Is it normal when using the transmission retarder to hear air releasing like when braking? When I let up on the throttle I feel the retarder engage, and when I accelerate again I hear air venting just like when I let up on the brakes. I also noticed yesterday on a fairly long downhill with the retarder engaged that my brake temperature rose, even though I never touched the brakes. Is this normal?
Dave & Kathy Bennett
2004 U270
Yes everytime retarder releases it vents air. Completely normal
Thanks. I couldn't find any mention of it by searching the forum and this is my first experience with a transmission retarder. I still don't understand why the brakes would heat up, though.
Dave & Kathy Bennett
2004 U270
I too have no clue as to why your brakes are heating up nor how you are monitoring them? The brakes should only build heat when they are used and they are not unless you have applied them or you have a caliper hanging up. I do happen to check brake temperature with a hand held pyrometer but nothing while on the fly.
Scott
Are you saying the brake pads smoke or are you referring to the building of heat on the transmission temp gauge?
You have a temp sensor on your brakes? Are you looking at the transmission temp gauge? The trans temp will increase when using retarder
Dub typed faster then me.
The coach has brake surface temperature available in the information center readout. I don't know how accurate it is, but I was only looking at the fact it changed when I wasn't braking. The only possibilities I can think of are a stuck caliper, as Scott suggested, or the readout is slow to update and was reflecting braking before I started down. Since I don't see consistently high temperatures (they fluctuate depending on the amount of braking) I am inclined to believe it's not a stuck caliper.
Dave & Kathy Bennett
2004 U270
Since a dragging brake is even a remote possibility you should get a Infrared thermometer and check brake rotor temps when you stop and then you will be sure of your rotor temps. A stuck caliper will cause heat that can be very expensive and a IR gun is around $20.00 at Harbor Freight. Majority of us carry a IR temp gun.
In my old coach after I had the brakes worked on by a guy that said he knew what he was doing but didn't, I started having brake overheating problems. After a few coach bucks later and a trip to MOT they found the brakes were not adjusted correctly after replacing the pins and installing helper springs.
Back to original question, the brakes and retard are not connected. If retard is slowing you down, the temp of transmission oil will go up. Once you apply the brakes I am guessing it will take a little while before you start seeing that temp go up.
I don't know about your newer coaches, but the brakes are connected to the retarder if the retard switch is on with my coach. More brake more retarder.
After reading the manual for the transmission, I see that there are a number of possible configurations for the retarder. One increases the amount of retard based on braking force, as you describe. I haven't felt that in my coach, but Foretravel may have changed how they set up the retarder over the years. That wouldn't affect what I was concerned about though, which is the opposite.
Dave & Kathy Bennett
2004 U270
One way the retard works is when you push down on the brakes the retard kicks in to start slowing you down. As you push harder on the petal the more retard effort you get, plus more effort from the brakes.
Another is where the retard is applied when you take your foot of the gas, once you give it throttle the retard is turned off, let off and retard is engaged again. Have to watch out for this one since a lot of cruise controls will disengage when the cruise tries to go into coasting.
Third is manual apply the retard by the joy stick, the farther you move the joy stick the more retard you will get. This is good for going down long hills, you can adjust your speed based on how much retard you are applying. You just have to watch out and keep the transmission temp under control. You can run the temp up to high if not watching what you are doing.