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I like everyone else found that the oil drain plugs are set up at Mitsubishi by some retired sumo yokozuna; getting the plug out without raising the car to get enough wrench and breaker bar (and pipe!) swing room is a trial. After my first oil change I set it up reasonably snug with the original washer and without the breaker bar - much less than original. At my second oil change I found it again as tight as the first time! I really am uncomfortable with that much strain on the threads of the cast aluminum sump.

As I have previously reported, I took a new OEM plug washer to my local Mitsu dealer. The service manager examined it and said, no, it isn't a standard Mitsu part, and no, he didn't consider it a single-use crush washer**. It is a quite hard form (or alloy) of copper and doesn't even scratch easily with a steel scribe. This would be one application where a squishy crush washer would be appropriate to give a good seal without straining the aluminum.

For anyone searching for a softer washer, the dimensions of the OEM as measured with a vernier caliper are: O.D. 31.8mm; I.D. 22.7mm; 1.2mm thick. Of the three dimensions I would judge the I.D. and thickness the most critical - the thickness as it is involved with properly positioning the pickup screen in the sump.

** Actually, I don't know how "crush washer" came into the W451 lexicon.
 

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Maybe M-B knew something when they didn't put a drain plug on the 450s? Anyway, will have the second oil change done on a lift where there's plenty of room for the longer handles to break it loose. Don't understand why it tightens up again - maybe the aluminum/steel combo reacting to heating? Anyway, would a softer washer help the situation while sealing as effectively? Inquiring minds, etc. :)
 

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I believe the alternate cycles of heating/cooling are resulting in the plug tightening up. BTW, if you overtighten a bolt/plug, you need to replace it.

Yellow-Smart
 

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No sump plug

My smart roadster and the older 450's don't have a drain plug at all, so you can't do a DIY oil change, you have to take your car to a smart specialist that has the sucky thing that they put down the dipstick hole to suck out the old engine oil.
Looks like they have changed it for the 451.
 

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I've looked in every catalog...

I like everyone else found that the oil drain plugs are set up at Mitsubishi by some retired sumo yokozuna; getting the plug out without raising the car to get enough wrench and breaker bar (and pipe!) swing room is a trial. After my first oil change I set it up reasonably snug with the original washer and without the breaker bar - much less than original. At my second oil change I found it again as tight as the first time! I really am uncomfortable with that much strain on the threads of the cast aluminum sump.

As I have previously reported, I took a new OEM plug washer to my local Mitsu dealer. The service manager examined it and said, no, it isn't a standard Mitsu part, and no, he didn't consider it a single-use crush washer**. It is a quite hard form (or alloy) of copper and doesn't even scratch easily with a steel scribe. This would be one application where a squishy crush washer would be appropriate to give a good seal without straining the aluminum.

For anyone searching for a softer washer, the dimensions of the OEM as measured with a vernier caliper are: O.D. 31.8mm; I.D. 22.7mm; 1.2mm thick. Of the three dimensions I would judge the I.D. and thickness the most critical - the thickness as it is involved with properly positioning the pickup screen in the sump.

** Actually, I don't know how "crush washer" came into the W451 lexicon.
I know of to look in for a soft aluminum or copper washer to replace this one and none of them have that size. (.875"ID X 1.25" OD)I also considered purchasing tube stock with near ID/OD sizing and couldn't find that either. I would part off a couple dozen on a lathe with ease if I could find the raw stock to make them out of. :)
 

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Discussion Starter #8
My smart roadster and the older 450's don't have a drain plug at all, so you can't do a DIY oil change, you have to take your car to a smart specialist that has the sucky thing that they put down the dipstick hole to suck out the old engine oil.
Looks like they have changed it for the 451.
The auxiliary diesel in my sailboat is like many marine installations (no space under the engine to drain oil (except illegally into the bilge). We routinely use a hand-pumped vacuum extractor through the dipstick hole, widely available at any marine supply outlet, including those in the UK.
 

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Discussion Starter #10
Stock

I know of to look in for a soft aluminum or copper washer to replace this one and none of them have that size. (.875"ID X 1.25" OD)I also considered purchasing tube stock with near ID/OD sizing and couldn't find that either. I would part off a couple dozen on a lathe with ease if I could find the raw stock to make them out of. :)
If there is annealed copper tube stock anywhere, it will be at McMaster-Carr (McMaster-Carr), but I think it will be tough to part-off 1mm+ (0.047"+) sections.
 

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...yes the temperature changes will affect the torque of the plug do to the differences of metals and their heat expansion rate...
...yes the use of anti-seize will protect your engine from galling up the threads if the plug is over torqued..., if you do not have a brand name anti seize compound like never seez a little bit of milk of magnesia in the threads will do the trick

jetfuel
 

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The auxiliary diesel in my sailboat is like many marine installations (no space under the engine to drain oil (except illegally into the bilge). We routinely use a hand-pumped vacuum extractor through the dipstick hole, widely available at any marine supply outlet, including those in the UK.
Thanks for that Old smart, we do have them over here as well as you said, I don't know about the smarts over there but ours need the Mercedes Winstar machine plugged in as part of the service, it reads and fixes faults in the ECU, so I take my roadster to one of the good indies that we have over here, as the Mercedes Dealers that sell and service the smarts really suck.
We use the fully synthetic oil so it lasts ages and does'nt break down with time, so I only have a service once a year as I only do about 5,000 miles as I have another car that I use, so I don't feel I need to change the oil myself anyway.
Happy motoring,
Ellis
 

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Checked in there first...

If there is annealed copper tube stock anywhere, it will be at McMaster-Carr (McMaster-Carr), but I think it will be tough to part-off 1mm+ (0.047"+) sections.
Old smart. NO deal and nothing the right size. Not difficult at all on a good lathe with a cobalt .060" parting tool. I'd make them slightly thicker...like around .060".
Find me some stock and I'll make some for us....:)
 

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Discussion Starter #14
Old smart. NO deal and nothing the right size. Not difficult at all on a good lathe with a cobalt .060" parting tool. I'd make them slightly thicker...like around .060".
Find me some stock and I'll make some for us....:)
If you make them appreciably thicker than original, might it pull the end-seal on the pickup screen off its seat?
 

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I forget the sealing method...

If you make them appreciably thicker than original, might it pull the end-seal on the pickup screen off its seat?
Was it a face seal on the end of the plastic screen housing or a sliding seal fit against the wall of an ID? IF it is the prior, yes...it could result in a bypass leak. If the later....there probably is room for .013" of play but not known for sure.
Better to stay with the original thickness then....good call, Old Smart. Making it the right thickness is no more difficult really. I thought I would allow for alittle crush. That being the case, then making them around .050" is probably more appropriate.
Ofcourse, I won't do any of this unless I/we can find some material. I hate to make the whole thing from a billet...alot of work there for what it cost to buy it from the dealer, you know?
 

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Discussion Starter #16
... Of course, I won't do any of this unless I/we can find some material. I hate to make the whole thing from a billet...alot of work there for what it cost to buy it from the dealer, you know?
Considering the slight parallel "grain" in the OEM material (and parallel on both sides), I think they may be punched out of rolled sheet stock.

Maybe the OEM washers can be annealed to soften them a little.
 

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I've looked quite awhile to try to find the socket/wrench size for the drain plug. Finally had to resort to just checking it - duh.

Anyway it is a 24mm, however 15/16" is just a tad snugger, but fits fine. If anyone doesn't have a 6 pt 15/16" socket, you can get a whole set of impact rated 1/2" drive 6pt sockets from Harbor Freight for $14.99 (and less if you have a 20% off coupon that they seem to run everywhere lately - even the WSJ).
 
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