f430040 Report post Posted October 12, 2022 I have a 2006 Mandalay 40E on the Freightliner XC-R chassis with the 400HP Cummins ISL and the side radiator. It has 134,000 miles on it. I’ve had ongoing issues with the engine overheating on grades, and I’ve spent thousands of dollars chasing it. I’ve done all the usual stuff; thermostat, the Source Engineering wax valve, confirming the cooling fan speeds, and even a new radiator. I am interested to know what your Intake Air Temperatures are. This information is available in the Silverleaf app, and may be available in other apps, too. I think the final item in my overheat chain may be the charge air cooler. I would like to know two things: The intake air temperature under normal cruise on a level road The difference between the intake air temperature and the ambient temperature I would also like to know the same temps when pulling a grade. I’ve been told that the Cummins spec on this is that the Intake Air Temp should never be higher than 43 degrees F above the ambient temperature. Mine runs a lot hotter than that. Your help will be greatly appreciated. Share this post Link to post Share on other sites
wildebill308 Report post Posted October 12, 2022 Have you ever cleaned the CAC between it and the radiator? Bill Share this post Link to post Share on other sites
rayin Report post Posted October 12, 2022 I agree with Bill; If your differential is greater than what Cummins specifies, the CAC is not doing its job. The coolant radiator is not part of that system. Share this post Link to post Share on other sites
f430040 Report post Posted October 12, 2022 Yes, that whole area was cleaned when the new radiator was installed at Source Engineering. Share this post Link to post Share on other sites
wildebill308 Report post Posted October 13, 2022 Querious, what were they doing that they took the wheels off? Bill Share this post Link to post Share on other sites
f430040 Report post Posted October 13, 2022 The wheels are still on. It’s an optical illusion. The wheels are all on jacks. They lifted the whole coach to get easy access to the radiator area. The rear wheels are hidden by the open basement door. Share this post Link to post Share on other sites
jleamont Report post Posted October 14, 2022 Air intake temperatures shouldn’t cause an overheating condition in the cooling system. Sluggish, lacking power poor MPG’s, all day long. Are you sure it’s actually getting hot, could it be a sensor issue providing bad data? since you’ve already conquered where I would have started I’d check the lower radiator hose, is it collapsing under load? are we sure the fan is engaging? what RPM are you pulling hills? How many PSI is the radiator cap? I would call Cummins with your engine serial number and see what PSI cap that engine is supposed to be equipped with. our coach would climb to 215 and it had an 8psi cap on it, I swapped it for a 14 PSI CAP, never had an issue again and I’ve never gone above 200 since. Per Cummins our vintage ISL could handle up to 18 psi. Share this post Link to post Share on other sites
wildebill308 Report post Posted October 14, 2022 I think Jleamont has touched on some good points. One of the most important is "what RPM are you pulling hills?" Are you downshifting to where it will accelerate and then hold that gear at about 2000 RPM till you get to the top of the grade? Bill Share this post Link to post Share on other sites
f430040 Report post Posted October 17, 2022 On 10/13/2022 at 8:23 PM, jleamont said: Air intake temperatures shouldn’t cause an overheating condition in the cooling system. Sluggish, lacking power poor MPG’s, all day long. High intake air temperatures certainly WILL cause an overheat condition! When the intake air temperature is 160 degrees F the engine will run a lot hotter than if the intake air temperature is 60 degrees. All that heat has to go somewhere. Are you sure it’s actually getting hot, could it be a sensor issue providing bad data? It’s getting hot since you’ve already conquered where I would have started I’d check the lower radiator hose, is it collapsing under load? No. are we sure the fan is engaging? Yes. what RPM are you pulling hills? 2,000 RPM How many PSI is the radiator cap? Good question…I don’t know. I’ll have to check on this. But this has nothing to do with high intake air temperatures. I would call Cummins with your engine serial number and see what PSI cap that engine is supposed to be equipped with. our coach would climb to 215 and it had an 8psi cap on it, I swapped it for a 14 PSI CAP, never had an issue again and I’ve never gone above 200 since. Per Cummins our vintage ISL could handle up to 18 psi. Share this post Link to post Share on other sites
jleamont Report post Posted October 17, 2022 (edited) If your air intake temperature is a legitimate 160 degrees you’ve got some serious design flaws or a hole allowing hot gasses to enter the intake. By chance did someone modify the engine bay layout or close off the places for hot air to escape? any exhaust leaks, perhaps a collapsed muffler (internal) By design air filters and almost all piping is on the opposite side of the exhaust. Only the turbocharger inlet should sneak over and drop into the turbo. Do you have a infrared temp gun, I’d get that engine hot and start looking at my engine bay and CAC temperatures. Edited October 17, 2022 by jleamont Share this post Link to post Share on other sites
wildebill308 Report post Posted October 18, 2022 You said " When the intake air temperature is 160 degrees F the engine will run a lot hotter than if the intake air temperature is 60 degrees." How do you know what the temp is if you don't have a gage? At what ambient temp? Do you know what your EGT (exhaust gas temp) is and what # boost are you pulling on the hills? The only time I had any problems with running hot on hills with my old coach was when my EGT was hi. Bill Share this post Link to post Share on other sites
jleamont Report post Posted October 18, 2022 22 hours ago, wildebill308 said: You said " When the intake air temperature is 160 degrees F the engine will run a lot hotter than if the intake air temperature is 60 degrees." How do you know what the temp is if you don't have a gage? At what ambient temp? Do you know what your EGT (exhaust gas temp) is and what # boost are you pulling on the hills? The only time I had any problems with running hot on hills with my old coach was when my EGT was hi. Bill I had the Mustang in traffic down here back in June and my air intake went up to 120, felt like I lost 1/2 the engine and it almost stalled out hen I mashed it from a traffic light 😂. 2008 we went across the Mojave in our gas coach, 120 was the ambient temp, my intake temp went up into the 140’s, coach was pinging like an old Cat diesel on acceleration but coolant temp never budged over 198 with a 195 thermostat. Share this post Link to post Share on other sites
jleamont Report post Posted October 20, 2022 Here is another post you might want to read; did anyone pressure test your cooling system for leaks? Share this post Link to post Share on other sites
f430040 Report post Posted October 23, 2022 On 10/19/2022 at 8:15 PM, jleamont said: did anyone pressure test your cooling system for leaks? No, however I’m not losing any coolant. On 10/17/2022 at 8:33 PM, wildebill308 said: You said " When the intake air temperature is 160 degrees F the engine will run a lot hotter than if the intake air temperature is 60 degrees." How do you know what the temp is if you don't have a gage? At what ambient temp? I DO have a gauge! It’s all in Silverleaf. Intake Air Temperature is one of dozens of performance stats that can be monitored. The ambient temperature at your location is easy to get via weather apps on the phone. Do you know what your EGT (exhaust gas temp) is and what # boost are you pulling on the hills? I do not know the EGT (it’s one of the few things not reported in Silverleaf). However, I think the computer controls the throttle to prevent excess EGT temps. I’m pulling roughly 30 psi at WOT at 1800-2000 RPM. Based upon what I’ve read on the net plus additional information I received in some private emails, I’m convinced that my CAC is not doing it’s job. I’ve already ordered it, and the folks at Freightliner in Gaffney will install it in February. Share this post Link to post Share on other sites
jleamont Report post Posted October 24, 2022 Best of luck to you, I hope it solves your problems. Share this post Link to post Share on other sites
wildebill308 Report post Posted October 24, 2022 Best of luck to you, keep us updated. Bill Share this post Link to post Share on other sites
