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| Subject: | Viscous Fan Clutch Survey - ***KEEP IT COMING GUYS*** | |||||||||||||||||||
| Posted By: |
RandalG
Centurion |
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| Posted At: | 12/19/03 12:52 am | |||||||||||||||||||
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Guys, Given the amount of interest there’s been over time about the operation of the radiator viscous fan clutch and its contribution to engine overheating and cracked cylinder heads, I thought it would be of value to this forum to do a survey and get feedback on what seems to be the “normal” operation of the fan clutch. The following survey includes a test to perform on your fan. If we all complete this test under similar conditions, we’ll have some reasonable data to interpret “normal” operation. Then you’ll know whether or not you need to give the viscous clutch some attention coming into this hot summer. I’ll collate the responses we get and make them available to those who've contributed to the survey. Let’s see what the consensus is! Make sure you answer EVERY question. If you don't, the info will be of little value. Garbage in = Garbage out! ------------------------------------------------------------ The Objective: The objective is to test what constitutes “normal” operation. The viscous fan clutch is normally fully engaged when the engine is cold. As it warms up, the silicon fluid becomes more fluid (less viscous) and releases the clutch somewhat. You’ll know this when you hear the fan whine reduce. Then after the engine’s reached operating temperature and it gets sufficiently hot, you’ll hear the fan engage again. This is the bi-metallic strip doing its thing, sensing the increased temperature and engaging the viscous clutch. (If I’ve got this wrong…. someone correct me). We want to test the fan clutch in its three operating conditions. Apply the tests as follows, note your results and then answer the survey that follows. It’s easy! It’s multi-choice!  The Test: - Mark the tip of one fan blade with a black permanent marker. This will be your marker blade. - Locate the marker blade about 1/8th rotation to the left of top dead centre (TDC). Spin the fan clockwise by pushing it with sudden force and releasing it. Note how far the marker blade spins freely from when you release it, to when it stops (measure the rotation as the number of fan blades that pass by until it stops). Assumptions: I'm assuming we all have the typical 7 blade Hilux Surf fan. If you have otherwise, please state the number of blades on your fan. The Conditions: Ok. Following are the conditions we want to apply the test. Note: the engine should not be running when you apply the test. (1) COLD – With the engine stone cold, apply the test. eg: First thing in the morning after it’s sat all night. (2) UNDER OPERATING TEMP – With the engine just under operating temp (before your temp needle reaches its half way resting spot ie: 1/4 on the dial), stop the engine and immediately apply the test. (3) HOT – With the engine HOT (make sure you’ve driven it for over 15 minutes and you’ve been giving it a good rev with plenty of turbo boost) eg: you’ve raced home from Christmas shopping in the heat of the day to catch the cricket on TV. Stop the engine and immediately apply the test. ------------------------------------------------------------ The Survey: (1) What Year, Model, Engine & Transmission is your car? (2) Do you find your engine runs hot or overheats under high load, low speed driving? (eg: 4WD low range offroad; driving in soft sand). a. Yes b. No (3) Do you find your engine runs hot or overheats under high load, high speed driving? (eg: highway driving & vehicle fully loaded or towing). a. Yes b. No (4) How much silicon oil is in your viscous fan clutch? a. Never touched it…. Don’t know. b. Original + 1 additional tube (1 tube = 18ml Toyota silicon oil) c. Original + 1 to 2 additional tubes d. Original + 2 additional tubes e. More than 2 tubes (5) Have you adjusted the bi-metallic strip? a. No b. Yes, by ¼ adjustment c. Yes, by ½ adjustment d. Yes, by ¾ adjustment e. Yes, by the full adjustment (6) After applying the test, how much free spin does your fan have with the engine COLD? a. No rotation b. Less than 1 blade rotation c. 1 Blade rotation d. 2 Blades rotation e. 3 Blades rotation f. 4 Blades rotation g. 5 Blades rotation h. 6 Blades rotation i. 7 Blades rotation j. More than 7 (specify number) (7) After applying the test, how much free spin does your fan have with the engine just UNDER OPERATING TEMP? a. No rotation b. Less than 1 blade rotation c. 1 Blade rotation d. 2 Blades rotation e. 3 Blades rotation f. 4 Blades rotation g. 5 Blades rotation h. 6 Blades rotation i. 7 Blades rotation j. More than 7 (specify number) (8 ) After applying the test, how much free spin does your fan have with the engine HOT? a. No rotation b. Less than 1 blade rotation c. 1 Blade rotation d. 2 Blades rotation e. 3 Blades rotation f. 4 Blades rotation g. 5 Blades rotation h. 6 Blades rotation i. 7 Blades rotation j. More than 7 (specify number) (9) How many blades does your fan have?
Edited by: RandalG at: 1/19/04 3:28 pm | ||||||||||||||||||||
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