Truck Brake Service in Texas?

[nick disjunkt]

Hi all,

I'm still driving around the south east of the US and I was hoping someone could recommend a place to get the brakes on my Mercedes 1823 looked at in Texas, preferably near Austin or San Antonio.

In the south of Florida I had a calliper fail to release on one side of the rear axle after being parked, and when I stopped to check what was slowing the truck down, the disc was glowing cherry red. After letting it cool down, it has worked fine since, and the disc and pads both have plenty of material left on them, but the disc probably need the surface remachined, and the parking brake is taking longer on that side to release. I suspect it's a problem with the parking brake side of the air chamber (the chamber on the other side was recently replaced as the diaphragm was leaking), as a problem with the parking brake valve would cause both sides to stick, and a problem with the caliper would happen with the ervice brake as well as the parking brake.

I've since driven around 1500 miles and have had no problems with the brakes but after it got to 20 one night, the parking brake needed more encouragement than it should have to release so I suspect the problem may reappear again at some point.

A freightliner garage that I visited in Tampa told me that air powered disc brakes are fairly new in America and did not want to waste my time trying to learn on the job.

Have any other manufacturers been using them for longer? or can anyone recommend me a general truck repair place that would be competent looking at the brake for me? The calliper is much like a car's, but larger, and the air chamber is pretty much the same as on drum brakes, so the technology is not too fancy.

I suspect we'll come across more European trucks in Mexico so if necessary I guess I can look for a Man garage on the other side of the border.

Thanks for any help,

Nick

 

[charlieaarons]

I would suggest obtaining the part you think is failing: the air chamber that has service and parking brake diaphragms in it.
If you give me the VIN of your truck I can look it up on the EPC, and you should order it from Germany.
A mechanic will do no good if they don't have the correct part to fix the problem.
I believe the nut at the end of the combination cylinder can "de-adjust" the parking brake all the way out if needed.

Charlie

 

[nick disjunkt]

Hi Charlie,


Thanks for your help, I have a WIS/EPC/STAR computer with me but thanks for the offer.

The problem reoccurred in Kerrville on another cold day and I had a chance to investigate more thoroughly.

When the parking brake valve in the cab was released, the parking brake light remained on, and the air pressure dropped fast. I quickly found that the air was being discharged from the load compensation valve which adjusts braking force based on the weight on the back axle. I spent a few minutes tracing the pneumatic pipes and it seems that the valve only operates on the service brakes. The only conclusion that I can draw is that the seal between the parking and service brake components of the combination air chamber is leaking intermittently, and the air holding the calliper off is being discharged backwards through the hose to the service brake side of the chamber.

After a mile of gentle driving (but still heating the disc up) the parking brake finally released, and the air pressure stopped dropping abnormally.

I don't know enough about the pneumatic system on the truck to be sure though. Does anybody have an idea about how the parking brake light on the dash would be operated? The light seems to be pretty accurate in telling me whether the parking brake is stuck on or not, but there are no sensors in the air chambers themselves. Also the calliper only has wear sensors so I guess that the sensor is elsewhere.

If the light is operated based on a pressure sensor somewhere in the line (perhaps in the rear axle distribution block?) I suppose it would know if there was insufficient pressure being retained in the parking brake circuit to hold off the calliper, but I am slightly concerned that the light is operated in such a way that it couldn't know if the brake has actually been released or not (such as a mechanical sensor in the parking brake valve in the cab), which would mean that the problem is unlikely to be related to the chamber.

I took the truck into a mechanic's in Austin, and they ran some tests on the chamber but couldn't get it to recreate the problem (it's intermittent anyway so this isn't conclusive). With slow application of air, the actuating rod operated smoothly and with no air loss between the service and parking brake sections. Given that I had to replace the chamber on the other side of the back axle last year due to a leaking diaphragm, I'll get them to change it anyway.

Taking the wheels off at least enabled me to get a better look at the heat damage. The pads are fried and need replacing as they're crumbly and scorched but the disc is only slightly warped (less than 1mm side to side) and otherwise in decent condition. It works fine as it is but I'll get it remachined when I get back to the UK. Getting it done here would mean disassembling the calliper and taking the rotor off, but Mercedes in the UK have a machine for resurfacing the disc in-situ.


Any further advice or help in diagnosing the cause of the problem would be appreciated!


Thanks and happy travels,

Nick

 

[Teflon]

Was reading your blog Nick and it sounds like you may still be in Texas. I hope that you have your issues solved. However, if you are still fishing for issues, may I make some suggestions.

1) One of the better non-dealership BMW motorcycle mechanics is Motohank who is in the little oilfield town of Dilley, TX. I doubt if Hank has the facilities to work on your truck himself but he speaks Spanish and certainly knows hydraulic disk brakes. He might be a good point of contact. If you are planning to cross the border at Laredo then Hank's shop is maybe one mile off of I-35.

2) Few US trucks use that style of brake but buses in the USA may (I think that Prevost and Newell use air disks; MCI might). There are several bus garages in Nuevo Laredo, and many Mexican companies operate Euro buses that you otherwise don't see in the USA. Likewise several Mexican-based bus companies have terminals in Laredo, which is the US side.

Just FYI US-style trucks (Kenworth, conventional Volvo and Freightliner) have pretty well killed off the Euro-style truck (Scania, Mercedes, and cabover Volvo) in Mexico these days. But Volvo, Mercedes and Scania sell plenty of buses and bus chassis in Mexico.

I can give you more detailed information and locations in a private message if you need them. If you cross at Laredo/Nuevo Laredo and take the toll road to Monterrey you will go by a couple of bus garages. Ironically, the biggest one operates US-built MCI buses and those probably still use air drum brakes but at least they would be a point of reference. And there is a huge Mercedes truck and bus dealer at you get into the outskirts of Monterrey; surely they could help you.

My notes on this indicate that this in Zapata Mercedes and Freightliner in 2003:


http://www.fototime.com/CF4086FF8A7BF1D/standard.jpg

 

[nick disjunkt]

Hi Teflon,

thanks for taking the time to write such a comprehensive post. We've had the brake chamber replaced now by a heavy truck garage in Austin so I hope that the problem is sorted. The info you gave will no doubt come in use and its reassuring to know that bus garages may have more experience of working on 'exotic' European equipment.

I guess that US domestic trucks are cheaper, and don't have all the complicated electronics that European trucks are fitted with to meet the high safety and comfort requirements of pampered European truckers.

Thanks again,

Nick

 

[incognito]

Hy,

i don't know your route but if you get to Golden Colorado there is Linden Engineering, repairs Unimog, Land rovers, Sprinters, pintz
http://www.lindenengineering.com/
hope this helps

http://blog.travelpod.com/members/loupsvoyagent
incognito