Jay NE Ohio Posted January 13, 2008 Share Posted January 13, 2008 My 88 Mack tri-axle seems to be running warm. I've only been running it a month and the weather has been cold. Empty it stays around 190 degrees. When loaded it is running around 220. Red line is 230. The radiator is full and clean. However, I never hear the fan kick on and off like my freightliner does. With spring right around the corner, I want to get this fixed before the weather warms up.How does the clutch fan work on these 350 Macks? I took a quick look, but did not notice any wires or air lines in that general area. What is the most likely cause of failure? Thanks for any insight.BTW: A while back I posted about the fuel tanks pressurizing on this truck. I had a crack in the head which was pushing air into the return line which runs through the heads. I replaced the heads with rebuilt ones and all is fine now. Quote Link to comment https://www.bigmacktrucks.com/topic/3290-how-does-the-clutch-fan-work/ Share on other sites More sharing options...
Doug Mitchell Posted January 13, 2008 Share Posted January 13, 2008 You're not running a winterfront, are you? They are not needed, and as I recall, void the warranty. Quote Old truck drivers never die. We just smell that way. Link to comment https://www.bigmacktrucks.com/topic/3290-how-does-the-clutch-fan-work/#findComment-16230 Share on other sites More sharing options...
Jay NE Ohio Posted January 13, 2008 Author Share Posted January 13, 2008 You're not running a winterfront, are you? They are not needed, and as I recall, void the warranty.No I am not running a winterfront. And it is long out of warrenty (1988 model).I tore off the fan clutch this afternoon. No wires, no air lines attached to it. I don't see any way to tear it apart. The hub turns by hand, so it is not locked up. I assume that it senses the temperature of the air by the little spiral thing (I have no idea of the technical name) and should lock it up at a certain temperature. Maybe I will stick it in the oven (when my wife leaves!) and see if it locks up???? I have attached a picture: Quote Link to comment https://www.bigmacktrucks.com/topic/3290-how-does-the-clutch-fan-work/#findComment-16233 Share on other sites More sharing options...
theakerstwo Posted January 13, 2008 Share Posted January 13, 2008 My 88 Mack tri-axle seems to be running warm. I've only been running it a month and the weather has been cold. Empty it stays around 190 degrees. When loaded it is running around 220. Red line is 230. The radiator is full and clean. However, I never hear the fan kick on and off like my freightliner does. With spring right around the corner, I want to get this fixed before the weather warms up.How does the clutch fan work on these 350 Macks? I took a quick look, but did not notice any wires or air lines in that general area. What is the most likely cause of failure? Thanks for any insight.BTW: A while back I posted about the fuel tanks pressurizing on this truck. I had a crack in the head which was pushing air into the return line which runs through the heads. I replaced the heads with rebuilt ones and all is fine now. If it is running 220 that may be the way the heads got cracked. If there is no air line to the clutch then you may have a viscosity clutch which is not a simple way to check but if you find that is the clutch you have then get back and i will help you troubleshoot it. I dont what to put my mine in deep thougth mode untill i need to. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/3290-how-does-the-clutch-fan-work/#findComment-16234 Share on other sites More sharing options...
Lmackattack Posted January 13, 2008 Share Posted January 13, 2008 Thats a hortan fan clutch. around $130 dollars from the mack dealer. They work like this.When the engine is started (cold start) the clutch should be "released" alowing the engine to warm up, you may see the fan spin ,this is ok as its drag from the spinning water pump alows it to spin slowly.when your engine temp gets above "X" temp (mostlikely around 195-200) the thurmo coil enguages the clutch to spin the fan. If the truck is getting hot in this cold weather i would think you have a diffrent issue. I can run a winter front and pull a load in 15 deg temps and the fan might kick on a few times on the highway. local roads the fan stays off. If the winter front is off the fan wont turn on all day... check the thurmostat, guage and sending unit to make shure those are not issues....Trent Quote Link to comment https://www.bigmacktrucks.com/topic/3290-how-does-the-clutch-fan-work/#findComment-16237 Share on other sites More sharing options...
Denny Posted January 13, 2008 Share Posted January 13, 2008 Jay, If your truck seems to warm up unusually quick, try changing the thermostat, it could be not opening all the way,would run hot also. That might be a quick fix, Might consider it . Quote Link to comment https://www.bigmacktrucks.com/topic/3290-how-does-the-clutch-fan-work/#findComment-16240 Share on other sites More sharing options...
Freightrain Posted January 14, 2008 Share Posted January 14, 2008 There should be some drag on shaft when trying to turn it. If it spins free, then it's broke.This is the same design they use in std cars(before they all were front whl drive and elec. fans). Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/3290-how-does-the-clutch-fan-work/#findComment-16244 Share on other sites More sharing options...
MidniteMechanic Posted January 14, 2008 Share Posted January 14, 2008 You have a viscous fan drive. They've been used for years, but I'm not a big fan of them.It would be best if you had a infrared temp gun, that would tell alot. I don't know what degree thermostat you have.But when the engine is running take the block temp near the water sending unit. That will tell you if the dash gauge is ok. There will be a few degrees difference. I've found ones that when water temp in engine is near 180 the gauge showed 200.Check the temp on the engine side of the thermostat, and then on the hose to the radiator. When the thermostat opens, you'll see the rad hose equal the temp of the engine. If the hose stays 'cold' and the engine temp keeps rising after the thermostat was supposed to open, the thermostat is stuck.If all is ok this far, when the engine is 'at temp' and running, check the temp at the top radiator hose and then the bottom hose that returns to the engine. The bottom hose should be somewhere between 8 & 10 degrees colder than the top hose. If this is not happening, this opens two possibilities, either the water pump is not circulating properly or the the radiator is blocked internally with deposits.Lastly if you made it this far, remember how the fan turned by hand when the truck was cold. Now when the temp gets to 220 like you say, shut off the truck and check how the fan turns. It should turn with much more resistance. If it doesn't it's junk, buy a new one or invest in an air clutch.By the way before anyone says you can't shut off an engine when it's that hot, it'll never hurt it for the short time needed to check the fan drive.WOW that was long winded!! But that's pretty much how I would do it. Quote Link to comment https://www.bigmacktrucks.com/topic/3290-how-does-the-clutch-fan-work/#findComment-16248 Share on other sites More sharing options...
theakerstwo Posted January 14, 2008 Share Posted January 14, 2008 You have a viscous fan drive. They've been used for years, but I'm not a big fan of them.It would be best if you had a infrared temp gun, that would tell alot. I don't know what degree thermostat you have.But when the engine is running take the block temp near the water sending unit. That will tell you if the dash gauge is ok. There will be a few degrees difference. I've found ones that when water temp in engine is near 180 the gauge showed 200.Check the temp on the engine side of the thermostat, and then on the hose to the radiator. When the thermostat opens, you'll see the rad hose equal the temp of the engine. If the hose stays 'cold' and the engine temp keeps rising after the thermostat was supposed to open, the thermostat is stuck.If all is ok this far, when the engine is 'at temp' and running, check the temp at the top radiator hose and then the bottom hose that returns to the engine. The bottom hose should be somewhere between 8 & 10 degrees colder than the top hose. If this is not happening, this opens two possibilities, either the water pump is not circulating properly or the the radiator is blocked internally with deposits.Lastly if you made it this far, remember how the fan turned by hand when the truck was cold. Now when the temp gets to 220 like you say, shut off the truck and check how the fan turns. It should turn with much more resistance. If it doesn't it's junk, buy a new one or invest in an air clutch.By the way before anyone says you can't shut off an engine when it's that hot, it'll never hurt it for the short time needed to check the fan drive.WOW that was long winded!! But that's pretty much how I would do it. You have it about right. I use a carboard blocker to cut off almost all of the air to rad. I forgot tell you that i cut a hole in the carboard at the point of the clutch the same size of the clutch so all the air that goes thru the rad. will go over the clutch which the sensor is in the front of the clutch. you need a photo cell tackometer and at maybe 1800 rpm check the rpm at the clutch pulley when coolant is cold and with engine running let it heat to about 200 to 205 degrees and check the rpm at the pulley and also at the clutch housing and at that temp the clutch should be locked up and turning 80% of the pully speed and it will not turn any more than that if it is good. It will be roaring loud at 80% and that is max air that it can move.Then back rpm down because the temp will come up fast.Some times it is hard to get carboard in between the air/air cooler and rad but this is a real test that has to be done when working waranty and is from the switzter manual and i have used it for years .It makes you look like you are slow but i like to use it to keep from doing like some of my freinds that just put on new clutch .I hate to put new parts on and then the dearlership has to pay for it if i am wrong. glenn Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/3290-how-does-the-clutch-fan-work/#findComment-16249 Share on other sites More sharing options...
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