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Topic: trans and engine temp - scare me or reassure me (Read 1621 times) previous topic - next topic

Re: trans and engine temp - scare me or reassure me

Reply #25 –
My U225 with a B5.9 had a 185 thermostat. You may want to check with Cummins to see why yours is running at 160. That sounds too low to me. Cummins in OKC told me that taking out the thermostat or running with the wrong one could damage the engine.

Mine had a transmission cooler in the radiator tank itself.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: trans and engine temp - scare me or reassure me

Reply #26 –
Quote from: Dave M –
On my initial trip home from Florida, ambient temps were in the 90s with high humidity. The temps on my 91 U225 5.9 Cummins were at about 200, and the MT643 Allison was around 160. By nightfall the outside temps has dropped to around the mid 60s, and coolant temps had dropped to around 160, with the tranny in the 120s.

Do any of these coaches come with an external transmission cooler? Has anyone added one? Just curious.

Steve

Two points.  Engine coolant temperatures of 160 when it is cool out and 200 when it is warm out is a classic symptom of a stuck thermostat.  The 160 more so than the 200.  The operating temperature should never drop below the thermostat opening temperature except perhaps at idle is very cold weather.

I have not added an external transmission cooler, but DID add a transmission type cooler to the fuel return line.  Particularly with the location of our fuel tanks in a pretty well insulated bay and the high bypass fuel systems on all modern diesels my fuel temperatures at the tank on hot days was over 130 degrees F.  Now, it is ambient plus just a few degrees.

A high bypass fuel system is one where for every gallon of fuel that goes to the engine, only a few ounces are burned,  the rest is used for cooling and lubricating the head and injection components and then returned to the fuel tank.

Brett
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: trans and engine temp - scare me or reassure me

Reply #27 –
"could not duplicate customer complaint"

Today in nearly identical circumstances - small hills, 100-degree weather, strong headwind, etc., the coach coolant temp was 180 before we made it out of the campground and never went beyond 190 0r 195, despite my being liberal with the pedal, hoping to duplicate the symptom.  Trans never went beyond 180.

There is a problem seen in stern-drive boats, where it overheats, the operator stops and inspects, finds nothing, and the problem does not recur.  The source of the problem is plastic grocery bags floating in the water.  They hang on the drive, cover the water inlets, and fall free when the boat is stopped.  Has anyone ever picked up a piece of road trash with the coach cooling air intake?

oldMattB
Matt B
1998 u-320

Re: trans and engine temp - scare me or reassure me

Reply #28 –
While traveling along the Skyline Drive in the fall a few years back our coach started to show higher temps then normal. Upon inspecting the side mount radiator I found an accumulation of leaves sucked up against the cooling fins of the radiator. I had to shut the engine down to allow the leaves to fall to the bottom of the compartment, I then cleaned them out as they cannot fall through to the ground. Also while traveling on a muddy stretch in Yellowstone National Park I had the same problem with mud from the roadway being sucked into the radiator fins and having to flush them out to get proper cooling... Any time my coach temperature starts to rise above normal I find a safe place to pull over and inspect the radiator fins....
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Gerry & Brenda
CHARLOTTE HARBOR, FL
1994 Grand Villa - # 4466
U300 Unihome - 6V92 Detroit
4 speed Allison - Jake Brake

Re: trans and engine temp - scare me or reassure me

Reply #29 –
Quote from: oldmattb –
We bought our coach in the cool weather.  When we drove it, the engine would stay about 180, and the trans would barely get a reading, maybe 120 on a long, not steep hill (not many big hills in East Texas).

Today engine and trans hit about 220.  We are towing a small car.  The outside temperature is 103-104, and the roadway is probably more like 120. The CAC was flushed thoroughly several months ago.

Is all "cool," so to speak?

BTW, we are in Lubbock, to visit the Buddy Holly Museum.

OldMattB

Assuming you have the standard thermostat for the engine (if Cummins ISL) it would be a 180F rating.  Thermostat ratings are based on the 'crack open' temperature; the temperature at which it just begins to open.  On a hot day and loading on the engine from the toad and a hill, it is not unreasonable to see 220F as your cooling system should have an adequate pressure cap.  Pressure cap ratings are specified by the engine manufacturer, not the chassis builder.  Pressure on the coolant increases the boiling point.  Coolants that operate at higher temperatures are able to remove more heat  (without film boiling) from an engine than lower rated pressure cap systems.  Over the years as engine HP ratings have increased the cooling systems have not been able to keep pace due to size constraints.  Radiators are essentially the same size.  Increasing the pressure cap ratings increases the coolant heat rejection properties.  Earlier ISC, ISL engines of a few years ago had Cummins required minimum pressure cap ratings of 7 PSI.  You can increase the cap rating but cannot go backward on any current engine. 

Maintaining your cooling system coolant freeze point at -34F (50/50) is important.  If you find the freeze point is lower than that, the glycol percentage is elevating.  Most diesel engine manufacturers recommend a maximum glycol content of 60% (-64F for EG).  Going beyond this by refilling low coolant levels with concentrate antifreeze is working against you.  At 65% glycol content, the heat transfer properties of your coolant are severely hampered not to mention also that the SCA in the coolant has less 'solvent' (water) to stay dissolved.
Gary Spires
Coolants, Cooling Systems, Filtration, Diesel Engines

Re: trans and engine temp - scare me or reassure me

Reply #30 –
We have been taught that a thermostat at 180 deg starts to open at the 180, and is  fully open at 200 deg.  any temp above that is due to lack of cooling ability.  Meaning if you go over the 200 into the 210 area, you have a problem and the temp will keep climbing until you do something like back off the fuel (throttle),  add water spray or get a better cooling system because the thermostat is fully open and the temp keeps climbing.

Re: trans and engine temp - scare me or reassure me

Reply #31 –
Quote from: Dave M –
We have been taught that a thermostat at 180 deg starts to open at the 180, and is  fully open at 200 deg.  any temp above that is due to lack of cooling ability.  Meaning if you go over the 200 into the 210 area, you have a problem and the temp will keep climbing until you do something like back off the fuel (throttle),  add water spray or get a better cooling system because the thermostat is fully open and the temp keeps climbing.

Dave,

That teaching is somewhat still true.  But, late model EGR diesel engines like the ISL 400 Cummins are designed to operate at "up to 230F".  That information comes from my counterparts at Cummins in the midrange service group.  That does not mean they will but the engine is capable of sustained operation in that range. 

The old rule of thumb is still true....."the thermostat controls the minimum operating temperature, your foot controls the upper end of the temperature range." 

A correctly functioning radiator system will drop the engine coolant temperature 7 to 15 degrees F across the core when the thermostat is wide open.  Engines that are operating at 220F assuming the dash gauge is really that accurate (doubtful) and maintaining that temperature during extended operation are still in control of the temperature.  When temps slowly but steadily rise under sustained loading, then the system may have a problem with coolant flow internally or air flow externally. 
Gary Spires
Coolants, Cooling Systems, Filtration, Diesel Engines

Re: trans and engine temp - scare me or reassure me

Reply #32 –
Gary, Glad to meet you here (WG4T), I seem to recall there was a listing of Cummins ISL spec sheet, showing thermostat 180f to full opening of 201f, my concern would be knowing it is full open at the 201f, and kept pushing it, watching the temp rise, knowing there is a problem, 230f scares me.
On the other hand I am sure you know Waukesha years ago started cooling their large gas engines with steam, running about the 400-450f range.  Not sure what ever happened as I got away from that class of engines and Cat.
For me, if I get to the 200f area I find a way to limit it to not exceed like a different gear anything to unload it.
Why on my 12V-71TT I had to spray the radiator with a mist, worked great. ;D

Re: trans and engine temp - scare me or reassure me

Reply #33 –
Gary, I am so glad you are with us on Foreforums. The subject of "how high is too high" frequently comes up. I'm sure it is different with different engines but I know the mechanical 5.9 Cummins had a top temp of 240. It used to scare me to death when it hit 220 but then I found out that was normal when pulling a load in high summer heat. I wish you had been around before I spent over $2000 trying to keep it under 200. Bye the way, that never happened. 
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback