[gtdump]

A while back I picked up a junker for parts. It's a 2010 and for the most part it's in good shape but was sold as having a bad engine, so there's no telling exactly what all is wrong with it.

I'm a busy person and it can take me a while to get around to finishing some tasks, this one included, so I tend to work on projects in small spurts of an hour here and there. This is one aspect of the Smart I really like, I can fit two of them into my garage bay so I can work on the parts car and still park my daily driver in there as well. Because it can take me some time to finish a task, it's important that I provide enough documentation for me to get things back together again after I've forgotten many steps, ergo this thread. Related is part of my disassembly process, I tend to take a number of pictures and most importantly I put all fasteners and removed parts into ziplock baggies labelled with what they were assosciated with.

I've done a little work to my other Smart and I'm no stranger to general automotive maintenance, but this will take me into previously unexplored territory so it should make for a fun ride.

Just so we know what it should look like when I'm done, here it is before I started molesting it. If you think there's a lot of "stuff" around it, be glad you can't see the entire garage; this area is relatively tidy!

I will need to drop the engine sub assembly to see what I've got, so the first part is getting at it. I will need to remove the side skirts, rear valance, rear panels, and crashbar; in order.
It sounds like a lot of work, but previous experience replacing the muffler showed it's really not that hard.

 

[gtdump]

Taking off the side skirts....
There are two palstic pins to remove in the rear wheel well...

Once these are out, you can reach under and grab the inside edge of the skirt where it meets the belly pan and pull down in a couple of spots where it clips into the body...

On my other car these came off easy, on this one the center clip needed a little persuasion with a screwdriver as a prybar.

Now on to the front wheel well where you need to pull down on the skirt and pop the plastic wheel well lining out to free it from the side skirt...

At this point there's very little left to do, just pop the rear clips at the top of the skirt and similar at the front...

Then all that's left is to slide the whole mess rearward and it should come right off... (I apparently forgot to take a picture of this step, so pardon some image recyling)

 

[gtdump]

The rear Valance is very easy to remove. First, pull the two plastic pushpins from the corners of the bumpber....

Then pull in the edges of the valance to free the ends from the rear panel...

Lastly, remove the two bolts, and pull the clips off the bottom of the valance mounts and lift the bottom of the valance rearward and up; it will pop off and it's removed.

 

[gtdump]

Now we need to remove the rear panel. I was kind of surprised the first time I removed this as to quite how easy it was to get off once I figured out how it was attached.

First, open the service panels inside the trunk to access the taillight wiring, there's one on each side...

There's a clip in there which connects to the taillight assembly, the retainers are on the ends of the clip and need to be squeezed inward to release them.

Just in case my description isn't good enough, here's a picture of the clip.

Don't forget to do both sides!!!

Edit: I missed an important step here, you'll need to remove the right inner service panel; I realized this after the fact.
There's one torx bolt to remove. Pardon the fact that the panel is removed in the picture...

I was told this one bolt and the panel comes off, but it was obvious that there was some other retainer but I couldn't see it. It appears to have snap fit retainers in several locations which I was 99% certain I was going to break the panel removing it, but the snap-fit sockets popped off before I could ruin it. More details are provided two posts down as image limits prevented me from inserting them here. (See post below for more details and helpful images)


To easily get at the rear panel you need to do something about the tailgate. When I changed the muffler in my other one, I removed the two bolts holding the tailgate on and slid the tailgate into the trunk, but there's a short bit of wiring in a rubber boot that was in the way, so this time I tought I'd be smart and take the skin off the tailgate. Lesson learned, it wasn't any easier so I put the tailgate skin back on and removed the tailgate via the two bolts near the engine access panel and slid it in the trunk again.

You might be ondering why I bothered removing it, surely you can get the rear panel off with it in place? Probably, but there are several bolts which hold the rear panel on which are a pain to get at with it still attached and it's just two bolts to save some frustration.

You'll need to remove two bolts on the sides, previously covered by the side skirts. On this one the clips are intact, on my daily driver one clip is broken and I should get a replacement someday...

Now there are 5 bolts around the trunk that need to be taken off, two on each of the sides and one in the center at the bottom...

Go around to the side where the fuel fill is, the rear panel pulls away from the body much like the side skirts did, just it pulls outward and not downward. (Sorry no pictures). Unscrew the fuel cap and slowly pull the panel over the fuel fill neck, but don't get too far as there's a sensor here we need to remove...

This is another squeeze clip, though this one isn't from the sides, but rather from the flat.

Now go pull the other side off and have a friend come help. You'll slide the whole panel rearward and set it aside...

Tada! See, that wasn't even too hard, was it?

 

[gtdump]

And.....I need to do some more work!

 

[gtdump]

Tonight's work was removing the rear wheel well liners. I'm not sure these needed to be removed, but they were easy to take off and now they aren't in the way.
Easiest step thus far, grab a ratchet, a 10mm socket and your trusty push-pin tool.

Pull the plastic pin, marked with the arrow...

The lower engine guard was already removed. No idea how it was attached as I didn't even look. I'm amazed it wasn't lost in transit from where I bought it to home.

Next is removing 3 nuts. When I first looked I saw a lot of crud in there and I couldn't even see if the nut was an e-trox, standard hex head, or something else. Happily, I reached up there past the cobwebs to knock the loose crud off to find the nuts are plastic....WIN!!! They're not rusted in place! They're locations are as marked...

In case you're having trouble visualizing where the bolts are, here's a shot of the liner after it was removed. Locations marked as usual...

The astute among you will have noticed my fancy Chewy brand low profile mechanic's creeper; if you can't get under the car on this, you can't get under.

 

[gtdump]

Continued from edit above....
In addition to the one torx bolt, the right inner service panel is help on by several snap-fit connectors. Here's a shot from the back of the panel to see what you'll be dealing with, the snap-fit connectors are the round white spots...

All this to get at the connectors to the ECU. There are two plugs attached to this part of the harness, the one connected to the ECU and another, smaller plug down near the grommet. The smaller connector is hidden behind the wiring harness, but is indicated by the arrow on the right in this picture...

There's a clip at the bottom of the ECU plug which moves downward which will allow the plug to be pulled out. It might be possible to do this without removing the service panel, but it would be difficult. Being my first time at this I wasn't sure what I would find, so removed the panel.

 

[gtdump]

It would appear I missed another connector in the harness with the ECU connector. It was tucked inside the panel with the connector for the lights. Not exactly sure what it's to, but it needed to be unplugged to push the harness through the hole once the grommet was pushed through...

The battery should have been disconnected, but if not do it now, next we're pulling the left hand seat and we don't need airbag issues.
There are 4 bolts which hold the seats in plus the anchor point for the seatbelt to remove. Obviously slide seat back to get the fronts and forward to get the rears.
Don't just yank the seat out, there's probably some connectors under it for airbags, seat heaters, etc...

Once the seat is out you can lift up the carpeting. The front carpet only needs to come up enough to unplug the TCU; it's the plug nearest the tunnel. Push in the retainer on top of the plug then swing the bail on the plug and it will come free. Here's a picture with terrible focus to help...

Clip the zipties and cut tape that hold it to the cable management clips to free it, lift up the rear carpet to expose the grommet. Push the grommet in and pass the harness through.

Over on the other side of the car on the top of the engine, disconnect the fuel line by pressing in on the green tab/button and pull the connector out...

While you're here, grab your 10mm socket and remove the engine ground so you can pull the ECU harness through...

Then go back in time to before you removed the tailgate and pop off one of the clips for the fuel line and work the hose off. Should have posted it earlier. I would edit, but tthe post where it belongs is at it's image limit so editing it isn't an option. For those of you reading before doing; horray this is your reward!

 

[gtdump]

I did not remember to take pictures of the brake line disconnection. It's pretty straightforward, there they are on the left side of the car...

I lowered the engine further and continued to disconnect items as I found them. I hopefully did not miss any items, but I probably did.

Rather than evacuate the AC I unbolted the compressor and tied it to the body. I might regret it later, but that's what I did...

There's some random connector a behind the compressor a bit, I almost missed it and may have stretched the wire. I will need to test it and see if I broke it...

While you're here disconnect the lead to the alternator, the same harness connects to the starter which will need to be dealt with on the other side. No images of the alternator.

One the left side, there's a line to disconnect...

There's a cable which goes to the transmission, prawl? Whatever it is, I found it easier to remove the left and center bolt and loosen the top right one to pry it out and remove the nut on top of the shaft to get the arm off. Careful, the two bigger bolts are mounts. Put the big bolt back when the mounting plate slips out...

Disconnect the starter lead...

And clip the zipties and that part of the harness should be free now...

Pretty sure the cause of the damage was a failed belt...

There's not much more to go. The engine is pretty much fully lowered and there's not much left to remove. I started on removing the coolant lines; I thought the lines were clamped with the annoying crimp bands, but thankfully these can be squeezd with pliers to loosen and when released, tighten back up. I got one hose off using a pair of bent-nose pliers, but a guest arrived so I stopped for the day.

Here''s a view of the clamps...

I'm pretty happy with progress thus far. I don't think I've worked on it for more than 1 hour in any given day.

 

[gtdump]

After looking, the unknown wire that may have been stretched appears to be the AC clutch wire. Will still need to test it, but at least now I know what it is.

 

[gtdump]

A pair of curved needle nose pliers were handy for getting some of the hose clamps, others didn't need it; three hoses in total.
Once that was disconnected, I could remove the subassembly and wheeled it over to my workshop area...

Now I need to start separating the motor from the assembly and the transmisison...

There will be some rust cleanup as part of the process as well, but this part is done.

 

[gtdump]

And just for grins, here's on of the last shots of it after disassembly. Rust cleanup and treatment, then off to reassembly.

 

[gtdump]

Subframe has been reattached to the De Dion tube. Everything torqued to specs.

 

[chetb]

Do you happen to have pictures of the chassis where the rear subframe bolts on(i know there's 4 bolts)? I've only recently started learning about cars, and from what i've learned on the internet it seems like when you jack up the car at the pinch welds on the chassis, all the weight of the rear subframe/engine/suspension assembly is on the threads of those 4 bolts. Does that sound right, or am i missing something?

 

[gtdump]

Do you happen to have pictures of the chassis where the rear subframe bolts on(i know there's 4 bolts)? I've only recently started learning about cars, and from what i've learned on the internet it seems like when you jack up the car at the pinch welds on the chassis, all the weight of the rear subframe/engine/suspension assembly is on the threads of those 4 bolts. Does that sound right, or am i missing something?

They're shown in a couple of the above images, but if one isn't certain what they look like it can be hard to recognize them. I've marked up one of the images of the assembly partly lowered which shows them pretty well, the locations on the other side are a mirror image. The two yellow arrows point to the bolt heads, the front one isn't easy to see, but the rear one is quite visible. These are the "record release bolts" or "lowering bolts" and are significantly longer than the ones which hold the subassembly in place for operation.

There are indeed only 4 bolts that actually hold the sub assembly in place; that might not sound like a lot, but bolts that size have a yield strength above the weight of the entire car. If the concern is that the bolts might be over stressed by lifting the car, I don't think it's much of a worry given the specs of the bolts. I've worked on heavy equipment where similar sized bolts held together significantly heavier loads without issue. Perhaps if the car were severely rusted it might be a concern, but at that point there should be serious safety concerns with the vehicle just sitting on all 4 wheels.

The lowering bolts are hex head, but the retaining bolts used for normal use are E-torx, E-18 I believe (I didn't make note of the size, going from memory).
Here's an image of the rear bolt before removal. The rust was only surface rust, which I cleaned up and treated with POR-15.

And here's one of the mount at the front with the subassembly removed. It was much cleaner than I would have expected given the appearance of the subassembly. The part that extends down with the the internal threads is where the bolt goes, so there are more than just the minimum number of threads necessary.

 

[chetb]

thanks @gtdump . that last picture was exactly what i was looking for. I assume the threads in that picture are located just in front of the rear passenger side wheel well. Would you happen to know how many threads there are? I'm still amazed that those threads are able to support 1/4th of the weight of the subassembly. Clearly I have a lot to learn. I just found

, going to dig deeper to figure out how to calculate the weight those threads can support.

PS: I'm not actually planning to remove the subassembly on my car, I'm only curious how the vehicle i use everyday works.

 

[gtdump]

I don't know how many threads there are, but the photo seems to show at least 6. Perhaps the next time I pull one apart I'll take a closer look and get a more accurate count. It is my understanding that just a few turns of thread provide pretty much all the strength and anything beyond that is redundancy.

The bolts themselves are M12x1.5 and a quick look at tables on design properties for metric bolts should give you some good reference numbers; I'd say the engineers provided plenty of margin.

I'd be interested in seeing what you come up with in your calculations. I'm no engineer, but I find myself referencing engineering data at semi-regular intervals. It's handy to know sometimes (yes, I am a huge nerd).

 

[chetb]

After some basic calculations, I can see why this works. For the M12x1.5 internal threads in the unibody, each thread has about 33 square millimeters in area on the weight bearing section. Evilution says the threaded length is 5cm, so that must mean there's a total of about 33 threads. So total area that's bearing the weight is about 1000mm2 or about 10cm2 ; No wonder the threads don't strip off. The internet also says that if you exceed the "minimum thread engagement area", then the bolt will fail before the threads strip off. Will attempt to calculate minimum thread engagement area over the weekend.

Attaching an image of my derivation in case someone is curious. I used the image and Dmin formula from ISO metric screw thread - Wikipedia
substitute D=12mm and P=1.5mm to get 33mm2