Engine heating?

[summutt]

Last month I was climbing a long 7-8% grade (15 miles, pulling my 8000# travel trailer) and as I neared the top, I heard a definite hissing sound & my wife saw (steam?) from under right side of engine housing (near the reservoir, I'm guessing). Typical of overheating, right? BUT the temp guage was reading normal, no overheating at all. Can this be the liquid in reservoir getting too hot, but not affecting engine? Shortly after topping summit, all back to normal.

Thanks.

[snoman]

Last month I was climbing a long 7-8% grade (15 miles, pulling my 8000# travel trailer) and as I neared the top, I heard a definite hissing sound & my wife saw (steam?) from under right side of engine housing (near the reservoir, I'm guessing).  Typical of overheating, right?  BUT  the temp guage was reading normal, no overheating at all.  Can  this be the liquid in reservoir getting too hot, but not affecting engine?  Shortly after topping summit, all back to normal. 

Thanks.

 

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If you are at a higher altitude, it will boil over at a lower tempature. YOur gauge sesor could be in error too as it read tempature down on head, not at thermostat. Myself I do not consider any overheating typical or acceptable. I would take steps to not repeat the experiance. Next time throttle back a bit and gear down and ease the strain because when she is blowing steam you are pulling it too hard for current cooling capacity.

[summutt]

Thanks, Snoman..you're probably right, although I was throttled back pretty good in 2nd gear and maintaining a pretty steady 4000rpm. I've climbed a lot of mountains with this setup without problems until this incident. I'll have to check my records but I think my dealer put in a new thermostat last fall claiming I was running a little too cold. I'll check into this.

[snoman]

Thanks, Snoman..you're probably right, although I was throttled back pretty good in 2nd gear and maintaining a pretty steady 4000rpm.  I've climbed a lot of mountains with this setup without problems until this incident.  I'll have to check my records but I think my dealer put in a new thermostat last fall claiming I was running a little too cold.  I'll check into this.

 

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Also bear in mind that at 4000 RPM cooling can be compromised because most clutch fans will not work above 3000 RPM or so and you will likely not get enough airflow through core from ram air on such a long hard pull especailly at higher altitudes where air is less dense. I would also suggest that you reduce RPM when it is warm on on a long pull and give the clutch fan a chance to engage because it is likely that you never heard it engage on this climb at 4000 RPM. I know people do it but I think 3500 RPM (or less) is better for a pull/climb that can last for a long period of time. Higher RPMs are okay for shorter periods of time but should not be used when cooling may be compromised. You might check for proper clutch fan operation to because as the bimetal coil that controls their operation ages, it tends to raise engagement temps not lower them

[summutt]

Thanks again. I'll do some research on the dutch fan thresholds and pay attention to what I'm doing. I usually don't travel in hot weather (summer) but it has been unseasonably hot where I was this spring.

[snoman]

Thanks again.  I'll do some research on the dutch fan thresholds and pay attention to what I'm doing.  I usually don't travel in hot weather (summer) but it has been unseasonably hot where I was this spring.

 

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For what it is worth, it is easy to tweak GM clutch hfans to be a bit more agressive (I have been doing it for over 20 years). Below is a link with instructions on how to do it if you are so inclined

 

Click Here

[Steady Eddie]

" I know people do it but I think 3500 RPM (or less) is better for a pull/climb that can last for a long period of time. Higher RPMs are okay for shorter periods of time but should not be used when cooling may be compromised..."

 

Motorcoach Guy here...we tow a 4000K# Jeep Grand behind our rig and try not

to exceed 3000 RPMs on ANY hillclimb. Peak engine torque is at 3200 RPMs so

we are right at it, and we just let the Allison trans do its' thing at 3000 RPMs.

If that means 45 MPH in the slow lane, then so be it.

 

Every long haul Trucker knows what we are doing, every Rver knows what we are

doing, (saving the engine) the only finger salutes we get are from young people

who haven't a clue..... .... they are rushing off to their next buy....