Looking for suggestions as what else to check to see why our MH3000 Allison transmission is running hotter than it’s past 10 yr history?
Short past coach history: 2005 36’ Beaver Monterey Ventura IV with a Cat C9, with 27K miles on it. Nominal running temps over the past years: engine 186 deg & TX 166 deg. Hottest ever recorded: Engine 203, TX 201 years ago. On our last major return trip home in Oct2015 down I-5, I noticed the Allison 3000 TX was running noticeably hotter than for the last 10 years, consistently up in the 188+ range. Once home, I discovered that the Sauer-Danfoss hydraulic fan pump/motor bolted to the curbside of the Allison was leaking at the bolted joint between the 2 major subassemblies of the pump/motor. That pump leak was ultimately fixed, due to recommendations for locating a replacement gasket solely from folks on this forum. I thought the problem was fixed.
Yesterday, I took the coach out for a test run since we had not had it out for last 4 months due holidays and a major renovation job in the house. As noticed before the pump leak repair, the Allison ran almost the same temp as the engine, up in the upper 178-182 (still not the same as it’s past history), this being on flat sections as well as multiple climbs, (one up to 1.75+ mile long), while still going at 50+ MPH along the coast. Ambient air temp was 55 degs. I stopped several times during the drive, checking for leaks and trying to hear if the hydraulic fan was running. Peering inside of the engine compartment, I couldn’t directly see the fan actually ever running since its shrouded, nor did I seem to hear it running, but maybe I just checked it at inopportune moments. (Note: I don’t know what temp the hyd radiator fan is supposed to kick in and be running.) Also while stopping, I noticed the TX temp bump up a few degrees at each stop, and then it would drop back down once moving again.
The last mile to our house is a twisty, skinny 2 lane asphalt road, consistent up hill 4%+ grade and I can only go about 15MPH up to due to limited visibility around several blind curves. At the bottom on the hill, the engine temp was 171 & the TX temp was 180. After the slow slog last mile, up hill w/ engine running at 95%+, engine temp was 176 and TX temp was 195: a 15 deg spike!
Does this consistent running hotter while moving and then excessive jump in TX fluid temp over a slow, 1-mile climb, w/ engine lugging, seem indicative of a hydraulic fan system failure? I guess it could be the pump/motor itself , the fan assembly, a plugged filter, etc. Or something else?
Things I’ve checked so far:
- Repaired external Sauer-Danfoss hyd pump shows no signs of new leakage, but that doesn’t mean that its actually working/pumping correctly either. I also do not see any new oil/fluid dripping or wet spots indicating a possible leaking/busted hose, fitting, etc under/around the engine, TX or radiator areas.
- TX fluid level, from the key pad: good. Level sensor seems to be working correctly, initially giving a “o L – 0 7” for fluid temp too low, and once fluid was above approx 140 deg, key pad went through its normal (7) 15 sec interval countdown and received the “o L - O K”. Note: After the above hyd pump was repaired in late2015, I did manually topped off and checked the TX fluid level via the dipstick, and also compared it at that time with the TX fluid keypad readout of “o L - O K”
- Hydraulic fluid level: good. Fluid still seems to be clear red. Hyd fluid filter last changed 3k miles & 18 months ago.
- Engine coolant (ELC changed 4 yrs ago) seems to still be good color, level is good, & I can look into the coolant overflow tank and see coolant circulating back into the tank via the overflow tube
- Is there an ease way to actually see if the radiator fan turning, or, at what temp/sensor event triggers the fan to turn on? I was assuming the engine coolant temp above some set level (e.g.: 180 deg?) was the trigger event.
Any suggestions as to what else to look at before trying to locate a qualified repair shop on the Oregon coast / Southern Oregon area would be greatly appreciated.
Thanks..
Bryan