The cardboard was tried and nearly completely covered the radiator but had minimal effect on the engine temp or radiator temp. Top of the radiator reached 77 degrees with the radiator covered on a 50F day. Max engine heat with radiator covered was 125F on the surface of the block.tglass said:Sounds like the thermostat to me. If the cardboard warms it up it tells me the engine isn't getting hot enough. Thermostat adjusts the internal temp. of the engine. Heat guns are a good device, but in this case you don't want external temp. They need to know the internal temp. flowing thru the engine and input and output actual temp. of the heater. Hard to get with a heat gun. Most engines are also built to perform best at the operating temp.
The inflow heater hose comes directly off the water pump to the cab heater. The return flow goes to the lower radiator hose and connects into a "T" in the radiator hose. The service manage believes the radiator core is relatively too big. Even with the air flow blocked off with a piece of cardboard, he thinks the fan still moves to much air on the back side and around the radiator and thus it still cools to much. If the cold radiator never allows the engine to heat up, then the engine can't heat the cab. I admit a closed thermostat should still heat engine to operating temp regardless if the radiator. There is slightly more heat in the cab at fast idle but not significant. Service manager and I talked about an air block problem in the cab heater, but that still would not explain an engine block temp of 125 at fast idle. He talked with JD today. He told me the the engineers have sent some solutions to the tractor designer who is going to evaluate possible options. JD acknowledges this is a problem in the 3000 and 4000 twenty cab models.mike311 said:radman, since your tractor isn't over-heating and your temp. gauge shows normal operating temp. , I would say your coolant system is fine. I would advise you to check and double check your heater hoses for kinks and sharp bends that would restrict flow. Check the hoses that go to the heater core in the top of the cab. Another possible problem it could be is air trapped in the heater hoses and/or heater core. My brother had the identical problem with his tractor (5425). Luckily, he noticed his heater problem while at the dealer, before delivery. It took a mechanic about 30 minutes to correct using a vacuum pump on the heater hose from the heater core. Mechanic said that it is common problem because any air in heater system cannot "work it's way out" due to the height of the heater core vs. radiator cap and overflow tank. Another thing to remember on your coolant system is that your radiator only has coolant flow when your engine(thermostat) temp. goes above normal operating temp. On the heater side of the sytem, the coolant is continuosly circulated from engine to heater core and back. I have seen new cummins diesels that could not maintain operating tempature at 0 degrees while idling but the heater worked fine(the truck would automaticaly go to high idle 3 minutes after parking and letting the truck idle). Basically, what I'm trying to say is that a cold radiator doesn't mean sh** to how a heater should work.