'99 Intrepid - Dealer Stripped Oil Pan Drain threads?

I went in to have the oil changed in my '99 Dodge Intrepid. The
mechanic told me that the threads were stripped on my oil pan when he
pulled the plug out. At first he told me that I would have to have a
new oil pan. After some research on the Internet, I found that it
might be possible to instead use a helicoil. I then called my mechanic
and told him this. He said they would try that. When he called me back
to say it was repaired, he said that he had used a "piggy-back plug",
which was similar to a helicoil.

Just thought I would post this out there in case someone else has the
same problem. Hopefully it will save you over $400 like it did me!


--
officehelp1981
------------------------------------------------------------------------
officehelp1981's Profile: http://www.usenetcars.com/member.php?userid=2663
View this thread: http://www.usenetcars.com/showthread.php?t=188477

officehelp1981 wrote:
> I went in to have the oil changed in my '99 Dodge Intrepid. The
> mechanic told me that the threads were stripped on my oil pan when he
> pulled the plug out. At first he told me that I would have to have a
> new oil pan. After some research on the Internet, I found that it
> might be possible to instead use a helicoil. I then called my mechanic
> and told him this. He said they would try that. When he called me back
> to say it was repaired, he said that he had used a "piggy-back plug",
> which was similar to a helicoil.
>
> Just thought I would post this out there in case someone else has the
> same problem. Hopefully it will save you over $400 like it did me!

Thanks for posting. Yes - it's a well known problem. Another simple
under-$10 solution is to buy what's called an oversize thread
(designated by the manufacturers as an "OS" thread) plug. Available at
any chain auto parts store on the oil plug racks along with the standard
thread replacement plugs and (generally awful quality) plug gaskets.

The helicoil would have been a good solution - the downside being that,
on the LH cars, there is not room enough to drill or tap straight into
the existing hole due to a frame member being in the way - thus there
would be the labor expense of removing and replacing the pan just to
install the helicoil.

Both the piggy-back and the OS plugs cleverly avoid the drill-and-tap
issue by having fluted self-tapping threads to form new threads into the
damaged hole (exactly like self-tapping screws, only bigger). All
that's needed is a wrench and about 10 minutes time.

You have to ask yourself who had been doing your previous oil changes
and stripped it out. But it is a very common problem (due to very
stupid people being hired for doing oil changes in certain dealerships
and quick change shops).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

You will have to have a drill press and a bolt drilling fixture to
drill a bolt and then, you will have to fit a place on the pan to
safety it to.

Aircraft use a lot of safetywire because low frequency propeller
vibrations loosen bolts badly and because "it's traditional". Safety
wiring is uesd less and less on modern aircraft and engines.

Cessna and Pipers and their overpriced junk Lycomings are hardly a
good standard for how to do things!

Bill Putney wrote:
>
> You have to ask yourself who had been doing your previous oil changes
> and stripped it out. But it is a very common problem (due to very
> stupid people being hired for doing oil changes in certain dealerships
> and quick change shops).
>

Well said. I posted a while back about having my drain plug
(repeatedly) rounded off by various oil change shops. Funny, it's
lasted 18 months and looks like new ever since I decided to change my
own oil. What worries me far more is what else has been, or might have
been, neglected or damaged during this most simple of maintenance tasks.
I also wonder how much damage might have been done by the screwdriver
a minute lube shop left in the engine compartment in my wife's Jeep, had
I not found it the next day.

Nomen Nescio wrote:
> ...Oil drain plugs are frequently overtightened because friction is all that
> holds it in place and "mechanics" are afraid it might work loose and fall
> out. That would be a catastrophy indeed. A ruined engine plus a $1,000
> littering fine in most States.

Yeah right. A littering fine? Get real.

> Well, friends, guess what? Most all bolts and nuts on cars are SPECIFIED
> by the factory shop manual to be overtightened. Its in the range of 50% to
> 100% overtightened when you compare torque specs from the manual to torque
> specs from standard fastener engineering sources.

Any time a torque is specified, it is based on two things:
(1) The type of metal, and
(2) The per-cent yield (relative to 100% yield for that particular metal
and the cross-sectional area of the threaded section).

Standard fastener charts are for reference only. They assume, again, a
certain material and a certain arbitrary yield factor. Any comptetent
engineer can make reasonable assumptions for yield (as long as it is not
supposed to be torque-to-yield) based on application and good
engineering judgement. I promise you that the torque it takes to strip
the threads in the hole for the drain plug in the LH car oil pan is
several times more than what the FSM specifies.

I brought up the material and yield factor being important in
determining acceptable torque values a year or so ago when you raised
this automotive industry "overtorqueing" issue, and you never responded.

Can you give an example of an automotive bolt that is specified at over
100% of its yield value based on the metal used? (Certain head bolts
don't count since they are intentionally torque-to-yield.)

> The reason why they can get away with it is because there's a lot of safety
> factor built in the fasteners.

No - not a lot. It's whatever the remaining yield is - i.e., if the
yield factor used to develop a certain torque spec. is 80%, then the
safety factor is 20% (until the bolt starts permanently stretching. I
will give you that the break limit is even higher, if you want to
consider *that* the safety factor.

> However keep in mind that overtorquing
> produces excess tension forces in the bolts which subtracts from the
> available shear resistance. That means the overtorqued bolt may be just
> fine: looks ok, holds in place BUT its only rated for tension, not in
> shear. Shear is like the McPherson strut-to-steering knuckle bolts. Its
> dangerous, particularly since those bolts are not even solid bolts, but
> full length threaded in many applications.

Whatever torque value specified would have been calculated based on the
cross-section of the threaded part, not the unthreaded part.

> Back to the oil pan. The oil pan screw should be put in with a gasket and
> torqued to normal engineering torques (based on diameter, pitch and
> material) AND THEN SAFETY WIRED. That is how they do it on Cessnas and
> Pipers and those bolts never strip or fall out.

No value added. No reason to do that. On a plug that is properly
installed, what is the statistical probability that the plug will work
its way out before the next oil change? If a guy doesn't know how to
install a drain plug properly, what are the chances that he will safety
wire it correctly, and if that's the case, why is he working on your car
at all?

> Don't argue on the right way to do things by saying its too expensive,
> takes too much time, cars are not planes, its always been done that way
> (done wrong always that way).
>
> As for Mickey Mousing install of an "oversize" plug, that's half assed
> hatchet mechanic negligence and can lead to a big assed lawsuit.

Unless the customer is not willing to pay for a new pan or the added
labor of pan removal to do a helicoil. I agree that the O.S. thread
plug is not best - but guess what - it works. I used it on my LH car to
buy me some time until I got a new pan.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

Bill Putney wrote:

> Any time a torque is specified, it is based on two things:
> (1) The type of metal, and
> (2) The per-cent yield (relative to 100% yield for that particular metal
> and the cross-sectional area of the threaded section).

Actually also of course on the minimum cross-sectional area, and on the
thread pitch. I assumed those things, but on re-reading what I wrote,
figured I better add those. OK - whether lubed or un-lubed (lightly
lubed usually assumed unless otherwise specified).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

wrote:

> You will have to have a drill press and a bolt drilling fixture to
> drill a bolt and then, you will have to fit a place on the pan to
> safety it to.
>
> Aircraft use a lot of safetywire because low frequency propeller
> vibrations loosen bolts badly and because "it's traditional". Safety
> wiring is uesd less and less on modern aircraft and engines.

Well I make my living repairing GE, Rolls, and P&W engines on Boeings and
Airbuses. I can assure you that plenty of safety wire is used everytime
something is replaced, adjusted, or refilled on an engine. But there's a
big difference between these engines, which demand a huge premium on
reliabilty, and a gasoline engine in the family automobile. The latter
needs to be affordable to average people and doesn't need to run
flawlessly or put hundreds of lives at risk. ETOPS (i.e. long distance
flights overwater with twin engines) aircraft demand an even higher
standard--the same crew can't even work on both engines!

Sure safety wire is important for aircraft. But it's a lot of trouble
and expense with very little return for cars on the ground.

> Cessna and Pipers and their overpriced junk Lycomings are hardly a
> good standard for how to do things!

So you must be a Continental fan, which powers the rest of the
Piper/Cessna fleet. Nothing wrong with Lycoming though, many of their
models are near bullet proof when they are properly used.

Nomen Nescio wrote:
> Mr. Bill Putney added to this dialog:
>
>
>>Any time a torque is specified, it is based on two things:
>>(1) The type of metal, and
>>(2) The per-cent yield (relative to 100% yield for that particular metal
>>and the cross-sectional area of the threaded section).
>>
>>Standard fastener charts are for reference only. They assume, again, a
>>certain material and a certain arbitrary yield factor. Any comptetent
>>engineer can make reasonable assumptions for yield (as long as it is not
>> supposed to be torque-to-yield) based on application and good
>>engineering judgement. I promise you that the torque it takes to strip
>>the threads in the hole for the drain plug in the LH car oil pan is
>>several times more than what the FSM specifies.
>>
>>I brought up the material and yield factor being important in
>>determining acceptable torque values a year or so ago when you raised
>>this automotive industry "overtorqueing" issue, and you never responded.
>>
>>Can you give an example of an automotive bolt that is specified at over
>>100% of its yield value based on the metal used? (Certain head bolts
>>don't count since they are intentionally torque-to-yield.)
>
>
> Mr. Putney, when you speak of "yield" I think you refer to "stress" from
> what I learned about strength of materials and related subjects in various
> shop classes. I am not an engineer, however. "Yield" is when the stress
> exceeds the elastic limit and permanent deformation takes place. With
> increasing stress (more torque) the fastener "elongates" (stretches)
> because of the stress of tension. If the fastener is not overtorqued, it
> returns to its original length. If overtorqued, it yields and when removed
> and measured, its longer. If greatly overtorqued, the fastener will either
> fracture, that is snap, or the threads will strip. Depending on pitch and
> fit, the threads may go first or the bolt will snap. So, yes, bolts are
> torqued to a certain percentage of maximum allowable stress beyond which
> the elastic limit is exceeded and the bolt yields.
>
> It is difficult to accurately calculate tension from torque due to friction
> effects under varying loads. I think these days some empirical approach is
> taken with stress & strain equipment to make up those torque tables I find
> here and there, published by bolt and nut companies and finding their way
> into textbooks and the like.
>
> I agree with you that there is more to it than following a table. A good
> example is con-rod cap screws. They must be torqued to produce very much
> more static tension than the dynamic tension forces during engine
> operation. This is to prevent the bolts from fatigue failure. Such bolts
> may very well be highly stressed on purpose. They also are not designed to
> be removed and replaced a lot of times such as oil pan plugs.
>
> It also occurs to me that oil pan plugs are screwed into a pressed steel
> pan where there the thread integrety may not be up to that of a standard
> nut. In aircraft there are thin nuts that are good only for 50% rating of
> a standard nut. The pan itself then may be a weak point. That would
> explain why pans strip out, not bolts.
>
> Perhaps one solution is to eliminate the drain plug altogether and design a
> quick-release drain that can lock open or closed. Such devices are found
> on aircraft fuel tanks so that a quick sample of gas can be examined for
> water or foreign matter. A quick release would speed up oil change and
> make it a lot cleaner: just attach a short length of hose to the valve,
> lead it into a container, open the valve, drain the oil, close the valve
> and remove the hose and container. Then replenish the crankase.

Your statements about what yield is are correct.

You still have made a claim but fail to give quantified examples, and I
still get the impression that you have looked at torque tables and
assumed general application without regard to the critical factors
(material, thread pitch, etc.) in a given specific application. IOW,
you need numbers to back up your claim. IOW - give me a torque value
out of an FSM, tell me the materials and the thread size and pitch, and
we'll do some calculations based on accepted yield values of that
material. There are accepted formulas for this. The formulas include a
friction coefficient, and you can plug either the accepted value
(determined emperically) for lightly lubed or dry, as the case may be.

The problems with oil pans stripping out is that the oil pans we are
talking about are made of aluminum, and we have idiots in shops who are
either using impact wrenches or are using breaker bars and pulling them
as hard as they can when putting the plug back in (I work with a guy who
used to work in a NAPA shop who told me that they had extra long
wrenches and that the typical oil changer would use those wrenches and
pull it as hard as he could - this in an aluminum pan - like I said:
idiots).

Fram and another company (Fumoto, IIRC), make popular quick release
drain valves to fit the common pan drain hole thread. I don't like them
for a couple of reasons, but that's just me. Let me age a few more
years, and I may start using them on my cars.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

"Bill Putney" > wrote in message
...
> Nomen Nescio wrote:
> > Mr. Bill Putney added to this dialog:
> >
>
> The problems with oil pans stripping out is that the oil pans we are
> talking about are made of aluminum, and we have idiots in shops who are
> either using impact wrenches or are using breaker bars and pulling them
> as hard as they can when putting the plug back in (I work with a guy who
> used to work in a NAPA shop who told me that they had extra long
> wrenches and that the typical oil changer would use those wrenches and
> pull it as hard as he could - this in an aluminum pan - like I said:
> idiots).
>

I had a partially stripped pan on my T&C when we bought it, this is
a steel, not aluminum, pan. I don't agree with the overtorquing idea,
while I'm sure some threads are ruined by this, I think the real problem
is not threading in the drain plug properly. Espically threading a plug
into aluminum, you really have to do it with your bare fingers, or fingers
in
thin surgical gloves, to feel out the threads to know if your going into the
pan right. And, if you go in wrong it takes little effort to cut enough of
a crossthread, that it will be very difficult to find the correct thread if
you back out and try again.

Most of these quick change places, the customer brings it in hot,
they pull the plug, half the time dropping it into the screen at the
bottom of the oil catch funnel, then all the hot oil cascades down over it,
then as soon as the oil stops coming out the oil change guy has
to get that hot, slippery plug threaded back into a hot pan asap so
they can go on to the next car. Half the time he's picking it up
with leather gloves, it's amazing he can get it started in properly in
the first place.

Ted

Nomen Nescio wrote:
>
> Mr. Putney, when you speak of "yield" I think you refer to "stress" from
> what I learned about strength of materials and related subjects in various
> shop classes. I am not an engineer, however.

Not a problem. I am

> "Yield" is when the stress
> exceeds the elastic limit and permanent deformation takes place. With
> increasing stress (more torque) the fastener "elongates" (stretches)
> because of the stress of tension. If the fastener is not overtorqued, it
> returns to its original length. If overtorqued, it yields and when removed
> and measured, its longer. If greatly overtorqued, the fastener will either
> fracture, that is snap, or the threads will strip. Depending on pitch and
> fit, the threads may go first or the bolt will snap. So, yes, bolts are
> torqued to a certain percentage of maximum allowable stress beyond which
> the elastic limit is exceeded and the bolt yields.

Everything you say is correct. Problem is, there isn't a drain plug in
the history of the world that would ever require torquing to bolt yield,
since it's not resisting a tension load, nor is it subject to dynamic
loading. More importantly, there is no possibility, ever, of developing
the entire strength of a steel fastener of substantial diameter, with
only a few millimetres of thread, as is the case with my Jeep.

Oh, and by the way, when the threads on a bolt hole go, they yield, so
Bill was kinda on track as well.


> It is difficult to accurately calculate tension from torque due to friction
> effects under varying loads. I think these days some empirical approach is
> taken with stress & strain equipment to make up those torque tables I find
> here and there, published by bolt and nut companies and finding their way
> into textbooks and the like.

Not that hard to calculate. There are well established tables of
friction coefficients for almost any combination of two materials
rubbing against each other. A certain portion of your torque is
resisted by this friction, the rest is resisted by the cumulative
bending resistance of all threads acting together. If bending on
threads due to torque minus friction resistance is greater than the
bending resistance of all threads, you get thread yield and eventual
failure.

> Perhaps one solution is to eliminate the drain plug altogether and design a
> quick-release drain that can lock open or closed. Such devices are found
> on aircraft fuel tanks so that a quick sample of gas can be examined for
> water or foreign matter. A quick release would speed up oil change and
> make it a lot cleaner: just attach a short length of hose to the valve,
> lead it into a container, open the valve, drain the oil, close the valve
> and remove the hose and container. Then replenish the crankase.

I like the idea of my oil not being changed by a bonehead that doesn't
understand that if they tighten the drain plug too much, they will
eventually pooch it. Now that's technical!