Radiator Overheating

[shopman]

The radiator on my B7100 HST overheats when mowing at a fast or full speed. Coolant comes out of the overflow hose atop the radiator. I was told there is no thermostat on this model. What is going on and how do I fix it? Thanks

 

[MarkV]

Are you checking the radiator screen? Pretty common to have to clean the screen several times a day bush hogging. You will also find an amazing amount of stuff you don't see built up in the radiator fins. A pressure washer or air compressor does a good job cleaning out.

MarkV

 

[B2400]

The B7100 doesn't use a water pump. It operates an a principle called "Thermocycle" which means that hot water rises and cold water falls. This is how the water moves thru the cooling system on your 7100...as the engine heats the coolant, it rises thru the engine . When the coolant enters the radiator, it is cooled and begins dropping thru the radiator and thus pushing the cooler coolant back into engine from the bottom hose. It is IMPERATIVE that the radiator be kept as clean as possible for this process to work at it's best! When my B7100 started doing what you are describing, I pulled the radiator out and gave it a good cleaning both inside and out. The fins tend to clog with dust and other debri which you can't see very well when radiator is mounted in tractor, but when out, is very visible as you can't see thru it! For starters try pulling the chaff screen out and then using a garden hose, gently flush the core from the fan side. It doesn't take a hi pressure stream, just a good volume of water. I'm betting it will look like your flushing mud back thru it as your cleaning!! After cleaning mine, it never got hot again even when brush hogging. I always made extra effort after that to keep it clean and now do the same with my B2400.

 

[cappys tractor]

I have heard of it referred to as thermosiphon.

anyway, in addition to keeping the outside of the radiator clean, you must ensure the level of the antifreeze is full to the top.

it must be able to flow freely inside the rad and through the block. the water does not flow on its own, it must use the heat difference between the radiator and the block to heat and cool.

on the outside, a blown head gasket will give similar problems too. better to have it looked at, prior to major engine damage.