Gary's Garage - The 500E Scramble for Amelia

Looking back over my Gary’s Garage articles, I see I have probably written more about my 1992 500E than any other car. I guess it’s to be expected for a 228,000 mile car, it’s a great car but high mileage and it’s a little more complex than most of the W124s.  My first Mercedes was a W124 (a 93 400E) and they are probably my favorite chassis (R129s are right up there too), but I think you need to be able to work on them yourself to make them affordable.  I was planning to take this one to Amelia and had some deferred maintenance to take care of.

I sat the car aside a while back due to a bad right rear wheel bearing. I didn’t want to jump into this job as it’s a bit of a pain but there’s a special tool to help remove and insert the bearing and with the tool it wasn’t too awful.  I did have a hard time getting the rear brake rotors off.  A big puller, penetrating oil, and a big cheater eventually pulled them off, though I whacked my head pretty good when the left one broke loose.  I noticed that the brake hoses had some cracking.  These were probably the original hoses; I sat the car aside until I could get around to changing them.

The brake hoses are cheap and are usually easy to replace, though you must bleed the brakes afterwards (you should replace the brake fluid on a Mercedes every two years anyway).  These were not as easy as I expected – the nuts holding the hose to the metal line would not budge. I had to resort to my special hose nut Vise-grips after spraying with penetrating oil.  The Vise-grips were effective, and I didn’t have to resort to the next (and ultimate) step, using heat.  I have a very small butane torch for this, but I avoid using it due to the fire risk. 

I replaced all the brake hoses and the front brake rotors and bled the brakes with some difficulty. I had previously tightened the front wheel bearings to remove front end play.  I also found some play from the idler bushings, so I decided to replace these too.  The idler bushings are on the right side of the steering linkage; they support the steering linkage on the opposite side from the steering gearbox. Most Mercedes have these bushings and it’s not unusual to have to replace them.

It had been several years since I did idler bushings on a W124 and I was surprised that the availability of the parts was much less and the original Mercedes part, the only option I found, was quite expensive. This is one job that goes a lot better with a lift! It was straightforward, other than the idler bolt hit the exhaust line making it hard to remove and even harder to reinstall. I considered tapping the exhaust to open the clearance, but the geometry didn’t allow that. Also tried loosening some of the exhaust supports but that too was ineffective.  I was able to tap it out, and I filed off a little bit of one flat of the new bolt for clearance. 

I was working on eliminating any suspension free play because the car didn’t feel right driving on the highway. I checked wheel alignment and reset the toe; the rear toe was excessive, and I reset it to specification. Though it was better after this work, it still wasn’t right. I also had to replace the tires; the fronts were 10 years old, and the rears were 8 years old. When I removed the tires, the 8 year old rears had noticeable bumps you could feel by running gloved hands over the tread area. After the new tires the car felt much better.

On the subsequent test drives, however, I received several warning lights. I don’t like warning lights. I had seen this intermittently before, an ASR light, and sometimes an ABS light.  This time I got ASR, ABS and a check engine light, which did not go away when I restarted the engine. I set up to read codes and found the ASR and ABS lights went away before I did anything. I used my blink code reader to access the codes.  I had a lot of codes, but the common denominator seemed to be failure of communication between modules. Though I was able to clear all codes, they consistently reoccurred.  I really don’t like warning lights so I had to do something.

Reasoning that the only consistency about the warning lights were a bunch of communication failure callouts, I thought it might be bad electrical connections. I disconnected the battery then removed all the modules from the module box (where the battery goes in a normal W124).  I used DEOXIT to clean all the plugs and the module connections.  I also unbolted the three ground connections just in front of the module box, sanded off any corrosion and used conductive grease when bolting them back together. I replaced all the modules, reconnected the battery and test drove the car – no warning lights!

After this test drive, I noticed some stains on the coolant expansion tank as well as a little coolant on the seam of the tank.  It appeared that the small hose on top of the tank was leaking.  When I removed the hose, however, I found the tank was cracked. I tried a temporary repair with JB Weld that didn’t stop the leak.  I tried to order a tank online from several Mercedes dealers, but the Mercedes system was trying to charge me hundreds of dollars for shipping. No matter which dealer’s site I was using, the small, lightweight plastic coolant expansion tank, about a $100 part, was showing $400 to $500 shipping! I called one Atlanta dealer online sales rep, who could see the issue but couldn’t do anything about it. Thus, I ordered a Mercedes branded part from a Mercedes dealer on Amazon.  The tank arrived late, on Tuesday – I needed to leave for Amelia on Thursday. I immediately installed the tank – and found that the coolant low level warning sensor, which inserts into the side of the tank, crumbled.  Since this was a pressure boundary in the cooling system, I had to fix this too before our trip.   

When I need a part the next day, I order from RMEuropean and specify next day delivery.  I ordered two of these low level warning sensors late afternoon on Tuesday, I saw a shipping notification within about 30 minutes, and I had the parts on Wednesday morning. Installation was easy and I was finally ready to leave on Thursday!

I had expected to do the brake work, suspension work and the tire replacement.  The warning lights and coolant leak were a surprise, and I was lucky to be able to deal with them before the trip.  The car did well and was great fun to drive (again!).  This was probably about $2,000 worth of parts, including tires and wheel refinishing - imagine what it would have cost had I not been able to do it myself!