Modify Dole thermostat

[Kelly]

This post is meant to stir the collective knowledge bank for approval/disapproval status for a possible modification.

The quote and photo below are from RobH2 and have intrigued me for quite a while. I too have been battling high temperatures but my ducks have been recently aligned and I think I'm down to some fine tuning in order to get this system to work better.

Jude's cooling: FWC with electric circulating pump on the fresh water side. With no thermostat (I have the older Dole thermostat mounted at the manifold exit) cooling is sufficient (150°F when warm) but is too hot for comfort with the thermostat in place (190°F when warm).

It seems that the thermostat is just forcing too much water through the bypass loop at high temperatures. RobH2's modification should let more water run through the block at all temperatures, thereby lowering maximum temperature as a function of the number/size of additional holes in the thermostat flange.

How does this sound?

From RobH2 (here's a link to his original post):

I noticed that the thermostat has a hole in it. I guess that's to let water through the engine in case you forget and start the engine with the bypass closed and the thermostat cold and shut. So I just drilled another hole with a 9/64" bit. If no thermostat is in place the engine is too cold and with the thermostat installed engine is too hot, why not make the thermostat less effective. The 9/64" bit was just what looked right to me...no science involved there.

Result?..and I ran full throttle in open water for 2 hours in 95 degree weather. The engine runs at 170 degrees with the bypass 1/2 open. If I close the bypass the temp drops to about 152 degrees or so. If I open the bypass all the way it runs at about 182 degrees. In my book, that's perfect. I think the aftermarket thermostats are the problem.

[hanleyclifford]

Kelly, I suspect your problem is too low coolant velocity coupled with the restrictive Dole thermostat. If you cannot get temp high enough with bypass wide open (thermostat removed), but get too hot with thermostat installed but bypass fully closed, then you may benefit from drilling the thermostat as suggested.

[Dave Neptune]

Question

Kelly, what is the temp rating of the t'stat you are using? I would think that if your t-stat is a 160* that the engine should hold temp close to the rating of the t'stat if all is well.
We often drilled a small "bleed" hole into t-stats to aid in getting blocks purged of air (full of water) so we could load them up to test. It was usually a single 1/8" hole and it had little affect on temp but warm ups did take a bit longer.

Dave Neptune

[Kelly]

Hello Dave,

As tested on the stove top, my Dole thermostat starts to open at 160°F.

In the next day or so I'm going to test my system this way:

run at 1500 RPM until I reach my normal "with thermostat" temperature: 190°F

Then, assuming the Dole thermostat is completely open, I'll start restricting the bypass loop to see if I can force more flow through the block and get cooler temperatures. I'm wondering if the bypass loop isn't presenting an easier path for the water to flow, thereby restricting flow through the block and HX.

Could be crazy but before I start drilling, I would like to have some more numbers.

[Dave Neptune]

Are you sure?

Kelly if it opens at 160 things should be OK when open in the engine.

I do have a curiosity question for you ~~ are you sure your guage is correct? It too can be checked in a pan of water with the t'stat however you will need a battery or a 12v DC supply. Might be worth checking.

Keep in mind the aftermarket t'stats don't close off the bypass as the original ones did. This drastically influences flow patterns regarding the bypass loop.

The issues you are describing are ones I have seen and is the reason I chose to eliminat the darn thing altogether. Once you have the valve set about the only variation you will see is influenced by ambient water temps and build up of krud in the exchanger or possibly the block. It does take a bit longer to get to temp and it will cool off a bit at idle. I run in a fairly constant water temp range and I only adjust every year or so if it runs a bit higher than the year before.

Dave Neptune

[hanleyclifford]

Question: Do you have a bypass shut off valve or are you relying on the double acting thermostat?
Edit: Sorry, stupid question. Doles are not double acting. The pic is confusing the discussion because it is late model. If you have a Dole set up like mine, you need a shut off valve in the bypass loop.

[67c&ccorv]

I recently removed the exhaust manifold on my 1967 A-4 and had it hot tanked cleaned.

Even after the hot tank cleaning the coolant passage way in the manifold was caked with scale and debris...a soft wire and soaking in CLR cleaned out the remaining gunk.

Cheers!

[Kelly]

Hanley,

Sorry about the confusion. The pictured late model thermostat with the newly drilled hole was the only example I could find (or that Shawn could find) of what I am contemplating doing.

Can you explain why you "need" a shutoff valve with the Dole setup? Was it not engineered to take care of temperature fluctuations by itself?

Dave,

No, I'm not sure about the gage as I've never tested it. From experience though, when the gage was reading 200°F+ the engine "felt" too hot and acted hot too. Now, when the gage reads 180-190°F, the engine feels right. But only a test would tell...

If I can't work through this issue, I too will run without a thermostat. I just thought that it would be nice to have an automatic temperature adjustment as was originally designed.

[hanleyclifford]

Hanley,

Sorry about the confusion. The pictured late model thermostat with the newly drilled hole was the only example I could find (or that Shawn could find) of what I am contemplating doing.

Can you explain why you "need" a shutoff valve with the Dole setup? Was it not engineered to take care of temperature fluctuations by itself?

Dave,

No, I'm not sure about the gage as I've never tested it. From experience though, when the gage was reading 200°F+ the engine "felt" too hot and acted hot too. Now, when the gage reads 180-190°F, the engine feels right. But only a test would tell...

If I can't work through this issue, I too will run without a thermostat. I just thought that it would be nice to have an automatic temperature adjustment as was originally designed.

Kelly, The Dole does not perfectly shut off the bypass loop and in addition constitutes a significant restriction in the system even when it is functioning correctly. That, coupled with your (now) much weaker flow rate due to the electric pump is your overheating problem. I have a similar issue due to a weak salt water side.

[ndutton]

Kelly,

In my mind there was always a concern over restrictions and electric FWC. That's why I made all the effort in enlarging the sideplate Tee and diverter and going to cast elbows instead of purdy machined ones. A thermostat would be another restriction but not in my case because I don't have one.

My strategy has been if I can achieve satisfactory temps without a thermostat, why bother?

During Wednesday's USS Iowa excursion I ran the engine non-stop for at least seven hours at varying RPMs and load. With electric FWC, late model cooling system, no thermostat and RPM sufficient for hull speed the gauge temp was 180 - 185. Lowering the RPM also lowered the temp to as low as 140.

Manipulating the bypass valve had no effect on operating temps regardless of RPM. I'm sure this has to do with the sideplate Tee/diverter modifications coupled with no thermostat restriction.

[hanleyclifford]

In the ideal FWC system with two mechanical pumps of roughly equal flow rate heat transfer is most efficient. When one side or the other is slowed down, compensation must be made somewhere. This is often done by reducing restriction and can also be augmented, as in my case, by adding exchanger capacity. I agree with Neil about the thermostat; if you can get the result without it, get rid of it.

[ndutton]

I'm at a point where I believe I can affect operating temperature by tweaking the prop thereby applying more or less load on the engine. In my case I'd lean toward either slightly less diameter or slightly less pitch.

Right now I'm pretty happy the way things are so I'm not making any plans but it's an option.