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Karlee1114 · 08-04-2008, 11:39 AM

We have an Allegro Bus on a Freightliner Chasis, Cummins 400 HP. We have been experiencing overheating issues since we purchased the motorhome. The MH has been in for service with Freightliner over 10 times and they have replaced everything they can think of. Now they are wanting to replace the radiator with a new "double" radiator that will require them to cut into cubbies and will hang lower in the back. Has anyone else had this issue? If so, what did you do...did you let them replace the radiator and where you satsified?

Karlee1114 · 08-04-2008, 11:39 AM

We have an Allegro Bus on a Freightliner Chasis, Cummins 400 HP. We have been experiencing overheating issues since we purchased the motorhome. The MH has been in for service with Freightliner over 10 times and they have replaced everything they can think of. Now they are wanting to replace the radiator with a new "double" radiator that will require them to cut into cubbies and will hang lower in the back. Has anyone else had this issue? If so, what did you do...did you let them replace the radiator and where you satsified?

quikduk · 08-04-2008, 01:08 PM

We have a Gulfstream DP and it has some issues that I am trying to work out as time and $$$ allow.

1. It is a rear radiator design with the CAC (Charge Air Cooler) sandwiched close (2-3") to the radiator and in front of it. BAD design IMHO as airflow is restricted.

2. It uses a non-viscous engine driven fan meaning no clutch to help save fuel and lock in when needed so it spins all the time.

3. The crankcase vent tube ("slobber tube") was aimed back into the rear fans airflow effectively helping plug up parts of the CAC and radiator cores.

I have relocated the slobber tube for now with a longer heat resistant tube and will plumb this into a modified race coolant recovery tank (ventilated with drain fitting) so eventually, it will not mark up my driveway when it drips...

nor plug the cores further.

I have degreased the cores and will continue to do so until they are perfectly clean, then before and after each trip as preventative maintenance.

I am also working on a fix for access to each cores inner "captured" side by making the bottom of the radiator shroud removable. I can then get a hose etc. in between the cores to help degrease and rinse them out as access is severly restricted from the fan side.

I will also most likely be adding the biggest set of double electric "puller" fans to the radiator on the outside surface to help increase the "draw" through the cores.

All of these are educated guesses at fixing the problem. It can run hot on hot days and pulling steep hills. The current and final adjustment is to our driving style. This thing is big (not as big as some but bigger than your average passenger vehicle) and we make sure to shift down at least one gear, possibly two in the transmission on steep, long ascents and when pulling heavy towed loads up the same grades. This makes the engine run around 1600-1800 RPM which helps cools the engine down while driving.

In extreme circumstances (pulling up an +11% grade with a +5,000# toad in +110 degree heat this past June) we pulled over for a few minutes and I ran the engine up around 1800 RPM in neutral (with the brakes set) while my DW made sandwhiches. The coach and I cooled off and away we went. We did this twice over the long grade and I suspect this will become S.O.P. until I can get the mods finished, and a pyrometer (used to measure exhaust temp) and a boost gauge (used to measure turbo boost/performance) added.

Good luck and let us know what you decide. BTW, I thought about making a side mount conversion but I would lose interior space and it would take some carefull engineering to make it work out...not to mention the $$$$$$.

quikduk · 08-04-2008, 01:16 PM

OAN, IF (and a BIG IF) the radiator gets replaced, why cant they go to a high capacity core or even a HCC aluminum model? These can be custom ordered from a variety of race car shops with any configuration and mounting immaginable. I would immagine that it would cool much better and wouldn't require a coach interior mod. Have it designed around your existing space limitations, expanded where possible and made as big as possible with the maximum flow and cooling possible.

There are some fluid dynamic calcs involved here but any competent race engineer can figure them out based on your engine/trans. published data.

Just another $.02