Skip to main content ↑ ↓
Topic: Operating Temp (Read 1203 times) previous topic - next topic

Operating Temp

Two days ago I traveled from Tucson to Chula Vista CA.  I took route 8 and the ambient temps were between 104-110.  This was not the heat of the pavement that we were riding on, I can't imagine how hot that was.  As you enter the greater San Diego County you have to climb a very long and steep mountain that is about 11 miles up from sea level to 4150 feet.  In doing so I was in 4th gear not pushing it and the outside temp was 104F.  By the time I got to the top my engine temp had climbed as high as 213 tranny to 205F.  What I am asking is with the ISX 600 that was the highest I have seen in 8 years.  Although my experience is limited to my coach what do you all think?  The engine temp went back to between 185-190 after the crest of mountain.  Thanks Elliot

Re: Operating Temp

Reply #1 –
Elliot,
  You did not state what your speed, RPM or what gear the tranny was in but 213 no is problem but if you are uncomfortable with that temp, manually downshift, slow down, and bring the RPM up. You should see the temp drop right off once the RPM's come up if you were low on RPM. Around 225 you should get some warning buzzer or light, your engine manual should define some of those critical temps. Read up on your engine operations manual for your engine and you will get best operating instruction.
205 on tranny is also no problem and same operational considerations as above. Synthetic transmission fluid is a preferred item if running in the mountains or stuck in lots of traffic.
Good luck,
Rick

Re: Operating Temp

Reply #2 –
 I run Cummins ISX in 4 of my semis. You got to the top of the hill in fine shape.
Dub McBride 1996 270

Re: Operating Temp

Reply #3 –
Elliot, we did that same run last Sunday. The ambient temp was 106 when we started up that hill.
By the time we crested, our eng temp was at 217 and I was in 3rd gear. Giving the outside temps,
 I thought we did pretty good! Don't recall my Trans temps but they were below the eng  temps hope this help ease your mind. I have an '03 U320 with the 450 Cummings.
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Operating Temp

Reply #4 –
Basics in warm weather on a long grade:

Gear down to where you are about 3/4 of the way to governed RPM (faster engine speed turns water pump faster) AND, at less than full throttle. Said another way, while lugging at peak torque RPM is great for MPG, when overheating (actually any time you temperature gauge indicates you are out of "thermostatic control" switch to "Plan B"-- see above.

Climbed from Mojave to Bakersfield middle of last summer, we certainly could have gone faster, but just dropped down to 4th gear, about 3/4 throttle and "toddled" up the L O N G , H O T grade.  Several DP's passed me-- I passed two of them on the side of the road further up the grade.

Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Operating Temp

Reply #5 –
Brett, actually that's what I did slowed in 4Th to 40-45 got off boost and ran about 1750-1800 rpm up the second half of mountain.  I posted to specifically see if 213 was hot as far of engine parameters.

Re: Operating Temp

Reply #6 –
Never would have given a second thought about 217. Everything working as its supposed to.

The sundstrand wax capsule temp switch for the fan has around 15 degree range from low to high governing the fan speeds.

Does not get to full speed until around 210.  Same as the high speed controller built into the m11 engine to electrically clutch in a radiator fan in a semi.

I am impressed  with the good info on actual use up grades in the heat.  No issues.

I can and have gone higher than the numbers shown here countless times in testing since 1984.

Versus unnecessarily pull over?  A Hundred personal deliveries in the summer heat to demonstrate the numbers shown here can be safely used.

Finally.....
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Operating Temp

Reply #7 –
According to the M11 and M11/ISM manuals, the upper temp limit for those engines is 212 (not sure about Elliot's ISX). Anyhow, I wonder how long that number could be exceeded and by how much?
jor
93 225
95 300
97 270
99 320

Re: Operating Temp

Reply #8 –
Quote from: jor –
According to the M11 and M11/ISM manuals, the upper temp limit for those engines is 212 (not sure about Elliot's ISX). Anyhow, I wonder how long that number could be exceeded and by how much?
jor

The 900 plus page tech manual shows the high fan trigger for an electric radiator fan on a big rig is 210.

The sundstrand wax capsule on the hydraulic side drive cooling range is 195-210 for the low to high fan speeds.

Not what you asked but it's a start.

I have been beat up since 1984 for suggesting then demonstrating that higher than 210 degrees will not damage any of the Diesel engines used in rv's.

Stupid to say this as every technical guru will quote the engine makers recommendations.

So as to my recent personal experience I ran our coach up from needles on interstate 40 towards Los Angeles under full power for 20 minutes at 60 mph at 36,000 pounds combined.

Never backed off.  Gauge got to 225 or so.  Been to 230 several times going west up into the Grand Canyon. 

While I have successfully gone past that I would not recommend this for the faint of heart and wallet.

Worked with the factories and chassis companies and the engine guys long ago to test the limits as our Foretravel store was in Irvine, ca and had a lot of desert users by default.

Same testing later with beaver, country coach, Monaco and others.

Birds over heated.  Not enough radiator area.  Monacos split radiator blew coolant under heavy load up hill at 100 degrees.

No damage after removing foot from throttle.  Monaco's engineering vp Enoch hutchcraft, my old drag racing buddy, was next to me in this new coach btw.

"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Operating Temp

Reply #9 –
High coolant and EGT temps over an expended period can have a cumulative effect. More on certain engines. I expect this is why the high horsepower Cummins ISX650 is starting to get a bit of a reputation for dropping valves. No matter how big your pocket book is, $20,000+ is a pretty big loss.

Who's in that much of a hurry? When the temp goes up, back out of the throttle and downshift. Cheap insurance.

Piece
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Operating Temp

Reply #10 –
It is a combination of heat, grade and altitude.  Backing off the throttle and downshifting is fine but it will continue to heat. I have pulled over once one the way up to Eisenhower Pass in CO on a hot summer day. I was almost to the top but did not know it.  The engine was 208.  I know that my 36 foot was a rocket ship but this 42 footer with slides and pulling a much heavier jeep is really only noticeable in the summer on grades. 
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Operating Temp

Reply #11 –
Exhaust temp and engine temp aren't necessarily related. One could burn a hole in a piston with an engine temp of 190. Never run above 1250 EGT for more than 20 or 30 seconds. Avoid 1350 altogether
Tom
1998 U320 40'

Re: Operating Temp

Reply #12 –
We drive up hills with an eye on exhaust temp (pyrometer) and RPM (tachometer), always manually shifting and driving slower when exhaust temps gets in 900's.  Our temp probe is just after the turbo so our readings are lower than actual temp in exhaust manifold or exhaust valves.
With our engine and rear axle, as a general rule, we are driving about 40 MPH in 4th gear, 30 MPH in 3rd gear and 20 MPH in 2nd gear (which we seldom have to use).  Since changing our lift pump we are seeing more consistent power and less need to downshift on smaller shorter hills.  Also Bernd, raised up our maximum boost pressure and adjusted injector pump to work with the greater boost, which has helped us.
Most pyrometers have installation calibration issues, but we found a much better design that does not need any calibration.  Our forum write-up is:
Digital Pyrometer & Boost Gauges - VEI Systems

Re: Operating Temp

Reply #13 –
Barry makes a good point. Post turbo readings are at least 150 degrees lower than exhaust manifold readings.

High altitude will raise EGTs. Waste gate turbos won't see a big difference but normal turbo or non-turbo engines will. High temps will raise the density altitude and raise the EGT. Eisenhower Pass at 11,000 feet on an eighty five degree summer day will see about a 15,000 foot density altitude to the engine (and people). A dirty air cleaner plus high humidity will raise it further.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Operating Temp

Reply #14 –
Pierce, the magic word "Density Altitude" I love but for the non fliers probably don't understand ? Especially if you have a PA28R-200.

Re: Operating Temp

Reply #15 –
one good reason to leave the engine stock and not bump up the fuel for more power. Rv ratings are already pretty high.
1998 U270 34'

Re: Operating Temp

Reply #16 –
Dave,

Your Arrow wing liked high density altitude better than our Grumman. Our owner's manual is very optimistic in the length of runway needed. Flaps add drag but not much lift for us.

A co-worker made two gear ups in the same Arrow. How?

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Operating Temp

Reply #17 –
Went up that same incline in March 08 in our 42' U320. That was the steepest incline that we had gone up. Used 2nd and 3rd gear for both the incline and decent, the retarder got used, and coach brakes used very little. We were in no hurry and trying not to make any mistakes. Can not remember the temperature readings.

Reese