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I was considering making a post here about this 2006 C55 AMG that I picked up to build and fix up, and a friend told me I should, so here we go!
This is my 2006 C55 AMG that I bought about a month ago for $2000 USD. I picked it up as a no crank, no start and figured if worst came to worst, I could part it out. I have wanted to own a C55 for a few years, and when I saw this one, I decided it was time.
I have a decent background in fixing automobiles since I grew up at my grandparents’ shop until I was about 19, always helping out and working there for a bit. So I decided to take on the challenge of fixing this thing up and giving it the second life it deserves.
So far, it has been amazing to work on. Everything is super simple and straightforward. When I got it home, the first thing I did was get under it and have a friend attempt to crank it while I tested the starter to see if it was getting power—and sure enough, it was! I bought a new starter and battery for it, along with new spark plugs, wires, and a crank position sensor, just to give it the best chance of starting. And sure enough, the thing fired right up like it had run 15 minutes earlier!
Since then, I have been doing a lot of maintenance and fixing small things that are not 100 percent on the car. I will be going through every single maintenance item to make sure it is completely sorted. The goal is to have a car that is still nice to drive on the street but can also head to the track or an autocross on the weekends and be pretty competitive.
Hopefully, you guys like the build and restoration. I for sure cannot wait until it is done!
Last edited by ThatSlow.W204; Mar 14, 2025 at 03:46 PM.
So after hearing it run, I decided to tackle some of the common issues these cars have to make sure they do not come up later. I already mentioned the crankshaft position sensor, but I also did the valve cover gaskets, transmission connector plug, new connectors for the coil packs, and new crankcase breather hoses.
Stuff that did not necessarily need to be done, but I decided to do while the car was already apart, included installing headers, flushing and replacing the coolant, and installing a new negative battery cable since that broke on my last W203 and looked like it was going to happen again. I also painted the valve covers since I had them off and had plenty of paint and primer laying around (+5hp hahah).
I will make another reply showing pictures of the headers.
here’s what the engine looks like now!
yes, I know I know. Everybody does red, but I had it and looks better than before. Plus I always liked having cars with black as the main color and red accents. I’d like to do the intake manifold in wrinkle black whenever I have that off someday.
So here are the headers. I was going to buy the VRP mid-lengths but was told they are just sourced from China, so I got them from the source for half the price! Picked these up for $420, and honestly, I am impressed. The metal is nice and thick, the welds are great, and any welds on the inside are smoothed out very nicely. I have gotten to see a lot of headers and systems during my time at the shop since we have installed many and always use them on our race cars and whatnot, so seeing the quality on these for the price was really shocking.
The extra plus? They fit perfectly! Install was super easy, and I had them on in no time. They look great on there too. I still have to take it down to the shop to connect the headers to the factory exhaust system, but that will be very easy.
Last edited by ThatSlow.W204; Mar 14, 2025 at 04:29 PM.
Very nice project and it's really nice to see projects, where these cars get saved. They are really underrated imo. I'm glad, I was able to convince you, to join the c55 journey
Very nice project and it's really nice to see projects, where these cars get saved. They are really underrated imo. I'm glad, I was able to convince you, to join the c55 journey
I’m also very glad you talked me into it, and thank you again. This thing is going to be great when it’s done, although a project truly never ends!
That’s a good project, where did you get those headers? You may want to make sure the breather holes in the valve covers aren’t plugged, the hole is about 1 mm and prone to gunking up. I have found that most of the valve stem seals on these engines are toast as well and replaced them due to high oil consumption. The only other issue I have encountered is the front cover coolant orings that swell and in some they begin leaking coolant into the crankcase and may become dislodged and find their way into the passenger head. .
I did some work on my ‘05 C240, but overall, it was a super solid car. I’ve also done a few things to my ‘13 C300. These cars have always felt pretty straightforward to me, especially the W203s. That’s a big part of why I grew to love them after being a GM guy for so long—the older, simpler ones are just really easy to work on.
That’s a good project, where did you get those headers? You may want to make sure the breather holes in the valve covers aren’t plugged, the hole is about 1 mm and prone to gunking up. I have found that most of the valve stem seals on these engines are toast as well and replaced them due to high oil consumption. The only other issue I have encountered is the front cover coolant orings that swell and in some they begin leaking coolant into the crankcase and may become dislodged and find their way into the passenger head. .
When I had the valve covers off to reseal them, I went through all the breather ports and passages to make sure nothing was gunked up like you mentioned. The stem seals on my C240 were shot—after idling for a bit or sitting for a few days, it would blow out a nice little cloud of smoke, haha. Hopefully, the ones in this engine are fine, but if not, it wouldn’t be the end of the world. The coolant O-rings worry me a bit more, but if they fail, it’ll just be another job to add to the list.
I am doing something similar to my recently acquired C55 but am really just DIY catching up on some deferred maintenance from previous owners and modifying gently as I go.
Two questions for you;
1) any CEL or anything with those headers? If not, please be so kind as to share that sauce/source!
2) of all the items you've replaced so far---which was the biggest PITA?
I am doing something similar to my recently acquired C55 but am really just DIY catching up on some deferred maintenance from previous owners and modifying gently as I go.
Two questions for you;
1) any CEL or anything with those headers? If not, please be so kind as to share that sauce/source!
2) of all the items you've replaced so far---which was the biggest PITA?
Thank you! Unfortunately, I haven’t had a chance to drive the car yet, so there’s no check engine light (CEL) at the moment. I also cleared all stored faults using Xentry to start with a clean slate and see what actually needs attention. I’m still waiting on a few more parts, but once they arrive, the car will be back on the road.
As for the headers, they will definitely trigger a CEL since installing them removes the primary catalytic converters. The ECU will detect that the catalytic converters are “not functioning,” but any competent tuner should be able to disable the associated fault code when you get a tune, preventing the CEL from coming on.
To answer your other question, in terms of repairs, I’d say the most challenging job is the starter—though it’s still relatively straightforward. The real difficulty comes if you run into issues with the two bolts connecting the catalytic converters to the manifolds. If they are seized or snap, it can be a real hassle to remove them. I got lucky with mine, and they came out without trouble.
For modifications, the headers are probably the trickiest. As mentioned, those two bolts on the cat-to-manifold connection can be problematic. Additionally, the exhaust manifold studs themselves can be a challenge—if one breaks, it can turn into a tedious job. They’re fairly easy to access when everything comes apart smoothly, but if a stud strips or snaps, it can make the installation significantly more frustrating.
With any of the bolts I mentioned that could potentially break or be troublesome, I highly recommend soaking them a few times with a penetrating fluid a few days before you start working, if possible. If you can go without driving the vehicle for a few days, this will give the fluid time to work its way into the threads. If you don’t have that much time, at least spray them well and let them sit for a few hours before attempting to remove them.
I’ve been doing more work on the C55 and kinda forgot to update my thread—might’ve missed a few things, but here’s what I’ve knocked out over the past few days. She’s getting close to being road-ready again!
New brakes all around
Flushed and replaced brake fluid, power steering fluid, diff fluid, and transmission fluid
Installed a PPE aluminum finned trans pan during the trans service to help keep temps down
Threw in some stainless hardware to dress things up a bit while I was in there
What’s left before she’s back on the road:
Hooking up the headers to the rest of the exhaust
New tires
Replacing the hood latch cable
All the remaining parts are already ordered—just waiting on deliveries. Shouldn’t be long now!
Here’s some pics of how the old fluid came out and the new PPE pan! Brake fluid Power steering fluid New PPE pan! Inside of new PPE pan New PPE pan installed!
Hello everyone! Long time no see. I kinda forgot about the post I had made, but anyway — bad news and good news!Sadly, my main phone got destroyed, and I haven’t been able to get anything off of it, so not many pictures. BUT I did eventually get the C55 back on the road, put some miles on it, and it was great! Just a bit dull, but I figured that was due to the 150k-mile suspension (more on this later) and the fact that the C55 isn’t the most “raw” car out there from the factory.
I still had a lot of fun and was really happy to finally own and drive one of the cars I’ve wanted for a long time. I did a few more mods — an intake, 82mm throttle body, lightly ported the intake manifold, and had Mercedes Swap Shop tune it — and then had even more fun!
That said, I’ve never really been a “straight-line speed” kind of guy. So a little while ago, I completely stripped the suspension out of the car — and I mean everything. Every control arm, tie rod, strut, shock, rear subframe… everything. Since it’s winter here now and I don’t want to rot the thing out, I’ve been piecing it back together slowly. Everything is being replaced with new OEM parts, or aftermarket in some areas. I still want to keep the car comfortable to drive on the street, so no fully solid bushings or anything crazy like that — just focusing on the key areas that matter so I can have a blast next summer.
I’ve also decided to let go of the 5G in it. After driving my C300 with the 7G for the last few years, it’s always been a dream to put one in a C55, and now I finally have the car to do it to! I sold the 5G, got a great deal on a used 7G with 80k miles, and with the help of Mercedes Swap Shop and a great friend (unclebenz, go check out his c55 build too!), I’ll be tossing that into the C55 this winter!
Sorry for forgetting to update! I’ll try my hardest to keep you guys posted on progress, and when it’s done, I’ll update you on how it feels next summer. Heres a few pics from when i did have it on the road, and stay tuned!
I'm so glad you picked up this raw gem and are fixing it up and customizing it. I think the M113 evo with the 7sp will feel way more agile. Let's see who will bring back their car to the street first, you or me Hyped and pumped for this build!
I'm so glad you picked up this raw gem and are fixing it up and customizing it. I think the M113 evo with the 7sp will feel way more agile. Let's see who will bring back their car to the street first, you or me Hyped and pumped for this build!
I cant wait to see how it performs, i also think it will be much more responsive!
Please keep us posted on the 722.9 swap. I also want to do that in mine.
IS there a cable adapter available or do you need a separate harness?
So there is no custom harness for the 722.9 swap, but the wiring itself is actually the easiest part of this swap! I’ll add some pics below, but you completely cut the original EGS52 out of the system.The 722.9’s VGS system only uses 4 or 5 wires, depending on generation (VGS2 is 5, VGS3 is 4), and that’s exactly what the EGS52 uses — 5 wires. Meaning the wiring is as simple as cutting all of the old EGS52 wiring out, splicing in the VGS-style connector, and that is all!The wires are: +12V, ground, CAN high, CAN low, and K-line (K-line is only used on VGS2).
*fair warning, I HAVE NOT BEEN ABLE TO TEST YET, PLEASE DONT RECREATE UNTIL EVERYTHING IS 100 AND THE CAR IS ON THE ROAD*
Egs52 Vgs3
Last edited by ThatSlow.W204; Dec 24, 2025 at 11:49 AM.
Thanks for the info. Please keep us posted on how it turns out.
No problem Once it’s fully done and being driven, I’m 100% going to make a separate post as a write-up/guide specifically about the 722.9 swap. I really hope it makes it much simpler for people to do it on their own, and when that’s done, I hope to see a few more of them swapped. I know there are a few people who would love to do it, but the information is unfortunately hard to come by.
The mechanical conversion is very straight forward, the wiring is really simple too. The hardest part was to find someone who can get programming done, but since you found a good shop to do that, that's covered as well. I'm also hyped to drive the 7G on mine. The extra gears should make a huge difference
The mechanical conversion is very straight forward, the wiring is really simple too. The hardest part was to find someone who can get programming done, but since you found a good shop to do that, that's covered as well. I'm also hyped to drive the 7G on mine. The extra gears should make a huge difference
It’s insane how simple the swap really is, yet so many people don’t even know if it’s possible. There isn’t much information about it online at all. Also, yes — the gearing should help a ton, paired with the much quicker shift speeds, and it’s supposed to be “more efficient,” meaning less loss of power from the engine to the tires.I think overall the difference will be huge.
The more I talk about it, the more excited I get.
Last edited by ThatSlow.W204; Dec 28, 2025 at 03:42 PM.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
Once it’s fully done and being driven, I’m 100% going to make a separate post as a write-up/guide specifically about the 722.9 swap. I really hope it makes it much simpler for people to do it on their own, and when that’s done, I hope to see a few more of them swapped. I know there are a few people who would love to do it, but the information is unfortunately hard to come by.
