First off, I noticed my SL600 ABC Expansion hose weeping a bit which would accumulate about a teaspoon of oil over the period of a week or so. It was clear this could become a huge problem soon so I looked at the routing and access and decided this should be easy. This project is probably very easy on the V8 cars, but as I began I found this to be more frustrating than it appeared. You can review my post and decide what action you want to take, but creating more access to the working areas is essential for getting this done with minimal pain. Removing the hose will not drain your reservoir as long as you keep the cap on and work quickly.

Tools:
Lift or jack & jack stands
Various sockets, ratchets and wrench lengths
Set of E-Torx
Torque Wrench
Flexible Ratcheting 17 & 19 MM (I used Tekton

WRN76113

WRN76113

) * I felt this was a must to accomplish the work.

Steps:
1. Lift Car - I used QuickJacks, but car should be all in air to relieve pressure
2. Remove paneling under engine, It is helpful to remove the side panels in front of wheels for more access.
3. Drain Main Circuit Coolant
4. Disconnect Battery
5. Remove Air Intake Elbows
6. Remove Transmission Cooler Line to Radiator (Passenger Side Hard Line to Radiator)
7. Remove fan shroud fasteners on left and right side and detach electrical harness by pulling upward.
8. Lift out fan shroud and set it aside. Place big piece of cardboard over the radiator as to not to damage fins.
9. Detach upper radiator hose from engine only, bend it out of the way when detached toward the headlight.
10. Remove Accessory Belt. Take a photo of routing.
11. Remove ABC Pulley by loosening three fasteners.
12. Remove the fastener on the expansion hose lower bracket which will unbind hoses.
13. Optional: Remove the fastener on the low pressure coolant circuit down pipe that holds it in position. Adjacent to the AC Compressor. This allows some wiggle room.
14. Optional: For bigger hands, consider unscrewing the fasteners to the AC Compressor so that the compressor lowers by about a half inch. There are three of them and that allowed my hands and wrenches a bit more space.
15. Detach expansion hose from return line connection, in front of passenger wheel location. Catch fluid and seal off hose from contaminants (I used a ziplock bag and zip tie).
16, Reach under the ABC pump and feel the orientation of the Banjo bolt. Notice is it on an angle pointed to the fender. Feeling the gaps around this will ensure you know how to get the new one in by feel.
17. Unscrew the banjo bolt and catch oil with microfiber or rag.
18. Snake out the hose through the minimal gaps you have.

At this point I would say just reverse order is possible, but that is a half truth. Getting that Banjo bolt in place by feel without removing the pump is tricky, real tricky. The new hose is stiff and will work against you at times. Similarly, if you rush it the banjo bolt will fall through the hose connections and drop inside the engine bay. Also the alignment of hoses will dictate the angle that the banjo is positioned (this is hard to describe but you may see what I mean when you begin working on it). So I will talk you through what worked for me.

19. Keep the red cap on top of the banjo until you snake it up to the abc pump. This will keep hoses aligned and contaminants out of the hose.
20. Bend the hoses outward to the front of the ABC pump to unthread the red cap on banjo bolt. Keep your fingers on that banjo bolt and dont let it fall through.
21. Have a second set of hands under the car holding the hoses off the ground but pushing the direction of driver side while you start to wrestle the hose and bolt back into place. The hoses have bends in the metal parts but the rubber will fight you every step of the way because you are cramming them into gaps of less than an inch with all sorts of combatting pressures.
22. Get your second set of hands to sort of push and twist until you feel like you have a perfect alignment on the bolt and it begins to thread. (Trial and error).
23. Once threading begins use that ratcheting wrench to get it on and snugged down. Torque is 40nm so it is pretty firm but not crazy. Do not over tighten because that could be the end of your pump.

Step 22 was the worst of it. After that you just need to reassemble the stuff in reverse order and make sure to prime your pump and rodeo out the air.

I know photos would be helpful but there really isn't much to see since there is no space in the engine bay. It literally would be photos of things you can not see for yourself but only feel with finger tips. You may ask why did I not remove the entire ABC pump, well because there are even more things to remove for that to happen including ABC reservoir and there is a etorx bolt on the back side of the pump which may have needed a long etorx wrench that ratcheted or something similar.

Was it worth the DIY on this one, Yes but I underestimated the frustration level with the banjo bolt and tried to cut a corner or two with the removal of items.

I hope this helps someone in the future.

 

Yeah, that double banjo setup will defininitely test your patience. Went through this about two years ago when my car developed a leak at the banjo bolt, had to disassemble it to replace the 3 o-ring seals.

I did it mostly as you did, with the pump in place as well as the reservoir and bracket. I didn't have an extra pair of hands around to help, so I used zip ties and baling wire to hold the lines somewhat in place while I wrested with getting the two banjo fittings lined up, getting the banjo bolt through them, and getting the banjo bolt started. All the while wondering why the hell didn't Mercedes just make both the expansion hose and the pressure hose a single part with a single banjo fitting. Seems like a double/stacked banjo like this on a high pressure system is an invitation for failure.

I didn't remove the transmission cooler line, but I did completely remove the upper radiator hose. One or the other has to be removed to get the fan shroud out, so I figured getting the radiator hose completely out of the way for increased access to the tandem pump area might be helpful. I also felt like I'd rather drain the radiator and refill with coolant afterwards than mess with transmission fluid.

You didn't mention that once you finally get that banjo bolt started, allow about 30 minutes to get it tightened because access is so tight you can only get 2-3 clicks per ratchet stroke Getting that bolt started took me close to 4 hours of trying before success. And I've got -extensive- experience doing this kind of "by feel" stuff, having worked on all kinds of questionable engine swaps in the past, V8 Vegas, Big-Block 1st Gen Camaros, etc......

I started having other issues with ABC about 10 months ago, so I've converted to coilovers now (VVK). Initially I recirculated the pump, but I'm currently getting the car set up with a power steering only pump using factory parts that are used on the G65, SL65 Black Series, and some other V12 models that weren't equipped with ABC. It's going to work perfectly, just having to do some minor fabrication for the pressure and suction lines. I'll be starting a thread on this soon with part numbers, pictures, fabrication details, etc.

For this current project I have removed the ABC and PS reservoirs along with the big plate/bracket that holds them. Also removed the LH coil pack so I can see and access as much of the tandem pump area as possible. You're right about the rear tandem pump mount, even with all the stuff I've removed there's no clearance to get a socket+ratchet on it, the turbo inlet is still in the way so you'll need a etorx wrench for that rear bolt. Also, having all this stuff out of the way let's you have a nice clear view of the banjo bolt from the side, but because of the angle that it threads into the pump it doesn't really improve access to it at all, you still have to get at it from the front of the car.

 

Bruce,


All very true, "You didn't mention that once you finally get that banjo bolt started, allow about 30 minutes to get it tightened".... I could have mentioned this but it felt like a darn victory lap after the "Getting that bolt started took me close to 4 hours of trying before success" like you said. Folks, for those of you that have not experienced the banjo bolt, it is barely tapered which means you need to align this thing nearly perfect inverted on an angle. I would say there is no margin of error for alignment because I bet I spent more than four hours trying to get it threaded the first time before the second set of hands helped. Once the second set of hands relieved some of the strain of the hoses, I was able to articulate the banjo bolt more freely and get it on there.

Regarding the Green O-Rings, when you order up the expansion hose, buy a few extra of these because who knows if you damage these things while trying to get it into position. They are only a couple bucks and once you have your car disassembled, you probably will want to finish the job without running out for more parts. They are not fragile but there are lots of ways you can damage them before installation.

Bruce, I am glad you confirmed the access on the e-torx behind the pump and the lack of access from the side of the banjo bolt. All throughout this process, I kept thinking I was missing a shortcut or a better path to access some of these items. I suspect there is not.

I will try do do a few more write-ups on common problems I think we all face including some PSE work I have been dealing with. Next on the project list is replacing the brakes for something with less brake dust and paying someone to change out the engine mounts.

 

I've determined that my 2005 SL600 is leaking ABC fluid. It is the tiniest of leaks and it is emanating from the banjo bolt area. Hard to see but appears to be weeping from the space between the two hoses that the banjo bolt holds together. A spot with some kind of seal or o-ring between the hoses. The expansion hose ( part A2303209553) was replaced by an Indy shop about 3 years back. It sourced from a Mercedes dealership. The hoses arent leaking.

Found this thread while working out a possible solution and I have a few questions...

1. Is it possible to get a torque wrench with socket on that banjo bolt by removing the radiator hose and/or entire radiator for space, serpentine belt and possibly somemother items? I was able to get a stubby flex head 19mm box end wrench on it in an attempt to tighten it down a few months ago when I replaced the radiator. Not sure if I got it up to torque (30lb ft). Felt pretty tight but now that it's leaking again I'd like to actually torque it down if I can. I've had the radiator out a couple of times so I can do that work with my eyes closed. If I've got to do most if the work involved in removing the entire hose and then dicking around for hours getting that banjo bolt inserted and threaded, I'd defer to having the shop do it. Time is money so to speak.

2. I saw in the thread a mention of a set of green o-rings (three?) or seals that are in place at the banjo bolt area. I have a sneaking suspicion that they might be the problem, not a un-torqued bolt. Does anyone know what these seals are called, MB part number(s), etc. I'd rather not replace the entire hose if I can source these seals. Maybe the removal of the entire hose wouldn't be necessary juat to replace those seals? Also, would the banjo bolt be easier to reinstall after putting only new seals in? You know, because the expansion hoses have developed a shape "memory" having already been bent to fit and installed in the car for 3 years.

Any thoughts would be appreciated. Wild azzed guesses need not apply as I've got that department covered already! 🤣

 

The banjo bolt does not have o-rings, it has crush washers, typically copper or aluminum. I have replaced them when the engine was out. I don't know the MB part number as I just used generic ones from a kit of many sizes.
Heck, the banjo bolt is a pain with the engine out; cannot imagine the difficulty when installed in a car. I recall tightening the bolt to more than 30lb-ft, probably more in the 40-45 range by feel.

EDIT: @TBAZ says the MB parts are actually green o-rings, but that is not what I had on my 29K engine and I went with crush washers.

 

ShoeBoote

1. I was not able to get a torque wrench on it (the depth down and inward was too significant). I suspect you could create a homemade tool to reach the banjo using a 19mm attached to an extension bar (cut and welded), but probably not worth it. Exact torque was not necessary, a firm 1/4 turn is all you need to seal this (practice on a different bolt to get the feel of 40nm).

2. The o-rings that in the original post are the following part number 028-997-65-48 and can be bought for about $1.25 a piece from local MB dealer. Yes these are actually rubberized green o-rings and not crush washers, I bought extra in case I damaged any of them on install. Even a small flat spot or nick will produce you all sorts of problems here. As far as changing these out without removing the entire hose, yeah I think you can bend it back a bit to open working space and replace the o-rings. Note that the middle one will require removing the banjo bolt to separate the two hoses (these o-rings are sandwiched between each surface). The worn in hose (memory) should install easier than a fresh one.....

Hope this helps you out, I tried to stay away from all speculation for you.

 

I bought when I did mine, and even cut about 1/2" off the end of the handle to get enough clearance to use it on that banjo bolt. I thought about skipping the torque wrench and just going for "feels very tight", but then I was uneasy due to the high pressure of the system, the difficulty of accessing the bolt again if I didn't go tight enough, and the risk of stripping the threads out of the aluminum pump housing if I went too far.

Mine had the green o-rings.

 

Mrvedit, I suspect there are variations in these hydraulic lines and the seals used (potentially there was a revision on the type of seal over time). What I am really saying is, I am no more right about this than the next guy; I am just sharing what I came across. Hopefully, we all keep these V12s running for another decade.

 

I was glad to be able to edit/correct my earlier post concerning the green o-rings. Unfortunately this forum only allows editing for 24 hours (or is it till midnight). AI systems read these posts and therefore often regurgitate false info.

I started rebuilding engines as a teenager; so 50+ years as a hobby mechanic. My retirement project has been to build/own several auto repair shops. This way I finally get my auto “fix”. Sometimes work on customer cars too despite having 8 mechanics.

Agree on keeping these V12 engines running. I still have the original 28,000 mile engine from my SL600. Bought a completely disassembled V12 AMG engine. May send block out for sleeve inserts as the factory coating wears out.

 

I can't remember if the replacement hose that was installed had crush rings or o-rings and I tossed the old hose they gave back to me before taking pictures of it.

 

Good idea with trying to get the feel for 30 lb ft of torque. I was able to get a small 19mm ratcheting box end on it. The banjo bolt was definately a bit loose. I could only get a click or two out of it each pull due to lack of space (radiator and sepentine belt off the car). Not sure if I had enough leverage to get the 30lbs of torque on that bolt. It felt pretty tight but that wrench had no leverage as it was real short. My tightening did solve the leak issue for a short time. After looking at the diassembly instructions I realize the pulley on the pump has 3 bolts holding it on. I wonder if taking that pulley off will allow enough clearance to get the longer ratcheting box end I bought on that banjo bolt.

I'll source those o-rings from Mercedes.

Thanks.

Two 19mm flex head ratcheting box end wrenches I sourced just to try to tighten the banjo bolt.


[QUOTE=TBAZ;9262765]ShoeBoote

1. I was not able to get a torque wrench on it (the depth down and inward was too significant). I suspect you could create a homemade tool to reach the banjo using a 19mm attached to an extension bar (cut and welded), but probably not worth it. Exact torque was not necessary, a firm 1/4 turn is all you need to seal this (practice on a different bolt to get the feel of 40nm).

2. The o-rings that in the original post are the following part number 028-997-65-48 and can be bought for about $1.25 a piece from local MB dealer. Yes these are actually rubberized green o-rings and not crush washers, I bought extra in case I damaged any of them on install. Even a small flat spot or nick will produce you all sorts of problems here. As far as changing these out without removing the entire hose, yeah I think you can bend it back a bit to open working space and replace the o-rings. Note that the middle one will require removing the banjo bolt to separate the two hoses (these o-rings are sandwiched between each surface). The worn in hose (memory) should install easier than a fresh one.....

Hope this helps you out, I tried to stay away from all speculation for you.

 

Interesting little tool. I definitely don't want to strip the aluminum housing. After tightening the loose banjo bolt a few months ago with a stubby ratcheting box end it is leaking again. I wonder if this is an issue related to not having it fastened down tight enough, bad o-rings or other issue. I saw that the pulley on the pump comes off after removing the three bolts holding it on. Do you recall doing this and if so doe sit create more room to swing a (longer) wrench (so to speak)?

 

I don't recall for sure if I removed the pulley, but I probably did since I was trying everything I could to gain more access space. Like you said, it's just three bolts that are easily accessed, so you might as well remove it - even if all you gain is a single ratchet click, it's worth it on this job

I'll measure the length of my torque wrench when I get home tonight. It's exactly as long as will fit in the available space.

I do remember that the limited access made it -very- hard to get the banjo bolt up to the torque spec.

 

This has been an ongoing issue for a while. I got the replacement hose from Mercedes back in 2023. I'd really like to know if it has the compression washers or the green o-rings. The leak appeared between the two hoses that the banjo bolt connects to the pump. There were little bits if greenish/blue material visible there. It's either jelled half dry pentosin or gasket material. I'd like to know which.

I've attached screenshots from my SDS showing diagrams and parts. The older hose and the green o-rings show a date of 03/2006. Not sure if that's a reference to parts being updated after that date or just the install up to that date on the original car. I never looked at the end of new hose I got in 2023. The banjo bolt end was somewhat sealed with a cap to keep debris out and I didnt screw with it.

During the course of troubleshooting I was able to get a mechanics endoscope in there to video the leak(s). Created the attached video to see if it jars anyone's memories (aka nightmares).


Hose, banjo bolt and washer.

References to the hose and o-rings with possible change dates.

Diagram that doesnt show any type of washers or o-rings.

 

The last picture and video didn't load on my last post. Here they are:

..

 

The overall length of my torque wrench is 9 inches. From the center of the socket holder to the end of the handle is 8.25.

I watched your video -- that green material you're seeing on the banjo fittings is the o-ring being forced out by system pressure. I have no doubt whatsoever that's what you're looking at, they're exactly that color.

This is a very high pressure system, much higher than typical power steering systems. If that banjo bolt was ever even slightly loose, those o-rings would be destroyed.

I suspect that the banjo bolt was not fully torqued when you had the expansion hose replaced, resulting in premature o-ring failure.

The center o-ring is fatally damaged. At this point the only way forward is disassembly for replacement of all three o-rings.

How many miles are on your car? There are other maintenance items you might want to consider that will affect how to proceed.

Edited to add - maybe it was properly torqued but the bolt backed out for other reasons. Maybe no liquid thread lock was applied, or threads weren't completely cleaned of ABC fluid before application of thread lock. Either way, the root cause is a terrible design by Mercedes. A stacked banjo fitting is a bad idea, made even worse by the fact that it's tightened into threaded aluminum. If it was tightened into a steel housing it could take much more torque, to an appropriate level for a 2500+ psi system.

IMO Mercedes should have used a single outlet hose leading to an intermediate block to split out to the two hoses using the same fittings that are used throughout the rest of the system.

 

Thanks for getting back to me on this. Good points. I was afraid it might be o-ring material. Makes sense that the middle o-ring has blown out. 2500+ psi and a little gap would allow for that. I also wonder if it was properly torqued but the differences in expansion of two different metals ( aluminum housing with a steel bolt in it), combined with the huge pressures in the system, attributed to a loosening of the bolt. I will say, back in August the banjo bolt was definitely pretty loose. The bolt was still in place but probably had zero torque on it. In August it left a puddle of ABC fluid when I parked it. Thought I had a hose blowout but that wasn't the case. In November I only noticed the drip when I removed the front plastic undercarriage shield on the bottom front of the car.

Just about 70K on my ride. I've done what I'll deem as preventive maintenance on the ABC: All accumulators, return accumulator, pulsation damper, replaced o-rings in both valve blocks. I've done 2 ABC flushes and filters in the last 40K miles I've owned the car. I figure alot of those components control pressure spikes so keeping everything freshy fresh equals less ABC line blowouts.

I try to stay on top of everything on this car before I have a problem get worse. I brought a MB scanner I keep in the trunk and a knockoff Star Diagnostic System that I use for deeper dives. The scanner I have in trunk has pinpointed problems I wasn't even aware of. Allows me to make fixes before they get out of hand.

I like to swing a wrench on just about anything that is in my wheelhouse. However, I'll take the car to a garage if the job looks to take an inordinate amount of time or is better left to those who possess a lift. Hence, the 2023 replacement of the high pressure hose with the banjo bolt when it was pissing ABC fluid. Wanted to get it done before it blew out. After reading up on that hose replacement, seeing all the comments about how it was a bear to do, that a second set of hands is beneficial (which I don't have), I finally opted to have that particular item done by an indy garage. The work held up for 2+ years. They do good work and I definitely would use their service again... maybe even for what looks like those green o-rings that apparently need replacement.

I will pick up that torque wrench on Amazon.

 

At 70K miles, I would consider doing the following -
Replace the ABC/PS tandem pump entirely.
New spark plugs with new insulator boots
Valve cover gaskets

At 70K, new plugs are recommended for the M275. Worn spark plug electrodes mean a wider gap, which make the coil packs work harder. The insulator boots also age and crack, which allows spark to short to the outer coil sleeve, causing misfires.

To replace the pump, the left side coil pack needs to come out. While it's entirely possible your current pump could last a good while longer, there have been plenty of accounts of ABC pumps needing replacement in the range of your current mileage. Removing/reinstalling the coil packs is not terribly difficult, but pulling them off of the spark plugs takes a lot of patience - the silicone spark plug boots usually have a pretty good grip, and you're pulling 12 of them all at once. The coil packs can be damaged if you apply either too much force or uneven force end-to-end, so overall you want to avoid removing/reinstalling coil packs unnecessarily.

The M275 makes a lot of heat, so it's pretty common to have rock-hard valve cover gaskets by 70K miles. It's common for them to develop slight oil leaks which accumulate in the spark plug holes, which can cause misfires and coil pack failure. Coil packs must come out to replace valve cover gaskets, so it's very common to do VC gaskets/spark plugs/insulators all at once.

 

Did the plugs when I had to replace the right side coil pack. Did the 12 plugs on the right side before I got the rebuilt pack back. Did the left 12 plugs a few months later when I was waiting for a new radiator to arrive. Did the leaky radiator too - that's when I noticed the banjo bolt was leaking yet again. 🤣 Same with the voltage regulator box which has also be replaced.

I'm going to hold off on the tandem pump at this point. My understanding is it's a very expensive part. I'd consider possibly going to coil overs with sway bars in lieu of that once I cost everything out.

Not sure how difficult the valve cover gaskets are. No leaks that I know of... yet.

I was considering having that Indy shop do a tranny fluid/filter change. I can do it but that mess is better left in a shop. I don't relish getting my phat azz under the car, taking a tranny fluid bath and then scrubbing my garage floor to remove all of the fluid that will somehow miss the pan.

Lets see, rear brakes and rotors - done.

Water pump for intercooler - done. Had to make a Rube Goldberg style vacuum "tool" for that job, no other way to get the air out of that system than by vacuuming it.

Cheap plastic transmission selector lever - replaced with aftermarket aluminum version. If you haven't done this you better consider it. Once the plastic one breaks you will be stuck in park with no manual override. No ability to do the repair as you need to get it out of park to get the shifter out of the car.

So far I havent had a motor mount issue. My understanding is putting replacement motor mounts in on the V12 is a bear. That's why I'll never do any hole shots with this car.

 

Sounds like you are taking very good care of your SL600.
I wonder if replacing the o-rings on the banjo bolt might be even harder on the V12 engine than the V8 engine.
I didn't think the ABC/PS tandem pump was even available new anymore. Only rebuilt units often of questionable life expectancy.
I'm pretty sure replacing the motor mounts in an SL600/65 requires removing the entire subframe; the mounting bolts are too close to the turbos. So close that the turbo cooling lines on the SL have a tighter design than on a CL600/65. Even with engine out and turbo cooling line removed, I had to remove the motor mount brackets from the engine and their three bolts are completely hidden behind the turbos. I replaced my motor mounts when swapping engines, and compared to the new ones they had compressed a lot by only 28,000 miles and 19 years.

 

Yeah, motor mount replacement on the SL600 is supposed to be diabolical. From what I've read, you are right about the subframe. The thought of that is a good thing as it keeps me from doing any Hollywood starts from traffic lights. 🤣