I did 3 tests
1. Coolant measurement, fan in Auto
2. Coolant measurement, fan in manual (continuously on)
3. IR readings of cylinder block and head
All 3 at approx 50F ambient, 1.5k rpm
Took video of data acquisition, then reviewed video, built an Excel SS to graph results.
Here we go.
This graph is test 1 and 2. It’s obvious that the fan and radiator are shedding lots of heat when the fan is continuously on. With the fan in Auto, 200F was reached in about 120 seconds. With fan continuously on, 200F was reached in about 320 seconds.
Armed with that data, broke out the IR heat gun (Fluke, top quality) and took many measurements across cylinder block and head, intake, exhaust and sides on a thoroughly warmed up engine.. Fully hot, had been running more than 20 minutes.
That graph looks like this-
The y axis is degrees F
The x axis is location measured e.g. “4 In” is cylinder 4, intake side.. etc.
I took measurements multiple times on multiple locations over ~5 minutes.
The data indicates cylinders 4,5,6 are ~10 degrees F hotter than 1,2,3. What does this mean? I don’t know. Does it matter? I don’t know. Sigh. Should have studied mechanical engineering and thermal dynamics, not software code… And are these temps reasonable for 6 cylinder engine?
And now it gets REALLY INTERESTING….
Decided to ‘burp’ the system. Basically, disconnect the fan switch, remove catch tank cap, run to red zone on the temp gauge (e.g. boil point). Watch the catch tank for level increase, bubbles. Reconnect fan (engine still running), watch catch tank level decrease. Add coolant as needed to keep system solid.
FSM says it will take up to 15 minutes and may be necessary to increase rpm to make this magic happen.
So I do all that. BUT, the big boil event never occurred. Jacked the rpm up 2k, waited some more. Didn’t time it (15 minutes), but I was at it for awhile. Ok, 4k rpm here we come. Good thing the idle adjust is easy to use… and still nothing. Temp gauge needle 1 needle width *past* the red zone and still no communication from main radiator to catch tank.
Twice, a little puff of steam from somewhere at radiator. Engine not making any weird noises like it was wanting lock up or parts getting too hot.
Started feeling guilty and wondering if I might be doing engine damage.. What if the tube from radiator to catch tank is pinched? So I manually activated the fan via handlebar switch, slowly cooled her down then gave up for the night.
Oh, here’s the 5 minute video of taking data.
Performed following tests (50F ambient, ~1,500 rpm)
Radiator water temperature check, fan in Auto
Time (Seconds) Temp (F)
50 148 Tstat opens
Radiator water temperature check, fan manually, continously on
Time (Seconds) Temp (F)
60 159 Tstat opens
Just on the off chance.............someone on this site had a simialr problem earlier this year and found the metal "neck" off the top of the radiator next to the cap, which the catch tank pipe pushes onto, was blocked. This caused similar probs to you, but was rectified as soon as unblocked.
Other thank that, are you using a standard stock rad cap and is it allowing the pressure past to the catch tank or not ??
If the incorrect width of rubber pipe for the catch tank is used and its too thick, it will be blocked where it pushes into the retainer / recess on the tank itself at the rear of the tank. ??