Cooling Questions U225

Topic: Cooling Questions U225 (Read 1482 times) previous topic - next topic

Cooling Questions U225

July 21, 2012, 10:39:24 am

Once summer decided to arrive (after a very cool and wet spring) it arrived with a vengeance. Our habit this summer has been to take one or two nights mid-week and getting away. Usually to someplace within 100 miles of home on a lake or river. Water temperature on the coach stays around 180F and transmission temp about 150F but the other day in 90-degree temps the water temperature decided to climb to over 200F. I slowed down to 50mph and it dropped back to 190F or so but the transmission temperature went over 200F and stayed over 200 for the rest of the trip.

I know that the temperature gauge on the dash doesn't always reflect the true coolant temperature, but I wonder what temps other U225 owners are running in hot weather.

Craig

Re: Cooling Questions U225

Reply #1 – July 21, 2012, 11:13:41 am

Craig,

Not familar with your U240 trans but should it lock up in the higher gears? If it has that capability, is it in fact locking up?

Our U300 locks up in the higher gears but in city traffic w/o lock up, the temp goes up rapidly, especially in San Francisco with all the hills and heavy traffic.

Pierce

Re: Cooling Questions U225

Reply #2 – July 21, 2012, 11:20:32 am

Pierce, it's just a 4-speed Allison and I don't know if it "locks up" or not, frankly. The heating is always on hills (which are everywhere around here).

Coolant levels are on the money.

I can't see any obstructions in the radiator but I'm planning to hose the radiator (from inside the coach) before our next trip.

Craig

Re: Cooling Questions U225

Reply #3 – July 21, 2012, 11:38:15 am

We had a similar event with our U240 coach a year ago. I wrote it off as "plastic grocery bag on the inlet." We did not hit 200 again until our hated, low-rated and ill-fated Vickers hydraulic pump failed.

Matt B

Re: Cooling Questions U225

Reply #4 – July 21, 2012, 01:53:25 pm

Craig,

Raise the bed. With a strong flashlight, look inside the fan shroud/between fan blades. The fan blades sling the dirt to the perimeter.

Verify that the perimeter, particularly the lower perimeter is as clean as the center. With a rear radiator configuration, it is common to clean it from the front (you are looking at the front of the CAC) once a year.

Brett

Re: Cooling Questions U225

Reply #5 – July 21, 2012, 03:05:06 pm

keep it rev'd up in 3rd gear . they get hot when lugged down

Re: Cooling Questions U225

Reply #6 – July 21, 2012, 03:25:48 pm

Craig,
Our 225 consistently ran hot when pushed by high ambient temps and slow, steep climb hills. It worried me at first but we never had a problem. I made sure our radiator and CAC were very clean and all the rest and verified the gauges with a digital thermometer.

Check your documentation but I think the trans was good to 250F and the engine over 212. Anyhow, when the temp started nearing the high mark, I'd pull over, put it in neutral and high idle it for awhile. Both it and the engine would recover. IMO, the trick is to keep your revs up, especially when pulling those long hills.

I'm thinking your engine and trans are OK.
jor

Re: Cooling Questions U225

Reply #7 – July 21, 2012, 04:05:08 pm

Thanks Jor. I'm going to clean the area (and the fan area - thanks for that reminder, Brett). I noticed that the transmission temperature does not fall as quickly as the engine temperature. At any rate, it's nice to know the parameters.

Craig

Re: Cooling Questions U225

Reply #8 – July 21, 2012, 06:53:47 pm

Craig

We just got home from Calgary Canada. We had some days of 100 degrees +, and on the hot afternoon's my engine gauge read 195 on the level and rose to 200 on the hills. On the steeper hills i just slowed and geared down.

Re: Cooling Questions U225

Reply #9 – July 21, 2012, 07:03:07 pm

But, that's really apples and oranges.

The U225 and U240 have COMPLETELY different cooling systems.

U225: rear radiator with solid driven fan. MUCH more prone to clogging the CAC.
U240: side radiator, with hydraulic fan-- on the 1995 U240 two fans with a two speed controller. And if the controller fails, it can stay on low speed and will overheat. Unplugging the controller puts the fan speed to high.

Brett

Re: Cooling Questions U225

Reply #10 – July 21, 2012, 07:07:08 pm

I had some transmission temp climb with my six speed in the desert two summers ago. Generally, my transmission temp stays with the engine temp but gradually gets just a bit higher so it alarmed me when it rose to over 200 (on the dash gauge). It was mainly during the long gradual grades. I think I tried shifting down to 5th and cut back the speed a little and with the higher RPM's it came down a bit. Might have been just the slowing down a bit that did the trick.

Re: Cooling Questions U225

Reply #11 – July 21, 2012, 09:46:56 pm

Quote from: Dwayne – July 21, 2012, 07:07:08 pm

I had some transmission temp climb with my six speed in the desert two summers ago. Generally, my transmission temp stays with the engine temp but gradually gets just a bit higher so it alarmed me when it rose to over 200 (on the dash gauge). It was mainly during the long gradual grades. I think I tried shifting down to 5th and cut back the speed a little and with the higher RPM's it came down a bit. Might have been just the slowing down a bit that did the trick.

230 is the time to notice. Not before. Absolutely normal to worry but all rv'ers are paranoid in my experience.

Hard to make a Rv cooling system like a car where the gauge never moves after it reaches operating temps. Too much cooling was a problem on early u280's. Had to block part of the radiator if I remember correctly.

Re: Cooling Questions U225

Reply #12 – July 23, 2012, 12:40:43 pm

Followed Brett's advice and looked closely at the shroud over the fan and no obvious signs of debris in the radiator fins or around the side of the shroud. I'll take a hose and clean the radiator from the inside next time we load up for a trip.

Many thanks to Flash for giving a number on the transmission cooling temperature. We're only paranoid because we are pretty sure something will go wrong any minute.

Craig

Re: Cooling Questions U225

Reply #13 – July 23, 2012, 02:03:25 pm

Quote from: wa_desert_rat – July 23, 2012, 12:40:43 pm

Followed Brett's advice and looked closely at the shroud over the fan and no obvious signs of debris in the radiator fins or around the side of the shroud. I'll take a hose and clean the radiator from the inside next time we load up for a trip.

Many thanks to Flash for giving a number on the transmission cooling temperature. We're only paranoid because we are pretty sure something will go wrong any minute.

Craig

Same with engine temps. Hundreds of diesel rides with owners to demo that 220-230 max up baker grade at 110 degrees does not loose coolant or damage the motor. Never lost a patient. If it goes past that by much then slow down and downshift. Normally not needed.

I know everything is ok if at 110 degrees and the motor runs 230 and at 80 degrees it runs 200. Direct correlation between the temp gauge in winter and summers ambient temp.

Done this many many times.

Glad I could save some worry time.

Re: Cooling Questions U225

Reply #14 – July 23, 2012, 02:14:24 pm

Bob,

I view engine operating temperatures differently.

I would definitely determine the cause (AND correct it) of coolant running hot well before 230 degrees F. Could be as simple as gearing down and backing out of the throttle, disconnecting toad and driving separately up a long steep grade in 100+ ambient temps, etc.

Sometimes the answer to "best practices" is different than "what you may be able to get away with".

Brett

Re: Cooling Questions U225

Reply #15 – July 23, 2012, 02:48:49 pm

Quote from: wolfe10 – July 23, 2012, 02:14:24 pm

Bob,

I view engine operating temperatures differently.

I would definitely determine the cause (AND correct it) of coolant running hot well before 230 degrees F. Could be as simple as gearing down and backing out of the throttle, disconnecting toad and driving separately up a long steep grade in 100+ ambient temps, etc.

Sometimes the answer to "best practices" is different than "what you may be able to get away with".

Brett

Agree with Brett most the time

but in this case totally. What you may get away with now may return to haunt you thousands of miles down the road. In the cast of our Detroit, reading many boat/marine DD forum posts have given me a healthy respect for elevated engine temperatures.

In warm weather, I have backed way off and shifted down to second gear to keep temps down when I could have gone up the grade at 55 in third but would have seen 220 on the gauge.

Images of 30,000 lbs by the side of the road with the 4 ways on keep me pretty conservative.

Brett, love your diplomacy! You should write a column for a RV magazine.

Pierce

Re: Cooling Questions U225

Reply #16 – July 23, 2012, 03:17:58 pm

Quote from: Pierce & Gaylie Stewart – July 23, 2012, 02:48:49 pm

Brett, love your diplomacy! You should write a column for a RV magazine.

Pierce

I do-- at least write articles. 13 in FMCA Magazine. The Allison Mode button article in the March 2012 issue was very popular.

Brett

Re: Cooling Questions U225

Reply #17 – July 23, 2012, 03:22:59 pm

Quote from: wolfe10 – July 23, 2012, 02:14:24 pm

Bob,

I view engine operating temperatures differently.

I would definitely determine the cause (AND correct it) of coolant running hot well before 230 degrees F. Could be as simple as gearing down and backing out of the throttle, disconnecting toad and driving separately up a long steep grade in 100+ ambient temps, etc.

Sometimes the answer to "best practices" is different than "what you may be able to get away with".

Brett

I respect your experience and you are being very conservative in your advise.

I have done telemetry drives with the engine and chassis guys back then with teardowns afterwards to verify no issues. Twenty years out of date info. I would not want a newer rig if short term 230 would damage the coach personally.

We used the 230 max temp up baker grade at 110 degrees as a guide line on turning up the engines power levels in those days. A 8.3 300 cummins mechanical motor could be turned up to 400 hp and the Allison man would sign off on the warranty as the load was so light versus a fire truck. My trucker customers ALL wanted more motor for the mountains.

Versus drive around the big grades where the pretty scenery was? " But bob the motor runs 210 up that hill!" Next time they took the pretty up hill road and found out it worked fine.

Too many mountains in the west. Mid west and east coach the temp gauges never move.

Rockies? Summer? Desert? You bet they move.

Re: Cooling Questions U225

Reply #18 – July 23, 2012, 09:42:14 pm

Thanks everyone for all the info. I watch the temp gauge and see that it does go above 200. When Kent Speers had the coach he chased high temps and was told the gauge was reading 10 degrees high. I have checked by stopping and using a heat gun the radiator and find things seem normal in the back.

I did clean the engine and the radiator and the fan with hose pressure and cleaner. Biggest surprise was the black fan blades are actually white!

Re: Cooling Questions U225

Reply #19 – July 24, 2012, 01:34:40 pm

Quote from: wa_desert_rat – July 21, 2012, 11:20:32 am

Pierce, it's just a 4-speed Allison and I don't know if it "locks up" or not, frankly.

Your Allison MT 643 should be locking up in 3rd and 4th gear.

Re: Cooling Questions U225

Reply #20 – July 24, 2012, 02:22:35 pm

Quote from: PatC – July 24, 2012, 01:34:40 pm

Your Allison MT 643 should be locking up in 3rd and 4th gear.

Third starts out unlocked then locks. Fourth is always locked.

Feels like it shifts 4 times.

Re: Cooling Questions U225

Reply #21 – July 24, 2012, 03:10:04 pm

For additional reading, here's an earlier thread on engine temperatures

trans and engine temp - scare me or reassure me

Re: Cooling Questions U225

Reply #22 – July 24, 2012, 11:00:45 pm

Quote from: Steve & Michelle – July 24, 2012, 03:10:04 pm

For additional reading, here's an earlier thread on engine temperatures

trans and engine temp - scare me or reassure me

Very interesting temp thread link. Matches what I have experienced long ago.

Re: Cooling Questions U225

Reply #23 – July 25, 2012, 12:24:37 am

That thread link was most enlightening; especially Kent's essay. Makes me feel a lot better about things... but I'm going to hose out the radiators and fan shrouds tomorrow anyway.

I was getting pretty worried about 200-degree temps and it looks like I was being a little paranoid. It didn't take that much of a hill to get that gauge up to 200; after all, the boiling point of the water that is cooling the engine is just a short ways away.

However, while the engine water temp did drop with some judicious driving, the transmission temp - once it got up to 200 - did not drop nearly as quickly.

A good cleanup is clearly called for. Thanks for all the data.

Craig

Re: Cooling Questions U225

Reply #24 – July 25, 2012, 12:56:39 am

Craig,

Others have installed sprayers for the radiator. Cheap and EZ with only PVC, a pump and a few fittings need. Using RO water keeps nasty white deposits from getting all over things. The good fog nozzles have little filters built in. Switch on 12V pump when it starts to heat.

Pierce

Affiliate Notice