Rear Brake Sensor Melting Brakes Overheating

Hello All, I searched the forum and did not find anything on rear brake senors melting. 2006 Adventurous RV not carrying much weight. Going down hills like Arrowhead the rear brakes both sides heat up tremendously and melt the OEM Brake Sensors. I have Drilled and slotted high carbon rotors and and excellent semi-metallic pads from Napa. I checked the rear calipers operation and found the driver side sticking. I will be rebuilding the Calipers and flushing Brake fluid. I don't think this vehicle has ABS because I have not seen a ABS light nor hardware. I have not changed the e-brake pads ever,but they are not binding. Any suggestions?

Thanks again in advance.

I had a similar issue with my '72 Blazer when it was really getting up there in age (kept it for over 30 years....). Those calipers can stick, and that will definitely heat things up -- a lot. Sticking could be due to accumulated crap in the caliper piston, or it could be the flexible brake line collapsing internally and creating a restriction.

If it were mine, I'd replace the calipers & flex lines and completely flush the brake system at the same time.

I am 99% sure you have ABS or ESP. Both perform ABS functions. You have wheel speed sensors at all four wheels, and a hydraulic pump/valve unit below the brake booster.

Right -- in thinking about this further... with ABS, I'll admit I don't know squat about how that might --could-- also affect your "sticking" caliper(s). Thanks for pointing that out, Midwest. Being a 2006 model, I'd also bet it must have ABS.

Also-- on my 2015 SS Agile, there's a load-sensing lever attached to the rear axle that senses load and apparently feeds back into the braking system. Mine had popped off --twice-- and I eventually replaced the broken lever with a Dodge part (identical). Could it be maybe that's not working properly so your rear brakes are getting too much power through the proportioning valve/system when going down step grades?

Again, I'm not sure how that particular system works, but in general, when going down a steep grade, there's a natural shift in weight to the front. A proportioning system -- as I understand it-- acts to reduce power to the rears so they won't lock up.

Here's what that lever looks like:

Is your van a 3500 cab/chassis? The cab chassis had the ABS system, and a brake proportioning valve at the rear axle. The valve can be adjusted via its linkage. Its also possible for it to fail, and both rear calipers may not retract.

Also, brake hoses (usually just one side though), can fail internally and prevent the caliper retracting. This is not common on a vehicles less than 20 years old though.

All NAS aka NAFTA Sprinters have ABS. To my knowledge ABS and ESP are different safety systems even though they both depend upon the CAB aka HCU module to modify or apply braking to enhance vehicle control.



ESP was optional for NAS aka NAFTA Sprinters up to 2003 MY. All Most all NAS aka NAFTA Sprinters 2004 and up have ESP. At least for T1N's, ESP remained optional for ROW Sprinters, but was included in all most all models destined for N. America.

vic

Added:
There was a comment that the 2004+ T1N 3500 Cab Chassis model (dual rear wheels) does have the mechanical brake distribution lever. I have no data about that. The cab chassis model is common for some, but not all, RV conversions.

Thanks Vic. The ESP’s intervention parameters would be difficult to choose without knowledge of the finished vehicle’s weight and centre of gravity, so it makes sense that RV cabs only came with an ABS program.

In the callipers I’m familiar with, piston retraction is provided by the rubber seal relaxing, which doesn’t exert much force.
Lack of slide pin lubrication, corrosion, residual fluid pressure...
A failed dump valve in the ABS hydraulic unit also has the potential to drag a brake, but I would check the caliper components first.

Note that the presence of any ABS unit complicates bleeding air from the brake system (you need a shop tool to command the solenoids to fully flush the pump unit...), so take extra care not to allow air to be introduced into the master cylinder while bleeding a flex hose or calliper. Keep the reservoir near full, and allow time for any air bubbles to float clear before pumping the brake pedal. (I know this appears obvious, but it’s much more difficult to recover from a momentary lapse when ABS is involved...)

-dave

You can get a list of all of the options MB built into your Sprinter by submitting your VIN to https://www.datamb.com/
The site offers a "pdf" button to retrieve the results (as well as simply displaying them).

It's very handy info to have.

When going downhill, can we assume you're down-shifting?

--dick

Thanks again for jumping on my issue. I will check everything again and add to the load leveling And the dump valve . Will keep you posted. By the way I have 2006 Sprinter 2500 Adventurous RV Roadtrek

LMSprinter1stGen said:

Thanks again for jumping on my issue. I will check everything again and add to the load leveling And the dump valve . Will keep you posted. By the way I have 2006 Sprinter 2500 Adventurous RV Roadtrek

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A 2006 2500 will not have a mechanical brake distribution lever assembly.

To my knowledge since NAS aka NAFTA 2004 MY the T1N brake distribution function is addressed electronically as part of the ESP safety system.

The T1N mechanical brake distribution lever system was included on NAS aka NAFTA 2003 MY and earlier. Some newer model Cab Chassis trucks may have the mechanical lever system.

vic

Aqua Puttana said:

...
The T1N mechanical brake distribution lever system was included on NAS aka NAFTA 2003 MY and earlier...

Click to expand...

Except cab/chassis. AFAIK they had the mechanical valve and no ESP through 2006.

Midwestdrifter said:

Except cab/chassis. AFAIK they had the mechanical valve and no ESP through 2006.

Click to expand...

He stated 2500 so I thought it was a regular Sprinter van vs 3500 Cab Chassis. Do the Cab Chassis models come in 2500? I really don't know the answer to that.

vic

Aqua Puttana said:

He stated 2500 so I thought it was a regular Sprinter van vs 3500 Cab Chassis. Do the Cab Chassis models come in 2500? I really don't know the answer to that.

vic

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I don't think they do. So he almost certainly has ESP and no mechanical valve.

The OP said his Sprinter was a "2006 Sprinter 2500 Adventurous RV Roadtrek" which according to Google is based on a standard panel van so rules out the cab chassis option.

For info, in Europe the single rear wheel is available as a cab chassis. Our AutoTrail is built on the medium wheel base version.

Keith.

Cheyenne said:

The OP said his Sprinter was a "2006 Sprinter 2500 Adventurous RV Roadtrek" which according to Google is based on a standard panel van so rules out the cab chassis option.
...

Click to expand...

I should have looked that up.

Cheyenne said:

For info, in Europe the single rear wheel is available as a cab chassis. Our AutoTrail is built on the medium wheel base version.

Keith.

Click to expand...

Out of curiosity I did a quick search.

The newer NAS 3500 Cab Chassis are single wheel. I don't see any 2500 listed for N. America. (Clicking "See All Models" gets no additional choices.)

https://www.mbvans.com/sprinter/commercial-vans/cab-chassis#lineup

But...

Back to T1N overheating brakes and wheel speed sensors.

vic

When I was hunting for why my brake pad sensor was showing continually, I found my rear sensor had melted/burned. My 2002 2500 has the ALB lever. Whether it is working properly I have no idea. I further discovered that the calipers' slide had essentially rusted solid, which MAY have caused the overheating. I removed the caliper, broke the slide free, lubricated and reinstalled.

It depends on which caliper you have on the rear. One design (Ate?) uses short but larger diameter rubber slid bushings with no boot. This design tends to wear more rapidly, and can let the caliper sag a bit , which can contribute to issues.

With the vehicle chocked in neutral, jack up one (ideally both) rear wheels. They shouldn't be dragging on the brakes, and both sides should be pretty close with the normal bearing drag. I generally am looking for 1 full rotation if I spin the tire good and hard.

Well Vic, I had no idea and crawled under the van and checked it was no where be found and i figure it did not apply.

Thanks will keep checking and will advise hopefully soon.

Hi again all,
I went through brakes front and rear, overhaul rear calipers. Bled and flushed system pneumatically. Lifted rear wheel of ground slightly to check if calipers released. They do. Now just have to check mountain driving down hill with down shifting. Let’s see if sensors will melt. Keep you posted

Aqua Puttana said:

He stated 2500 so I thought it was a regular Sprinter van vs 3500 Cab Chassis. Do the Cab Chassis models come in 2500? I really don't know the answer to that.

vic

Click to expand...

For the record I’ve seen T1N single rear wheel box vans used by UPS. And in Mexico they were pretty common for deliveries. The most unusual I’ve seen was in Mexico, a T1N tractor/trailer hauling appliances.

Gary