aeb28

2004 SL600 5.5l v12 Bi-Turbo.

Something on the front driver's side (left) is going out and I am having a hard time determining what it is exactly. It is located almost directly below where the coolant hose attaches to the radiator, just above the lower access panel. It is a cylindrical object about 4-5 inches long and a few inches in diameter, it has one plug in the rear. It is hard to tell exactly, but it seems 1" hoses connect to it. I suspected they were coolant hoses, but they seemed much cooler to the touch than what I know for a fact are coolant hoses.

I had a very small coolant leak from the top radiator hose a while back, and it may have leaked some coolant on whatever this part is since it sits about 1.5 feet below it.

The sound like a bearing going out that is intermittent, and typically only starts after the vehicle has come up to temperature. It is not like a belt tension pulley (very loud and continuous), but sounds more like if you have ever heard a small blower fan motor going out. It almost sounds like a very old-fashioned car horn. I have a boat-bilge fan go out a while back, totally unrelated to this other than the fact it sounded very similar. I have gotten no check engine lights except for an occasional ABC light, which I believe is unrelated. The sound will come and go seemingly at random for a minute or two while the car is warmed up, and I have experienced no other symptoms other than an obnoxious sound so far.


I am having a very difficult time even figuring out what system this part belongs to, let alone what it is/does. The only part number I can located without tearing things apart is a bracket that it mounts to which is A230 504 04 40

Would like to avoid taking it in at all costs, nearest reliable dealership is about 6 hours each way. I have a Mercedes specific code reader, I have not found anything suspicious.

Racin_fool

It's probably the auxilary pump for the charge air cooling system. I've replaced a few of them over the years and they also sound like what you are describing for noises. I can probably find a part number for you for that pump if you post up the VIN

As for your ABC light, check the fluid levels in the reservoirs. Does the light come on while going over bumps (like speed bumps or driveways) or just while you are out driving around on normal flat roads?

aeb28

Thank you Racin_fool, not really comfortable posting the VIN here but I will start looking into the aux charge air cooling pump. How involved was the replacement, and how impactful will it be if it suddenly goes out (ie. will my wife get stranded somewhere if I do not get on this right now)?

As for the ABC, I have a very small/slow leak at the pump itself. Only on the ABC side, power steering has had no problems. That has caused the light to go on in the past due to the level getting a bit low, but adding about 1/5th of a quart over the last 2 years has kept it where it should be. The ABC light comes on at random about once every 15-20 drives (drive about 10-20 minutes at a time over a month or so). Sometimes comes on when I pull out of the garage, sometimes while driving, haven't noticed a pattern. Will double check codes sometime this week.

Rudeney

FYI, posting your VIN publicly is not a big deal. Most websites where cars are listed for sale (ebay, AutoTrader, CarFax, KBB,) require the VIN to be posted. You can't get information about the owner or anything nefarious like that.

ItalianJoe1

Is your intercooler system full and bled properly? If the pump has air in it, it makes a growling noise akin to a bearing failing.

aeb28

I have been doing some searching around this forum, I had thought the coolant shared a circuit with the intercooler. Apparently this is not the case with SL and AMGs. This vehicle is an SL600 with the SL500 AMG package from the factory. I suspect then the intercooler has its own circuit. I will check it when I have a chance.

What would be the correct procedure to bleed the Intercooler circuit if that is the case? I would make sense that could be my problem. I read that pump turns on at 47oC IAT and pump turns off at 35oC IAT. Would explain the intermittent nature of the sound.

ItalianJoe1

It's a split system on all the v12s.

The factory bleeding procedure uses a low vacuum siphon system, and is quite terrible honestly. There are some members on here who have written up better methods using an actual vacuum pump. It has to be vacuum filled as the inlet/outlet of the heat exchanger are not at the top, so it gets air-locked. It took me a long time to get all the air out of mine without having a strong vacuum pump, the next time I take it apart, I'll be using a strong a/c vacuum pump to remove the air.

aeb28

Thank you for that info. I do have a AC vacuum pump, not really sure exactly what would be the best way to pull a good vacuum on it. Maybe I would attach it where the cooling line comes into the intake manifolds? For now I think I will just try to add some coolant to it.

Does it need to be topped off to the pressure relief cap? I don't see a way to check the fluid level. I see a place to attach a line for an overflow reservoir, but no reservoir itself. I see a lot of people adding them aftermarket on this forum it seems. I am assuming it uses the same OEM mercedes coolant?

ItalianJoe1

Yes, best thing is to attach to the bleeder ports on the lines, pull from them and feed back in using a T fitting, I like to cycle the pump a little bit to get closer, then re-run the vacuum/fill cycle, until you only get clean clear coolant coming out.

It should be basically full.

The lack of an overflow is a retarded move by MB, it needs the overflow as the system functions just like a radiator, and without it, it just draws air back in afterwards, which is retarded. Add a bottle, or accept the fact that it will always keep getting air in it.

Yes same blue coolant as the engine, I run a fairly high percentage of water in it, with just a little coolant, but I don't get freezing temps here. The system is low pressure/temperature in theory, so the coolant concentration doesn't do much other than protect things. Very important to have the pump working properly though, if not it will boil the stationary coolant right out. I have mine wired to run the pump anytime the engine is running, keeps the intercoolers cooler to the touch for sure.

aeb28

Thank you, knock on wood I have resolved it. My HVAC manifolds fit perfectly on the top of both manifolds. I topped off the system with distilled water (about 1/2 cup) then pulled a vacuum with an HVAC evacuation pump. I pulled it down as far as I could without pulling coolant through the sight glass.