FW Cooling - Coolant Temp

[Al Schober]

This is my second season with FW cooling and I have a question. How do I get the engine coolant temperature up? I can raise the engine temp with the thermostat, but all the coolant goes through the manifold and off to the heat exchanger and never seems to get very hot. I checked it at 1400 RPM in gear (tied to the dock) and the coolant left the engine at 124 F and came back from the heat exchanger at 98 F. No sense trying to run a water heater with those kinds of temperatures! And please don't tell me to shut off sea water flow to the heat exchanger while I'm making hot water...

[hanleyclifford]

If the coolant is leaving the engine at 124 degrees, your thermostat is not working. As for the cabin heater, run the coolant to the heater first, then to the exchanger.

[Al Schober]

ReState...

Hanley,
No problem with engine temp, but the bypass water recombines in the thermostat, bringing the coolant temp down to the 125 F range for the trip through the manifold and back to the heat exchanger. If you know of some way to access that nice warm engine water, please let me know! Perhaps I could pull it out of the front of the head through the water temp hole?
Water is needed for heating potable water (ie: for a shower), not for cabin heating (I've got a kerosene thing for that).

Al

[hanleyclifford]

It sounds like your thermostat is not closing passage thru the block to allow th coolant to warm sufficiently upon start up ( I'm assuming we are talking late type head here).

[ndutton]

No problem with engine temp, but the bypass water recombines in the thermostat, bringing the coolant temp down to the 125 F range for the trip through the manifold and back to the heat exchanger. If you know of some way to access that nice warm engine water, please let me know! Perhaps I could pull it out of the front of the head through the water temp hole?

Al,
I see your point. If you pull the coolant out of the front of the head I'm thinking you could return it into a Tee added between the thermostat housing and manifold. I expect you'd need a check valve in the return line so the coolant doesn't backwash. I'm not real clear on how much flow you can expect out of the sensor port and whether or not you'll create other problems pulling coolant out of there (i.e., reducing flow after the sensor port to other parts of the engine).

[David Masury]

I have a fresh water cooling system on my A4, factory installed in 1975 and I can tell you that the temp in the resevior can be very different from the temp in the engine. While mucking around with the A4 years ago, in trying to get everything right(?) I bought an in block temperature gauge from Don's online store. Plugged it in right in the front of the engine, direct reading right at the thermostat. When the engine warmed up I was getting a nice 175-180 degrees, the temperture gauge in the resevoir read 140 degrees. I have a 180 degree thermostat, so I felt that the cooling system was doing it's job and that the engine was under control, thermally.

The other thing is that the raw water side of the system is dependant upon the water temperature you are going through, here in southern Maine it varies a lot, but generally speaking I can count on the temp in the resevoir to be consistant at 125-140 degrees.

David

[Al Schober]

Dole Thermostat?

I think what I need is a thermostat that's remote from the engine. This thermostat would recirculate the coolant until it came up to temperature, and then send coolant to the heat exchanger as needed to limit the temperature. Didn't the original Atomic 4 engines use a remote thermostat?

[Al Schober]

FW Cooling - How about this?




Hope this picture shows up - it doesn't in the 'Preview'?
With the revised system, the bypass coolant doesn't go to the thermostat housing. All that comes out of the thermostat is hot coolant which goes to the water heater. The flow back from the water heater then recombines with the bypass coolant and goes to the exhaust manifold and heat exchanger. Alternatives I see are to run the bypass coolant to the heat exchanger inlet or simply to the pump inlet.
Any thoughts on this?

[ndutton]

Al,

Like it, very interesting. I'm inclined to add a check valve at the water heater outlet to insure NONE of the bypass coolant enters the water heater through the back door.

You do, however, lose any heating benefit from the manifold. That was likely negated anyway with the mix of the bypass coolant in the thermostat housing with the original configuration.

It will be interesting to see if there's a noticeable difference in your water heater performance.

[lat 64]

But but but...

And please don't tell me to shut off sea water flow to the heat exchanger while I'm making hot water...

Um.. ah.. Thats actually the way I did it.
It works great! I don't make hot water, but I have a cabin heater.
See the thread at: http://www.moyermarine.com/forums/showthread.php?t=3653
post #12.
The heater is in parallel circuit with the heat exchanger.
I close the water(engine coolant) to the heat exchanger and let the heater cool the engine. The temp rises a bit but not to overheating.
I don't have any stats on what the temperature is that goes to the cabin heater. The hoses are never too hot to touch, but the cabin gets warm at around 20 degrees F. air temp.


russ