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My $0.02:
Make sure you're getting enough airflow through the coolers. Not just plenty of open area in front of the coolers, but make sure there's a good path for the air to flow through and out of the engine compartment. If there's no place for the air to go, you'll get less pressure drop across the cores, and much less airflow. Out the sides would likely be better than under the vehicle from a pressure perspective, but may not be practical. I'd relocate the trans cooler too. Not only will it reduce airflow through the radiator, but it will also heat the incoming air, so your radiator will think it's a much hotter day than it actually is. Another member mentioned you'd routed coolant elsewhere/added something to the coolant circuit. Is this the case? As long as the engine is stock (or close to it) and there are no transmission temp issues, there should be no issue with radiator capacity in normal conditions. |
Originally Posted by gman07
(Post 3180742)
My $0.02:
...Another member mentioned you'd routed coolant elsewhere/added something to the coolant circuit. Is this the case? As long as the engine is stock (or close to it) and there are no transmission temp issues, there should be no issue with radiator capacity in normal conditions. |
I think the thought is that the water pump cannot circulate that much extra fluid/distance, it is not a positive displacement pump so it will only push so much fluid than it will just spin its wheels so to speak. That is what the reference to an aux pump was back a few posts, to help the water pump circulate.
It shouldnt be hard to check, just put valves at the take off points to isolate the water heater loop. This will put it back to normal for testing purposes anyways. Removing the t-stat may have a similar effect as it will allow more volume to ciculate but is only a bandaid at this point. |
Originally Posted by ClassA4x4
(Post 3180744)
Yes, the coolant is routed (t'd to the air heater hoses) to a heat exchanger 15 feet away for providing hot water for the RV. Shouldnt it help the heat dissipation?
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Originally Posted by BILTIT
(Post 3180761)
I think the thought is that the water pump cannot circulate that much extra fluid/distance, it is not a positive displacement pump so it will only push so much fluid than it will just spin its wheels so to speak. That is what the reference to an aux pump was back a few posts, to help the water pump circulate.
It shouldnt be hard to check, just put valves at the take off points to isolate the water heater loop. This will put it back to normal for testing purposes anyways. Removing the t-stat may have a similar effect as it will allow more volume to ciculate but is only a bandaid at this point. It seems logical to me that the total coolant flow through the radiator would be just the same regardless of how many branches the coolant has to go through, given the same pump capacity. The only difference would be that individual branches (e.g. Heater core, exchanger) woud get the proportional fraction of that total. So if I block off the exhanger lines, the heater core will get 100% of the flow, and that 100% through the block and radiator. With the exchanger connected, the same 100% volume will flow through the radiator and block, but this time the heater core will only get 75% volume and exchanger only 25% volume, assuming the exchanger pipes have 3x the resistance that of the heater core. Am I getting it wrong? |
That would be true for a positive displacement pump, which a water pump is not. Too much restriction will cause inadequate flow due to the water pump design. A quick way to test if you have reached the limits of the pumps capability is by isolating the water heater loop.
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How big is your radiator compared to these used specifically for diesel motorhomes?
Maybe just the physical size and aerodynamics of the motorhome have the radiator to its limits. Aluminum Radiators, http://www.cgj.com/store/category/motorhome-radiators Brass Radiators, http://www.activeradiator.com/catalo...adiators&Make= Unfortunately nobody seems to have the BTU rating listed anymore. http://www.irv2.com/forums/f258/dies...ing-10005.html You said you have the origional fan shroud in place, but how much space is there between the fan tip and the shroud and how far in into the shroud does it extend? Do you have a Cummins Thermostat or one from the Auto Parts? How about the Water Pump? Open Impeller or Closed Impeller? I know this might sound like a dumb question but is there any chance you have your water pump spinning backwards, it can be done. http://i16.photobucket.com/albums/b3.../DSC06439a.jpg Any slight possibility you might have a combustion leak into the coolant? Is your converter lockup or non lockup? Do you have any Fluke HVAC DMM or IR/ Contact with remote Type-K thermocouple capabilities to get some accurate readings? Any pictures of your rig head on, side view. Jim |
Originally Posted by ClassA4x4
(Post 3180769)
I think the connection to the water heater exchanger is not so much for coolant circulation but more for passive heat absorption, since the lines are in parallel with the heater core plumbing. The water pump will normally circulate the coolant through the shortest path. The water heater exchanger is not the sole water heater, there is a 110v heater element in the tank. Btw, the exchanger alone gets the water hot after some time of driving.
It seems logical to me that the total coolant flow through the radiator would be just the same regardless of how many branches the coolant has to go through, given the same pump capacity. The only difference would be that individual branches (e.g. Heater core, exchanger) woud get the proportional fraction of that total. So if I block off the exhanger lines, the heater core will get 100% of the flow, and that 100% through the block and radiator. With the exchanger connected, the same 100% volume will flow through the radiator and block, but this time the heater core will only get 75% volume and exchanger only 25% volume, assuming the exchanger pipes have 3x the resistance that of the heater core. Am I getting it wrong? Whatever coolant is going to the domestic water heater is coming off the engine and returning to the engine, bypassing the radiator. If the domestic water is hot, it won't extract any heat from that coolant. BTW..... ethylene glycol in very small amounts is a serious poison, causing the formation of needle crystals that destroy the kidneys. Risking getting any into the domestic water supply is a very dangerous thing to do. Now both Jim and I have suggested you set up some thermocouples and investigate what's actually happening before you throw parts at it. |
Originally Posted by ClassA4x4
(Post 3180769)
I think the connection to the water heater exchanger is not so much for coolant circulation but more for passive heat absorption, since the lines are in parallel with the heater core plumbing. The water pump will normally circulate the coolant through the shortest path. The water heater exchanger is not the sole water heater, there is a 110v heater element in the tank. Btw, the exchanger alone gets the water hot after some time of driving.
It seems logical to me that the total coolant flow through the radiator would be just the same regardless of how many branches the coolant has to go through, given the same pump capacity. The only difference would be that individual branches (e.g. Heater core, exchanger) woud get the proportional fraction of that total. So if I block off the exhanger lines, the heater core will get 100% of the flow, and that 100% through the block and radiator. With the exchanger connected, the same 100% volume will flow through the radiator and block, but this time the heater core will only get 75% volume and exchanger only 25% volume, assuming the exchanger pipes have 3x the resistance that of the heater core. Am I getting it wrong? By adding another branch in parallel with that, you've actually decreased the total restriction of the coolant system (since it's in parallel), and your pump will flow more coolant than it was before. However, since it's a centrifugal pump, it will generate a lower pressure rise at this higher flow rate. This means that there will be a lower pressure delta across the block/head/radiator, and less coolant flow to these components. Whether or not this makes a significant difference in cooling ability depends on the restriction of the components you've added and how much heat they're getting rid of. |
Volume of extra coolant to move becomes a restriction to the pump aswell. Only way to know is to do some temp checks and isolations.
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Originally Posted by Jim Lane
(Post 3180793)
You said you have the origional fan shroud in place, but how much space is there between the fan tip and the shroud and how far in into the shroud does it extend? Do you have a Cummins Thermostat or one from the Auto Parts? How about the Water Pump? Open Impeller or Closed? Is your converter lockup or non lockup? Jim Radiator, Shroud, water pump, and fan are all stock 93 Dodge Cummins swap. Thermstat is Cummins brand. Fan blade tips are half and half in and out of the edge plane of the shroud. Trans is 47RH's stock LU converter, but lock-up is set to release(off) when boost is above 18 psi. When doin hard climbs, Boost is around 25 psi at 2700 rpm or so, OD off. When on OD, boost shoots up to 32 but then engine temp and egt will try to peg too hot. |
Originally Posted by Jim Lane
(Post 3180793)
Do you have any Fluke HVAC DMM or IR/ Contact with remote Type-K thermocouple capabilities to get some accurate readings? Jim |
Just to qualify the original post. I'm not advocating radical mods since the overheating can be prevented by putting it in 3rd and running the engine at 2700-3000 rpm while climbing. And it's a problem only over very steep climbs (although I'd love to take the motorhome over Pike's peak :-)
At this time I'm inclined to address the following: 1. Airflow - A. Relocate aux trans cooler anf its fan B. Install a high-cfm fan in place of the aux tranny cooler C. Build a tunnel in front of the coolers/radiator to the grille to concentrate ram air by blocking the top and sides D. Install air dam ( would it be effective still if air dam directs air at the engine, after the radiator? I have the winch blocking behind the bumper). Air dam will be easily removed when rock-crawling. E. Smooth out the winch mounting plate and loose the turbulence underneath F. Install ram air intake side scoops/grills ducted into the side of the engine, if I can find good looking oes appropriate for the vehicle (Ferrari ones maybe?) 2. Install shutoff valves on the water heater exchanger lines and observe for extended periods during trips. |
Originally Posted by ClassA4x4
(Post 3180830)
I just realized right now, yes I have one with a probe. But now I need two :-( one pre-radiator and the other post radiator. And I'm not sure if the probe will reach from the cab.
The lead material and the connector type has to match each other and the meter. |
3. A cheap mechanical temperature gauge with numbers to measure actual coolant temperature to set a baseline?
sent you a PM too. |
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