Keeping our trucks cool, tricks of the trade

[txgp17]

Guys,
In January I was transferred and went from a 2002 model truck to a 2008. Both had Detroit 60's, but the 08' has a cooled EGR valve. The 08' runs noticeably hotter than the 02'.

The manufacturer of the 08' did a few things I've not seen before. The engine cooling fan engages and remains engaged (no cycling) whenever;

1. the midship transmission is in PUMP mode, or;
2. the ECU receives a throttle command from the pump panel throttle.

Since this truck has both a cooled-EGR, and a transmission retarder, you can imagine the radiator is working pretty hard. I've found that when I park, it helps to force the fan to engage, removing massive amounts of heat from the engine compartment, but the thermostat never lets the engine drop below 180°.

The OEM on this truck used a lower quality heat exchanger for the transmission. It went bad before the warranty was up, and cost a pretty penny to repair.

I've also noticed that our newest two Pumpers have auxiliary heat exchangers mounted in the upper radiator hose/line, that are not valved at the pump panel. Whenever you engage the pump, they're cooling the engine before it even reaches the radiator. Doesn't seem like a bad idea to me, unless you're in a really cold climate.

What are some of the tricks of the trade (both designing, and on-scene use) that you guys use to ensure the truck and all it's components stay cool?

Do you think heated water from a heat exchanger should be routed back to the pump intake, or to the tank?

I've read where copper/nickle alloy is stronger and more corrosion resistant than copper alone. Do you specify a certain material for the heat exchangers?

[FWDbuff]

I have seen booster lines tied to the front bumper, spraying a gentle fog mist at the radiator...

I have seen smoke ejectors pointed at the undercarriage of rigs.....

[txgp17]

I have seen booster lines tied to the front bumper, spraying a gentle fog mist at the radiator...

Seen it, and done it. Volunteer Fire Dept pumping a commercial structure fire with a 71' ALF on a Ford C-700 with a 477 V8. It had an auxiliary cooler, but for some reason it wasn't cutting it that day.

[DFDMAXX]

On a commercial chassis open the hood, this will allow much more air to flow through the radiator.

This way the fan doesn't have to pull air in through the front grill, and then force it past the engine to exit under the truck.

With the hood up everything in wide open, nothing to restrict airflow.

This works VERY well on certain trucks.

[Tim1118]

I know you said your newest truck is an '08, so it may not completely apply, but keep in mind that manufacturers are aware of cooling issues, and some of the newer motors will be just fine running hot. Especially with these new emissions, it would be wise to check with either the manufacturer of the truck, or even the engine manufacturer to get input from them. As with a lot of things in the fire service, there may be nothing wrong unless the truck is telling you otherwise. If this is an issue, and by that I mean that it's causing problems or limiting operations, I would get the manufacturers involved.

[Rescue101]

Don't worry about the 180. That Rig is DESIGNED to operate EFFICIENTLY at 195 every day of it's life. Run cooler, you increase carbon and varnish generation and DECREASE Engine life. These aren't your Grandfathers Diesels,they are designed to run HOT and long. T.C.

[rm1524]

Unless you get a high temp alarm there is not a problem. The newer motors run at a higher temp.

As for opening the hood I have to disagree. When you open the hood you are having to pull air around and over the hood to get to the radiator. To cool a motor you need to be getting as much air as possible through the radiator, not around it or behind it.

[DFDMAXX]

Unless you get a high temp alarm there is not a problem. The newer motors run at a higher temp.

As for opening the hood I have to disagree. When you open the hood you are having to pull air around and over the hood to get to the radiator. To cool a motor you need to be getting as much air as possible through the radiator, not around it or behind it.

Air is being pulled through the radiator, that is the function of the fan shroud; to make sure the air being pulled through the fan comes from the radiator, not from around it.

You can disagree all you want, that doesn't change that fact that it works on many of the trucks I deal with. All commercial chassis that were never engineered to sit and pump. They were made to drive down the road with the benefit of the increased airflow to force air in the small grill opening, and help exhaust it from the rear of the engine compartment after travelling through a cramped engine compartment with a low profile hood that doesn't lend itself to interior airflow.

One might ask why such a cab would be used to build a fire truck out of. I know I asked why, and never got a good answer.

[Rescue101]

Guess we're going to have a lovely time disagreeing. I've got three commercial cab Engines(Navistar 2674's)and we're NEVER cracked a hood open(for cooling purposes).......EVER! Comes down to speccing and knowing what you want the vehicle to do. You can pump these wide open for a week at a time and they will never go over 197F.The LAST rig we ever owned that we opened the hood while pumping was our 1939 Diamond T/ Buffalo. Been a few thru here since then and we've never had a problem with overheating Engines. I've also seen some like you describe but of those with problems, most were POORLY specced for application. A Concrete mixer spends quite a lot of time stationary spinning mud and they don't overheat. And many are on Commercial chassis. Spec,spec,spec and DON'T skimp. T.C.

[txgp17]

Don't worry about the 180. That Rig is DESIGNED to operate EFFICIENTLY at 195 every day of it's life. Run cooler, you increase carbon and varnish generation and DECEASE Engine life. these aren't your Grandfathers Diesels,they are designed to run HOT and long. T.C.

I know the engine can handle it, it's the transmission fluid I'm mainly concerned about.

When the ATF gets to a certain point, the TCU will cut out the retarder to reduce heat buildup. I'm at a semi-busy station, and a couple of back to back calls gets that ATF up to 250º easy. The last thing I want is for it to cut out right before I have to make a panic stop.

I wish the truck had a larger heat exchanger for the ATF.

As for opening the hood I have to disagree. When you open the hood you are having to pull air around and over the hood to get to the radiator. To cool a motor you need to be getting as much air as possible through the radiator, not around it or behind it.

I disagree. Every truck I've been on, whether it's cab-over-engine, conventional cab, or custom. When you put the hood/cab up, the cooling fan moves more air. I've gone to far as to time the intervals of the fan clutch cycling while doing a pump service test to verify it.

[Rescue101]

I know the engine can handle it, it's the transmission fluid I'm mainly concerned about.

When the ATF gets to a certain point, the TCU will cut out the retarder to reduce heat buildup. I'm at a semi-busy station, and a couple of back to back calls gets that ATF up to 250º easy. The last thing I want is for it to cut out right before I have to make a panic stop.

I wish the truck had a larger heat exchanger for the ATF.I disagree. Every truck I've been on, whether it's cab-over-engine, conventional cab, or custom. When you put the hood/cab up, the cooling fan moves more air. I've gone to far as to time the intervals of the fan clutch cycling while doing a pump service test to verify it.

Based on MY experience with our Platform(NO tranny retarder)it runs around 250 as well(without PUSHING it).Outside of installing a bigger tranny cooler I don't know what else you can do. Run Castrol Transyn and ask your Allison rep about it but I think you will find 250 is NORMAL. T.C.

[rm1524]

TXG and DFD - I will try raising the hood or cab and see. I have pump testing coming up the end of Aug. We have never had a problem with one overheating. The fan will cycle, but they do that going down the road.

Have had the pump panel temp gauge show the truck was overheating but the cab gauge showed within normal range. That was a bad gauge, it showed 100 sitting in the station with everything cold.

For the tranny I think that 250 is around the normal operating temp.

[FIREMECH1]

Keeping our trucks cool, tricks of the trade....

Replace ALL fluids annually, except engine oil. Backwash your radiator and all other heat exchangers annually, or semi-annually. Replace thermostats every 5 years. Keep on top of the maintenance, and you shouldn't have any problems.

Engine temps should be 195 to 210.

Tranny temps should be 225-265.

And for what ever reason, keep that damn lid shut!!!! Just because you notice the fan is cycling less with the cab/hood up, you have to remember that you're not letting the fan do its job, pulling air across the radiator to COOL the fluid in the cooling system. You're doing more harm than good.

FM1

[DFDMAXX]

Replace ALL fluids annually, except engine oil. Backwash your radiator and all other heat exchangers annually, or semi-annually. Replace thermostats every 5 years. Keep on top of the maintenance, and you shouldn't have any problems.

Engine temps should be 195 to 210.

Tranny temps should be 225-265.

And for what ever reason, keep that damn lid shut!!!! Just because you notice the fan is cycling less with the cab/hood up, you have to remember that you're not letting the fan do its job, pulling air across the radiator to COOL the fluid in the cooling system. You're doing more harm than good.

FM1

Actually its not the fan cycling that I notice, the fan is engaged full time when pumping. When I pump more than 60% pump capacity the engine temp rises above 230 and alarms sound. When I open the hood, the temp drops and never gets above 175.

No, it shouldn't be that way. The truck was spec'd wrong and engineered wrong for this application. All parts working the way they should, checked and double checked.

That is why I stated that opening the hood works very well on CERTAIN trucks. You can't tell me it doesn't work on these freightliners, just like I can't tell you it WILL work on your trucks.

If it works, do it. If it doesn't work on yours then don't.

[txgp17]

250°F in the sump is when Allison says it's overheating. From the Allison Owner's Manual:

3.4 HIGH FLUID TEMPERATURE - The transmission is considered to be overheated when any of the following temperatures are exceeded:

• Sump fluid 121°C (250°F)
• Fluid to cooler 149°C (300°F)
• Retarder out fluid 165°C (330°F)

The section on reduced retarder function begins here.

This the increased loads placed on the cooling system for emissions, I think it's wise to spec a Jake Brake rather than a transmission retarder.

And for what ever reason, keep that damn lid shut!!!! Just because you notice the fan is cycling less with the cab/hood up, you have to remember that you're not letting the fan do its job, pulling air across the radiator to COOL the fluid in the cooling system. You're doing more harm than good.

FM1

Assuming the truck has a properfan shroud, isn't the fan pulling air through the radiator's cooling fins?