Thermostat change, fuel mileage bump

[Godwin]

As long as I can remember I've had a 82C t-stat in the 2F. On the aftermarket gauge the running temp would settle at 180F. Cold temps hit AL in early December and the 2F was running really cold, maxing out about 160F. I swapped out the t-stat only this time I dropped in a 88C unit. The upper o-ring was also replaced as the old was rotten. Now the 2F runs at ca. 195F plus I have improved heat output in the cabin.

When the 2F was running cold mileage was down in the 11 mpg range, with the t-stat swap and increased operating temps I've noticed a minor fuel mileage increase, up to ca. 15+.

 

[Code Red]

From 11 to 15 sounds like a pretty major increase to me. I would love to go from 11 to 15.

Do you think the same would hold true on a 3FE? I might try it anyway. These last few cold weeks in GA have me wishing the heater was a little hotter.

 

[Godwin]

From 11 to 15 sounds like a pretty major increase to me. I would love to go from 11 to 15.

Do you think the same would hold true on a 3FE? I might try it anyway. These last few cold weeks in GA have me wishing the heater was a little hotter.

The o-ring that tops the thermostat is a more critical item than may appear and if it is not in good condition and allows water passage around the t-stat the engine fluids will not warm sufficiently. You could pull apart the housing, check the o-ring and see what t-stat is currently installed.

My posted mileage jump may be a little misleading. The 11 mpg low was with mixed driving and if it had been consistent highway the mileage would have normally been bumped to ca. 13-14. The coldish engine did add to a reduction of fuel mileage but I am seeing some increase in fuel mileage but I don't expect anything > 1.5 mpg which will put this, for my FJ60, in the 15 range.

 

[OSS]

Another confirmation. Good to hear.
Since thermostats are cheap and so are the gaskets & 4 bolts. I've become a firm believer in my own philosophy (I guess that's clinically self flagellating) that the thermostat & gaskets and 4 t-stat bolts should be replaced every 5-6 years at a coolant change. That upper rubber gasket on top of the t-stat doesn't last very long. The t-stat can function fine for over a decade, but once the upper t-stat housing gets popped off to check/replace the rubber gasket, the t-stat is just begging, pleading, to be tossed in the dumpster.

 

[Godwin]

Another confirmation. Good to hear.
Since thermostats are cheap and so are the gaskets & 4 bolts. I've become a firm believer in my own philosophy (I guess that's clinically self flagellating) that the thermostat & gaskets and 4 t-stat bolts should be replaced every 5-6 years at a coolant change. That upper rubber gasket on top of the t-stat doesn't last very long. The t-stat can function fine for over a decade, but once the upper t-stat housing gets popped off to check/replace the rubber gasket, the t-stat is just begging, pleading, to be tossed in the dumpster.

Agree. This t-stat and o-ring were likely 10-11 years old, installed when I rebuilt the 2F, and not just years but miles also > 200k.
I replaced the water pump within the past year+ but did not replace the t-stat etc. I also do not replace the coolant often enough which could have been a factor.

 

[OSS]

Join the club. I don't think most people w 2Fs change the coolant at the recommended interval. I know I'm guilty of that. It's such a messy pain and getting all of the air out of the system afterwards seems to take forever. It's time for me to change the coolant (according to the recommendation
on the coolant bottle) but I'm not going to do it. Let it sit a few more years. Never hurt anything in the past.

 

[hj 60]

Thank for the advise, I have ordered a (diesel) gasket and thermostat, first time and maintenance change so I was just waiting for it to fail.
I will keep the old one in the rear panel as spare, cant throw stuff away sadly,
Ordered standard 88 degrees Celsius, not Sahara (or hot heavy towing/load) 82C but I dont understand that diesel and gasoline have the same 88C operating temp, I thought diesel is running far more hotter than gasoline? but it seems both engine type are about 100 degrees Celsius at best.

Opened several online stores and finally ordered here (europe) : Thermostat 88° für BJ40 BJ42 BJ45 BJ75 HJ60 HJ61 - Wüstentauglich

Closed all websites.
Then shop emailed he was in spain and could deliver in 3 months.
Back to the websites

 

[OSS]

Here's the Toyota part number for the 2H thermostat: 90916-03103

Make sure you order the upper gasket too.

Both the diesels & gasoline engines on the 60 cruisers used 88°C thermostats standard.

 

[morganism]

I think the higher temp really helps combustion, and also seems to keep the carbonization from building up, especially if you still have an EGR valve.

 

[peterabbitcook]

@Godwin I read in Moses Ludell’s Truck & Land a Cruiser Bible that the primary reason for using a higher temp thermostat is to handle higher combustion temps from EGR. So I find this is really interesting since your engine is desmogged.
Do you still have a 3FE manifold on your engine, and did you ever install some sort of fluid heat riser on the bottom of your intake manifold? I think that would make a difference on fuel economy as well.

 

[Godwin]

@Godwin I read in Moses Ludell’s Truck & Land a Cruiser Bible that the primary reason for using a higher temp thermostat is to handle higher combustion temps from EGR. So I find this is really interesting since your engine is desmogged.
Do you still have a 3FE manifold on your engine, and did you ever install some sort of fluid heat riser on the bottom of your intake manifold? I think that would make a difference on fuel economy as well.

I think a higher operating temperature increases atomization of the fuel and improved combustion.

Yes I am still running the 3FE exhaust but no longer see a need to add any type of heat riser to the bottom of the 2F intake. Since the initial addition of the 3FE exhaust I've had the carb rebuilt by JimC and I've cleaned up the hack desmog. Temps this morning were just below freezing but the 2F cranked up and ran well.

 

[OSS]

higher combustion temps from EGR

EGR lowers combustion temps (that's the whole point of EGR). The"bible" got it wrong.