Bus running too cool...

uncle ned · May 16, 2020, 02:47:28 PM

Scot sounds like you have a good cooling system and a good running engine.

On Huggy i have to take it easy in the summer and in the winter carry my cardboard for the radiator.

Uncle ned

sledhead · May 16, 2020, 03:06:08 PM

I had the same problem when Leids rebuilt mine and the shutters were used a lot in the cold weather and for a short time I used 190 deg thermos but found after the engine finally got hot the 190's were to hot so went back to 180 's . if you can fix the shutters

dave

chessie4905 · May 16, 2020, 04:08:49 PM

You know how many guys here wish they had your problem?

luvrbus · May 17, 2020, 04:09:55 AM

Just use a full blocking set of thermostats, how cold is the transmission running believe it or not Detroit engineers knew what they were doing with the double oil cooler, are the 2 blower doors above the engine open or closed ?, 168 I wouldn't worry to much about it

chessie4905 · May 17, 2020, 05:24:51 AM

Good real life benefit of installing the separate trans cooler.

chessie4905 · May 17, 2020, 05:25:22 AM

Good real life benefit of installing the separate trans cooler.

luvrbus · May 17, 2020, 05:43:25 AM

Quote from: chessie4905 on May 17, 2020, 05:24:51 AM
Good real life benefit of installing the separate trans cooler.

Not really Allison wants those transmissions running between 180F and 220F for long life,you check the fluid level at 180F

sledhead · May 17, 2020, 06:49:19 AM

could you put a switch up at the dash to turn on and off the fan for the trans cooler ?
I installed a switch for the cat rad fan on the dash with a light , as when I got the coach the rad fan was on hi all the time and it took forever to heat up and if it was cold out it never did . now 95 % of the time I run the fan on low and only turn it on hi if I am pulling a large grade and the temp goes down fast as soon as I turn it on .
on a plus side my mileage went up from the 6.7 all time on the cat computer to 8.1 now and that is in a short 3 year time frame . but now I control the fan setting so I need to watch the temp gauge now and then . but do that anyway

dave

chessie4905 · May 17, 2020, 01:41:16 PM

Part of the installation would be temp control sensor for fan/s. Also most of the heat issue conversions are non electronic Allisons that aren't so fussy about temps.

Scott & Heather · May 24, 2020, 04:48:36 AM

I'm not disagreeing with cliff, cause I respect his years of knowledge but it's important to note that I have had extensive conversations with an Allison trans specialist in Maryland who is one of the last guys still supporting the 700 series trans. He's very very familiar with the the 740/748 which are nearly identical transmissions one just has electronics, and he said running a cool 700 series will absolutely not hurt the trans. He said the trans will heat up its own fluid to a good running temp and be fine. If it's super duper cold weather, he recommended not turning the trans cooler twin fans on, but he said he's seen large trans coolers on the 700 series is with no coolant exchange system in the mix running cool temps their entire lives without causing any damage to the trans. I really pushed him on this subject because I was worried about this and he assured me very confidently that heat was the greater of the two enemies much more than cold would ever be unless I was running in northern Canada. I'm absolutely glad I removed the coolant heat exchanger because I'm running amazing temps for a 500hp two stroke. Very very happy. I run the trans cooler fans all the time right now and will only turn them off once I'm seeing cold winter weather.

luvrbus · May 24, 2020, 06:16:06 AM

Excessive heat build up over 220F is the enemy not normal operating tempature,Allions will only heat in the torque converter mode or wrong fluid levels not in lock up that is why a fire trucks have a lock up when pumping is to prevent excessive heat.Watch the heat when you use the retarder those will heat in a hurry so will the World Allison with the retarder

Scott & Heather · May 25, 2020, 05:42:16 AM

I am definitely curious how hot it gets when I activate the retarder. I love the retarder as I don't hardly have to use the brakes now for a normal slowdown to stop. I am running a fresh filter and fresh transynd fluid in the trans so that helps.

Jim Blackwood · May 25, 2020, 06:49:51 AM

I have the retarder too so your experience with that will be helpful to me.

Jim

buswarrior · May 25, 2020, 07:18:53 AM

All the retarding/braking energy that used to become heat at the brake drums, goes into the transmission.

Physics, the energy has to go someplace.

It is incumbant on the driver to still throw the gearbox and engine into the mix to help slow/control speed.

Scott has an isolated cooler, with its own fans, Jim, you need the high revs of a downshifted engine to circulate coolant hard, and for the cooling fans to spin hard, to dump the heat overboard.

What killed the B500R in the DL was drivers going down mountains, in top gear, retarder on full, engine idling, huge heat into the transmission cooler, and no where for it to go. Burned Transynd was one symptom.

As the problem emerged back then, Allison demanded frequent fluid changes or would not honour the warrenty.

So, no free lunch, driver still needs to be smart, and do the right things, to share the load, and maximize cooling.

Happy coaching!
Buswarrior

luvrbus · May 25, 2020, 08:17:19 AM

Quote from: Scott & Heather on May 25, 2020, 05:42:16 AM
I am definitely curious how hot it gets when I activate the retarder. I love the retarder as I don't hardly have to use the brakes now for a normal slowdown to stop. I am running a fresh filter and fresh transynd fluid in the trans so that helps.

With a retarder you need a gauge on the torque converter they can get over 350F in a hurry and 330F intermitted use is all Allison says is ok,? is your joy stick control or pre set with just the switch