Richard888

So before I go in and replace the pump, just wondering how far I need to go. I've read other posts about PS, and although my symptom is a whining pump, my steering feels fine. No stiffness or inconsistencies with the feel. I've filled up the reservoir, which was empty, with CHF Pentocin 11S green can, but it still whines and no leaks on the ground. I added the pentocin, jacked the front end and turned the wheel back and forth a number of times, started the car and turned the wheel, and drove it around the block a few times. Whine is quieter, but still noticeable. More noticeable when parked and at idle than under acceleration. Maybe because of road noise. In any case, I see people who made the whine go away by just changing the reservoir which is much easier to replace than the pump itself. I'm assuming since the reservoir isn't leaking it's the pump, so my question is, shouldn't the steering feel different or can is it the pump even though there is no steering problem? Also, CHF pentocin should be fine, right? Wishful thinking to think it's a clogged filter on the reservoir? Thanks!

fkong777

top off power steering fluid. Turn the wheel lock to lock 2 to 3 cycle.

maxusa

I just replaced a whining PS pump, and can tell you that your diagnosis is likely correct. How many miles do you have on this PS pump? I started hearing my unit at 55K miles and finally replaced at 79K miles. Quiet and smooth as silk. Regarding the PS fluid, check the Mercedes approved list 345.0 on BeVo. I used Pentosin CHF 11S, p/n 1405116. Buy half a liter more than needed to flush the system.

https://bevo.mercedes-benz.com/

Richard888

Car has 135k miles. I topped the fluid, bled the system.
Looks like I'll just replace the pump and the reservoir. Anyone have any issues using the CHF pentosin?

Thanks!

Richard888

Well, the removal of the reservoir/pump was a little pain but installing the new reservoir and pump was a lot easier. However, car still makes that whining sound from the pump area. Fluid level remains constant. Turned on to accessory, turned wheel back and forth a dozen times. Started the car and turned wheel many times back and forth stop to stop. I bought a remanufactured Bosch pump, OEM resevoir, filled with OEM fluid. Car is quiet when idle, but makes noise when pressing accelerator parked and driving. Steering wheel turns nice and effortless.

Tempted to just buy another pump and try again. Any thoughts?

Richard888

Quick update... Before I went to go buy another power steering pump, I wanted to check to see if the pulley spun without noise. Took off the belt and it turned nice and smooth with very little friction. However, the pulley underneath made a grinding noise that I could actually feel when I spun that particular pulley. It appears it is the AC compressor. I didn't even think of that since the AC works fine. Time to search how to replace that thing. Stay tuned...

Richard888

To save time, I bought a shorter serpentine belt and by passed the AC compressor. A 2335mm belt did the trick. Definitely it was the AC compressor because the car isn't whining.

2 things... I'm assuming a 2010 gl450 is a clutchless ac compressor and where can I find the appropriate bearing or pulley assembly?