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Discussion Starter · #1 ·
Most of my trucks don't make any noise but a 1300 I used to own and my 1550 make suck a racket that it's embarrassing. Particularly bad when going slow at in stop and go traffic or at in town stop lights with people standing on the street corner. That truck stands out enough without the warning alert.

Has anyone come up with a good solution to this problem? I seem to remember talk about this long ago.
 

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Unimog Moderator
250GD Wolf
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Unimurr has a good article, on my mobile, but if you can't find it i will dig it up later.
 

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U1550L/37 Doka, U1700L/38, Merc 1017A
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the updated calipers have allot more mass to them. i wonder if it has something to do with this.
 

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Discussion Starter · #5 ·
Thanks.

Google translation.

Remedy for brake squeal

Warning: You are working on the brakes. These are security-related concerns of the vehicle. If you do not have the sufficient skills, they are looking at an authorized workshop for brake systems.

The following information has been prepared with great care and tested the reconstruction in practice. A guarantee of accuracy is not accepted. Changes to the vehicle may void the guarantee. The conversion is at your own risk and responsibility. Unimurr accepts no responsibility whatsoever as a result of such changes.


The conversion



By using non-asbestos brake pads come with the front axles to type 747 in some vehicles unpleasant squealing when braking. This affects everything from the type 406, 416, 417, 424 and 435

The cause lies in the changing friction behavior of asbestos-free brake linings. This occurred on vibrations during braking, the brake calipers to bring the resonance. An unpleasant squeaking is the result.

DC has a service bulletin to be sent to the workshops, where attempts in several steps to remedy the situation. If I did not succeed, which led me to a proprietary solution. But first things first. First, implement the recommended steps of DC. The following things should be checked in each case:

Bolts: at each caliper are a fitting screw and a standard screw fitted for attachment. The screw must fit on the disc inlet side to be mounted. That is to say. Where in the direction of the rotor enters into the saddle must sit the set screw. The bore has a Reibale on Ø16, 5mm H 9 = +0.043 mm are taken. I have it drilled out carefully with a regular drill with a diameter of 16.5 mm and it worked well. Screws reap principle with separating agents. Copper paste, ceramic paste or the like. The tightening torque of bolts M16x1, 5 is at 403, 406, 416 and 417 300Nm. At 424 and 435 250 Nm.

Shielding: Check the installation position of the shielding. The opening of the shielding must be also on the rotor inlet side.

If these measures are not successful, DC recommends weights bolted to the brake calipers to the mass ratios and thus change the resonance frequency. I do not want to go, because this measure hardly lead to success.

Really the only solution connecting the brake calipers with a steel band.

The top two screws that hold the caliper halves are replaced with longer screws.

Caution: Under no circumstances accept any which suitable screws. You must use the original screws ATE: A 435 990 72 19

It is to expansion bolts which are tightened to the maximum strength just above the yield strength of steel screws.

The screws go in sequence.

Caution: Never simultaneously solve both screws on a brake caliper. In principle, solve the second screw until the first screw is tightened with 58 Nm.

Keep the prescribed tightening torque exactly one. Overstretching of the screw can lead to breakage of the screw and the bursting of the caliper during emergency braking.

With the help of a band now projecting threaded 25x5mm steel is screwed from saddle to saddle.

Measure the distance from center screw thread measuring center. Similarly, the steel strip length. These dimensions vary from vehicle to vehicle and should always be determined, "On the Spot". The ends of the steel strip must be ground after the contour of the saddle.

Note: A projection of the steel strip on the caliper also leads to the contact with the rim and can have devastating consequences.

If the steel band in the contour correctly processed, the holes with a diameter of 10.5 meters to be drilled. The contact surface on the caliper is not flat. So I made from the same strip steel material, a disc that provides a flat surface as a base for the steel band. This band steel plate must be the topography of the caliper are adjusted. Then the whole thing with washers and nuts M10 screw SW 15th Safe side, I would also buy the washers and nuts at DC, because they fit together in the hardness.

Finish. Now surely any squeaking is eliminated.

Furthermore, for people who want to use a bicycle speedometer for accurate speed measurement: The steel strip is a great bracket for the speedo sensor.
 

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Discussion Starter · #6 ·
I'm not sure I'm 100% up to speed with all that. But I'm kind of distracted right now working on something else technical. Maybe a translation from German brain patterns to North American brain patterns is needed ;)
 

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1987 416 Doka
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Has anyone tried this? My 416 brakes squeal too and I've been tempted to give something like Unimurr's adaptation a go.

The guy sure seems to do things right, so I'm pretty confident the mod works, but just thought I'd ask out there...
 

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Unimog S 404.114
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guude,

many guys here did it like Franz Murr, all of 'em succesfully. even the MB service stations. it's in their manuals since years.

gut mog! justus.
 

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Discussion Starter · #10 ·
I had a brake incident 2 days ago.

I was driving the 1550 and I found that the brakes only squealed if I was going slow and applying light pressure. If I got on them hard they didn't make any noise. So I was running an errand and it was hot out. About 100'F. I was on the highway for a few miles and then onto a secondary street with lights every few blocks. I had probably made 4 stops when I noticed the brake pedal feeling odd. I had a spongy pedal and no brakes first pump then they came back and I was able to stop at a light. Then the next light it happened again and they did not come back and the pedal went to the floor. I used the park brake to stop and pulled onto a side street. When I checked, the small fluid reservoir was empty and the big one was full and flowing over. They are inside of an aluminum box for race purposes, which looks cool but makes a quick check more unlikely, however I had never had any problems with the brakes so I hadn't checked anything before I drove the truck. I was all the way across town from my shop but rather than pay a several hundred dollar tow bill I drove it using the park brake. That was a teeth grinding experience equal to having to drive my Scout home in rush hour Miami twice without a clutch starting it in 1st gear after each stop then matching rpm. I made it w/o a crash. I was gong slow to give myself room to stop but people would pull around me and then get right in front even though there were 2 lanes. : /

I haven't investigated yet but it acts like I boiled the fluid and it overflowed. I just don't see how that could have happened with so few stops and only one of those from highway speed. There wasn't a brake dragging as is evident from rolling along just find and using the park brake to stop.

Anyone have something like this happen to them? I'm having trouble with almost every vehicle I have at the moment.
 

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U1000Ag
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I am guessing worn/broken seals in the master cylinder
That will allow fluid to move from one reservoir to the other during pumping action
Picture below gives you some idea. However just a guess - I am no expert on the Mog master cylinder and others might have more correct answers
 

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Discussion Starter · #13 ·
That sounds logical. It could have happened because I was standing on the brakes harder.

Last I heard they were not selling rebuild kits for master cylinders and I'll bet new one costs at least $1500, so it might be time to get creative if that is the problem.
 

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U-406/416
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Also check you caliper bolts, I had a bad squeal it ended up that one caliper was under toqued and vibrated very little, but enough to cause a squeal.
 

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Discussion Starter · #16 · (Edited)
That's good to know Trev. Kelvin Kurkowski told me years ago that they were no longer available. Maybe it was just one of those things that come and go and at the time they were out and now they provide them again. He also told me they were like $1200 or more quite a few years ago. EuroTruck going direct is a great thing.

Who knows how many things are like this. When my pick up pump went out on the 421, Mercedes wanted $1100 for one and no rebuild kits were available. The local Bosch repair center told me that a Caterpillar used the same kit and they did if for $85.

Guess I need to pull it apart and see what is going on. Along with the other 20 things I need to pull apart to see what is wrong. Not all on this truck of course.

SnowMog I'll check the calipers too. Can't hurt to check.
 

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Unimog Moderator
250GD Wolf
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You need to hire a dedicated Unimog mechanic for a month or two. Get all your rides up to snuff (posting massive amounts of pictures for us to drool over, of course), and call it good for a few years ;)
 

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Discussion Starter · #18 ·
Yeah tell me about it. Alone with a Honda mechanic and a KTM mechanic and an Audi mechanic etc to infinitum... lol

I've actually talked to Jay about this in the past but he has too much of his own stuff going on.

Besides it was all good a couple of years ago and in a couple more years it will be other stuff that is messed up. It's an on going battle. What I really need to do is get rid of 90% of what I own and then I could concentrate on just a few things. But that is a lot easier said than done and priorities change. Think how long it took Trucktor to sell his really nice looking Doka. And it had to finally go to the opposite side of the earth to materialize.
 

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Discussion Starter · #20 ·
I took the 1550s master cylinder apart today and everything looks like new. The cylinder bore is spotless.

It really does seem logical that the problem of transfer of fluid from the small reservoir to the large one would indicate a piston seal problem but I don't know.

I hope I can simply buy a seal kit to renew while I have it apart but it would not need anything else.
 

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