View Full Version : 2008 Mercedes R550 4Matic(V8 "minivan")

12-19-2020, 09:14 PM
So it's been just over 4 months since purchasing this "sports grand tourer", Mercedes name for what is essentially a minivan, this thread will detail my experience with the vehicle. This is a high mileage example with a questionable/non existent maintenance history outside of what was done and logged in the maintenance booklet that comes with the owners manual, of which no receipts are available.

Mercedes offered three models of the R class with a V8, the reliable one R500(5L V8 M113), the one no one knows exists R550(5.5L V8 M273), and the one with the lowest production numbers that everyone wants, the R63 AMG(6.2L V8 M156)
The R550 was sold exclusively to the Canadian market and is powered by the 5.5L V8 M273(382bhp/391ft/lb tq) that is used by the other "550"models of that era in the Mercedes line up, mated to the very common 7 spd 722.9 transmission. The R550 came with a large number of options as standard equipment, however the original owner of the vehicle I purchased opted out of the Distronic(adaptive cruise control) and cooled seats, so it's not exactly fully loaded. You could say that's just two less components that could fail but considering the amount of electronics and systems already in the vehicle those two options, specifically the cooled seats would have been nice.
Still despite the difference in straight line power, this R class is far more comfortable compared to the WK1 I owned prior and has no issue moving through traffic when needed, its still slow but I was pleasantly surprised at how well the 5000lb vehicle moved through traffic and performed on the road coming back to Calgary from Edmonton. The 4 corner airmatic suspension despite its reputation does an awesome job absorbing the "imperfections" of the local roadways and overall ride quality is miles above the Jeep I drove to Edmonton in.
After its first wash in my possession:

Now on to the juicy bits, I'll start off by saying that I knew I'd be getting into some "maintenance catch up" after I looked at and test drove it and now looking back if I knew what I would have had to do in the first 3 months of ownership I'm not sure I would have purchased the vehicle but for what I was looking for and its cost, at the time I anticipated it wouldn't be too bad.

Let's start out with what I found during the initial test drive and viewing, for a lot of people these things would turn them away from a vehicle but I research my prospective vehicles problems and their fixes/solutions prior so unless its an expense that I feel is too costly I don't generally let it deter me from at least making an offer accordingly, but I am also a glutton for punishment so here we go, initial findings:
-Front/Rear pads and rotors appear very worn
-Radiator fan running high the entire time vehicle was running but operating temperature/coolant level is fine
-Some rust on the body
-Evidence of oil leak on front of engine near oil filter housing
-Power rear hatch has issues opening and closing
-No Distronic or cooled seats

With what I found and how it drove I decided to put in an offer and after some back and forth it was accepted I drove it back to Calgary, nothing came up on the drive back and I was actually excited about it. Once back in town I had a reputable shop do a diagnosis and inspection on it and they effectively confirmed the brakes, the rad fan control module resistor, recommended replacement of oil filter housing, and not surprisingly power train fluid change( I had already done the oil), and rad has a minor leak. With this information in my hands I quickly got to ordering parts, the R class shares a substantial amount of hardware and electronics with the ML(W164) and GL(X164) class so it wasn't all that bad sourcing good quality parts for reasonable prices once I got to cross referencing part numbers etc.
-Had a local shop do the fluid changes(front/rear diff, transfer case, coolant flush/change, and transmission)
-Installed new pads/rotors front and back(also replaced wear sensors)
-Replaced air filters(they weren't terrible, preventative)
-Replaced thermostat(Have to remove it to replace oil filter/cooler housing, so done as a preventative)
-Replaced oil filter housing/oil cooler(gasket was in bad shape on this, replaced entire unit instead of just the gaskets as was recommended by the shop that did the inspection)
-Replaced radiator(pretty hard to complain about a new rad from a reputable Canadian company costing $180 shipped to your door)
-Replaced rad fan with one from a local R350 equipped with the 3.5l v6 M272(a bit bigger design than the stock R550 fan but it stills fits fine with a little finesse to get it in place)
-Managed to get the hatch to operate how its supposed by positioning it in its fully open state and using the fob/button on bottom of door to open/close it. The power lift gate on the Mercedes of this era were not designed to be manually opened and closed so when people do manually close them it can cause damage to them in various ways.

As the weather cooled down the wife mentioned that the heat wasn't very good, after a bit of running around I took it to a shop that was able to determine that the heater core was plugged. They flushed the heater core and found that the silica bag inside the coolant reservoir had ruptured sending the beads throughout the heating system plugging the heater core. They managed to clear the core and get a reasonable amount of flow through the core but recommended I take it to another shop that would have proper equipment for the cooling system flush, I followed their recommendation and after a second coolant flush heat is no longer an issue.

The C4 Star Diagnostic System I ordered finally arrived and I begin familiarizing myself with it, performing tests on various modules and getting a good idea of what is going on and what has gone on with the vehicle, I don't intend on getting into anything overly crazy like programming with it I just more or less wanted it for its diagnostic capability, although there are a couple of tools out there that are cheaper like the iCarsoft MB II that are supposed to be very good.

A couple weeks go by and I notice the passenger side rear is sitting awfully low compared to the other 4 corners, I had read plenty about it and knew sooner or later I would have to deal with the Airmatic system, but damn so soon? Luckily the leak on the airbag is very minor/intermittent and the compressor is rarely operating when it needs to pump up the bag, a new Arnott airbag is ordered from RockAuto, about $197 shipped which based off what I've read is pretty damn good. The bag arrives after a couple days and only takes me about an hour to install and we are back in business, of course the bag that had failed is not a Mercedes unit but an old Arnott unit, and although Arnott offers a lifetime warranty on their products the warranty is not transferrable and you of course need the receipt of initial purchase to get the warranty replacement.

That leads us out of the repairs performed and into the "wants";
-Some minor aesthetic stuff(passenger rear taillight has a crack in it, small things)
-Ordered and received a new Android head unit to replace the Mercedes COMMAND unit with, just waiting on the MOST converter as the vehicle has the Harmon Kardon system which has fiber optic cables that do not plug directly into the android unit.
-Rear muffler delete; this is something I often hmm and haww about, I enjoy being able to silently move through traffic/cruise without making a big scene but after hearing a few M273's with minor exhaust mods done, they actually sound really good, and there are times I feel like I want to make a bit of noise. I was looking at the AMG rear diffuser and AMG quad tips awhile ago so we will see what happens.
-Custom tune; got in touch with a company that offers custom email tunes with their handheld unit, just started looking into this though.

12-19-2020, 09:31 PM
The new pads and rotors, exciting!

The backside of the oil filter housing/cooler

New tstat/housing installed

The old airbag

With the new winter wheels, I prefer the look of these more than the AMG ones I picked up before the snow hit

12-20-2020, 12:25 AM
Good on you for getting the car and doing a lot yourself.

Where did you get the C4 STAR?
Which Andoid unit did you order? I'm interested in getting one... just not sure which is better...
Is that a specific shop you take it to when it's not something you can do?

12-20-2020, 10:56 AM
Good on you for getting the car and doing a lot yourself.

Where did you get the C4 STAR?
Which Andoid unit did you order? I'm interested in getting one... just not sure which is better...
Is that a specific shop you take it to when it's not something you can do?


I got the C4 STAR from Alieexpress, seller is China FLYOBD Supplier Store, so far the unit works very well.

I also bought the new head unit from Seicane it was 70% off so nothing amazing but I did wire it up to run it and does look promising, I'll see what happens when everything else comes in for it.

My go to shop now is Raybern Motors, he was recommended to me by the guy I bought the rad fan off, so far I'm happy with his work and pricing and he appears quite knowledgeable with Mercedes as well as other euro car brands.

03-26-2021, 08:42 PM
Time for an update;

Ended up replacing the driver side front airbag, took a fair bit longer than the rear as it requires the strut to be removed(air bag sits on the strut where a coil/spring would be normally) and cost a bit more than the rear at $390(Arnott). Lowered the ride height as I had increased it about 11/4"over stock as the bag was leaking where the bag folds at the bottom and with the leak now on the vertical portion of the bag it was no longer leaking allowing time for the new bag to arrive and less wear on the compressor.

Also did the rear muffler delete(vid to come)

EDIT: Still haven't put the new head unit in as I'm waiting on a fiber optic MOST converter to arrive, the first one I ordered from Aliexpress ended up never arriving and I had to dispute it and get my money back.

04-04-2021, 12:20 PM
Rear muffler delete done
Noise clips: