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Alternator Decoupler Pulley and serpentine belt

11K views 18 replies 6 participants last post by  Aleks 
#1 ·
Have some squeeling and rattling issues in the belt area. Not aure what it is but i want to check my altinator and idler pullys but not sure of how to go about it. Not a lot of room to work with. Im not a mechanic but know enough. Just wondering the easiest way to get belt on and off to check these things. What do i do!
 
#4 ·
Odds are that if you've got noise in that area, it's the alternator. The decoupler pulley they have is not the best idea that Dodge ever had. It's easier just to replace the complete alternator rather than try to find and replace the pulley. Just do a search and you'll see what I'm talking about.
 
#7 ·
Chrysler kind of had to, since the World engine is largely an Asian design and the Asians adopted the decoupler pulley. Also, we have a Mitsubishi Electric alternator,
so it just follows that Asian design practices are adopted.

Also, due to design and gearing, the alternator represents the second largest rotating mass in the belt system (crankshaft is the greatest). Without a "soft freewheeling connection" between the alt and the belt, the belt and tensioner would be quickly destroyed as mechanical energy of the alternator and crankshaft flows back and forth through the belt.

Remember we have a very high output, high RPM alternator (115 or more amps) as compared to the cars of yesteryear (my LTD had a 50 amp low RPM unit). The decoupler pulley is the price we pay for having a high performance alternator.

There are several videos on the internet Gates, Litton, others, that demonstrate the system with and without the decoupler pulley - one look tells you why its needed.
 
#9 ·
Thanks for the Gates post, Dave. I have not seen that before and found it very informative. I wonder if they could just incorporate a decoupler pulley in the belt tensioner instead of the alternators? Seem like it would be easier to diagnose and replace instead of the alternator being replaced at a greater expense.
 
#10 ·
I wonder if they could just incorporate a decoupler pulley in the belt tensioner instead of the alternators? Seem like it would be easier to diagnose and replace instead of the alternator being replaced at a greater expense.
No - the tensioner is just an idler pulley, it does not drive a load.

The decoupler pulley has a clutch mechanism in it to allow the alternator to be driven by the belt at the apropriate time, and to be disconnected from it at the appropriate time. It is meant to keep an even mechanical load on the system.

The spring tensioner is the reason for the decoupler, as the video shows. Without the decoupler, the tensioner bounces all over the place as mechanical energy transfers back and forth between the engine and alternator. The decoupler drives and releases as necessary to keep an even flow of mechanical power from the engine to the alternator.

Why spring tensioners, you may ask? Because very few folks know how to adjust a hard tensioner correctly. The spring tensioner is calibrated to keep a "normal" belt tension at all times, but "it sucks" at controlling belt tension under varying and bidirectional loads. The decoupler pulley smooths out this load.
 
#12 · (Edited)
#14 · (Edited)
So the first application was on a GM vehicle in 99.
They emphasise not to replace the alternator just for a worn spring.
OK on GM as fist ever user on Opel. Toyota was the first "mass user" for the US.

Due to labor involved, replacing a complete alternator assembly is usually more cost effective, and less likely to have "other" problems. Most remanufactured alternators come with a "lifetime" warranty to boot.

Also, most DIY'ers won't have the special tool needed.

At least here in the US - a remanufactured alternator is a walk-in over the counter purchase, the decoupler pulley is normally a "special order" item with a few days lead time.
For us, a complete "change out" saves time, effort, and aggrivation. Americans will almost always pay extra for "quick and convenient" - that's our culture.
 
#13 · (Edited)
http://www.amazon.com/Gates-37018P-Alternator-Pulley/dp/B003TUCETI

$50





2007 Dodge Caliber 4-Cyl. 2.0 L
Application Product Type Part # Comments
Belt Drive System
Front End Accessory Drive Components
Serpentine; W/A.C.
Automotive V-Ribbed Belt (Standard) K061005
Serpentine; W/O A.C.
Automotive V-Ribbed Belt (Standard) K060802
Tensioner Assy.
Belt Drive Tensioner 39053
Alt. Decoupler Pulley
Decoupler Pulley 37018P
Idler Pulley - Lower
Belt Drive Pulley 36323
Idler Pulley - Upper
Belt Drive Pulley 36322

Cooling System
Coolant Hose
Upper; W/Man. Trans.; W/O Eng. Oil Cooler
Molded Coolant Hose 23190
Upper; W/CVT
Molded Coolant Hose 23193
Upper; W/Man. Trans.; W/Eng. Oil Cooler
Molded Coolant Hose 23192
Lower; W/Man. Trans.; W/O Eng. Oil Cooler
Molded Coolant Hose 23187
Heater Inlet
Molded Heater Hose 19480
Heater Outlet
Molded Heater Hose 19479
Connector - Coolant Filler Neck
Solution Kit 32948K1
Radiator Caps & Testers
Radiator Cap
Safety Release Radiator Cap 31518 (16 psi)
OE Type Radiator Cap 31528 (16 psi)
Cap Adapter
Radiator Cap/Cooling System Tester Adapter 31413 System adapter on tester


Water Pump (Standard) 42144

Fuel Cap
OE Equivalent Fuel Cap 31838
Regular Locking Fuel Cap 31836

Fuel Cap Tester Adapter
0Fuel Cap/System Tester Adapter 12422 (Tan W/Grey Ring)

Oil & Lubrication System
Oil Caps

Oil Filler Cap 31118

Information provided by Gates Automotive Product Application

http://www.gates.com/part_locator/index.cfm?location_id=3598
 
#15 ·
KNOCKING sound by altinater

You need to replace decoupler pully and the idler pullys. Just replace all the idler pullies they are cheap and u are alrwady down there so it saves hastle later down the road. Most say u need a special tool for decoupler but all u need is a half inch drive impact and a 17 mm allen bit. Don't even have to take out altinater. Good luck
 
#16 ·
You need to replace decoupler pully and the idler pullys. Just replace all the idler pullies they are cheap and u are alrwady down there so it saves hastle later down the road. Most say u need a special tool for decoupler but all u need is a half inch drive impact and a 17 mm allen bit. Don't even have to take out altinater. Good luck
Any video of getting the pulley off without the special tool? Would definitely be interesting to see.
Yes, if you have the money, might as well replace the idler pulleys too, maybe even the tensioner unit.

Since the belt is off for this process, might as well replace it too if the original is a few years old.
 
#17 ·
The Gates service recommendation is to replace at 50,000 miles the

Idler pulley,
OAD decoupler pulley,
Serpentine belt

For reason Dave mentioned it is cheaper for labor to do all three at same time.
 
#18 ·
I don't understand this. I was about to install a 250 amp high output alternator. Then I come across this: Remember we have a very high output, high RPM alternator (115 or more amps) as compared to the cars of yesteryear (my LTD had a 50 amp low RPM unit). The decoupler pulley is the price we pay for having a high performance alternator.
115 amps is NOT high output. Even a chrysler 200 that takes the same alternator and the jeep patriots are 140-160 amp. Are you saying that if I get a autotech engineering 250a alternator put in the decoupled pulley won't be there? I want to do at least 200 amps for my sound system. What is thr solution? I am having the loud knocking and whirring my car sounds like a damn tractor right now. So if I don't go to the dealer, some random shop might just put in a rebuilt with no decoupled pulley? The quotes I have gotten are $300-500. The high output is $300 for the alternator and $60/hr for labor but he said it is a direct fit and won't damage the car or charing system.
On another note AAA came to check my battery and he disconnected my car battery while the car was running and now I am popping code p1607. What I am reading is my alternator might be fine and I should just replace decoupler, idler, and serpentine ? But then some say it all comes with a new alternator assembly?
 
#19 ·
The OEM alternator comes with the decoupler pulley.
The recommendation is to replace - repairs are not economic.
 
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