I recently had the hoses changed on my 560SEC.   I was originally planning to do this job myself, but when I inspected the hoses under the car it seemed apparent they had not been changed since the car was imported from the UK in 2005.   After seeing this, I decided no to tackle this job myself and I’m glad I didn’t as the old hoses put up a good fight.    I figured since the 300SE was an Australian delivered car, the job would be much easier.

W126 brake hose replacement requires different hoses depending on the model.   Based on my 86 300SE and 87 560SEC and SEL, these were the required hoses.

300SE

Front: 129 428 00 35

Rear: 126 428 03 35

560SEL/SEC

Front: 129 428 00 35

Rear: 126 428 01 35

I haven’t looked but I suspect the rear hose difference on the 560 models is due to the anti-squat suspension geometry.    I found that the attachments to the caliper were easy to remove, but I was only able to get one of the connections to the brake hard lines off easily.   Even after letting the other ones repeatedly soak in penetrating oil, they still wouldn’t move.   I was using the correct flare nut spanners but I still couldn’t get them to budge.

In the end I had a mechanic from up the road help me and we only got them off with vice grips.   This is not ideal, but the only way to get them off.    Cutting open the old hoses didn’t show any restrictions, but they were very hard and were starting to get some minor cracking on the outside.    I think next time I will not tackle W126 brake hose replacement myself and just send the car into a mechanic.

With the new hoses installed, the next step was to bleed the brakes.   I had bought a new vacuum bleeder a few months ago and this would have been its first use.

The power bleeder is quite easy to use, however I ran into another problem.   I couldn’t get my system to hold pressure.  At first I thought it was just a minor leak from the cap.   It turns out the rubber grommets on top of the housing for the fluid level were leaking quite badly and fluid poured out when I tried to bleed the brakes.    I’ve ordered a new set of grommets but also a new fluid reservoir in case there are more leaks.

As so many W126 parts are going NLA as Mercedes-Benz loses interest in the model, it will be good to have one on the shelf even if I don’t use it today.   The new housing is an upgraded part and it looks like it doesn’t need the rubber grommets.

In the short time I used the bleeder before I noticed the leak, I found it quite easy to use – the best system for bleeding brakes I’ve used so far.  I am confident it will be quite a simple job once I get the parts in I need.

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The first thing I found was that it was quite hard to remove the old rotors.   Not only were the rotors rusted to the hubs, but the old rotors was catching on the handbrake shoes.   I was able to turn the wheel by hand, but I think it was dragging a little.   It took a couple of huge whacks to free the rust on the hubs, and a lot of pulling to get them over the shoes.

I used a wire wheel to clean off some of the rust on the surface.  After that I applied some copper grease to stop it rusting in place next time.     Putting on the new rotors was almost impossible.   The handbrake shoes fouled on it quite badly and I had to adjust the handbrake shoes quite a lot.  Not just a few teeth, but probably a full turn.   I wonder if this was also part of the dragging?     Before I had adjusted the handbrake, I could not turn the new rotor at all even with two lug bolts at a long pry bar.     After the cleaning the braking surfaces, I was able to fit the new rotor.

At this point I also bent and fitted the new hard line I had damaged in part 1.   The lines do not come pre-bent and I so purchased a bending tool.  It is important to do more than minor bends with the tool as you can kink the lines and impair brake function.

The new 450SLC rear caliper fitted quite well, but there was a problem.   The new caliper had a slightly different place for the brake line than the old one.   Other than that, it was almost identical.      I did some research and found the source of the problem.

For one reason or another, Mercedes-Benz decided not to equip North American 450SLCs with the anti-squat rear suspension.   I imagine the decisions was based on the lower power output of those engines.   It is a strange decision though, as while the power is lower, there is still plenty of torque that is the main cause of the squat on acceleration.    Not equipping the cars with this suspension also meant a different arrangement for the brakes.   On the rest of world SLCs, there is a brake hose that connects the hard line from the car to another hard line that brings it to the 450SLC rear caliper at the front of the rotor.   This is the system that my car is equipped with.    On the North American cars (and the 350SLC, 280SLC etc), there is the normal arrangement of a hose from the hard line right into the caliper.

This is why the brake hoses I purchased first time around had a male/female arrangement and these new calipers had a slightly different arrangement for the brake hose.   The brake calipers I have, are part number 1234200583 and 1234200683.   The new correct brake calipers for my car have a 126 part number.   These calipers are far more expensive than the 123 part number 450SLC rear caliper.

On the passengers side I was able to get the hard line to connect to the caliper.   I am a bit concerned that it is very close to the bump stop.   On the drivers side, I was not able to bend it the way I wanted and it rubs on the bump stop.   I don’t think this is very safe as a large bump could damage the line.

From looking at the caliper, I think a new (slightly longer) line could be fabricated that clears the bump stop and connects to the caliper.   I don’t really have the ability or tools to do this, so I will take the car to a brake specialist.  This should be the best way forward rather than getting a new set of calipers.   I was also unable to get the hose off the drivers side, so will have them do that at the same time.  What they found and the w9ork they did is covered in part 3.

I bled the brakes, first with my vacuum pump and then had a friend help me bleed the brakes further with the traditional method.   There must be a small amount of air left in the system as the pedal is a little spongy.  I didn’t re-bleed as when the new lines are fabricated they will need to bleed in any case.

I also tested the handbrake and it is able to stop the car and is not dragging.

My final task was to fit my new MBCNSW grille badge.   I put it on the opposite side as my Mercedes high mileage badge.   Looks pretty good.

For what should be a simple job, this one has taken a long time.   I’ve probably spent more than two full days on it.

The post 450SLC Dragging rear brakes – part 2 appeared first on Classic Jalopy.

Last time I took the car on a longer drive, the noise was getting worse, and I noticed after I returned the rear wheels were hot to the touch.   Too hot to touch.    I realized that my noise had been dragging rear brakes all along.

Both sides were hot the touch, so it wasn’t just one bad caliper.    I went back and checked my maintenance records for the car and saw that the brake hoses were last changed in 2003 when I purchased the car, and one of the hoses changed again about two years after that.  16 years is about all the life that can be expected form these hoses, so I decided to replace them.   I also thought it would make sense to replace the master cylinder, as it is more likely to be causing dragging rear brakes on both sides.     Unlike when I had a similar problem with the Jag, the brakes were not locked hard on, just dragging.

Today, I did some further inspections.   I removed the rear wheels and looked at the condition of the calipers, pads and rotors.

The rotors were still within the spec from the workshop manual.   The hoses looked old, and not particularly flexible.   It was also quite hard to push in one of the pistons to remove the pads, even with caliper disconnected from the brake system.     This led me to remove the caliper for further inspection.

It was the same story on the other side.   Removal of the calipers showed that the heat had made the seal rather crispy.

These calipers can be rebuilt.  I may just replace them as the pistons don’t look great and the heat may have done other damage.   I am not sure if it is to do with the heat, or the 16 years on the car, but I found it almost impossible to remove the flexible hoses.  Even using the flare nut wrenches I managed to damage one of my hard lines.   I have liberally soaked the other side in penetrant to see if that will help when I get the new calipers.

While I was at it, I also replaced the master cylinder.    The brake fluid looked pretty good from a visual inspection.   I was quite surprised how much vile black fluid there was in the rear chamber of the reservoir once I removed it.   This is even after a flush about 18-24 months ago.

Some stained old shirts helped me protect the paintwork from the brake fluid.   In contrast with the flexible hoses in the rear, the lines were easy to remove from the master.   The coolant expansion tank needs to be unscrewed to get the master out. It does not have to move very far, so it does not need to be emptied.

Next steps are to remove and replace the hoses from the rear, fit new calipers to the rear and replace the front hoses while I am at it.   At this point I do not have any indication that the front calipers need to be replaced or rebuilt.  This is covered in part 2 and part 3.

The post 450SLC Dragging rear brakes – part 1 appeared first on Classic Jalopy.

• New Spark plugs
• Transmission fluid and filter
• Rear end fluid change
• Brake fluid flush

We used NGK spark plugs as they offer non-resistor plugs that are easy to find.   The original spec for these cars called for non-resistor spark plugs, which are much harder to find now.   The plugs that were already in there were Beru and in reasonably good condition.

For the transmission, we changed the fluid, filter and pan gasket, but didn’t drain the torque converter.   When doing this it is important to not over tighten the pan and warp it and ensure that no debris is allowed to get inside the transmission.

The brake fluid was was much easier using a vacuum pump to make sure that all the old fluid was removed from the lines.

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