2006 800CC CDI Diesel Engine "Rebuild" Tips

[ZCMK123]

Hello All,

 

I have a 2006 Fortwo Cdi that I have had for a few years now. Being US based, I have a difficult time finding parts, but I have kept the little guy up and running for the most part, but he has had a very rough start from cold for the last few months. It used to reliably start with some ether, then it needed ether and a battery assisted jump, then needed to be plugged in and heated with my oil pan and in-line coolant heater, now all of the above and it still isn't happy. I recently did a ton of work on it, rebuilding the high pressure fuel pump, cleaning out all of the fuel lines, changing many sensors (CPS, fuel rail pressure, MAP, air temp, etc), and ensuring that grounds and other electrical mods(fuel pump and headlight relays) were in good shape. Despite all of this work, it still has a rough start. I have checked the SAM and ECU, the only thing out of line was some oil on the bottom ECU plug. Not sure where this came from, but it was cleaned and didn't seem to change much. This then prompted me to perform a compression test.

 

On the compression test from left to right, I got around 140psi, 150psi, and 675psi. From what I have read on this forum and others, ~350psi is considered OK to good compression. I have not torn down the engine itself, but I planned on cracking it open and seeing what I find. My question to this group then becomes, what should I pre-purchase ahead of time? I planned on getting this gasket set: (Elring 535.890) I have read that the intake gaskets at the minimum are good to swap out as they are known to go bad. I figured this kit was a decent start, but are there any other staples that I should swap? I have a testing kit to try and perform a leakdown test to check rings, but I think I am destined to teardown this engine eventually anyway. My fortwo has ~265,000 km on it currently.

 

Thanks for all of the content on this forum thus far and I appreciate any help.

-Zach

[stickman007]

I've come across a few higher mileage OM660 engines now. Similar symptoms, white smoky starts and long cranks with lots of misfires. I believe that most likely the issue is that your intake valves are burnt or completely worn. Rather than planning a full engine rebuild, (difficult to source parts for the bottom end), I would aim to pull the head and inspect your cylinder head. Replace your valve seals, intake valves, lifters (both exhaust/intake), rockers, and head bolts. Parts should run you about $800ish all together from the dealership and way less if you do aftermarket. I'm currently working on an engine with 220k and the cross hatch still looks great with no scoring on the cylinder walls.

 

I'll post some pics with sunken intake vales. Check with Willys (Jonathan), I think he's our most recent guy to fully rebuild one of these engines if you want more tips. The few that I've replaced intake valves ran way nicer afterwards. Also pay attention to broken lifters and rockers - also a common issue if not the root cause to worn valves.

 

Izzy

[stickman007]

Pic of YEGSmartie's cylinder - currently working on

 

 

 

Valves from a previous OM660 cylinder head job with hard start symptom

 

 

[Willys]

OK, I am a lunatic when it comes to rebuilding an engine, I can't just do the simple things and let the rest be. I used a German company called MW-SMART They are good people but you must prepay as some bad apples in North America have stiffed them after they ship the parts leaving the rest of us to hold the bag so to speak. You can find almost every internal engine part or complete rebuilt engines from them. I suggest you decide what you want to do, then order parts, not order a head gasket and hope that'll solve it. You will find worn valves and seats, maybe guides, maybe oil pump chain and sprocket, cam chain and sliders, pistons and rings, rockers get cracks, lifters get worn so it's best to change rockers and lifters as a set. I changed almost everything except block, head,cam crank and crank bearings(simply because this was the only part not available at the time for my engine) But mine were well within the specs required.

OR.....you can source a good running used engine and hope it lasts you long enough? They are out there. I got one for $400 with less than 100kms. Yes you can find cars for that in bad shape but.....a good running engine isn't easy to find.

Again, this company is good to deal with and their shipping isn't that bad if you order many items to fill the box so to speak to help with the price etc. 

Hope this helps and if you need more info, PM me and I'll be happy to chat.

 

[ZCMK123]

Hello Gentlemen! Hope you had a good weekend!

 

This helps a ton. I have finally stumbled upon MW-Smart and I placed a decent sized order from them. The only things that I did not order and now thinking that I should have would be the rockers and valve springs. I am not sure about the pump sprockets, hopefully mine will be alright. 😬

 

Not sure when you bought your last set of parts from MW-Smart Jonathan, but they are selling what they call the Engine Overhaul kit. It includes new pistons, rings, valves, bearings, oil filter, head gasket, valve gaskets, and head bolts. I bought this, new timing chain, chain guides, chain tensioner, and valve lifters. I am not new to engine work or engine rebuilds, but this will be my first diesel. Thanks for the invite to PM. It is appreciated and I will have to do that once I get started.

 

The engine runs like a champ once I get it going, which makes me believe more and more that it is the valves.

 

Another quick question, has anyone "bulletproofed" the OM660? My father has used studs instead of bolts for the head on various of his diesel trucks now, and insists that I do the same on my rebuild. Any advice or opinions on this topic from the rebuild crowd?

[Willys]

You're welcome....and glad to see you found the web site MW-SMART helpful. When I was hunting my total rebuild they either had individual parts or complete rebuilt engines.  I'm not new to engines either but as you say this is my first diesel.  Remember, something I do forget also, it's a .8 of a litre in size...lol.   So...for what I'm, we're building, I think stock parts will be good enough. But what do I know? 
I just trashed the rear main seal which should be an easy install....lol....not today....lol.
When I was gathering parts pistons and rings were very hard to find even at this site. They had one set, a 3 over sized set so I jumped at them. My cylinders were so warped or wavy that it took 2 over just to get them close to perfect, so 3 over worked out well for me.
 IF, you want to chase HP there is a guy called Tom Bailey who has found 200 plus hp out of this engine. I belong to many smart car FB sites and he is on one of them. He has dyno pulls to show his progress etc.  Not much left is stock. I also don't see the need but understand the thrill of the hunt.

When you get the engine stripped down check for out of round cylinders, I was shocked!  It's supposed to be from too short of heat cycles and shutting it down, ie a short trip to the shops and back....never getting the engine temps up before shutting it off.  I found it when I was checking the gap on the old rings and saw light peeking up between the ring and cylinder wall...in many places.

 

[ZCMK123]

Extremely helpful. I stumbled along one of your teardown posts a while back, but I haven't found it again since. Good to know about the pistons however. Having done a smart engine rebuild, what do you suggest for getting access to the engine? I have dropped it and the transmission before, but I have not removed the subframe. I have the passion trim, so Air Con, all the typical fuel and coolant lines, the works. Would it be easier to disconnect the subframe in it's entirety and wheel it out or should I just drop the engine and work around the body?

 

I am not looking for more HP per-say, but I would be interested in potentially more boost. I am consistently getting around 15psi currently. I found a thread or two discussing going higher, but then the engine goes into limp mode. Any idea what the upper bound is and why it goes limp?

 

Finally, I do have all of the necessary diagnostic tools to check the cylinders, I planned on carefully inspecting them before replacing a bunch of stuff and calling it a day. Thanks for the call-out!

[Willys]

I run mine at 15.5 psi boost no more, it seems to like it there, simply to keep it from going limp, no-one likes a limp.....lol.  Yes you can turn it up on the waste gate adjuster but....you can't stay in it for longer than 5 seconds at a time or risk going limp.  So, imho it's just not worth it...to each their own. I have heard that you can adjust the ECU to allow you to go higher but that is far out of my abilities! I hate electronics!
As for working on the engine or anything under the trunk so to speak, I have found it is always easier to drop the sub frame even if just 10 inches on longer studs or rods, easy to make. But if doing serious work just drop the entire sub frame out and roll it out and work in comfort. Once you have done it once you'll never understand why you did anything the old way...lol.
I made up two separate power cables, one for the starter and another for the alt. so you can work on them easier than fighting with a single multi use cable. I attached them just in front of the sub frame by shortening the original cable and added a battery sized connecter so to speak. 

[ZCMK123]

Hey Willy,

 

Thanks for the info. I will likely keep the turbo at a stable point then!

 

I have officially started the tear down. I have been following this guide to remove the sub frame:

https://www.fq101.co.uk/how-to-guides/fortwo-450/engine/178-engine-replacement

 

I have looked on this forum slightly but I haven't found any explicit guides, just call-to-action to do it because it is worth it over dropping the engine. 

 

Now to my question, like I said, I have the passion trim, which includes the air conditioning. It is running great, very cold. I do not currently have the means to drain and refill the refrigerant, so is there a way to remove the sub frame without disconnecting the air con lines? I have pretty extensive knowledge of the left/drivers side of the car, but not a ton with the other. Any tips or pics for removing the sub frame?

 

Also, can you give me some more details or pics regarding the power cable mod you speak of?

Edited September 26, 2024 by ZCMK123

[Willys]

I remove the rear fender, bumper assembly before just to make it easier to roll out the sub frame. I also install just steel rims on the rear to help lower the sub frame so i do not have to lift the body as high.  I'm sure I am forgetting things but this is the main jist of it.....

 

As for removing the sub frame......there are 4 main bolts which require some force at times to break free.  Then take drivers side wheel off, inner fender skirt, take out the 4 screws holding on the air intake tube to the air box, remove brake lines and cap as you do not want to drain the brake system if you can avoid that as it requires a complete bleeding of the master and ABS pump etc( real pain if you do not have a good scanner that can do this ), undo the ABS wiring, There is a main ground wire(braided wire) that runs from engine to body rear centre(it usually disintergrates at some point in time and should be replaced with either new or homemade welding wire substitute),  
What I do is, block all wheels then use two scissor jacks just in front of rear wheels and slowly equally lift body up away from sub frame. After removing the 4 main bolts. You may also want to stabilize the front of the sub frame with a jack stand so it doesn't flop forward.  As you lift the body up you will see what is holding you back and loosen each item as you go. 

You also will soon be able to get your hands to the air con pump which you should be able to remove or loosen from engine to keep the whole system intact if memory serves me well. I removed my AC system to gain more room to work as I rarely turn it on anyway. 

Sooner or later the sub frame will be free enough to walk it out from under the body. 

 

As for the wiring you will find it all unclips as you lift the sub frame, same for the fuel line. On the righthand side of the subframe is the glow plug controller, it has a large plug which needs to be undone. The alt and starter wire is a serious pain in the rear to get at when working underneath the car. So what I do is run separate cables to each item, then join them 10 inches or so in front of the sub frame. I then shorten the main battery power cable to match the new cables and simply use new battery connections to join the three wires together when the time comes. I then wrap the connection well with heater hose etc to make sure it never shorts while driving. 

Once you get the sub frame out I simply lower the body down just for stability reasons.

I hope this helps and as said before I'm sure I have missed more than a few steps but they will be very obvious as you go. 

I am preparing to do the same thing with my beater in the next day or so. I plan on cutting away anything that makes it difficult to use the old car as a work test station to test engines after rebuilding them instead of rebuilding them and then going through the hassle of re and re-ing it to find out it isn't running perfectly before installing into  the final car. Probably a ton of work for no reason.....?????  But it's getting scrapped any way so why not?

 

Again hope this helps.....

 

That page describes a gasoline engine which has obviously different components etc but the main idea is the same. I have impact gun for larger bolts so no need to loosen bolts before lifting? But using just steel rims is far easier.  No need to disassemble the sub frame except the air con and connections before rolling it out as a unit either. Once you have done it once you will never work on the engine or sub frame area without dropping it at least on longer bolts to allow your hands to fit easily.

[ZCMK123]

Hey Willy,

 

Great advice, that sounds way smarter than the guide I was following.

 

Just wanted to throw in a quick update. I have the subframe ready to come out, just haven't gotten to the bolts yet. I will likely try and work on it a bit after I do some more kitchen remodel work.

 

Anyway, how long should this shipment from MW-Smart take to make it to the America's? I ordered it 2 weeks ago and the tracking number still shows "Order data transmitted electronically."

[Willys]

I did all mine well before COVID so I can't say how long it may take, but you can always keep on them to get a shipped out date....?  I'm sure it took a few weeks at least to get to me but nothing went weird or nobody screwed a shipment up. I bought many shipments from them and once they saw I was one of the good guys I didn't have to pay up front, just as a normal every day customer.  Like I said before I have nothing but good things to say about these guys.  I just know they are very busy with all the Smarts they have on their doorstep so to speak. They also do or did all the service work etc etc at their shop, so this is just part of their business. It's not just a parts shop place like many Amazon businesses.
If I can help just ask and I'll do my best.

[ZCMK123]

Good afternoon all. Took a 2 month break to casually remodel the kitchen, as one does obviously

 

I just wanted to throw in an update and say that I got the parts from MW Smart and the sub frame is separated from the chassis. I have to agree that this is the best way to work on this thing after the first attempt! Thanks a ton for those who have commented. I will continue to post some updates as I dive further into the engine.

 

-Zach

 

 

[Willys]

Excellent...!

Let the fun start.....check your rockers and lifters for wear patterns as that will restrict their movement as the engine runs. Don't mix up the lifters and rockers as if you do not replace them all they will be wear matched .  Also check for cracks in the rockers which considering the bulk of them seems impossible but they do crack.
IF you are taking pistons out, reinstall rings and shine a light up from below to see if there is any gaps between rings and walls of cylinders in multiple locations/hieghts in each cylinder. Mine had many gaps which forced me to bore my cylinders out 2 over just to get the waviness out. I ended up buying 3 over pistons as that was all that was available at the time.  Like i said let the fun begin.

[ZCMK123]

Hey all good news and bad news.

 

I have found the main source of my issues with starting the engine. The intake and exhaust valves on pistons 2 and 3 were completely shot. They look quite bad, tons of carbon build up and deformation. I did get new valves, springs, rockers, lifters. Everything but the little retaining clips. Everything listed will be replaced.

 

I also got new pistons and some new bearings for the conrods. My dad and brothers helped me take a look at the main crankshaft bearings as well, and indeed those are on their way out as well, plenty of copper coloring showing.

 

That leads me to guess which sized new bearings I need now. I measured the main crankshaft diameter, and all 4 sections were damn near 45mm concentrically. I then measured the connecting rods and they were also concetric and pretty close to 40mm. Does anyone here know what standard size the crankshaft and connecting rod diameters should be?

[ZCMK123]

Update everyone,

 

I was able to find the specifications for the crankshaft as well as the main bearings. The crankshaft should be 44.9mm in dia, the standard bearings should be 3mm thick and the cutout that the bearing sits in should be 51mm in dia. I also used a plastigage to show that my current tolerance between the bearing and the crankshaft is around 0.10mm.

 

As I stated in my previous post, I measured around 45mm for my crankshaft. I have since measured the bearings to be around 2.85mm thick but the lower crankcase that holds the bearings was stock at 51mm dia. This led me to purchasing the stock thickness 3mm main bearings from MW Smart. Hopefully they arrive before the new year, but with Christmas, I will not hold my breath. I guess it is time to clean the crap out of these parts. Thanks again for all of the help!

Edited December 17, 2024 by ZCMK123

[Willys]

Ouch those valves are in great shape...lol.  Time for new seats....a good machine shop should be a help. Give them the head and valves and also ask about valve guides....I replaced mine also.....I also was able to reuse my main bearings after plasti-gaging them, so was lucky. I think my guides came from some mini van a dodge caravan I think that my machinist made fit.....but could be wrong or that was another engine ......but this sounds right..?
The only things I didn't replace was the block, crank ,head, crank bearings, rods, cam. If I remember correctly..  Everything else was replaced with new. All from MW-SMART. Oh...the vacuum pump for the brakes on the righthand end of the engine I got from Romania, also excellent, just searched it and found it there as MW-SMART didn't have a new one.