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subzero350

3410H enhanced engine cooling

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subzero350

About a month or so ago we had some hot weather and I noticed the 10hp briggs on my 3410H struggling a bit after it had been running for a while. The flywheel intake screen was clean (I clean it and the engine's cooling fins religiously) so that wasn't the problem. My exhaust system is wrapped with header wrap to reduce under-hood temps, which helps.

I used to have a plastic fan blade mounted on the front of the crank in the past but removed it when I installed the front PTO for the snowblower because it wouldn't clear the hood.

I was curious as to how hot the engine was getting so I installed a GM coolant temperature sensor into the oil drain plug location and operated the tractor until it started acting funny again. I then measured the resistance of the temp sensor and used the chart below to determine the oil temperature in the crankcase was at about 220 deg F.

Temperature vs Resistance Values (Approximate)

°F---OHMS

302---47

284---60

266---77

248---100

230---132

212---177

194---241

176---332

158---467

140---667

122---973

113---1188

104---1459

95----1802

86----2238

77----2796

68----3520

59----4450

50----5670

41----7280

32----9420

23----12300

14----16180

5-----21450

-4----28680

-22---52700

-40---100700

temp_sensor.jpg

I removed the grille screen and modified the bottom of the hood so I could install an 8" plastic fan blade I took off of a universal 8" electric cooling fan/motor assy. I bolted the fan blade directly onto the end of the crankshaft. This particular fan blade had a metal center section that is strong enough to replace the spacer/washer used on the front PTO to retain the PTO spring.

After installing this fan, I continued mowing and periodically checked the oil temp and found it never ran over about 180 deg F with this fan in place. So I dropped the oil temp by about 40 deg just by adding this secondary fan.

fan.jpg

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subzero350
quote:Originally posted by Rick3410

This is really interesting data. Nice work. Did the 40 degree difference fix the sluggish running problem?


id="quote">
id="quote">Yes.

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subzero350
quote:Originally posted by Rick3410

Can you recommend a good source for a fan? I am having the same problem and this seems like a good solution.


id="quote">
id="quote">Sure can. http://www.summitracing.com/search/part-type/electric-fan-replacement-fan-blades?tw=fan%20blade&sw=Electric%20Fan%20Replacement%20Fan%20BladesMy fan blade measures 8" in diameter, but an 8.5" would probably fit also. You might be able to fit an 8.5" or bigger one depending on how much clearance you have. Summit lists all sizes including 8".Once you get the blade, you'll need to drill out the center mounting hole so the crank bolt fits snugly thru it (to keep it centered).

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RickS

I wonder if one installed a small electric fan on the grill if one would see the same reduction in oil temperature. As I see it any additional movement of air under the hood of the tractors is a good thing.

So has anyone installed a small electric fan and if so should the fan blow hot air out the grill, or pull cooler air through the grill and under the hood?

Rick........

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subzero350

The problem with these tractors is the hot engine air blows forward directly onto the muffler. Then as you are traveling across the yard, this hot air just recirculates under the hood and can make its way back to the flywheel air intake area where it just gets recycled thru the engine. Putting some kind of fan on the grille under the muffler can force cool air to blow onto the engine.

As long as the charging system in your tractor is strong enough, I don't see why you couldn't just mount an electric fan on the grille to do the same job.

I will say that wrapping the exhaust system and muffler in header wrap did also help greatly reduce under-hood temperatures.

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BLT

Determining what is good and what is bad is a feel good thing as Briggs and other engine people do not give any base cooling values to work with, such as maximum ambient temperature, inlet temperature at fan, temperatue exiting cooling fins and oil temperature.. They perform their own test at their factories or mower mfg site to insure that mower being produced will not impede good engine operation to a clean engine.

Also air cooled engines have no thermostat to regulate block temperatures, so the best that they can offer is keeping the is keeping fins a screens clean after every mowing if possible.

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John_in_Oxford
quote:Originally posted by subzero350

The problem with these tractors is the hot engine air blows forward directly onto the muffler. Then as you are traveling across the yard, this hot air just recirculates under the hood and can make its way back to the flywheel air intake area where it just gets recycled thru the engine. Putting some kind of fan on the grille under the muffler can force cool air to blow onto the engine.As long as the charging system in your tractor is strong enough, I don't see why you couldn't just mount an electric fan on the grille to do the same job.I will say that wrapping the exhaust system and muffler in header wrap did also help greatly reduce under-hood temperatures.


id="quote">
id="quote">Was just about to ask about the wrapping, and I see you answered it.OK, one more: Does wrapping the exhaust make it any QUIETER?

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goatfarmer

Using that sensor, one could, theoretically, mount an oil temp gauge, no?

Is it the high underhood temps making the fuel boil, or cause a vapor lock condition in the carb?

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Burntime

I was going to put a temp sensor on my command. There was a sensor that fit in a plug. My guess is you could find or drill and tap a spot on a briggs block to do the same. The guage I was looking at had temp and voltage...

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BLT

There is only one place to put a sensor in a Briggs CI engine, like the top picture of this thread. You also have to make sure that oil dipper on conn rod won't hit it.

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Kent

VDO used to sell a head temperature gauge that the sensor mounted underneath the sparkplug. They also sold an oil temp sensor that was actually a dipstick... which might work with some modifications. Don't know if they still do, but they used to...

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subzero350

The exhaust wrap didn't make the exhaust any quieter - sorry (I wish it did!).

I had fuel boiling in the carb issues before I did the exhaust wrap. Ever since I did that, it never had that issue again.

I can tell you this little 8" fan blade puts out a lot of air at full throttle. It blows quite a bit back past the carb and the generator with the hood closed.

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Brettw

I wonder if wrapping the muffler is causing some very high exhaust gas temperatures to build up? Obviously if you had boiling gas prior to the wrap, there was heat being released from the muffler. It seems like a good idea, but I wonder if the actual engineering could be tested and calculated, if that wrap isn't actually adding to the internal cooling problems. When you consider all of the factors that contribute to the cooling; fan, clean fins, tins all in place, carburetor intake air and fuel mixture, exhaust flow, etc., this one "fix" with the wrap may be causing a problem? Just a thought.

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subzero350

I tried adjusting the carb richer and all it did was sputtered and started spewing black smoke. So it wasn't a mixture problem.

The fan is sucking air from the front of the tractor and blowing it back on the engine. I do not think it fights the flywheel fan since the air that fan blows across the engine comes out on top and above the crank mounted fan.

Wrapping the exhaust shouldn't cause the engine to run hotter. The exhaust doesn't get sucked back into the engine (or at least it should not). All the wrap does is keeps the heat in the exhaust instead of letting the heat transfer from the muffler to under the hood. If anything, the header wrap should improve the scavenging effect of the exhaust system.

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GLPointon

Did you ever check to be sure ther is no mouse nest in the blower housing blocking air flow? I know thats Very common.

The fan and sensor seem like a great idea/improvement for high temp problems. I like the idea of a thermostatic electric fan too so the front PTO can stay intact dOd

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subzero350

No mouse nest and the head gasket is not leaking.

The standard GM cooling fan switch they commonly used in the 80's turns the fan relay on at 226 deg F and off at about 216 or so. That might install right into the oil drain plug location as I think it is the exact same thread size as the coolant temp sensor I'm using to plug my oil drain hole.

The aftermarket makes cooler fan temp switches - just make sure no matter what temp switch you use for your electric fan you wire in a relay so the electrical load of the fan motor is not put on the switch itself. An example for the wiring you could use is below:

Relay Terminal 85 - connect to fan switch (switch will ground to turn relay on, you can also wire up a simple toggle switch to this terminal as well so you can have override control)

Relay Terminal 86 - Switched IGN 12v (+) voltage (if you only want the fan to be able to run with the key on) or you can wire this up directly to constant battery POS (+)

Relay Terminal 87 - Connect to battery POS (+) terminal power and protect with an in-line fuse of the size recommended by the fan manufacturer.

Relay Terminal 30 - connect to fan motor POS (+) terminal.

Fan motor NEG (-) terminal connects to ground.

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