1984 190D New Home & Brake Problem
 

Yesterday I brought my "new to me" manual 190D home. The car had zero rust and the engine had been rebuilt by a Mercedes dealer a short time before.

The engine ran great. I was surprised that I was cruising 70mph and only pulling 3,000rpm. From what I have read I thought the engine would be working a lot harder.

The problem that I had is that I lost a lot of brake pedal. The pedal would almost go to the floor and then felt like I would hit something hard. The car would stop then. I tried pumping up the breaks before I would stop, but that did not seem to help. When I got home bled the brakes and it did seem like I could pump up the brakes and as long as I maintained pressure the pedal would hold. After letting of the pedal and driving a while the old symptoms would return.

I thought I would try replacing the master cylinder and the cost shocked me. $241 at fast lane. What is the difference between the 83 300D ($85) and the 190D($241). I keep reading about ABS, but I find it hard to believe that a car with manual seats and manual door locks would have ABS.

Are there different versions of the 190D or does my 1984 190D definitely have ABS? Is ABS brakes a lot harder to trouble shoot? What have I got myself into? I love the car. I can run 75 to 80 mph on the freeway with no effort (smooth a silk) and it seems to have decent pickup (better than 40mpg).

I know I got a lot of questions and I guess questions I should have asked before I got the car, but it’s my car now and I’m got to get this 190D working right. This is the most informative site, but I have not hit upon a lot of the 190D stuff. I didn’t figure it would be more complicated than my 83 300D. I think I was wrong.
:)

1. It probably does not have ABS, very few 84's have ABS. In fact, I believe that it was not available until '85, but I am not sure. If you have ABS, it is unmistakeable. You will have a large box in the engine bay that says ABS on the cover and brake lines going from the master cylinder to the ABS control. Also, there will be an ABS light in the instrument panel set of lights under the gauges.

2. Check to see if you have an original vacuum pump (no screws on the cover plate). If so, then replace it with the new one. You may have a bad vacuum pump which can cause your problems.

3. The master cylinder is different for the 123 than the 201, so you cannot interchange these. I have never replaced a master cylinder on either the 123, the 126 or the 201 (I carefully bleed the system often).

4. Lastly, check to see if there is a leak in any brake line. Sounds funny, but I had a leak in the line going to the back end. The leak was caused by rust that had initiated at the place that the line exits from under the plastic underbelly panels.

Well I just got back in from doing a valve adjustment on my 123 (couldn't wait any longer). While I was out I took a look at the 190D and here are my findings. After bleeding the brakes yesterday and getting the results that I did I checked the fluid level and it was still full. I checked all the brake lines and I couldn't find any leaks (which makes sense). I also checked the vacuum and it was showing 20". Not great, but not bad.

This car definitely does not have ABS. there is no "BOX" and no extra lines going to the master cylinder, but for some reason Fastlane has the master cylinder priced at $241. I called up Advance and got a price of $104. I'm going to do some checking with my MityVac to see if I can't find a leak some where. With cost to repair costs like these I need to find the problem and not replace and hope for the best.

If the booster holds solid vacuum, the next step I would take would be bleeding all the lines.
Might just take care of the problem.
$100 for a master cylinder sounds like a good deal; though they are a $35 used part.

The master cylinder for 201s IS a $200+ item. It's very unlikely that you have ABS - it was an expensive option.

Marshall

And the advance auto master cylinder is "eh" at best. I've seen many bad off the shelf.. You do whatcha gotta do though...

I did find that Autohauz in Phoenix has the Master cylinder for $166 that's almost $80 cheaper than Fastlane. I first need to figure out a way to check Brake Booster. I have a MityVac i just need to figure out how I can use it on the booster.

The guy I bought the car off of told me that he replaced the Master Cylinder (from a junkyard). I seriously doubt if he changed out the seal in between the master cylinder and the booster, so that's the first (after I check the booster) thing I'm going to do.

Booster failures are quite rare (but possible). You might try disconnecting the vacuum to the booster and then drive the car (with the caution that you will need to press HARD on the brakes to stop) and see if the problem persists. If it does, then it's NOT likely to be the booster.

Sometimes the seal from the master cylinder to the booster lets go and the booster fills with fluid. This can impare function, but I don't know if the symptoms match what you have described.

Marshall