Smart Fortwo Engine repair


My poor Smart Fortwo ate oil. A lot. I wont be wrong if I say 2 litres for a 1000km. It is a common mode of failure with these cars. One little plastic valve breaks and eventually your engine is busted. That, of course if you dont know it is broken. Oil rings get stuck and engine starts to consume oil.

When buying my Smart, I knew it consumed oil. I drove happily with it one Summer and when Winter came, I thought that I should do something to it. Of course problem had escalated. The exhaust manifold had  cracked, turbo gone beyond repair, etc..


Cracked turbo manifold. Some of you maybe spotted also that the wastegate actuator retaining circlip is missing.


Cylinder head, still in the engine.


A big lower block from the engine. In order to remove connecting rods from the crankshaft, this had to be removed. If those two grey plates in the center of the block was open, removing of the block was not needed. From the internet one can find that somebody slized those plates away when block was still in the engine. I did not had the courage to do that.. I also hesitated to do that when part was out. Maybe those plates has something to do with engine rigidity. So they left untouched.


Engine from underneath, after removing that block. Crankshaft and connecting rods can be nicely seen.


In the middel of engine stripping process.


Sympton of the disease. Stucked piston oil ring.


Dirt in the piston grooves.



I put new piston and oil rings in. Before that I naturally cleaned pistons and grooves.


Cleaned pistons and new rings inside cylinder block. Arrow is pointing right when watching to front from the back of the car.


Because engine was open, I took the opportunity to change chains, slides, chain tensioners and sprockets for timing and oil pump. I also fitted a new oil pump.


New and old oil pump side By side.


A new oil pump in it’s chamber. (Btw, changing it was a waste of money, it had not wear at all.)


When putting on new oil pump’s sprockets I found out that old and new sprockets were different in size. I figured out that with new sprockets oil pump’s shaft was going to rotate a bit faster than before. New parts are in the lower part of the pic. The rightmost part goes in the crankshaft. Interesting part is that it is friction mounted. So the nut which goes on the end of the crankshaft should be in the right torque! Nut also holds multirib pulley in place.


This is a little over 115 000 km used timing sprocket from other end of camshaft.

I also fitted a new oil pan, with a drain plug in it. No picture of it, sorry!


During reassembly I had at least two oops-moment. The first was when I fitted pistons back to engine. I forgot to remove that little nozzle which sprays oil to piston from underneath. Of course connecting rod got stuck to it and nozzle got severe damage. Luckily one member of the Facebook group I belong helped my to sort it out. On the right is obviously unbroken part.


Another oops-moment was when I was torqueing connector rod bolts. My torque wrench was out of calibration and I used too much force to that bolt and it snapped. When that happened I thought that game was over. How on earth I was gonna get that snapped bolt out from connecting rod? Further investigation revealed that it was not a big deal. The bolt came out with just turning it with fingers! Phew, that was a releaf! Actually, it did not went all the way off, it just stretched. The light is visible through bolt.. 🙂


Luckily I checked oil level regularly so engine did not run dry thus cylinder head was salvageable. It only needed new valve guides. I let a proper shop to do that.


Another angle of the refurbished cylinder head.



Refurbished cylinder head in its place. Manouvering in space like this is really painful!


In the middle of the process..

The rest of the job was just a hard work. In the middle of reassembly I thought that maybe I have taken just a little too big bite. Eventually all went well and I have droven my Smart almost a thousand kilometers after that major engine overhaul!


A box full of new spare parts. Worth of it is little over 1200€! In total I spend to this engine rebuilt about 1600€. Smart parts aint cheap.. So better keep my Smart in good condition from now on!