Cold John Deere 6404

Have changed anti-freeze and thermostat. Engine will not heat up above 160 degrees. Book recommends 190.

It is a 1974 Ammarine conversion, used a barrel style thermostat. Would an automotive style with less flow ability help or cause water pump issues.

Thanks, Steve M

Is the thermostat stamped with it's opening temp, and/or have you tested it in hot water to confirm what temp it opens at?

And how is your engine cooled? Keel cooler, or raw water heat exchanger?

And are you in particularly cold water?

And has it always been this way, or is this a new development of some sort?

Engine temp

For John Deere's a lot of people (if raw water cooled with built in heat exchanger) put the t-stat in backwards by mistake.

Also they are a maintenance item, so replacement like you did is a good idea, however, could be wrong temp. Also new does not mean better, if their operation is in question remove & put in water on stove & monitor with candy thermometer to be sure opening at right temp..

Make sure it is in right.

Good luck,

m.

My JD 6404 was running at 140 degrees. After changing the thermostat with no improvement, I found the temperature sender had gone bad. New sender solved the problem.

Have you verified that the gauge is reading correctly with an IR temp gun or some other independent gauge?

Did the temp change to 160 after you changed over the coolant and thermostat? Or did you change them because the temp was 160? If you changed something and the temp changed your likely culprit is the thermostat.
Make sure you have the right thermostat. For example, there are several different temp ones for Lehmans.
Shoot the sender with an IR gun to check the running temp.

Hal Northstar said:

My JD 6404 was running at 140 degrees. After changing the thermostat with no improvement, I found the temperature sender had gone bad. New sender solved the problem.

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My temp sender is ok - checked with a laser temp gun. How hot does your engine run now? Does it have the barrel style thermostat or the automotive style? Mine is the barrel style and to me it just looks like a flow through thermostat. It opens in a pan of hot water but I don't see how it makes any difference since it is just an open barrel between the top and the bottom of the thermostat housing.

Engine is a 1974 Ammarine conversion. It is raw water cooled with a heat exchanger. Have only had the boat since last June and that style of thermostat is what was in there and Hatton Marine who helped me change it wanted to stay with the same style but still at 160.

Is it 160 at normal cruise or at the dock?

Xsbank said:

Is it 160 at normal cruise or at the dock?

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160 at normal cruise, takes about 25 minutes to get there. I am in the northwest so the water is cold.

If it's any help my NA Hino's will only run 160-165f at cruising rpm. WOT they'll get up to 175f, I'am on the Mississippi River and water temps run from the 40f to 80f.

My JD 6068 after cooled in the PNW cold water will run at 160-170 at slower speeds with less load and take several min. to get there, at 60-80% load they go to 170-180. The cold water is significant.

I don't see why the cold water matters as there is no circulation of the coolant through the heat exchanger until the thermostat opens. Just sayin...

Could the thermostat be installed inverted?

Xsbank said:

I don't see why the cold water matters as there is no circulation of the coolant through the heat exchanger until the thermostat opens. Just sayin...

Click to expand...

does the thermostat also affect the after cooler and if not will that affect the rate of warm up? I don't know for sure just throwing that out my motors have after coolers and I vaguely remember something about cold water and after coolers. If somebody out there knows please chime in.

Hi Hal,

I have two 6404 D's in Newport RI. Would appreciate any help you could give me regarding thermostats and location. Thanks !!

Hal Northstar said:

My JD 6404 was running at 140 degrees. After changing the thermostat with no improvement, I found the temperature sender had gone bad. New sender solved the problem.

Click to expand...

They are located aft just above the heat exchanger. Took me awhile to figure that out. Im going to open mine up today. That engine, port runs at 150 for some reason. My Stbd at 170.

Some engines have a thermostat bypass so the engine always has some circulation. If you're running a bus heater, that circuit usually bypasses the thermostat. In cold water the bypass is often restricted to help the engine warm up.
My Detroits have a 1/2" bypass, but it doesn't hurt warming.

I pulled my Thermostat on the cold engine. 150deg. Checked with laser gun. The thermostat is a NAPA 170 barrel. It actually opens at 190 in a boilng pan. I have a spare Caltherm that similarily is a 170 but it opens and closes at 180.

Can anyone confirm if the thermostat sits with the barrel up or down. (i.e. Barrel up would place it in the reservoir . Mine was spring up. I do not have bus heat but I do have a hot water heater circuit off that engine.

Barrel up or down? I cant find a reference in the manual as to whihc is correct.

Thanks

FYI

NAPA part number is 358-170

Caltherm ct2200-02

both are t170

The napa actually looks like you could adjust it as there is a thread and nut onthe bottom