Quick question on running without a thermostat

[Bratina]

At spring commissioning, I ran my engine for the 5 minutes that it takes me to motor from the slings to my slip with the thermostat out, and without the bypass hose clamped. Tomorrow I have a longer (maybe 20 minute) run to the mast crane.

Question; should I clamp the bypass hose for that short run to the mast crane, or does it not matter? The water is very cold here (Lake Ontario).

Second question; I left the thermostat out because the housing sat proud when I installed the thermostat, with a small gap between the housing and the gasket. I didn't want to crank down on the bolts too much, and assume the thermostat wasn't sitting correctly in the housing.

That's never happened to me before (I've r/r the thermostat many times). Did I get unlucky with placement, or should I have torqued the bolts down and it would have compressed anyway? It was fine without the thermostat.

[ndutton]

With no thermostat I'd close the bypass for sure. It's the only way you can guaranty flow through the block. I suspect you are correct that the previous poor fit was the thermostat not properly seated in its groove.

[Bratina]

Thank you Neil.

[JOHN COOKSON]

You could try leaving the thermostat out for now and use a valve in the bypass just before the thermostat housing then see if you can balance water flow around\through the engine. The goal would be to not to long of a warm up time and a good temperature at cruise RPMs.

TRUE GRIT

[sastanley]

Remember the function of the bypass...it allows some water around the closed thermostat (if installed) during warm up, so that cooling water still gets to the manifold (heat is generated there first) and more importantly to the soft hoses in the wet exhaust system (where that heat goes as soon as it exits the engine) while waiting for the t-stat to warm and open.

With no t-stat, you want to close the by-pass to make sure you get enough cooling water thru the block..Since the t-stat is gone, anything coming up thru the head and block will make it to the manifold and wet exhaust directly after startup (if the bypass is closed.)

Sometimes if the bypass is left wide open, there are preferential flow characteristics to the manifold/exhaust that might let the head and block get to hot.

The only disadvantage to running the bypass closed with no t-stat is a cooler running engine.

[CaptainCronos]

So what happens if the bypass is closed or non-existent, and the thermostat is in place?

[zellerj]

The thermostat on an Atomic 4 is different than typical. Water can flow "across" the themostat - horizontally, and "through" the thermostat vertically.

When cold, the thermostat allows water to flow easily across the thermostat and on to the exhaust manifold. This may limit the amount of water circulating through the block and the head allowing the block to reach operating temperatures more quickly.

As the thermostat warms, the thermostat pinches off some flow across it, thereby directing the water to take a sharp left at the side plate T and cool the cylinders and circulate through the block and head, exiting through the thermostat and towards the exhaust manifold.

Without a thermostat and a by-pass valve, the fear is that too little water will flow into the block at the T thereby causing the engine to run too hot - unbeknownst to the gauge that is feeling the cold water running across the thermostat housing and passing by the gauge sending unit.

[Bratina]

So what happens if the bypass is closed or non-existent, and the thermostat is in place?

My understanding is that the bypass clamp would cause the water never to reach the thermostat, and so the effect would be the same as if the thermostat was removed.

Actually that brings up a great question: my winterizing MO has been to remove the thermostat, clamp the bypass hose and then run antifreeze through the block. Is the removal of the thermostat necessary? For peace of mind alone (and because it doesn't take long, and because I have the 3-spring thermostat still) I'll continue to remove it, but I'm not certain it's vital.

As for my thermostat seating, I ran the engine with the thermostat removed and the bypass closed without issue to the mast crane and back, other than my idle being set too low and the engine bogging down a little at 600rpm (I'll adjust the set screw).

After stepping the rig I checked again the housing, and the old gasket was stuck to the top part of the housing, meaning that the thermostat had to compress the gasket into the indent. I switched it so the mew gasket is against the head, then the thermostat, then the housing, and it cinched down well. I'll check my manual to confirm that it's the right away around, but there were no leaks on my test running afterwards, and it appears to sit flush now.

I've long contemplated removing the thermostat and adding a bypass hose, but it's worked well for 45 years (outside of the issues with seating this time) in cold Lake Ontario waters. Perhaps if my 3-spring thermostat gives up then I'll go down that route.

[CaptainCronos]

The thermostat on an Atomic 4 is different than typical. Water can flow "across" the themostat - horizontally, and "through" the thermostat vertically.

When cold, the thermostat allows water to flow easily across the thermostat and on to the exhaust manifold. This may limit the amount of water circulating through the block and the head allowing the block to reach operating temperatures more quickly.

As the thermostat warms, the thermostat pinches off some flow across it, thereby directing the water to take a sharp left at the side plate T and cool the cylinders and circulate through the block and head, exiting through the thermostat and towards the exhaust manifold.

Without a thermostat and a by-pass valve, the fear is that too little water will flow into the block at the T thereby causing the engine to run too hot - unbeknownst to the gauge that is feeling the cold water running across the thermostat housing and passing by the gauge sending unit.

On my engine, the entire engine block is the new version. The cooling jacket plate has the old fashioned 90 elbow. It's plumbed directly to the pump. The thermostat is missing. The engine never got above 140F (when it was running). I am wondering what adding a thermostat will do in this configuration. The output for the "bypass" on my thermostat housing is completely plugged off so I have no bypass system so to speak.

[ndutton]

On the late model cooling system the bypass MUST be present when a thermostat is installed and MUST be either blocked (removal = the same as blocked) or at the least restricted when one is not. What the bypass does is provide full coolant flow to the manifold and exhaust regardless of thermostat position (open, closed or somewhere in between). Without that full flow you risk overheating damage to the exhaust line.

Keep an eye out for an epic post on the late model cooling system coming to your computer screen soon. How soon I cannot say because it's not coming from me but SOON.

[zellerj]

On my engine, the entire engine block is the new version. The cooling jacket plate has the old fashioned 90 elbow. It's plumbed directly to the pump. The thermostat is missing. The engine never got above 140F (when it was running). I am wondering what adding a thermostat will do in this configuration. The output for the "bypass" on my thermostat housing is completely plugged off so I have no bypass system so to speak.

I believe you are OK with this configuration. It is the same as those of us with a T instead of an elbow, with the thermostat removed and the by-pass closed off with a valve. My engine runs at 140 too. I don't believe that running this cool is harmful to the engine.