-
oil temps on downhill grade
was noticing that on downhill grades with the retarder on level 3, my oil temp would climb to about 230. Once I came off retarder, it came back down to 200. Is this normal?
-
36 Replies
-
Yes.
On your vintage coach I suspect the transmission temperature sensor is on the output side of the retarder so the harder the retarder works the higher you will see those temp.
If you want to experiement watch the temperature as you apply brakes with the retarder master switch on. The heavier the application of brakes the higher the retarder temp. The same thing applies as you go from the lowest setting to the highest on the stalk.
Your transmission computer should protect the transmission if temps reach 300 degrees by limiting the effectiveness of the retarder. I used 230 as a personal upper limit and could easily do it with managing speeds and gears.
-
Thanks Jon,
that is what I was thinking it was. It was 7% grades for 4-7 or so miles at a time, trying to keep it between 45 and 55 without using that much brakes. Never really made it all the way to 230, was probably in the 220 range. As soon as I hit the brakes (and I presume took pressure off the retarder), the temps came down immediatly.
-
Charles if the master switch is on and and the stalk all the way up or off the harder you push on the brake pedal the hard the retarder works its still on with the master switch on even if the stalk is all the way up when you push brake pedal, if the stalk is pulled down it works as soon as you let off the throttle no brakes pedal needed
You may know this already hope it helps -
Peter: If your comments didn’t help Charles … they helped me understand the retarder more. I recall Jeff explaining the retarder when we first picked up the coach from ETLC (everyone remembers that the first time I drove our Prevost and the second time I’d ever driven a Prevost was after I bought the coach, had Jeff spend a month zeroing everything out, and I’d spent significant dollars doing that), but that day was like drinking Crown Royale from a fire hose.
-
Peter,
Yes, I have been using the retarder as you described. Set it to the lowest setting and use it when I only want it to come on with the brakes. For other times (coming down grades) I set it to two or three (really never gone past three) and let it come on as I come off the accelerator pedal.
I just couldn’t recall if I had seen the temps rise while it was working so hard. Could have been I was paying more attention to what was happening in front of me or around me to watch the dash/gauges.
Outside of that, I need to really figure out how to use the upshift/downshift for climbing/descending and get optimal power to climb and use some of the engine to brake on the descents (although the retarder seems to do just find by itself for that).
-
Charles, here is the short version.
If the main retarder switch is “on” the retarder will automatically engage directly proportional to how heavy you use the brakes. You can confirm this by watching the transmission temperature gauge with the stalk in the zero (lowest) position. Your transmission temperature will climb with brake application, faster if the brakes are used for a hard stop.
To use your 7% grade as an example, your plan should be to use the retarder to assist in maintaining a target speed. Since your 4th gear tops at at 55 MPH at about 2100 RPM, let’s use 50 as a target speed for going down that grade.
Slow at the top to 50 or below, manually gear down to fourth, and start out with the retarder in the second position. As in two clicks from zero with the stalk. If that holds your speed good. If not go up a click to the third position. If it holds speed good. If the speed decreases, go back a click to the 2nd position. If the speed increases you can go up a click to the 4th position or as you approach 55 use a steady firm brake application to about 45 and repeat the process. In that example your transmission temps will likely never exceed 220 or 230, but those temps are very conservative. I happened to pick 230 because it is marked on the gauge.
Your retarder is like a torque converter in reverse. The higher the setting on the stalk, the more effective it becomes and as fluids are compressed they heat up which is why you see the temps rise.Later model coaches are apparently measuring transmission temp at the oil pan so the temps you see are not what other with later model coaches see.
-
Thanks Jon for pointing out how to use the gears and retarder together.
On a related note, how much does elevation affect the performance of the DD S60? I know in my FJ Cruiser and wifes XTerra, driving at higher elevations, we noticed a difference in power. Coming over some passes yesterday between 7000 and 8000 ft elevation, the power didnt seem as it did at lower elevations (even 6000 ft)?
-
Cgallant, my understanding is that diesels are not affected by elevation. Am I right Jon?
Jon, our trans temp sensor must be in a different location as you mentioned on newer coaches, I don’t see a temp change while using the retarder.
Mark
-
This is just personal experience based on seat of the pants measuring.
The S-60 does real well at higher elevations because the turbo spins up and builds boost pressure quite well. Combine that with good gearing to get the coach to step away from a traffic light pretty briskly with a rapid RPM build up and in my opinion altitude has minimal impact. Because of turbo boost the engine does not act like it is at altitude.
The 8V92 owners and previous owners on here will tell a different story about their coaches with that engine. My 8V92 did well, but only on sea level highways. As altitude increase it got more and more sluggish. The problem with the 8V92 was the turbo and blower weren’t really effective much below 1500 RPM (which is often a Series 60 shift point) Until the RPM came up an 8V92 was pretty slow, but once it got 1500 and above it did real well. The key is the turbo. As long as the boost is up the engines act like they are at sea level, but until boost builds all engines suffer a performance loss due to elevation.
If you want to see a Prevost owner in pain, watch an 8V92 driver at altitude, like Colorado Springs, trying to start up a grade from a complete stop. He will step on the pedal, and when nothing happens the look he gets will be like you would get if your couldn’t get your engine above idle. Given enought time and black smoke that 8v92 will eventually get rolling, but until it does the driver is left wondering if he should get out and push.
-
Charles, the operator’s manual for my bus says that the normal operating range for the B500R transmission is 200-250 degrees.
Jon, I think that was me you saw in my 8V-92 equiped XL40, except it was Mammoth Lakes at 8,000 feet. A place we love to camp requires turning left from a stopsign on an upslope at about 8200 feet onto US 395, a 4 lane 65mph divided highway. Not fun with an 8V towing a car on a busy holiday weekend, plus I think the resulting smoke is still visible up there years later.
-
Actually it was me in Colorado Springs on our first trip with the bus to higher elevations. I thought the engine had gone bad until I realized we were at altitude.
The S-60 is a dream however.
-
what is the stalk?
-
hey John, when I hit my brakes with the retarder in the first or second position my gauge has gone up to 300 but comes down very quickly. Do you think that is normal? Or is there something I can change to fix that?
-
Tony,
Do you have a Jake brake or a retarder? A retarder has a master switch on the dash and a stalk on the RH side of the steering column that looks like a miniature turn signal. The stalk has seven positions with each one being increasingly more effective at braking.
The “off” position is with the stalk all the way up.
If your braking raises the transmission temperature gauge up to 300 degrees it is definitely engaged. A retarder automatically applies if the master switch is on regardless of the position of the stalk and applies braking force proportionate with how hard you are stepping on the brake pedal. Nobody has ever posted their temp reaches 300 so I would have that checked out. My reason for saying that is if you have something wrong with your brakes and have to stand on them pretty hard it suggests they are not as effective as they should be and the retarder is doing a lot of the braking.
You might have a serious problem.
-
Tony,
Whatever you have going on may be normal, although 300 sounds really high, for your bus, my 01 XLII Liberty would turn on the dash warning light when tranny temps got to 250. Does yours turn on any light or warning?
Log in to reply.