Overheating problems?

[racingbob]

I am new to the world of motorhomes and this site. I currently have a 38 ft 5th wheel and am contemplating purchasing a 2005 Tiffin Phaeton 40 QDH, with a 350 Cat. I plan to tow a 28 ft. race trailer. I live near Las Vegas in the desert heat. Here's my dilemma: I have been told that I will have serious overheating problems due to the rear radiator and that the problems wouldn't exist with a side radiator. I have also been advised that it doesn't matter either way as long as the radiator is maintained and kept clean. Looking for any advice to help me make an informed decision...

[racingbob]

I am new to the world of motorhomes and this site. I currently have a 38 ft 5th wheel and am contemplating purchasing a 2005 Tiffin Phaeton 40 QDH, with a 350 Cat. I plan to tow a 28 ft. race trailer. I live near Las Vegas in the desert heat. Here's my dilemma: I have been told that I will have serious overheating problems due to the rear radiator and that the problems wouldn't exist with a side radiator. I have also been advised that it doesn't matter either way as long as the radiator is maintained and kept clean. Looking for any advice to help me make an informed decision...

[Route 66]

Racingbob, welcome to iRV2.

I've linked your post to our Tiffin forum, and I'm sure you'll have some help soon.

[wallynm]

If properly design then NO. Even a side radiator design can be improperly designed. IMHO - Under load and high ambient heat you may need to increase the engine RPM by going to a lower gear to get more air low across the radiator hence more cooling.

[RV Wizard]

racingbob, I like the side radiator for the fact that you can get to the engine much easier for maintenance. Tiffin does build on the Spartan chassis with side radiator also. If you can go for the ISL 400 Cummins too and it will not have to work as hard and probably run cooler in the desert heat. Good luck and welcome to our website; I am sure you will enjoy it.

[SargeW]

Bob, either will work for you. The key is to keep the radiator clean. However, as you are into racing I do not need to preach the value of regular maintanence. Pushers with rear radiators have been around a LONG time. It's all about taking care of the little things to make your machine perform as designed. The most important thing is to ensure that the coach you are considering has the GCWR to handle what ever you are pulling. It is does, then no worries. Hook it up and go!

Sarge

[BrianSue48]

There have been a lot of discussions on various forums about overheating. My experience is that you need to follow the instructions in the owner's manuals. Some instructions are obscure and not everyone is aware of them. Most overheating occurs when pulling hills in hot weather. That hill out of Las Vegas toward LA on I-15 is a prime example. So the Freightliner manual, the Cummins manual, and the Allison manual all say to keep your RPMs up around 2,000 when pulling hills. This means you will have to manually push a button to downshift in many cases. The transmission probably will not do it for you. So the important thing is to watch both the temperature gauge and the tach. As RPMs drop the temp may rise. Normal engine temp is around 204 with a Cummins. On our Bus the warning lights and buzzer will go off at 220. If I see the temp rising to 212 I think it is time to push the button down - at 215 I will downshift. Our normal cruise speed RPMs run around 1,500 to 1,600 - if a hill causes RPMs to drop and outside temp is high chances are I will need to downshift. With the Allison 6 speed transmission you have 4 regular gears and two overdrives. As I recall you can still run around 55mph at 2,000 RPMs in 4th gear. On that hill out of Vegas at around 117 degrees outside I once had to drop down to 35mph I think in 3rd gear - I was still passing some of the trucks. It has been my experience that people overheat because they do not know they actually have to drive at times - that is not expect the vehicle to automatically do everything for them. Hope this helps.

[Pigman]

Racingbob, Depending on exactly when the Freightliner chassis was manufactured, and what their contract with Tiffin called for, the engine crankcase vent may or may not have been extended rearward beyond the rear radiator. If it terminates forward of the radiator, the fan will suck these oily fumes into the radiator and charge air cooler and the resulting oil film will then attract dust and dirt, eventually clogging the radiator. The 05 Freightliner maintenance manual calls for frequent radiator cleaning, however, most Freightliner maintenance folks either will not do it, charge extra for cleaning, or simply lie about it. At best, it is a nasty messy job, but doable yourself or by them.

If the radiator is kept clean, the breather tube extended beyond the radiator, and you watch temps as you take on tough hills, there should be no problems. Enjoy.

[afrank1971]

Bob, I have a Freightliner chassis rear radiator with a CAT 350 in my Winnebago Journey. I pulled a 4500 lbs Honda Pilot up the hill on Highway 156 (Lee Canyon Road) to the Dolomite / McWilliams Campground at the top of Mount Charleston just west of Vegas, in July, without incident. As I started up the hill, I didn't worry about my RPM's, and the heat did start to rise. Then I downshifted, decided I wasn't in a hurry, and kept the RPM's at 2000, the rig actually cooled down going up the hill and then maintained proper temp all the way to the top. That same trip saw the Rockies, Durango, Yellowstone, etc... lots of hills. I also pull a 28 foot race trailer back and forth to the desert several times a year, usually loaded to the max at 10,000 lbs. There are no Rockies between me and the desert, but I have never had any trouble with overheating. The CAT is a good engine, and if you keep the radiator clean, it should serve you well. Good luck.
Alan

[oee77]

Hey Bob,
Glad you asked the question, I had the same problem with my motorhome on the hills and by trial and error began to manually downshift to 4th gear and the engine would cool off as I climbed. I wasn't sure if it was the right thing to do but I guess its normal.

[chasfm11]

We have a rear radiator setup and since I started maintaining it a couple of times a year, we've had no problems. The former owner put about 24K miles on our RV and had taken it to Freightliner for reported overheating problems. The Freightliner dealer worked with Freightliner Custom Chassis and made several modifications (exactly what, I'm not sure.) We had two thermostats replaced soon after our purchase for the opposite problem - failure to come to temperature.

I spray the Charge Air Cooler (the side of the radiator "sandwich" closest to the engine) carefully with Simple Green. The key is to get the cleaner around the perimeter, outside of the direct fan path. I let it soak in about 1/2 hour to 45 minutes and rinse with a garden hose (not a pressure washer) from both sides. If the water doesn't start to run clear within a minute, I stop, repeat the Simple Green application and let it sit about another hour before rinsing. I've only had to resort to the double rinse twice.

We've pulled some pretty good hills and I generally allow the Allison to make shifting decisions unless I need power to pass. The thermostat never climbs more than a couple of degrees.

[historyljc]

Racingbob, all Phaetons are rear radiator. If you want a side radiator you'll have to step up to a bus. I'll add one more thing to the excellent advice already posted, make sure you DO NOT use a high pressure hose on the radiator cooling fins. It will bend them and the radiator will not cool properly. Big bucks for a replacement.

[auburnej]

Learning from towing. Clean radiator. I also use simply green and normal water pressure from a hose . DO NOT USE A PRESSURE WASHER. No high pressure. I pull hills in lower gear. Manually down shfit. Higher RPMS move more air. As recommended by Freighliner dealer in Montgomery, I change air filters 2 or 3 times a year. That little bubble guage does not tell the truth. The turbos, either Cat or Cummings need to really get good air. Keep your tire pressure in your tow car/trailer correct, rolling good.