Overheat on Long Grade

Topic: Overheat on Long Grade (Read 2839 times) previous topic - next topic

Re: Overheat on Long Grade

Reply #25 – September 21, 2014, 03:57:32 pm

Dave,

On a lot of engines, coolant goes directly from water pump/pre-thermostat to the dash heater lines. This gives faster heater warm up at the expense of slower engine warm up.

Re: Overheat on Long Grade

Reply #26 – September 21, 2014, 04:10:22 pm

I second Brett's suggestion about using a real radiator. Tranny cooler won't do it. There are four small screws accessible from the outside to remove each grill. Measure for the size and then go to ebay for something that will match up. While the heater hoses are small, the lower flow rate through the aux radiator(s) will allow a larger drop in coolant temp. VW did that with the Vanagon with a flat washer with a hole placed in the supply pipe to restrict the flow through the front radiator. The aux radiator will need good ducting so ram air is forced through the radiator, not around it.

I installed a five cylinder Mercedes engine in a MBZ 309D van. The engine was too long and the front radiator would no longer fit so I fitted a large truck radiator flat behind the transmission. A little ducting and it worked fine.

Pierce

Re: Overheat on Long Grade

Reply #27 – September 21, 2014, 04:23:41 pm

I guess I am lucky. In all the years that I owned FT diesels with a Cat 3208 and a Cummins 8.3 I never had overheat problems and I have traveled all the states with most of it in the west. I always found that on a long grade as engine temp started to climb that a down shift to lower gear and reduction in speed and increase in RPM maintained temps without a problem. I have been on grades in CO, WY, MT, UT, CA etc and never had one overheat on me.
AND I never felt like I had to be the first one to the top of the mountain.
Gary B

Re: Overheat on Long Grade

Reply #28 – September 21, 2014, 04:28:12 pm

Makes sense for auto use, I always think industrial apps.

Re: Overheat on Long Grade

Reply #29 – September 21, 2014, 05:24:12 pm

Quote from: Pierce & Gaylie Stewart – September 21, 2014, 04:10:22 pm

I second Brett's suggestion about using a real radiator. Tranny cooler won't do it. There are four small screws accessible from the outside to remove each grill. Measure for the size and then go to ebay for something that will match up. While the heater hoses are small, the lower flow rate through the aux radiator(s) will allow a larger drop in coolant temp. VW did that with the Vanagon with a flat washer with a hole placed in the supply pipe to restrict the flow through the front radiator. The aux radiator will need good ducting so ram air is forced through the radiator, not around it.

I installed a five cylinder Mercedes engine in a MBZ 309D van. The engine was too long and the front radiator would no longer fit so I fitted a large truck radiator flat behind the transmission. A little ducting and it worked fine.

Pierce

I agree with using a radiator, not a trans cooler. A trans cooler will greatly restrict the flow of the system unless it is installed as a loop. The radiator hoses on my U225 were 3/4". The inlet/outlets on the NASCAR 24" X 24" dual core aluminum radiator were only 5/8" so I had 3/4" I/O welded on. The flow from a 3/4" line is better than you think. I plumed it using a two "T"s and a ball valve. To take it out of the heater circuit I had only to reach under the front end and turn the handle stopping the flow to the radiator. As I recall the used radiator was under $200 from ebay.

On the U225 there was plenty of room behind the A/C condenser. I use our dash air and didn't want to sacrifice our air conditioning. The condenser did not have to be moved or even removed for installation of the new radiator. The whole installation took less than five hours. I made bracket out of 1 1/2" aluminum angle from the hardware store and used old inner tubes to prevent wear on the aluminum radiator from vibration. The hardest thing to find were the 3/4" Tees.

Re: Overheat on Long Grade

Reply #30 – September 21, 2014, 05:50:09 pm

Quote

Also cummins documentation states 180-212 for the M11. That's why I killed it at 210. I try to do my best to keep the 15-20 coach bucks in my pocket

Thanks for all the comments. You guys really put my mind at ease that our cooling system is in good shape.

My local cummins shop foreman mentioned in passing that the normal two speed hydraulic cooling fans do not go into high until 210.

My 97 is variable speed.

Most of the specs are for trucks. We are 1/2 weight. M11 crosses into heavy duty engine series. G

Re: Overheat on Long Grade

Reply #31 – September 21, 2014, 06:19:06 pm

All the radiators I found were LOTS bigger...

Craig

Re: Overheat on Long Grade

Reply #32 – September 21, 2014, 06:34:16 pm

Quote from: Kent Speers – September 21, 2014, 05:24:12 pm

I agree with using a radiator, not a trans cooler. A trans cooler will greatly restrict the flow of the system unless it is installed as a loop.

I figured that the trans cooler would be at least as good as the heater. It is already in a loop, right? I mean, when you shut the heater down there is no coolant flowing through it, right? Or do I misunderstand how this works?

Craig

Re: Overheat on Long Grade

Reply #33 – September 21, 2014, 08:40:43 pm

Quote from: Kent Speers – September 21, 2014, 11:03:43 am

One day I accidentally turned on the heater while chugging up a hill and the temp gauge dropped 10 degrees. That prompted the idea of install another radiator behind the grill and A/C condenser and plum it into the heater return hose behind the heater core. This dropped the running temps by an average of 10 degrees during hot weather.

I'm very skeptical that the dash heater or your added cooler have that much of an effect. I wonder, instead, if the return flow from the heater passes right over the temperature sender.

Making HP makes heat. Many car engines run "cool" around 205-215F. If it's holding steady around 210-215 and you are maxing out the HP, nothing is abnormal.

One would have to talk to the packaging engineer at FT to get all the facts, but I rekn' they design the required amount of heat removal to be just about that of full HP of the engine. This means, when you make more HP, the temperature will climb.

Remeber, RV's usually have increased HP ratings (recreational) from the commerical continuous duty ratings.

Re: Overheat on Long Grade

Reply #34 – September 21, 2014, 09:06:21 pm

Yup, if youget BTU's/hour of heat transfer for the primary radiator (fan on high) and for a "supplemental" radiator, you could easily determine whether this was a fool's errand or a significant contributor to proper engine operating temperature.

I can tell you that from a practical standpoint, I have used the dash heater to maintain proper operating temperature on long hard pulls where I wanted to stay at peak torque RPM for lower fuel consumption. Sure, only when ambient temperature would not overheat the interior.

But, I have no problem using dash heater on the upgrade if the dash A/C can bring it back down on the downgrade. Did this more to prove a concept than to use as an every-day solution.

Re: Overheat on Long Grade

Reply #35 – September 21, 2014, 11:09:19 pm

I am curious as to how much cooling capacity has been lost in the last 15 years. Has the radiator ever been professionally cleaned inside and out? Has the engine been flushed of scale and deposits? How much coolant flow has been lost due to age of the pump? Has the thermostat been replaced in 15 years?

While most of my experience is with air cooled aircraft engines, the principles are the same. When cooling capacity is slowly reduced over time, actual engine temperatures tend to remain constant until such time that enough capacity has been lost that the thermodynamic system bootstraps and you get significant temperature increases.

Re: Overheat on Long Grade

Reply #36 – September 21, 2014, 11:14:01 pm

Had several customers install aux cooling on u225's. Front radiators with spray bars and one left and right in the drivers side engine compartment. Both helped. Always wondered about less slip in the torque converter?

Re: Overheat on Long Grade

Reply #37 – September 22, 2014, 10:38:43 am

This seems to be a common issue with U225s that are based in the west. Pierce had the issue, I have the issue and Bob (who was based in the west) noticed several others (presumably on coaches that were much newer at the time).

Judging from ads in various RV magazines, extra cooling is a common issue among DPs anyway.

Once you get to 400 and 500 (and 600!) hp engines with side radiators and big hydraulic fans the issue probably goes away. But the U225 had 230hp to begin with and even though ours has a Banks Stinger package (basically better turbo) the mountains in the west still might be more work than the guys in Texas thought it would ever encounter. Probably not that much of a big deal going from OH or NY to FL. But where I live it's not at all uncommon to go from 700-feet (the Columbia River at Vantage, WA) to 2400' in 10 miles and then another three big climbs and descents; all just to get to Yakima (100 miles).

Heck, I can remember pretty clearly when a lot of cars had this problem.

Craig

Re: Overheat on Long Grade

Reply #38 – September 22, 2014, 11:08:23 am

The solution, drop a gear and don't push as hard on the pedal.

Re: Overheat on Long Grade

Reply #39 – September 22, 2014, 11:26:34 am

Craig,

And I have noticed other U300 owners have also run a bit warm in hot weather. I slow/shift down but in summer, the endless grades on I-70 are frustrating. I have the twin large hydraulic fans and a spotless radiator and no, the issue does not go away as this post's topic originator, Piku has learned.

In driving a 7700 lb fully loaded horse trailer to Ohio in warm weather behind our 3000 lb Toyota RAV4, the temp gauge never moved even over Eisenhower Summit in first gear. So know a cooling system can be designed to have a huge reserve capacity. Ours is marginal at best.

If you mount a front radiator, you might consider a 12V pump (centrifugal only) to help the coolant back to the engine. High temp, 40 liters/min pumps are just under $100. Won't get that flow with friction loss in the hose but it will help. Probably mounted up front where the return hose heads back and powered off the hot side of the ignition solenoid with a switch in the line. I ran my HID headlights off the same terminal.

Pierce

Re: Overheat on Long Grade

Reply #40 – September 22, 2014, 11:37:35 am

If you extract maximum HP continuously out of a car like we do out of our engines on long climbs, it will probably increase in temperature as well.

Also, rear engine, side radiator vs a tractor trailer that has a massive front mount radiator...............they have tons of airflow that doesn't require HP robbing fans to pull.

The BEST solution from an effectiveness and efficiency stand point would be to mount the radiator up front...or have massive scoops on the side.

Designing machines is always about trade offs. Climbing mountains is what % of hours spent driving each year? Downshift, go 5-10mph slower.....

Re: Overheat on Long Grade

Reply #41 – September 22, 2014, 11:50:20 am

You have to figure that they designed it at the min spec for cummins not to intrude into the house part. The new coaches have much bigger cooling packages though and they do intrude. I think it would be a small price to pay.

Re: Overheat on Long Grade

Reply #42 – September 22, 2014, 12:01:44 pm

Quote from: krush – September 22, 2014, 11:37:35 am

Also, rear engine, side radiator vs a tractor trailer that has a massive front mount radiator...............they have tons of airflow that doesn't require HP robbing fans to pull.
The BEST solution from an effectiveness and efficiency stand point would be to mount the radiator up front...or have massive scoops on the side.

You said it all! But why didn't they listen in the GVs? Look at all the room up front. There are already AC plumbing, fuel hoses, heater hoses, power steering hoses, electrical lines running forward so a couple more pipes would have not even been noticed.

Our 4107 had a huge side radiator with direct drive off the engine. Never even got warm. U300s still have 2Wx4Lx2H feet of wasted space in front of the muffler on the driver's side.

Pierce

Re: Overheat on Long Grade

Reply #43 – September 22, 2014, 12:08:50 pm

Quote from: John S – September 22, 2014, 11:50:20 am

You have to figure that they designed it at the min spec for cummins not to intrude into the house part. The new coaches have much bigger cooling packages though and they do intrude. I think it would be a small price to pay.

New coaches also have much more HP, right?

Re: Overheat on Long Grade

Reply #44 – September 22, 2014, 03:16:25 pm

When I was driving big rigs cross country I always put my radiator fan on high BEFORE I started the climb. I did have to turn off the air conditioner a couple times going up the grapevine in mid summer, but I never overheated. Did have the pedal to the metal, don't drive like that now no hurry.

Roland

Re: Overheat on Long Grade

Reply #45 – September 22, 2014, 04:26:20 pm

yes and no. THe small ISX is not much more than the 500 ISM but they run hotter so I guess they need more cooling.

Re: Overheat on Long Grade

Reply #46 – September 23, 2014, 01:52:57 am

Quote from: krush – September 21, 2014, 08:40:43 pm

I'm very skeptical that the dash heater or your added cooler have that much of an effect. I wonder, instead, if the return flow from the heater passes right over the temperature sender.
...

(just getting time to come up to speed on the forum again...)

And the effect of turning on the dash heat (coolant valve control) is exactly what causes our dash temp gauge reading to go down (1999, ISC engine). If you look at the placement of the sensor on an ISC, it's in the coolant loop that goes to the heater, and when there is no flow there, the radiated heat from the turbo will increase sensor temp dramatically.

On our coach, the original water heater had the engine coolant loop running through it, and I suspect that was enough to keep the sensor more accurate. When I had to replace the water heater several years ago, the only one I could get fast didn't have the engine heating loop, and dash temp started increasing dramatically under load. I only figured out what was happening after replacing the sensor and noticing the placement. Now I only go by the VMSpc reading.

And BTW - there is a shutoff valve in our water compartment that cuts off coolant flow to the water heater. If that's closed, there will be no flow past the sensor until the dash heater valve is opened.

Re: Overheat on Long Grade

Reply #47 – September 23, 2014, 02:14:49 am

Quote from: kenhat – September 21, 2014, 12:50:00 pm

Piku,

You might want to check into your high/low switch on your fan motors. I installed a warning light on mine to tell me when high mode kicks in. I've found mine doesn't kick in until my gauge is reading close to 200˚. I've been told it should kick in around 190˚ to 195˚. It could be my gauge is off by a few degrees. I think I'm going to do what Dave Katsuki did and install a switch to manually activate high speed mode when I know I have a hill to climb. That way I can pre-cool everything down and have some reserve for the hill.

I've seen 2 types of high/low switches. Mine is controlled electronically via a solenoid where as others (Dave's) are controlled mechanically. I helped Dave install a solenoid on his (actually I just drove him around to several hydraulic shops as he gathered parts he did all of the dirty work ) to override the mechanical switch. He reported that he noticed a pretty big improvement in cooling on hills using it. He also promised to write up a tutorial on how to install one. I'm calling you out Dave!

It's coming! It's coming! Actually I was putting it off 'cause the coach has been sitting still all summer, so no more real experience with the manual control until we move next week.

Re: Overheat on Long Grade

Reply #48 – September 23, 2014, 06:11:25 pm

Quote from: Carol Savournin – September 21, 2014, 10:15:02 am

One reason we LOVE having the Silverleaf display ... you can read the "load" on the engine and the temperatures when you hit an area like that. We learned how to adjust gears and speed to keep the load in a good range and can only imagine what we were doing before that education!

We agree! The Silverleaf VMSpc has already been most useful, and already I wouldn't want to be without it.

Re: Overheat on Long Grade

Reply #49 – September 23, 2014, 11:31:48 pm

@Dave From Jackson to Denver it's all downhill! Look forward to seeing you and Nancy next week.

see ya
ken

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