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McCown · 09-28-2010, 04:54 PM

My Coach still runs hot in hot weather, the red light comes on long hills. We have put a new charge air cooler in it, because it wasn't getting enough boost. Wechanged injectors, put in rebuilt head and still runs hot. Cummins in San Diego bypassed thermastatic valve so hydralic fan would run on high all the time, no help. What to do next?

Bandit2002

Jimmyzw22 · 09-28-2010, 05:24 PM

What engine model and horsepower is it?

EngineerMike · 09-28-2010, 07:45 PM

If they bypassed the t-static valve, i.e plugged the end of the two hoses together, I think they set the fan on low. Check the fan blade rotation when idling. If you can actually see fan blades, the above is true; or check to see if the hoses are plugged into each other.
The valve is "normally open" and closes as the wax inside heats and expands. So fan rate is faster w/less flow from the valve, not higher w/full flow past the valve. I'm guessing this situation is new and not initiated from the Cummins guys messing w/the valve, so they may have exacerbated the real problem or they may not have. I'm just addressing the way you explained their "fix."

If the fan is on high, and maybe even if it isn't, you may not be getting proper coolant flow thru the radiator. You should be able to check the coolant tanks on front & back of radiator w/a handheld infrared temp sensor after idling, driving, etc. and see if it coincides w/the temp gauge. If the radiator is cooler than the engine gauge indicator, then the "water pump" could be shot. W/the Cummins emersed impeller design, IIRC, the fins that generate coolant flow could have eroded off if the coolant was not up to spec long enough. This situation is unusual but not unheard of.

McCown · 09-29-2010, 09:41 AM

Quote:

Originally Posted by Jimmyzw22

What engine model and horsepower is it?

WRV Alpine 40'. 400 hp.

SteveS · 09-29-2010, 10:13 AM

Have you checked instrumentation? Just because you may be getting information from sensors that indicate it is hot doesn't really mean it is. You could be getting false readings about the temp. If you use an IR heat sensor/gun and check the temperature of the hose returning coolant to the radiator, you can find out what the temperature actually is. You might not really be overheating.

Renipladlo · 09-29-2010, 11:05 PM

McCown - not to complain, but it would help if your signature was update with the Year, Model, i.e., 40 MDTS-2007 S/N XXXXX or something like that please look at mine herein as one example.

Now search earlier posts under the similar subject to check, and Dale G was having a problem with his engine running warmer than he felt it should. He noticed the rubber gasket material between the radiator grill and the side of the coach was not closing off the hot air being blow down by the fans and was just being sucked back into the intake side of the radiator. This was not all his problems but part of it, so check to make sure this gasket is really sealing this place off. Search for other posts in this section to find that subject, and see the photos posted. Then check your coach, it might be the same. EM also made some great points so you might have Cummins do a more thorough job and check coolant flow, etc to make sure it's not the water pump.

Now how long are the hills, how high are the hills, what gear, what RPM, etc. In a previous discussion it was discovered that climbing hills you should be hanging in with 4th or 5th gear, at around 18-2000 RPM’s being the target range, as this really gets the air moving in the cooling area, some food for thought. The governor will keep you from over revving the engine, but watch the tach with safety first on driving and road awareness.

EngineerMike · 10-01-2010, 07:10 PM

Before going further I'd change the heat sensor. Its cheap compared to a lot of the things you've done, and if it is sending bad readings it will screw up your diagnosis. You can do the manual checks w/the IR gun as an alternative to make sure you are really getting hot.

MKelley · 11-03-2010, 08:15 AM

On long hills the engine temp goes up and the temp light comes on. Checked fan speed at the top of the hill with the temp light still on and the fan was turning vary slowly. On a 1999 with a 330hp is this a wax valve problem or could there be some other problem?