OK, got some time tonight.
First on order is the temp sender. Trying to use the old one was a bit of a kluge because it was too big for the port in the head
and I cobbled together an adapter. I got some slight leaks
Knowing what thread the port was cut to is also a problem. At least one source indicates that it is 5/8" UNF. However, most temp senders are NPT. And 3/8" NPT 5/8" UNF are close to each other (if you know UNF and NPT then you know the differences)
It turns out that west marine
had 2 of the senders I was looking at in stock. This boat uses a dual station sender (2 gauges, on at the helm
and the other below) and 3/8" NPT would fit so I picked one up on the way home from work. ( WM # 1654854 | Mfg # 18-5897 ) Plus I had some rewards coupons in my pocket.
Back on the boat I pulled the header tank and drilled a 1/16" hole in the thermostat ( Slant 13478 ) The idea here is that air can escape and that in a cold engine
some hot water
gets through. More on that later.
With the header tank still off and the temp sender not installed I put a funnel into the port on the head
and poured 50/50 antifreeze
into the head until it started to come out of the hole in the thermostat.
At that point I reinstalled the header tank topped off the port in the head. Then I installed the temp sender and filled up the header tank.
With the fill cap still off I (moment of truth) started the engine
. Amps up to 40 at idle, a few bubbles working their way out of the expansion tank fill. Top off coolant
as needed and when the coolant
started to expand I put the cap back on.
Letting the engine warm up gradually I kept taking a look at temps with the IR temp meter. No leaks
and perhaps a slight mositure around the temp sender. Perhaps it needs another 1/4 turn when the engine cools down again.
Up the rpm
and the alternator
is putting out 80 amps into at 95% full 700ah LiFePO4
bank (100 amp alt). The regulator
is set to 13.9 v.
Temps keep rising and eventually settle at 180 degrees (via the gauge). The IR temp meter reads 185 on the head bolts - Ran it a full rpm
with no load and the temp stayed rock steady. The return coolant temp went from about 90 F at idle to 110 or so at near WOT with the gauge reading rock steady.
Ok, back to the hole I drilled in the thermostat. When using the original thermostat the temp would rise and rise and go up to about 210 F then after a time fall back to 185 F. This was always something that worried me (was it sticking, faulty etc).
The reason this happens is that with a thermostat without a hole there is no warmed coolant on the temp sensing (wax) side of the thermostat. So the thermostat stays closed until the conduction from the hot side to the cold side is great enough to allow the thermostat to open (and it does in a rush). It looks like it is stuck then releases.
And in my case because i removed the heater circuit there is more or less no coolant flow until the thermostat opens up which can cause localized hot spots in the head.
By drilling a small (1/16") hole in the thermostat I now do ger some coolant flow from the hot side to the cool side when the thermostat is closed. This allows some circulation in the head while the engine is coming up to temp and of greater value to me it allows the wax pellet to cause the thermostat to open in response to the coolant temp. No more "sticking" - the temp just rises to 180 F and stops there.