TOPIC:

Engine coolant thermostats generally come in 2 different opening temperatures. 195 deg F and 180 degrees F. The thermostat opens at the designed temp be it 195 or 180. That should be the maximum temperature seen during operation. When the thermostat opens, the coolant in the radiator exchanges with the coolant in the engine. Then the thermostat closes. Coolant in the rad starts to cool until the thermostat opens. On an extremely hot day lets say it's 100 deg F outside, the temp differential between the coolant in the rad and the outdoor temp would be 95 deg. F. the coolant obviously won't cool down as much as it would if the outdoor temp was 69 Deg. F. In this case the thermostat will tend to open up more frequently because the coolant returning to the engine is hotter and not as able to pick up as much heat.

The only reason anyone would have to replace the radiator with a more effecient rad is if the engine is required to put out high horsepower on a continuous basis like pulling heavy loads through mountains or under racing conditions. Otherwise, the stock rad should do the job provided it's clean and all of the tubes in the rad are flowing properly. The only other situation that can happen is if the coolant is continuiously exchanging between the engine and the rad when a faulty thermostat is not stopping the exchange of coolant between the rad and the engine. In this case the temperature indicated usually continuiously rises until there a boil over and you finally stop the engine.

The thermo switch for the fan should come on around 210 -220 deg F. There needs to be a buffer zone between what temp the switch sees when the coolant first comes into the rad at 195 F and what temp the fan comes on at. But you don't want the fan coming on just before the coolant starts to boil which should be around 240-250 deg. F. depending on which coolant you are using, what percentage of coolant and water and what rad pressure cap you are using.

Never had any issues with temperature (79A1). Got caught in a traffic-jam in the summer with outside temeprature around 30°C on the German Autobahn and had to stop and go for over one hour. Temperature went up, Radiator started and cooled it down, went up again.

The standard Equipment should cope with it if it works properly, hope you can detect the bug.

Holger

I'm running a 50/50 Glycol mix and stock radiator cap

I plan on tearing back into it today, I'll put the thermostat on the stove and see what temp its opening at and make sure my radiator bypass isn't stuck open

Thermostat seems to be in working order, it cracks open around 180 degrees and is almost fully open by 212

Water pump impeller looks fine and its engaged on the shaft, so it must be working

my last thought is that the thermostat isn't shutting off the bypass pipe all the way, I read on the voyager forum that some people are putting spacers in to make it close all the way. Has anyone had to do that on a KZ? They seem to have the same setup

benspilk09 wrote: Thermostat seems to be in working order, it cracks open around 180 degrees and is almost fully open by 212

Water pump impeller looks fine and its engaged on the shaft, so it must be working

my last thought is that the thermostat isn't shutting off the bypass pipe all the way, I read on the voyager forum that some people are putting spacers in to make it close all the way. Has anyone had to do that on a KZ? They seem to have the same setup

2 things to check if I were you.
First, since you pulled the thermostat, I would do a dimension check from the seat in the head where the bypass valve seats to the base of thermostat housing where the thermostat sits and compare that to the bypass valve on the thermostat to the face of the thermostat where it mounts. There have been a few reports of a difference which has allowed the bypass valve to not seat at all. That will cause the coolant flow which should be circulating around in the engine to be flowing through the engine and also flowing to and from the rad. That's not good.

Second, a lot of the KZ1300's have been sitting idle for years and those who have actually had a rad shop take the rad apart to clean the tubes have reported that a lot of the tubes were plugged even though they had tried a flow check using a garden hose and thought the rad was fine. Unless you have a boroscope and can see down the side of the rad and view the tubes in the rad. The only other way to check the condition of the tubes in the rad is with an infrared camera or heat gun. I wouldn't discount a plugged rad.