SD22 FAN clutch

[asavage]

Your radiator manufacturer in Queensland is simply marketing a three or four row radiator. Fact of the matter is the forwardmost row does the most cooling because it gets the coolest air. The last row does less cooling because the air hitting it has been heated by the rows in front of it. To market such a dense core radiator as a positive thing speaks to the dim view they hold of their customer base.

Just because the delta T is lower on the rearmost rows does not mean there is no delta T there. Fact is, more rows of cooling area in a radiator does impart more heat transfer. Though doubling the number of rows does not double the heat transfer capacity.

[philip]

Your radiator manufacturer in Queensland is simply marketing a three or four row radiator. Fact of the matter is the forwardmost row does the most cooling because it gets the coolest air. The last row does less cooling because the air hitting it has been heated by the rows in front of it. To market such a dense core radiator as a positive thing speaks to the dim view they hold of their customer base.

Just because the delta T is lower on the rearmost rows does not mean there is no delta T there. Fact is, more rows of cooling area in a radiator does impart more heat transfer. Though doubling the number of rows does not double the heat transfer capacity.

"Fact is" the additional row(s) further impedes air flow and with hotter air passing over the final row. A radiator is only as good as the air supply flowing through its core. Do you recall during the '70's when Chrysler used large single row radiators with tubes you could almost drop a dime through?

[asavage]

"Fact is" the additional row(s) further impedes air flow which further lowers the "delta T" in the rear most row(s). A radiator is only as good as the air supply flowing through its core.

While adding rows does impede airflow, they aren't staggered so the impedance is not all that great. Put another way, the airflow through the first row is not substantially reduced by the addition of a second row.

Do you recall during the '70's when Chrysler used large single row radiators with tubes you could almost drop a dime through?

Yup, I do. Cost savings. And you could catch larger bugs with 'em

[philip]

"Fact is" the additional row(s) further impedes air flow which further lowers the "delta T" in the rear most row(s). A radiator is only as good as the air supply flowing through its core.

While adding rows does impede airflow, they aren't staggered so the impedance is not all that great. Put another way, the airflow through the first row is not substantially reduced by the addition of a second row.

Do you recall during the '70's when Chrysler used large single row radiators with tubes you could almost drop a dime through?

Yup, I do. Cost savings. And you could catch larger bugs with 'em

Ahem. Air flow through the "first row" would not be "...substantially reduced by the addition of a second row." WHY? Is not the first row in front of the second row? What did I miss? Further, with the tubes not staggered, the heat lost by rows subsequent to the 2nd row is compromised and that wind is heated as it passes through. Law of diminishing returns when more than 2 rows exist.

[asavage]

Law of diminishing returns when more than 2 rows exist.

Diminishing, yes. Zero, no. A four-core radiator will transfer more heat from the coolant to the air than a two core. Twice as much heat as a two-core? No. But there's still a benefit. You implied otherwise when you said . . .

To market such a dense core radiator as a positive thing speaks to the dim view they hold of their customer base.

[davehoos]

I believe there called Sunshine Radiators. I haven't purchased one for a few years and names change. In aplications like 5 liter V8 Triumph Stag they work well. We use them here on the farm and cleaning is a problem. Slow moving tractors mostly stationary.

Very rare to see stagged core tubes and when they are it's often wider spacings. Aftermmarket radiators are flooding in from asia. A friend importing these has told me of problems with the thickness of the tube walls. The thicker walls take too long to heat up and transfer heat. They thought they did the right thing overcoming the short life span of the original product. Good to see that some new cars have a dummy row in front.goes back to the war time radiators and bullet resistance.

Im using single row alloy radiator in the skyline. The Oz model has largertanks than the japanese made models but I think thats to standardise with the 2 row optional A/C core. These are ok as long as the engine does not get hot. Then you park on the road side. The RB20E is so slow to warm up that the fan runs locked for the first 20 min highway. It's best to run for a few minutes then switch off.

The 910 here uses a Natra radiator twin row having fine spacing. But when you look at different models they have different size tubes. The early Japanese radiator looked huge but it was mostly top tank.

[philip]

I'm a big fan of electric radiator cooling fans. Here's some background:
SNIP
But when I'd drive down to SoCal, it was pretty marginal, I'm talking like 90° weather and up it would keep up in non-tow conditions, but there were a couple of instances when I would have liked more airflow. I'm pretty certain that I would not have been able to tow in that heat, and I can recall going up Grapevine foot on the floor, 65 MPH and having the fans kick on -- that's bad, because elec fans can't contribute at highways speeds, but the OEM fan can. In that situation, I could not dump heat as fast as I was creating it.
SNIP

Al: I was out to Indio today. It was a relatively "less hot" day for early May. Only 103 degrees.

On the way back (west I-10), I encountered the usual 30+ mph head winds while ascending Whitewater Grade. The little SD got a workout. Full throttle for a couple of miles, the lowest speed was 52 mph in 5th. Never needed 4th. I ran the A/C from Indio clear back to San Bernardino.

Considering I have NO engine fan, had the A/C ON, and at full throttle for about two miles when I took these photos ... not bad!

[Zoltan]

I noticed on my 82 truck, that the fan turns on as soon as I start the engine and stays on. What would be the right sequence to trouble-shoot?

thanks

[philip]

I noticed on my 82 truck, that the fan turns on as soon as I start the engine and stays on. What would be the right sequence to trouble-shoot?

thanks

Let me first say that the OEM clutch is the "thermally controlled" viscous drive type. It has a little coil spring on the front side facing the radiator. All viscous drives will -initially- keep the fan running close to engine speed. The thermally controlled variety -should- limit fan speed to about 1500-2000 rpm once air temperature flowing over the clutch is above 130-150 degrees and then run close to engine speed when air temperature is above 190 degrees.

In bench testing both my OEM clutch and the two aftermarket clutches with a heat gun, it took alot more heat than I expected just to get the coiled thermal spring to move. Might take Death Valley in August to heat the spring sufficiently.

When I had the go-'round with Four Seasons about testing two of their clutches I bought, their on-vehicle test sequence just did not work well. An SD22 running with no load (other than fast idle speed) takes forever to get 'hot' (ie coolant temperature above 205 degrees) when there is the smallest breeze through the radiator. So ... the thick viscosity fluid in the clutch maintains too much minimum drag in spite of the thermal spring keeping the venting port open.

I did buy a used thermal clutch on ebay that oddly enough, does perform correctly. It drives the fan close to engine speed until the engine thermostat allows coolant flow. It then limits fan speed (I hear no more fan howling). I have not tried it in hot weather yet because running around since last November with no fan at all works just fine.

The few times I've been caught waiting in line (idling for 5+ minutes) on an 80+ degree day, simply turning the heater & fan on High will keep the temperature meter below the mid way point.

[Zoltan]

Instead of taking out the fan, wouldn't it be simpler just to put in a piece of cardboard in front of the radiator?
Now that I pay more attention to the temp gauge, I, too, see that most of the time, the engine runs cold.

[philip]

Instead of taking out the fan, wouldn't it be simpler just to put in a piece of cardboard in front of the radiator?
Now that I pay more attention to the temp gauge, I, too, see that most of the time, the engine runs cold.

You might refer back the the first post in this thread about why I delved into the fan matter in the first place. Two issues: Fan noise & fan belt life.

IF this were a stationary engine that operated under constant conditions, then a piece of cardboard and no thermostat would suffice. But that's NOT the real world of a motor vehicle.

In the real world, the cooling system has to contend with:

1. ambient temperatures from well below freezing to 130°F.
2. how much additional cooling is added by the driver operating the cabin heater.
3. more widely varying amounts of heat generated by a diesel engine, ie sustained full throttle to prolonged idle.
4. times when air flow through the radiator is compromised, ie driving along with a strong tailwind or prolonged idling in 90°+ heat.
5. rain cooling the radiator.
6. Air Conditioning condensor PREHEATING the air entering the radiator.
7. additional heat being introduced from the engine oil heat exchanger.
8. ... and any other variable you care to imagine.

So with all that in mind (pregnant pause) -assuming- you have the proper design thermostat installed, that is working correctly, that is of the correct heat rating (180°F), and a clean radiator, then your percieved "running cold all the time" is likely a reporting deficiency.

[Zoltan]

OK, "running cold all the time" not entirely acurate, but I'd say 90% of the time the needle hangs around the first third of the C-H field. The only time it goes beyond half is when I drive full throttle at 45 mph in 4th gear uphill for about 2 miles.

As for the thermostat, I am surprised that the stock thermostat is set to 180F. I thought that diesels need to run a little bit hotter than gasoline engines in order to achieve better combustion. In my 86 Ford diesel (a 2L engine made by Mazda), the factory thermostat set to 195F. I wonder if I replaced the stock thermostat to a 190F one, I'd get better performance and could save a bit of gas. I don't have a A/C, and outside temp rarely goes beyond 92F here in Hawaii.

[philip]

OK, "running cold all the time" not entirely acurate, but I'd say 90% of the time the needle hangs around the first third of the C-H field. The only time it goes beyond half is when I drive full throttle at 45 mph in 4th gear uphill for about 2 miles.

Page back to page 1 of this thread. You'll find a temperature meter photo. The reading you have most of the time is NORMAL.

As for the thermostat, I am surprised that the stock thermostat is set to 180F. I thought that diesels need to run a little bit hotter than gasoline engines in order to achieve better combustion. In my 86 Ford diesel (a 2L engine made by Mazda), the factory thermostat set to 195F. I wonder if I replaced the stock thermostat to a 190F one, I'd get better performance and could save a bit of gas. I don't have a A/C, and outside temp rarely goes beyond 92F here in Hawaii.

1) This is an OLD TECH diesel. Coolant temperature does not affect fuel consumption or power anywhere near as much as air temperature does ... followed by having the smoke screw setting optimized for your altitude. If you can see ANY black exhaust smoke in the side view mirror on that 2 mile grade when you have your foot on the floor, the smoke screw needs readjustment.

2) A hotter thermostat will NOT achieve your goals.

3) SDxx burn DIESEL. Do not put gasoline in the fuel. (I'm sure you simply made a slip ).

4) Just like a gasoline engine, do have a clean air filter installed.

[philip]

SNIP

The few times I've been caught waiting in line (idling for 5+ minutes) on an 80+ degree day, simply turning the heater & fan on High will keep the temperature meter below the mid way point.

Update: It's early July in Los Angeles. Ambient afternoon temperature hits 100 degrees. Since last November, I've been running the truck with no fan installed.

On this 100 degree day, I can still idle along in 2nd gear with the commuter snarl with the heater ON to keep the engine temperature close to 200 degrees but ... no more air conditioning ... right when I'd like MOST to have A/C !! Once I could keep a minumum speed of 30-35 mph, I could cut the heater and run the A/C, and have the engine happy too.

So when I got back home, the viscous fan got reinstalled. Ahhh!

[ecomike]

While pulling my water pump yesterday I got a good look at my fan clutch. I think it is the OEM clutch. This clutch is built like a Sherman tank compared clutches I had on 400 cu in V-8s. This the largest, heaviest duty clutch I have ever seen. Looks like it would outlast the engine and maybe even me!

I also noticed that it seems have two halves, front and back, that come apart with just bolts. There are bolts on both sides. I am guessing it is user repairable, although I do not know how or what you would refill it with. I seem to recall hearing it is silicone fluid inside these clutches. Anyway, from the looks of this beast it should outlast me.