Author Topic: Climbing A Grade  (Read 12787 times)

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Offline jimnina

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Climbing A Grade
« on: August 20, 2015, 06:44:57 PM »
We have an 2003 39' DP with CAT 330HP w 6 spd ally trans. The problem we are having is getting up a grade without overheating.I think the biggest problem is the nut behind the wheel :P.
Every time we drive !-26 going through South Carolina I can't seem to make it without having to pull over to cool down.
We bought the DP mainly to go out west when we retire in 3.5 years. But, heck I can't even drive the smaller mountains on the East side.
My better half is worried so I thought I would ask some folks that have mastered the process.
I have tried both modes on the tranny. I have tried full throttle and less than full throttle.
I have even tried watching the RPM's and I think I can tell when I have failed the test.
Any help will greatly benefit me and my better half.

Online Brett Wolfe

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Re: Climbing A Grade
« Reply #1 on: August 21, 2015, 06:12:45 AM »
jimnina,

Welcome to the Diesel RV Club.

Yes there are some driving techniques that will lessen the chances of overheating.

But, the first thing to do is verify that the FRONT of your CAC (Charge Air Cooler) is not blocked and that your crankcase vent hose (right side of engine-- 1" ID open hose) has been routed to behind the fan shroud. 

Here is a link to a discussion on this: http://forum.dieselrvclub.org/index.php/topic,6601.0.html

Please let us know what you find.

Another thing to check are your water pump belt tension (can be checked from underneath-- driver's side of engine.  It is the small V belt, not the large serpentine belt.

Also how old are your thermostat(s)?

After making sure that your cooling system is operating as it should, we can discuss driving techniques.  Basically you want to keep the engine between 2000 and 2100 RPM and hopefully at less than wide open throttle when overheating occurs.

Offline antiqueclockservice

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Re: Climbing A Grade
« Reply #2 on: August 21, 2015, 06:37:06 AM »
Hi folks,

I just finished climbing steep grades on US95 in Nevada in 100 deg. temps.  Got a bit warn, but no overheating.  I found 2300 rpm works best for my CAT C7. 

Best,
Phil
Best,
Phil

Online Brett Wolfe

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Re: Climbing A Grade
« Reply #3 on: August 21, 2015, 08:55:37 AM »
Phil,

What may work, but is past peak HP RPM and very close to governed RPM (2400).

If you look at the HP and torque curves you will see that past 2200 both drop off rapidly: http://forum.dieselrvclub.org/index.php/topic,6623.0.html

Offline David.e.atherton

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Re: Climbing A Grade
« Reply #4 on: August 21, 2015, 01:18:18 PM »
jimnina, heating. sounds like your radiator is plugged up even when it looks clean possible
first choice of problem. looking at your little plastic tank on top is it full of coolant, next is
little hose by radiator cap spitting water, or steam out bottom of hose when super hot. Along side
of road does engine cool down real quick on temp gauge. answer to the above is yes than
second possible choice of heating. thermostats ( 2 ) you may have one sticking half way open.
have you changed coolant in your radiator since you owned motorhome and is it green in color.
Bertt, can update you in this area with coolant. remove and install new thermostats. getting a
IF heat gun to ge reference to engine operating temps at radiator on top tank and at bottom tank.
Dave Atherton Retired Cat Mechanic.

Offline jimnina

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Re: Climbing A Grade
« Reply #5 on: August 21, 2015, 01:39:49 PM »
Brett,
Thanks for the reply. The hose, CAC, and belt all look fine. I guess I should also mention that I have only had the coach a little over two years.But I did have to replace the engine due to lack of maintenance by the previous owner. I had the CAT dealer do the repairs, so all of the thermostats, belts, and hoses were replaced at that time. They also cleaned the radiator while it was out.
Long story short, Big hole in air filter washed out turbo, head, and cylinders past factory specs. The Radiator was also 2/3rd clogged up with oily dirt. Since the motor only has 11K miles on it could that be helping me in not being able to keep it from overheating?

The RPM tip and throttle info should help me tremendously. I guess I wasn't googling the right spot for the RPM sweet spot for this type driving.. Off topic but will the fuel mileage increase as the engine breaks-in? We avg about 8 MPG Flat towing a Honda Accord Coupe

Online Brett Wolfe

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Re: Climbing A Grade
« Reply #6 on: August 21, 2015, 02:08:28 PM »
Has the engine always heated up on grades, or is this a recent occurrence?

And, please confirm that you have shined a flashlight inside the fan shroud (access from bedroom) and that the lower perimeter of the CAC is as clean as the center.

Also, that the crankcase breather has been extended.

Cleaning the front of the CAC is really an annual chore on a rear radiator coach.

Yes, MPG usually improves as the engine breaks in and you do the first valve adjustment (about 30K miles for the first valve adjustment.

Offline David.e.atherton

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Re: Climbing A Grade
« Reply #7 on: August 21, 2015, 04:04:33 PM »
jimnina, you  just said answers lots of questions in trying to help you. first of all getting 8 mpg
pulling car is excellent milage. ( no problem on that end )  11,000 miles in two years is also
answering lots of questions. was the work preformed at a cat dealer ,I can see that just put in a reman block or a reman engine. With this being said I feel you do not have a problem just need to
Go out and work the engine and put some miles on motorhome.
Dave Atherton retired Cat mechanic

Offline antiqueclockservice

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Re: Climbing A Grade
« Reply #8 on: August 22, 2015, 06:22:10 AM »
Hi Bret,

Had a running hot experience yesterday on US93 between Boulder City NV and Kingman AZ. Going up a long grade (102 degrees outside).  2000 rpm with the guage starting to climb, downshifted to 4th gear and held 2300 rpm.  Temp started to come down.  I got just a blink on the dash readout of 221 degrees water temp but at the higher rpm the warning cancelled.  I am thinking that 2300 reduces the heat of rejection from the motor and increases the water flow.  Is my thinking flawed?

Best,
Phil
Best,
Phil

Offline David.e.atherton

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Re: Climbing A Grade
« Reply #9 on: August 22, 2015, 08:14:40 AM »
Phill, climbing the grade under load at higher rpm's the engine ( stayed at temp where if at lower
rpm's heat would been extreme). Reason heui system uses the diesel fuel to cool the injectors
with excess unused fuel going through injecters returning back to the fuel tank. It is spelled out
in tech service manual, heating conditions will be present if lugging condition are present with
engine under load. Diesel fuel is used to fire the injectors, cool the injector and movement of fuel removes air bubbles from fuel rail in cylinder head returning diesel fuel back to fuel tank.  Dave Atherton Retired Cat Mechanic

Offline Pinkertonk

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Re: Climbing A Grade
« Reply #10 on: August 22, 2015, 02:33:04 PM »
David, does this mean that when rolling hills or climbing near peak torque RPM and the engine starts to overheat, downshifting and running at a higher RPM will help cool the engine down?
Kerry Pinkerton
2003 Fleetwood Discovery 3126 Cat
77 GMC motorhome
North Alabama

Online Brett Wolfe

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Re: Climbing A Grade
« Reply #11 on: August 22, 2015, 03:20:38 PM »
David, does this mean that when rolling hills or climbing near peak torque RPM and the engine starts to overheat, downshifting and running at a higher RPM will help cool the engine down?

Absolutely.

It takes the same HP to climb a grade at a certain speed.  If that HP is generated at a higher RPM (lower throttle setting), two very important thing happen:  The water pump turns faster.  The fan turns faster.  Both help the engine run cooler.


Offline David.e.atherton

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Re: Climbing A Grade
« Reply #12 on: August 22, 2015, 05:16:38 PM »
Jimnina and Pinkertonk, I have suggested different thoughts on heating with engines but have asked questions that would be nice if answered so we can help both of you. Question number 1, how much
coolant have you added to radiator little plastic tank ? Second question when heating at peck, is
there any fluid or steam coming from little hose at radiator cap. Third does engine cool down real
soon after you climb long grade or stopping half way up grade to cool down. I take it both of you
have rpm's around 2000 or higher and transmission out of mode operation. This information would
be very helpful. Dave Atherton Retired Cat Mechanic

Offline Pinkertonk

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Re: Climbing A Grade
« Reply #13 on: August 22, 2015, 05:50:38 PM »
Guys, I don't have an overheating problem.   I am just brand new to diesels and trying to get up to speed as fast as I can.  The whole concept of running at max torque (for me 1440 rpm) is going to take some getting used to.
Kerry Pinkerton
2003 Fleetwood Discovery 3126 Cat
77 GMC motorhome
North Alabama

Offline David.e.atherton

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Re: Climbing A Grade
« Reply #14 on: August 22, 2015, 07:42:09 PM »
Pinkertonk, I can see what your thinking ,but your going to have a heating problem trying to
climb a grade at max torque at 1440 rpm's, your injectors will opened for max fuel but engine rpms
are below where engine cannot pick up any power so engine will go into lug mode. if you
scroll up to Phil's post climbing grade at 2300 rpm's, this is what you are looking for, thanks Phil
Dave Atherton Retired Cat Mechanic

Offline Ava

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Re: Climbing A Grade
« Reply #15 on: February 24, 2016, 04:31:56 PM »
On my 94 Bounder with 5.9 Cummins and 6 speed Allison I have found I can make it up any of the hills so far with 4th gear at about 2000 rpms.  My foot is not to the floor, the temp gauge goes up slightly and returns to normal within a few seconds of leveling out. 

Offline RIch

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Re: Climbing A Grade
« Reply #16 on: December 31, 2016, 08:34:36 PM »
Guys, I don't have an overheating problem.   I am just brand new to diesels and trying to get up to speed as fast as I can.  The whole concept of running at max torque (for me 1440 rpm) is going to take some getting used to.

Where did you get the idea that you should run at max torque? You run at whatever RPM you want when on level ground.

When climbing grades, you want max HORSEPOWER, not torque. The HP peak in most diesels is in the 2,000 to 2,200 area. In my coach, 65 mph in 5th gear does it.

Offline ziggyh

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Re: Climbing A Grade
« Reply #17 on: January 01, 2017, 07:09:27 PM »
I have found claiming long steep grades at 14-1500 rpm makes heat, on short climbs not much change, at 1800 rpm on a long climb heat production is less.  I also take a little run at a climb if traffic permits and slow at the top, would rather start a decent on the slow side vs too fast.
ZiggyH

2007 Revolution LE
C9

Online Brett Wolfe

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Re: Climbing A Grade
« Reply #18 on: January 02, 2017, 05:58:32 AM »
Just a word of caution when referring to "proper RPM":

The larger the engine (actually, the longer the stroke) the lower the operating RPM range.  So, one answer does NOT fit all.

And that range is from "peak torque RPM" at the low end up to "peak HP RPM" with that peak HP RPM many times being a little lower than "max/governed RPM".  And, above that is "max RPM, no load" for when using exhaust/engine brake.

So, while a smaller engine may operate up to 2,600 RPM, that speed could tear apart a larger engine.
« Last Edit: January 02, 2017, 02:02:01 PM by Brett Wolfe »

Offline RIch

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Re: Climbing A Grade
« Reply #19 on: May 28, 2018, 07:50:35 PM »
No matter what you do, you cannot over-rev a diesel engine in a modern motor home. The ECM will not allow it. If you attempt to over-rev the engine by holding the transmission in a lower gear at wide open throttle, you’ll just hit the rev limiter and stop accelerating.

Offline David.e.atherton

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Re: Climbing A Grade
« Reply #20 on: May 28, 2018, 10:27:17 PM »
Rich, Answer your question you have many fails safe along with the Engine ECM. However
Different cases like  over RPM on long grade. Do it yourself home mechanic going out of
the window. Making unwarranted repairs in areas they think will give more power. Add on
aftermarket parts. Adjustment to the turbo wastegate beyond spec. Rich might want to add
being you are new lack of understanding about the turbocharger wastegate. To many feel
the higher the boost pressure is the more power you have. This is a incorrect statement your
engine gets its power via: air fuel mix and same time engine ECM provides more fuel until
Your Fuel Rate control shuts off your fuel. ( the fuel rate control is preset at factory and cannot be reset. Going back on your wastegate which pack more air into your engine the waste
gate controls the RPM of the turbocharger for example Cat 3126 E had 24 pounds of boost
pressure now is in full open. Many people play with wastegate adjustment and end
up taking your engine out. To answer the above question at start of post the engine ECM
will not prevent from an engine runaway . Ask Dave Dave Atherton Retired Cat Mechanic


Offline RIch

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Re: Climbing A Grade
« Reply #21 on: June 04, 2018, 07:44:36 PM »
...Rich might want to add being you are new lack of understanding about the turbocharger wastegate...

I’m new to this forum, but have been driving turbocharged diesels and flying turbocharged gasoline engines in aircraft for many years. I fully understand how a turbocharger works and what a wastegate is. However, most modern diesel engines in motor homes don’t even have a wastegate in the turbocharging system. That’s old tech.

Modern diesels use a Variable Geometry turbocharger. No wastegate.


As for the rest of your post, it is thoroughly confusing.
« Last Edit: June 05, 2018, 08:30:41 AM by Brett Wolfe »

Offline David.e.atherton

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Re: Climbing A Grade
« Reply #22 on: June 04, 2018, 09:32:18 PM »
Rich, think you have a valid point on engine turbochargers however not all engines  Caterpillar
have the internal sliding ring that moves via internal arm operated on electrical from engine
ECM. We are talking later Cummins engines ( earlier ISB, ISC and ISL engines ) have a
external wastegate. All the Caterpillar engines have external wastegate. Again let me explain
The wastegate opens at a factory set measurement to control turbocharger rpms to prevent
engine run away. The air/fuel ratio of fuel into engine is controlled by a preset factory eating.
To many operators feel the higher the boost pressure is the more power the engine is putting
out, this is a incorrect thinking. After the FRC limint is reached wastegate is in full open
Position and excess boost pressure is dumped out the exhaust and engine rpms is maxed
Out  Dave Atherton Retired Cat Mechanic

Offline dbhutchins

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Re: Climbing A Grade
« Reply #23 on: September 02, 2018, 08:58:17 AM »
Some excellent info here, gents. Thanks for all of that.  But I'm new enough to the big DP world that I'm not certain what you all mean by overheating.  My 48,000 lb Country Coach with Cat C-9 runs pretty consistently at Coolant temp in the high 190's/low 200's, oil temp around 210-220.  When climbing I see increases to around 210 and high 220's respectively.  I'm thinking these are normal temps.  Can somebody educate me?  What ARE temps to cause alarm, if these do not?  Much appreciate any inputs...
Don Hutchins
'08 CC Allure 470 #31613
Don Hutchins
'08 CC Allure 470 Cat C-9 w/ Cat tranny