W210 Differential Drain Plug Questions

[shertex]

Went out on this beautiful New England morning to change the differential fluid on my 98, only to discover that BOTH plugs (fill and drain) are sufficiently rusted that there's no chance a 14mm hex socket is going to fit in there.

Obviously the first thing to do is to order new plugs. Then, once those are in hand, what's the best way to proceed? Lots of PB Blaster until I get a good tight fit? My fear is that I'll find them sufficiently deteriorated that I won't be able to get them out.

Is it worth trying a 13mm socket or is there too much risk of rounding it out?

Any advice appreciated.

[jay_bob]

AeroKroil is your friend.

On a scale of 1 to 10

wd-40 = -1
3n1 oil = 2
pb blaster = 5
AeroKroil = 10

[Jeremy5848]

Whatever you do, remove the fill plug first!

I confirm the usefulness of Kroil as a penetrating oil. I suggest applying it every day for 2-3 days and drive the car normally. Warmth and vibration will help the Kroil penetrate and will also help you clean up the plugs. When you do make the attempt, have the differential warm from driving.

Question: do the plugs have an "indent" for an Allen wrench or an "outdent" for a socket? From your description, it sounds like the latter.

Jeremy

[shertex]

Originally Posted by Jeremy5848

Whatever you do, remove the fill plug first!

I confirm the usefulness of Kroil as a penetrating oil. I suggest applying it every day for 2-3 days and drive the car normally. Warmth and vibration will help the Kroil penetrate and will also help you clean up the plugs. When you do make the attempt, have the differential warm from driving.

Question: do the plugs have an "indent" for an Allen wrench or an "outdent" for a socket? From your description, it sounds like the latter.

Jeremy

Yes, I remember well the fill plug first warning!

I will get me some Kroil.

Plugs have an indent for Allen....what I was calling a socket is male.

[shertex]

This is interesting....from a Smith and Wesson forum, of all things.

Machinist's Workshop magazine actually tested penetrants for break out torque on rusted nuts. Significant results! They are below, as forwarded by an ex-student and professional machinist, Bud Baker.

*Don't forget the April 2007 "Machinist's Workshop" magazine comparison
test.*
**
*They arranged a subjective test of all the popular penetrants with
the control being the torque required to remove the nut from a
"scientifically rusted" environment.*
**

*Penetrating oil ..... Average load*

None ..................... 516 pounds
WD-40 .................. 238 pounds
PB Blaster ............. 214 pounds
Liquid Wrench ..... 127 pounds
Kano Kroil ............ 106 pounds
ATF-Acetone mix....53 pounds

*The ATF-Acetone mix was a "home brew" mix of 50 - 50 automatic transmission
fluid and acetone.*
*Note the "home brew" was better than any commercial product in this one
particular test. Our local machinist group mixed up a batch and we all now
use it with equally good results. Note also that "Liquid Wrench" is about
as good as "Kroil" for about 20% of the price. *
**
Your mileage may vary.....

[Skid Row Joe]

Originally Posted by Jeremy5848

Whatever you do, remove the fill plug first!

I confirm the usefulness of Kroil as a penetrating oil. I suggest applying it every day for 2-3 days and drive the car normally. Warmth and vibration will help the Kroil penetrate and will also help you clean up the plugs. When you do make the attempt, have the differential warm from driving.

Question: do the plugs have an "indent" for an Allen wrench or an "outdent" for a socket? From your description, it sounds like the latter.

Jeremy

Good advise!

[Jeremy5848]

The ATF-acetone mix is interesting; have to try that sometime. Y'all please remember that the flash point of acetone is -20C (-4F). In its liquid state acetone is bad enough; vaporized acetone is a bomb. Think SAFETY and with anything more than very small amounts work outside.

[shertex]

Do you think with enough time and patience I should be able to get the 14mm to fit? Or might I have to try 13mm?

[Stretch]

Originally Posted by shertex

Do you think with enough time and patience I should be able to get the 14mm to fit? Or might I have to try 13mm?

Just scrape the inside of the allen head orifice out with an old electrical screw driver and then fit the 14mm key. If necessary tap with a hammer to get it in there.

My preference is always the type of (14mm) allen key set in a 1/2" drive socket (they are available to buy like this - not something cut down and hammered in by Mungo)

Don't try and be clever and use a wrong size - you'll only make trouble for yourself

[Jeremy5848]

Agreed. Get the 14 mm indent clean and you'll be able to carefully tap an Allen bit in as far as possible. It's possible that an impact wrench might be better than a long breaker bar and breaking loose the plug without stripping it.

[TMAllison]

Originally Posted by Jeremy5848

The ATF-acetone mix is interesting; have to try that sometime. Y'all please remember that the flash point of acetone is -20C (-4F). In its liquid state acetone is bad enough; vaporized acetone is a bomb. Think SAFETY and with anything more than very small amounts work outside.

I used that mix on my stuck #6 GP for close to 90 days, x2-3 applications a day in my garage housing a gas clothes dryer and hot water heater. Didn't really help. I think its good stuff, but I don't think that 4 oz of Acetone and 4oz of ATF is particularly volatile. I did keep lid on the bottle but applied it liberally on the head of the GP a zillion times.

I wouldn't store 55 gals of mix in an open container and I would never leave the lid off the Acetone even in an open garage.

[Jeremy5848]

Quantity has nothing to do with volatility. However, you're right that a small quantity like 4 oz. of acetone is unlikely to cause a serious problem. Nonetheless, I included the warning for those who may not be aware.

[Stretch]

Originally Posted by Jeremy5848

Agreed. Get the 14 mm indent clean and you'll be able to carefully tap an Allen bit in as far as possible. It's possible that an impact wrench might be better than a long breaker bar and breaking loose the plug without stripping it.

Continuing the theme of safety => If you are using an impact wrench / gun thing make sure you use the correct bits that are designed for impact tools. Normal sockets and bits can shatter / crack / splinter = possible pain damage hurt

[pimpernell]

Originally Posted by shertex

Went out on this beautiful New England morning to change the differential fluid on my 98, only to discover that BOTH plugs (fill and drain) are sufficiently rusted that there's no chance a 14mm hex socket is going to fit in there.

Obviously the first thing to do is to order new plugs. Then, once those are in hand, what's the best way to proceed? Lots of PB Blaster until I get a good tight fit? My fear is that I'll find them sufficiently deteriorated that I won't be able to get them out.

Is it worth trying a 13mm socket or is there too much risk of rounding it out?

Any advice appreciated.

Had the same issue with my 96E300d. Tried to do it myself climbing underneath, hands filthy, and not too happy to find out that the fill plug was not going to budge. Took it to my indy, up on a lift, using an impact wrench the plug was out in 5 seconds. Total cost $75 which included the refill. Some jobs just ain't worth doing yourself, if you screw up the plug, you will pay for it in the long run.

[Zulfiqar]

hmm - I think texas cars are pretty easy in this case. I just took a regular allen socket with a tommy bar and got it out, I had to heave on it to get it moving.

A little heat and some penetrating oil works nice and I can vouch for the ATF+acetone mix and its fantastic - be careful with it though if you are dealing with heat too.

for the diffy case I used kroil after heating up the case, the oil was sucked into the threads and after three such "feedings" the plug moved.