Bypass valve location

[tsell]

I have been running my A4 for the last 7 years with the manual bypass, installed between the Tee and the thermostat housing, and I have never seen temps over 120, even with the bypass fully open. Would moving the valve to the T-stat outlet give better control over the temperature? It seems like that would mimic the action of the thermostat in restricting flow and allow me to dial the temperature. Would that overheat the exhaust manifold? Any thoughts or comments welcome.

[JOHN COOKSON]

I'd check the thermostat first. It may somehow be stuck in the open position.
Also you could use IR thermometer to be sure the gauge is not lying.
If you have a original "three legged" thermostat it is a "double action" thermostat - that is as the thermostat opens it allows more water to flow through the engine and less water to go around the engine ie the "bypass".
Many members are happy with a cool running engine.

ex TRUE GRIT

[sastanley]

tsell..yep..it could overheat the exhaust side. I would not restrict the flow headed into the manifold, and I would not move the bypass. Have you confirmed your t-stat works by boiling it on the stove? Where is the boat, and what are the typical water temps? Edit - I see Vermont..sorry..

[tsell]

I do not have a thermostat installed, and have had significant carbon on the plugs. Since I just did the head gasket yesterday, I had a chance to have a good look at the valves, and the carbon build up on them, along with the top of the combustion chamber made me start to think about optimal operating temps, and how to achieve them without a thermostat. For sure I am concerned about the exhaust manifold temps.

[ndutton]

Originally Posted by tsell

. . . . . made me start to think about optimal operating temps, and how to achieve them without a thermostat

Huh? That's the reason FOR a thermostat.

[sastanley]

I think cooler engine temps will produce that carbon build up. I am running 180-190° in summer (Ches. Bay water temps are high 80's), but I am FWC.

[tsell]

Originally Posted by sastanley

I think cooler engine temps will produce that carbon build up. I am running 180-190° in summer (Ches. Bay water temps are high 80's), but I am FWC.

I found Don’s excellent explanation of the thermostat in our engines in the tech tips, which definitively answered my musings.

https://moyermarine.com/nljune2018/

[Dave Neptune]

I ran for 34 years with no t-stst @ 130* and my stock plugs were always a creamy chocolate color as they should be. An engine can be adjusted to run at most any temp. It is the fuel air mix that causes black and sooty plugs as well as proper timing not necessarily a low temp! I did run a bit to the lean side and never any trouble.

Dave Neptune