With a leaking oil cooler seal on my M273 I changed that out as well as the power steering reservoir and with some time on my hands, This is the exact sam.procedure for the V6 M272 as are the parts.


Old Power Steering O Ring

Cleaned internals of Oil Cooler

Rear of New reservoir. Small yellow plugged inlet is return line. Large one is to the pump.

Power Steering Reservoir O ring Part No.

MB Part Number Reservoir

circlip at rear of Reservoir

MB Logo sctratched out of Lemforder Part

O ring Part Number

Elring Seal Part No.

New Seal (top) v old seal

New seal (left) v old seal tbickness
I thought I'd detail it here in case it's useful for others. I know this is already addressed in other posts but it's a money saving job for anyone that I reckon the stealership would hit you up for about $1500.

Tools
Torx and etorx set 3/8 inch
3/8 inch small ratchet
stubby (2 inch?) socket extension
Torque Wrench
Clip Puller
Pliers
Part cleaner
Pump or syphon to remove old fluid
Part Number are shown below

Note: This is to change the oil cooler seal without removing the oil filter housing (which is a much bigger job) so the power steering reservoir needs to come off first.

This is what I did;

Removed engine cover and top radiator hose at the thermostat and folded hose back out of the way
Drained the power steering reservoir with a pump or you could let it drain out of the return line at the back of the reservoir.
Remove the return line (small diameter rubber hose)
Remove the circlip at the back of the reservoir. I got it out with a pick. Cpuldnt get enough purchase on it with long nose pliers. It's a tight fit so the pick gave me the leverage.
There are 3 bolts that hold the reservoir to the block. Loosen those and pull the reservoir toward the radiator.

I removed the lower camshaft sensor to provide some extra room to access the cooler screws.

Now you can get at the oil cooler. 5 x torx nuts and it's off. Clean the grooves that hold the gasket and install gasket. I cleaned the surface of the cooler with a nylon sponge and soaked it in part cleaner to flush it before hot water and soap and allowed to dry.

The new seal was an Elring part (see below).

I'd done this job previously and could only find a Chinese branded seal - that's why it failed inside 50,000km.

Torque Setting for the oil cooler screws are 12Nm

POWER STEERING PUMP INSTALLATION

I emoved the old seal from the inlet to the power steering pump and cleaned the housing. Install a new O ring - it's flatter than the usual O rings and I added some steering fluid to give a smooth seal on the reservoir.

I removed he large yellow cap from the back of the new reservoir (left the small one in for now) and reattached it with the torx bits. There are 3 bolts. Start with the one that's deepest and closest to the thermostat, then the lower bolt and then the upper bolt. You'll have to use some force to get it seated with the new seal. Bolt Torque is 9Nm noting my original one was loose when I removed it so maybe give it a bit more.

Push the circlip back on at the rear. Reinstall the camshaft sensor. and the the radiator hose making sure to put the clip on the thermostat housing before you push the hose back in.

Put a small juice bottle on the end of the return line. This way you'll minimise contamination of the new reservoir with old fluid. Keep the yellow plug in the return line entry on the back of the reservoir or all your new fluid will spill to the floor.

Fill the reservoir and with the front wheels in the air if possible, Turn from lock to lock about 6 times. DO NOT START THE ENGINE WHEN DOING THIS. It's really tight but it's the only way to do it.

Drain the juice bottle and do it all again 4-5 times making sure you keep the fluid up. This system takes about 1 Litre so you'll need about 1.5 ltrs to flush it properly.

Once it flowed clean fluid, I reinstalled the return line and tightened. Drove amd checked the fluid a few times as well as motor oil and coolant.

It's tight under the bonnet on the V8 but would be much easier on the V6. A good small 3/8 ratchet and short stubby extension are required.

The reservoir I bought was Lemforder which is the original part. Even had the MB Part Number on it with the MB logo scratched out - see photos.

Time - about 2 hours.

 

Agreed on the power steering reservoir. I tried to flush my power steering system before changing the reservoir and the fluid would not come clean, not matter how many times we did a drain and fill from the reservoir. So I changed the reservoir and voila, we were able to get the system running clean in no time. 👍

 

its a good time to replace the oil filter housing seal together at the same time...

 

Yes, I did that the first time I replaced the oil cooler seal but that time I had a genuine part for the housing as opposed to the cheap Chinese part I had for the oil cooler. It's a much bigger job.

 

I replaced the oil filter housing seal and oil cooler seal together with parts from rockauto and Fcpeuro, 3 year 30k miles ago. so far so good. I kind of enjoy working on the M273.

 

Agree. It's a good engine and it looks intimidating to work on at first and there's always some MB madness occasionally but for me it the right blend of challenge and convention.