Torquing Drain Plugs w/Crush Washer

[Shannow]

The most "confident" outcome would be "get mating faces 0.60" apart, then give an extra 1/2 turn...or whatever their robots do at the factory...seating torque + rotation

Feel is subjective, as per OP, there's a number of points to pass through that "feel" different, and then the lubrication status of the threads affects the clamping tension give or take a significant percentage of torque applied.

Crush washers and torque aren't complimentary, but a drain plug, crush washer, and leakage aren't a structural decision, nor a flight risk.

I've seen perfectly sealed sumps with stripped threads and silastic..then had to retap them and find a fibre washer to suit.

 

[Trav]

Quote:
if Honda felt that tightening a drain plug was better accomplished by feel, then why do they specify a torque number?

It looks better than "tighten it till it feels tight" in the service manual.

 

[demarpaint]

Originally Posted By: Trav
Quote:
if Honda felt that tightening a drain plug was better accomplished by feel, then why do they specify a torque number?

It looks better than "tighten it till it feels tight" in the service manual.

Yes, sure does lol. Or better than "tighten it to tight, but no that tight".

 

[Tegger]

Originally Posted By: mechanicx
The washer crush is why you felt the torque or "tightness" drop momentarily.

If this is true, then there's something very wrong with the washer being used. In 30+ years of changing oil, I have never gotten a "momentary drop" in torque. In every case -- except when faced with stripped oil-pan threads -- torque has increased steadily until the wrench clicked.

 

[Tegger]

Originally Posted By: rationull
Originally Posted By: Tegger
None of you people seem to be familiar with Hondas and their notoriously fragile oil pans.

Do these "notoriously fragile" oil pans include just the older style steel ones, or the aluminum ones too? The aluminum pan + plug on my Civic didn't seem weak in any way compared to others I've seen. Not disagreeing, just looking for information.

Any fragility won't be evident until a couple or three years of overtorquing has occurred.

Steady overtorquing eventually expands the threads in the pan until they finally won't hold anymore. Remember that bolt threads only contact their receiving threads over about half their actual surface area, so it doesn't take much expansion for the threads to begin slipping.

The fragility definitely affects the steel pans, but I don't know about aluminum pans. Aluminum pans are formed by a different process than steel ones; theoretically, their drain-bolt threads shouldn't be affected with the same fragility as the steel pans'.

 

[zeezee]

I have never found that a torque wrench provides accurate results in an application where lubricants are involved. As a result, I almost never use one when I am changing oil or replacing a transmission pan, etc. If I do use one, I set it to a more conservative value.

Unless you can guarantee that you are getting 100% of the lubricant removed from the threads, there will be a certain margin of error. Is it any worse than undertightening it? I don't think so. I'd rather have it undertightened without leaks than strip the threads.

I am interested into whether or not Honda's spec is for a pre-fill/drain or post-drain bolt.

I've seen torque wrenches that were set to the appropriate spec, where the operator has caused damage to either the threads or indentation the surface of the part (e.g. a transmission pan).

 

[Tegger]

Originally Posted By: rationull
I don't think I was clear -- what I meant was that it's important to understand the conditions the torque spec applies to if you're concerned enough with precision to use a torque wrench in the first place. That seems legitimate to me, and the previous conversation at least brought the point up.

Correct. In certain high-precision cases (such as head bolts, main-bearing caps, and crankshaft bolts), the automaker may be very particular about the use of oil on certain areas of the fastener. This particularity has entirely to do with control over tightening torque. In most other applications, the threads are assumed to be dry and clean.

And once again: Oil-pan drain-bolt torque figures always assume WET threads. ALWAYS. Think about it: How on earth are you going to get the pan-threads clean of oil after draining the oil? It's impossible, and NOBODY does it. The ONLY time the drain bolt would ever have even a chance of being installed into dry threads would be when building a brand-new or freshly-overhauled engine, or installing a brand-new pan. And that would happen just once.

 

[zeezee]

Originally Posted By: demarpaint
I'm just wondering, if Honda felt that tightening a drain plug was better accomplished by feel, then why do they specify a torque number? Obviously they aren't confident enough in people having the right feel? I know strenght plays in, some people are bigger and stronger, or use longer tools which give more leverage. Others have no clue have much 29 pounds of torque is. I think in the end a torque wrench is a safer bet than feel. JMO


Car manufacturers specify a torque for every bolt on the car. It isn't just limited to the oil drain plug. What they do not (and frankly cannot) take into account is the amount of lubricant that is on the pan threads.

Regardless of what someone does, they should always check their vehicle for leaks, especially as it ages and seals begin to break down.

 

[Tegger]

Originally Posted By: zeezee
I have never found that a torque wrench provides accurate results in an application where lubricants are involved.

Then you'd better not rebuild an engine or remove a crank-pulley bolt. In certain high-precision cases, oil is often specified on specific parts of the fasteners.

Originally Posted By: zeezee
I am interested into whether or not Honda's spec is for a pre-fill/drain or post-drain bolt.

All automakers assume WET threads on drain bolt torque figures. See my other reply for why.

 

[KrisZ]

Here is how my drain plug looks like at almost 90k miles. I think it has the original washer, but it could've been changed by the dealer as they performed some of the early oil changes.

For the life of me I just can't understand why some people say that it HAS to be changed every sinlgle time the drain plug is pulled.

 

[surfstar]

My '93 MX6 has 339k miles - I bought it at ~80k - so I've done over 50 oil changes myself (5k mi) over the years and who knows about the first 80k miles.
Bought a big pack of crush washers from rockauto the first year and change them each time at less than $.10ea. Never torqued, just go with what feels right. No leaks. No stripped threads.

Its not that complicated to figure out. Do what works for you and if it ain't broke...

 

[mechanicx]

Originally Posted By: KrisZ
Here is how my drain plug looks like at almost 90k miles. I think it has the original washer, but it could've been changed by the dealer as they performed some of the early oil changes.

For the life of me I just can't understand why some people say that it HAS to be changed every sinlgle time the drain plug is pulled.

Because it doesn't really. It doesn't take much torque to ensure the drain plug will seal even with a reused washer or to ensure the the drain plug won't come loose. IMO if the washer really needed to be replaced every use, then a reusable rubber or fiber washer should've been specified. I've seen reusable washers last about the life of the engine. There's nothing wrong with using a torque wrench and a new washer, but after tightening many bolts with a torque wrench and tightening bolts in general you can develop a feel for when a non-critical bolt is tight enough but not over tightened. Unless you are threading into low grade and possibly hot aluminum if you are damaging threads then you're just a gorilla.

 

[demarpaint]

Originally Posted By: mechanicx
There's nothing wrong with using a torque wrench and a new washer, but after tightening many bolts with a torque wrench and tightening bolts in general you can develop a feel for when a non-critical bolt is tight enough but not over tightened. Unless you are threading into low grade and possibly hot aluminum if you are damaging threads then you're just a gorilla.


This is true. The problem is when people haven't tightened enough bolts to "develop a feel." It's then that bad things can happen. A least they have a shot with a torque wrench at not causing damage by over tightening something.

 

[JOD]

Originally Posted By: Tegger


And once again: Oil-pan drain-bolt torque figures always assume WET threads. ALWAYS.


This is incorrect. Unless the manufacturer specifies otherwise (some do) torque specs are listed as dry fit. There are a few reasons for this: consistency (they don't know if you're cleaning the threads dry or not) and new assembly (torque specs are typically generated for assembly plants then copied to factory service manuals) are two big ones. I can't speak to every Honda drain plug, but on a 2003 CR-V and a 2007 XR650R, the specs for the drain plug bolts are for an unlubricated fastener.

Another thing you're discounting is that the OEM requires a new crush washer. Are you lubricating the area between the drain plug head the the washer? Does the crush washer being used have the same yield point and the same coefficient of friction as the OEM washer? Because this area (bearing surface)is responsible for anywhere from 40-60% of the total bolt torque. Thread friction is responsible for approximately 30-40%. Bolt stretch (which is the ONLY factor which matters with respect to the tension of the joint) generally comprises about 10% of the total torque--but 100% of the responsibility for keeping the drain plug from falling out. So keep in mind that a 5% error in friction torque at the bearing surface can make for a 50% difference in joint tension. So, as was already said, claiming that a friction-based torque wrench "must be used" and then using it incorrectly doesn't really make much sense.

I don't really feel like being attacked over this, and obviously some folks have an emotional investment in their torque wrenches. So, if anyone wants to better understand the relationship between torque and bolt tension, I'd suggest giving this PDF link a read, or better yet, buy John Bickford's bookon the subject.

If you just want to tighten your drain plug, you can either just do it by feel if you feel comfortable, or use a torque wrench. But just remember that the torque wrench is no guarantee against stripping the bolt, nor is it necessary.

 

[Trav]

Quote:
But just remember that the torque wrench is no guarantee against stripping the bolt, nor is it necessary.

Yeah thats right just toss it in the bin on the way out of the garage or just use it as a breaker bar.

 

[Vikas]

Originally Posted By: Trav
Quote:
But just remember that the torque wrench is no guarantee against stripping the bolt, nor is it necessary.

Yeah thats right just toss it in the bin on the way out of the garage or just use it as a breaker bar.

Now you are arguing for arguing sake :-( For the current discussion i.e. oil drain bolt scenario he is right and YOU KNOW IT!!

 

[zeezee]

Originally Posted By: JOD
Originally Posted By: Tegger


And once again: Oil-pan drain-bolt torque figures always assume WET threads. ALWAYS.


This is incorrect. Unless the manufacturer specifies otherwise (some do) torque specs are listed as dry fit. There are a few reasons for this: consistency (they don't know if you're cleaning the threads dry or not) and new assembly (torque specs are typically generated for assembly plants then copied to factory service manuals) are two big ones. I can't speak to every Honda drain plug, but on a 2003 CR-V and a 2007 XR650R, the specs for the drain plug bolts are for an unlubricated fastener.

Another thing you're discounting is that the OEM requires a new crush washer. Are you lubricating the area between the drain plug head the the washer? Does the crush washer being used have the same yield point and the same coefficient of friction as the OEM washer? Because this area (bearing surface)is responsible for anywhere from 40-60% of the total bolt torque. Thread friction is responsible for approximately 30-40%. Bolt stretch (which is the ONLY factor which matters with respect to the tension of the joint) generally comprises about 10% of the total torque--but 100% of the responsibility for keeping the drain plug from falling out. So keep in mind that a 5% error in friction torque at the bearing surface can make for a 50% difference in joint tension. So, as was already said, claiming that a friction-based torque wrench "must be used" and then using it incorrectly doesn't really make much sense.

I don't really feel like being attacked over this, and obviously some folks have an emotional investment in their torque wrenches. So, if anyone wants to better understand the relationship between torque and bolt tension, I'd suggest giving this PDF link a read, or better yet, buy John Bickford's bookon the subject.

If you just want to tighten your drain plug, you can either just do it by feel if you feel comfortable, or use a torque wrench. But just remember that the torque wrench is no guarantee against stripping the bolt, nor is it necessary.


Better than I could have said it. I have to agree with this based upon my experience and all of the torque specs I've ever read that have been flat-out *incorrect* when applied to wet bolts.

Unless it explicitly indicates wet, always assume it's dry.

 

[demarpaint]

Anyone here confident enough to torque down a head, connecting rods, or main bearing caps in an engine w/o a torque wrench? Or better yet do a complete rebuild w/o a torque wrench? How about buying a reman engine that you knew was assembled by someone guessing torque? Just wondering.

Tightening a drain plug is not rocket science but IMO a torque wrench is an important tool to someone rebuilding an engine. Reading this thread can give the impression that torque wrenches and torque values are meaningless. JMO

 

[JOD]

Originally Posted By: demarpaint
Anyone here confident enough to torque down a head, connecting rods, or main bearing caps in an engine w/o a torque wrench? Or better yet do a complete rebuild w/o a torque wrench? How about buying a reman engine that you knew was assembled by someone guessing torque? Just wondering.


I wouldn't be confident using either operator feel or a friction-based torque wrench to assemble an engine--and engines are not assembled this way, either OEM or rebuilt. There are a variety of other methods used where proper bolt tension is critical: Torque-to-yield fasteners, angle torque, bolt elongation and even direct bolt tension measurements (at the OEM)are used. No one is assembling an engine on friction torque or feel alone (or they shouldn't be).

Originally Posted By: demarpaint
Tightening a drain plug is not rocket science but IMO a torque wrench is an important tool to someone rebuilding an engine. Reading this thread can give the impression that torque wrenches and torque values are meaningless. JMO


I can't speak for anyone else, but that's certainly not what I meant to imply. I don't think torque values or meaningless, nor that torque wrenches are useless. What I do believe, and has been pretty clearly demonstrated by those who've researched and written on the subject, is that friction torque is both fairly imprecise and very inaccurate; thing is, it's "good enough" for most things, since there's a pretty wide acceptable tolerance. In places where that tolerance isn't as big (say a head bolt), other methods are used (TTY bolts or angle torque).

Torque values and wrenches aren't "useless", but they don't offer very much in the way of precision either, and most people don't realize this fact (which is why I posted in the first place). It's easy to set your torque wrench to 11 NM and hear that satisfying "click" and think "job well done!". But the fact is, that click doesn't mean what many people think it means. Understanding the relationship between bolt friction and bolt tension removes this mystery and gives a better understanding into fastened joints--and also explains why you can do everything "right" and still have a failure with the joint. Some will seek to understand, some won't. But, the information is out there for anyone interested.

 

[demarpaint]

Let me clear something up, from a DIY'er POV. As a back yard mechanic I've successfully rebuilt engines for cars and boats as well as outboard engines with a good torque wrench. I can guarantee you this, they would not have been assembled properly w/o a good torque wrench. Granted anything can go wrong, but IMO for my applications I cut my risk down substantially by using the torque wrench.