If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Explanation needed of Mercury Marquis cooling fan clutch operation
My Mom has a 1995 Mercury Grand Marquis with a radiator/engine
overheating problem. The temperature skyrockets on occasion during slow, stop/go driving. Upon stopping and opening the hood with the engine still running, I see that the water pump belt-driven cooling fan is not turning(the smaller aux electric fan is running[while AC is on]) and the belt is not slipping. I've been told my various shade tree mechanics that there is a clutch that gets the fan blade turning, but as to how the clutch is activated, I get varying stories. Some say the clutch is centrifugally activated due to the RPM of the drive belt. Some say the clutch is electrically activated by a fan clutch switch but the location of said switch is not known...some say in the radiator, some say in the thermostat, some say in the engine block. If there is a switch, I'm thinking it's thermostatically activated, but that's a guess on my part. That stuff about centrifugal activation kind of has me puzzled. I'm used to GM vehicles' electric cooling fans, having had to replace one on a Celebrity, and two on a Century. Voltage present to fan, but fan doesn't work...bad motor. No voltage to fan motor, switch problem. Simple. I'd appreciate a "How it Works" tutorial on a, for lack of a better name, mechanical cooling fan. Thanks for any information or insight you can provide. Also, if you know whether it's the clutch or switch that is the more common culprit. Danny getting hot in Yorktown, VA |
Ads |
#2
|
|||
|
|||
Explanation needed of Mercury Marquis cooling fan clutch operation
"Danny" > wrote in message oups.com... > My Mom has a 1995 Mercury Grand Marquis with a radiator/engine > overheating problem. The temperature skyrockets on occasion during > slow, stop/go driving. Upon stopping and opening the hood with the > engine still running, I see that the water pump belt-driven cooling fan > is not turning(the smaller aux electric fan is running[while AC is on]) > and the belt is not slipping. > > I've been told my various shade tree mechanics that there is a clutch > that gets the fan blade turning, but as to how the clutch is activated, > I get varying stories. Some say the clutch is centrifugally activated > due to the RPM of the drive belt. Some say the clutch is electrically > activated by a fan clutch switch but the location of said switch is not > known...some say in the radiator, some say in the thermostat, some say > in the engine block. > > If there is a switch, I'm thinking it's thermostatically activated, but > that's a guess on my part. That stuff about centrifugal activation > kind of has me puzzled. > > I'm used to GM vehicles' electric cooling fans, having had to replace > one on a Celebrity, and two on a Century. Voltage present to fan, but > fan doesn't work...bad motor. No voltage to fan motor, switch problem. > Simple. > > I'd appreciate a "How it Works" tutorial on a, for lack of a better > name, mechanical cooling fan. Thanks for any information or insight > you can provide. Also, if you know whether it's the clutch or switch > that is the more common culprit. > > Danny getting hot in Yorktown, VA > The engine driven fan is equipped with a viscous clutch. It operates by allowing the fan to spin more freely( slip) when the clutch hub is cool, but as the hub gets heated up by the hot air flowing through the cooling radiator it begins to grip more completely and does not allow as much slipping of the fan on the hub. Inside the fan clutch are some metal clutch plates immersed in a viscous silicone material. That material gets thicker as it gets hotter and the thicker fluid causes more friction between the fan clutch plates. When it is fully warmed up we say it is engaged because very little slippage is occurring between the engine pulley and the fan blades. Some types of fan clutches also have an internal spring that uncoils as it gets hotter. This spring applies more pressure to the clutch discs and causes them to have more friction. Either way, there is no electrical switch or thermostat so to speak, that is used. The fan clutch is a sealed unit and is replaced whenever it fails to perform as required. To check it for proper operation, you should warm the engine up to normal operating temperature then have an assistant turn off the ignition while you watch the fan. If the fan continues to spin for more than one second after the engine stops then it needs to be replaced. Some more information on cooling fans he http://www.cdxetextbook.com/engines/...ght=fan+clutch hope this helps. -- Kevin Mouton Automotive Technology Instructor "If women don't find you handsome, they should at least find you handy" Red Green |
#3
|
|||
|
|||
Explanation needed of Mercury Marquis cooling fan clutch operation
As Kevin has posted, those hubs work to increase viscoelastic coupling as
the temperature increases so that the fan rotates faster at higher temperatures than they do when the engine is cold. If you had a direct drive fan (which cars used to have) they would always run at full speed, increasing noise and draining horsepower. (A fan can easily consume 2-3 horsepower) If this fan isn't turning adequately with the engine hot, then the engine is likely to overheat when you are driving at low speed. At highway speed you may get enough air flow that it will not overheat, but the problem will be back again as soon as you slow down. Now, what do you do about it: (1) Replace the viscous hub with an aftermarket or dealership one (2) Replace the whole mess with a 'flex fan'. (I prefer the stainless steel ones) Both, IMHO, are good options. One may be substantially cheaper than the other. |
#4
|
|||
|
|||
Explanation needed of Mercury Marquis cooling fan clutch operation
"Danny" > wrote in message oups.com... > I've been told my various shade tree mechanics that ------ Just one other little word of counsel...You will hear a lot of things from people, many of which seem to make sense, but which may not be totally correct. Automobile systems are more complicated now than they have ever been before, and a good mechanic needs to be current with the actual theory and facts about how systems work before he (or she) can troubleshoot them properly. The more you learn about how the car works, the more you can do for yourself, and the more you can avoid bad advice. Dealership mechanics can be just as guilty at putting out misinformation as others. Learn how things work, and you will save yourself time, heartache, and LOTS of money. |
#5
|
|||
|
|||
Explanation needed of Mercury Marquis cooling fan clutch operation
Kevin and HLS, thanks for the information and description of how a
viscous hub clutch works. HLS, could you give me some more information on a "flex fan." I can't find a lot of information on it, other than a company called flex-a-lite, and I'm not sure that they carry what you're talking about. I've found several references to a Hayden HY2795 as a suitable replacement for a 1995 Grand Marquis as far as viscous hub clutches. Thanks again. Getting cooler in Yorktown, VA...Danny |
#6
|
|||
|
|||
Explanation needed of Mercury Marquis cooling fan clutch operation
The saga continues on my Mom's 1995 Mercury Grand Marquis with an
overheating problem. I had the viscous hub fan clutch assembly replaced since it would barely turn with the car at and above normal operating temps. The new viscous hub fan clutch is now doing the same thing as the old one(and I know there is a new one in place as the mechanic, a friend who I trust, showed me the old one). When I drove the car home(roughly 8 miles in stop and go traffic) the temperature gauge was within 15 degrees of the top of the scale. Once in my Mom's drive way, I opened the hood and there was the radiator cooling fan spinning at 25 rpm or so...so slow I could make out each blade distinctly. I cut the engine off and then restarted. From inside the car, I could see the top of the fan blades inside the open hood and saw them take off at a blur. After 15-30 seconds, the fan slowed down to the previously mentioned ineffective speed. I turned the car off and restarted once again. This time the fan started up at high speed and ran at high speed for the next ten minutes until the temperature indicator had dropped down to the 190-200 degree level and I turned the car off. Any suggestions? It may have been an optical illusion, but it seemed that the fan shaft just beyond the water pump belt hub was not moving very fast either. Is there another clutch where the water pump belt rides on the bulbous hub/base(just outside the engine block)? The belt does not appear to be slipping. Is there any reason that the water pump belt would be operating at a slower rpm than the engine's rpm? Thanks for any advice/suggestions. Danny in Yorktown, VA |
#7
|
|||
|
|||
Explanation needed of Mercury Marquis cooling fan clutch operation
"Danny" > wrote in message oups.com... > The saga continues on my Mom's 1995 Mercury Grand Marquis with an > overheating problem. I had the viscous hub fan clutch assembly > replaced since it would barely turn with the car at and above normal > operating temps. The new viscous hub fan clutch is now doing the same > thing as the old one(and I know there is a new one in place as the > mechanic, a friend who I trust, showed me the old one). When I drove > the car home(roughly 8 miles in stop and go traffic) the temperature > gauge was within 15 degrees of the top of the scale. Once in my Mom's > drive way, I opened the hood and there was the radiator cooling fan > spinning at 25 rpm or so...so slow I could make out each blade > distinctly. I cut the engine off and then restarted. From inside the > car, I could see the top of the fan blades inside the open hood and saw > them take off at a blur. After 15-30 seconds, the fan slowed down to > the previously mentioned ineffective speed. I turned the car off and > restarted once again. This time the fan started up at high speed and > ran at high speed for the next ten minutes until the temperature > indicator had dropped down to the 190-200 degree level and I turned the > car off. > > Any suggestions? > > It may have been an optical illusion, but it seemed that the fan shaft > just beyond the water pump belt hub was not moving very fast either. > Is there another clutch where the water pump belt rides on the bulbous > hub/base(just outside the engine block)? The belt does not appear to > be slipping. Is there any reason that the water pump belt would be > operating at a slower rpm than the engine's rpm? > > Thanks for any advice/suggestions. > > Danny in Yorktown, VA > Perhaps the water pump bearings are binding and causing the belt to slip. Although a slipping belt usually makes a squealing noise, sometimes they do not. I would suggest removing the belt and checking all the pulleys by hand. Spin them and feel for any roughness or play in the bearings. If everything feels ok it may be that the new fan clutch is defective. That does happen sometimes. Also keep in mind that the viscous clutch relies on hot air flowing through the radiator to cause it to warm up and engage. If the radiator fins are filled with debris and not allowing sufficient air flow, the clutch may not get warm enough to engage when it should. Also consider that the temperature indicator may not be reading correctly and the engine is not actually as hot as is being indicated. Perhaps the sending unit or the wiring or even the gage itself has a problem -- Kevin Mouton Automotive Technology Instructor "If women don't find you handsome, they should at least find you handy" Red Green |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
squeaking clutch at friction point | sandheep | Mazda | 26 | February 17th 06 01:30 PM |
Question: removal of Windshield wiper on 1985 Mercury Grand Marquis | [email protected] | Technology | 3 | December 28th 05 12:53 AM |
Does X-TREEEMME Cold affect clutch operation? | SteveBrady | Jeep | 12 | December 22nd 04 05:32 PM |
stuck caliper... | Abeness | Honda | 113 | December 7th 04 01:22 AM |
Clutch died on '96 Golf 1.8 | Wakeley Purple | VW water cooled | 12 | October 21st 04 10:31 AM |