of washer which the transmission doesn't have)
2) apply thread sealant? or loctite? (concerned that this affects torque required and could either become loose in future or worse, be a pain if needed changing in future)
3) torque to spec - but what spec? (I've seen 27Nm or 35Nm).
I'd rather not spend £100 on a torque wrench that I might not use again - but I'd also rather not lose all the oil if it vibrates.
It's not something that I've ever been concerned with on previous plugs/cars, so unsure why I'm approaching paranoia with this!
Thoughts on options 1/2/3/other welcomed please.
Otherwise default is option 1 - perhaps with a vertical paint pen line for occasional piece of mind.
I want to just change the oil on what I think is an MMT6 gearbox (2014 mk4.5 mondeo 1.6 diesel). Simple job!
How worried should I be about the torque of the drain/fill plugs on re-fit?
1) just tighten to a sensible level, wait a bit, then check and nip up? Wait a bit longer and recheck. (this would be my default approach - and how I've done multiple gearboxes and hundreds of engine oil changes - although latter usually have some type of washer which the transmission doesn't have)
2) apply thread sealant? or loctite? (concerned that this affects torque required and could either become loose in future or worse, be a pain if needed changing in future)
3) torque to spec - but what spec? (I've seen 27Nm or 35Nm).
I'd rather not spend £100 on a torque wrench that I might not use again - but I'd also rather not lose all the oil if it vibrates.
It's not something that I've ever been concerned with on previous plugs/cars, so unsure why I'm approaching paranoia with this!
Thoughts on options 1/2/3/other welcomed please.
Otherwise default is option 1 - perhaps with a vertical paint pen line for occasional piece of mind.
Edited by C-J on Sunday 23 June 11:18
Edited by C-J on Saturday 29th June 19:46
It's only an 8mm allen key.
Your biggest risk is tightening too much ( and stripping the hex part ), or doing something silly like putting thread lock on it, and never being able to remove it again.
If you were to use an actual allen key, or regular spanner with allen key hex, it's unlikely you'd ever tighten it too much, and also unlikely it would be too little.
It's only an allen key, just tighten it a sensible amount. If either of the above are hurting your hand doing it, it's probably too much.
Your biggest risk is tightening too much ( and stripping the hex part ), or doing something silly like putting thread lock on it, and never being able to remove it again.
If you were to use an actual allen key, or regular spanner with allen key hex, it's unlikely you'd ever tighten it too much, and also unlikely it would be too little.
It's only an allen key, just tighten it a sensible amount. If either of the above are hurting your hand doing it, it's probably too much.
That plug is not carrying any load and only needs to be tight enough to seal. If it needs to be more than snugged up to prevent it leaking, there's probably something wrong with the seal.
This would be a good time to step back and start thinking about which fasteners you would expect to be sensitive to being torqued correctly. Fasteners carrying mechanical loads or clamping a gasket typically need to be torqued correctly, and the range of acceptable values is sometimes quite narrow. Smaller fasteners into soft metal typically don't need much torque but are sensitive to being over torqued.
This would be a good time to step back and start thinking about which fasteners you would expect to be sensitive to being torqued correctly. Fasteners carrying mechanical loads or clamping a gasket typically need to be torqued correctly, and the range of acceptable values is sometimes quite narrow. Smaller fasteners into soft metal typically don't need much torque but are sensitive to being over torqued.
stevieturbo said:
It's only an 8mm allen key.
Your biggest risk is tightening too much ( and stripping the hex part ), or doing something silly like putting thread lock on it, and never being able to remove it again.
If you were to use an actual allen key, or regular spanner with allen key hex, it's unlikely you'd ever tighten it too much, and also unlikely it would be too little.
It's only an allen key, just tighten it a sensible amount. If either of the above are hurting your hand doing it, it's probably too much.
Cheers - and good suggestion to use a standard Allen key when refitting. Your biggest risk is tightening too much ( and stripping the hex part ), or doing something silly like putting thread lock on it, and never being able to remove it again.
If you were to use an actual allen key, or regular spanner with allen key hex, it's unlikely you'd ever tighten it too much, and also unlikely it would be too little.
It's only an allen key, just tighten it a sensible amount. If either of the above are hurting your hand doing it, it's probably too much.
And yes, agree overtightening is the one to avoid.
That's not an error that I've made yet!
Irrespective of the refitting of the plugs (I agree with using an allen key by hand), REMOVE THE FILL PLUG BEFORE THE DRAIN PLUG.
If you get the drain plug out and then discover that the fill plug is totally seized or rounded, your day just got a lot worse than if you find that out first and can decide whether to keep going.
If you get the drain plug out and then discover that the fill plug is totally seized or rounded, your day just got a lot worse than if you find that out first and can decide whether to keep going.
GreenV8S said:
That plug is not carrying any load and only needs to be tight enough to seal. If it needs to be more than snugged up to prevent it leaking, there's probably something wrong with the seal.
This would be a good time to step back and start thinking about which fasteners you would expect to be sensitive to being torqued correctly. Fasteners carrying mechanical loads or clamping a gasket typically need to be torqued correctly, and the range of acceptable values is sometimes quite narrow. Smaller fasteners into soft metal typically don't need much torque but are sensitive to being over torqued.
No, nothing ever leaked from there.This would be a good time to step back and start thinking about which fasteners you would expect to be sensitive to being torqued correctly. Fasteners carrying mechanical loads or clamping a gasket typically need to be torqued correctly, and the range of acceptable values is sometimes quite narrow. Smaller fasteners into soft metal typically don't need much torque but are sensitive to being over torqued.
And yes, agree speciifc torque is critical for load bearing etc.
The root of my query was all the different approaches that I'd seen on the Internet such as loctite (where loads was applied more like welding!)
Oh, and that when trying to clarify the correct oil it was a Ford mechanic that (unprompted) advised of the torque required (26Nm so different to the Kuga video). No idea if correct, but in hindsight perhaps he was inferring to NOT overtighten.
As mentioned, until now with all plugs etc I'd just use feel and common sense. It is the Internet examples that made me question that approach!
InitialDave said:
Irrespective of the refitting of the plugs (I agree with using an allen key by hand), REMOVE THE FILL PLUG BEFORE THE DRAIN PLUG.
If you get the drain plug out and then discover that the fill plug is totally seized or rounded, your day just got a lot worse than if you find that out first and can decide whether to keep going.
Thanks - yes absolutely! Something that I've always done on my cars due to having seen a mate not in the past.If you get the drain plug out and then discover that the fill plug is totally seized or rounded, your day just got a lot worse than if you find that out first and can decide whether to keep going.
I did a test earlier today and the fill one was actually the easiest that I recall.
The drain plug was significantly harder but with a bit of patience it freed off fine.
I've popped a thin vertical paintline on - assuming no leaks in use this week I'll do the actual draining at the weekend.
Edited by C-J on Sunday 23 June 15:13
The old good'un tight.
In a serious note I wouldn't use a torque wrench for stuff like that. Just be sensible with regards to the size of bolt and what you're screwing it into. A dab of blue threadlock if you're worried about it rattling loose.
I think a good mechanic or DIYer could get with 10% of torque specs just by feel.
In a serious note I wouldn't use a torque wrench for stuff like that. Just be sensible with regards to the size of bolt and what you're screwing it into. A dab of blue threadlock if you're worried about it rattling loose.
I think a good mechanic or DIYer could get with 10% of torque specs just by feel.
People used to refer to 'finger tight', 'hand tight', and I'd expand that to 'arm-' and 'shoulder-tight'
None are precise, but you can imagine using a spanner in your fingers, in your hand using the appropriate set of muscles, then the forearm and finally the whole arm and possibly body weight to tighten the nut/bolt. I would say that these approximate to less than 10lbs-ft, 12-15, 20-30 and more than 30lbs-ft.
It's also dependent on your position - applying body weight from under the car as you tighten a drain plug is difficult! But arm tight is possible, and quite sufficient for this application, IMHO!
John
None are precise, but you can imagine using a spanner in your fingers, in your hand using the appropriate set of muscles, then the forearm and finally the whole arm and possibly body weight to tighten the nut/bolt. I would say that these approximate to less than 10lbs-ft, 12-15, 20-30 and more than 30lbs-ft.
It's also dependent on your position - applying body weight from under the car as you tighten a drain plug is difficult! But arm tight is possible, and quite sufficient for this application, IMHO!
John
ChocolateFrog said:
The old good'un tight.
In a serious note I wouldn't use a torque wrench for stuff like that. Just be sensible with regards to the size of bolt and what you're screwing it into. A dab of blue threadlock if you're worried about it rattling loose.
I think a good mechanic or DIYer could get with 10% of torque specs just by feel.
please dont locktight a drain plug ever, its most likely a steel plug in ali thread, never a good idea.In a serious note I wouldn't use a torque wrench for stuff like that. Just be sensible with regards to the size of bolt and what you're screwing it into. A dab of blue threadlock if you're worried about it rattling loose.
I think a good mechanic or DIYer could get with 10% of torque specs just by feel.
i agree with yhe point on getting close to the torque, altho there is no stain on the plug, it wont come out.
C-J said:
3) torque to spec - but what spec? (I've seen 27Nm or 35Nm).
Is there a workshop manual? That usually lists it.Failing that something like autodata will list the tightening torques for common service points.
C-J said:
I'd rather not spend £100 on a torque wrench that I might not use again - but I'd also rather not lose all the oil if it vibrates.
A cheap torque wrench is like £20.You'll likely find the correct torque is less than you expect, but close to what you've been doing anyway.
Jakg said:
C-J said:
3) torque to spec - but what spec? (I've seen 27Nm or 35Nm).
Is there a workshop manual? That usually lists it.Failing that something like autodata will list the tightening torques for common service points.
C-J said:
I'd rather not spend £100 on a torque wrench that I might not use again - but I'd also rather not lose all the oil if it vibrates.
A cheap torque wrench is like £20.You'll likely find the correct torque is less than you expect, but close to what you've been doing anyway.
CJ if your asking how much to do up a drain plug of filler plug trust me you do need a torque wrench 
it wont go to waste long term anyway just look after it Lovely weather today so after a run and oil nicely warmed I removed undertray and NSF wheel, levelled the car, drained fully and refilled. All good!
Nipped up using an allen key, however as access/control was not great i redid with a short handled socket set for piece of mind. Little to no extra torque required. So using an allen key was a good tip. Cheers.
Vertical paint mark on both plugs. Popped a torch light in the car to check still aligned over the next few journeys.
The other really obvious thing that I didn't consider was that I had to undo the drain plug pretty much all the way before any oil came out! Whilst it might be a bit different when the transmission is spinning, presumably like an oil sump plug there is a good amount of redundancy built in - the plug needs to be pretty loose before losing oil.
Nipped up using an allen key, however as access/control was not great i redid with a short handled socket set for piece of mind. Little to no extra torque required. So using an allen key was a good tip. Cheers.
Vertical paint mark on both plugs. Popped a torch light in the car to check still aligned over the next few journeys.
The other really obvious thing that I didn't consider was that I had to undo the drain plug pretty much all the way before any oil came out! Whilst it might be a bit different when the transmission is spinning, presumably like an oil sump plug there is a good amount of redundancy built in - the plug needs to be pretty loose before losing oil.
Edited by C-J on Saturday 29th June 19:50
Edited by C-J on Saturday 29th June 19:52
Thanks for inputs folks.
Having done hundreds of engine oil and tens of transmission oil changes (part of my first job was working with transmissions) I still have absolutely no idea why I was paranoid about torque etiquette on this one - to much Internet surfing planting random thoughts in my head!
Re torque wrenches (especially cheap ones?) my fear is that they go out of spec and I wouldn't know. Is drift even a thing?
Or if used occasionally, kept boxed in between and not dropped do they usually hold spec?
Any decent makes at the low end of the market?
For the simple to.middling DIY Jobs that I do I'd usually (except for these particular drain plugs!) trust my own sense and manual tools. Of course that might change if I invest £20 in a new torque wrench toy!
Having done hundreds of engine oil and tens of transmission oil changes (part of my first job was working with transmissions) I still have absolutely no idea why I was paranoid about torque etiquette on this one - to much Internet surfing planting random thoughts in my head!
Re torque wrenches (especially cheap ones?) my fear is that they go out of spec and I wouldn't know. Is drift even a thing?
Or if used occasionally, kept boxed in between and not dropped do they usually hold spec?
Any decent makes at the low end of the market?
For the simple to.middling DIY Jobs that I do I'd usually (except for these particular drain plugs!) trust my own sense and manual tools. Of course that might change if I invest £20 in a new torque wrench toy!
C-J said:
Thanks for inputs folks.
Having done hundreds of engine oil and tens of transmission oil changes (part of my first job was working with transmissions) I still have absolutely no idea why I was paranoid about torque etiquette on this one - to much Internet surfing planting random thoughts in my head!
Re torque wrenches (especially cheap ones?) my fear is that they go out of spec and I wouldn't know. Is drift even a thing?
Or if used occasionally, kept boxed in between and not dropped do they usually hold spec?
Any decent makes at the low end of the market?
For the simple to.middling DIY Jobs that I do I'd usually (except for these particular drain plugs!) trust my own sense and manual tools. Of course that might change if I invest £20 in a new torque wrench toy!
buy a really good torque wrench and use it for the critical things that require a set torque, like big ends/heads etc, otherwise use normal tools and feel, a bad toque wrench can cause all manner of pain.Having done hundreds of engine oil and tens of transmission oil changes (part of my first job was working with transmissions) I still have absolutely no idea why I was paranoid about torque etiquette on this one - to much Internet surfing planting random thoughts in my head!
Re torque wrenches (especially cheap ones?) my fear is that they go out of spec and I wouldn't know. Is drift even a thing?
Or if used occasionally, kept boxed in between and not dropped do they usually hold spec?
Any decent makes at the low end of the market?
For the simple to.middling DIY Jobs that I do I'd usually (except for these particular drain plugs!) trust my own sense and manual tools. Of course that might change if I invest £20 in a new torque wrench toy!
just do things up till it feels tight, you sound like you have some experience with spanners, so should have a good feel for whats right.
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