HOW TO: change serpentine drive belt (3.7L)

Discussion in 'How To' started by Corwyyn, Dec 23, 2007.

  1. Corwyyn

    Corwyyn Full Access Member

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    Since I had to write this up for another thread I decided to add it to the general 'how to's'.

    Here is what you'll need to replace your serpentine belt:

    1 - 15mm socket on a ratchet or break-over handle. The socket I show is a deep socket but this is not critical.

    1 - replacement serpentine belt, Mopar #53032037AK or equivalent.

    First open the hood and find the tensioner pulley:
    [​IMG]

    Then take your socket and place it on the center bolt. Rotate the handle clockwise, the tensioner will rotate up and in:
    [​IMG]

    Now remove the serpentine belt from the tensioner pulley, then release the tensioner pulley. You can now remove the serpentine belt. Following the diagram:
    [​IMG]
    place the new serpentine belt around all but the tensioner pulley; the grooves in the belt will fit in the corresponding grooves in the pulleys. Rotate the tensioner pulley up and in one more time and thread the belt around then release the tensioner. Visually inspect the belt one more time to make sure it is threaded properly, then start the engine and verify that everything is turning properly. There, you've changed you serpentine belt yourself and didn't get ripped off by a dealer :)

    And for clarification, although I specified making the tensioner the first pulley to remove the belt from (and the last to place it on), this is not completely necessary. Another good first/last location is the idler pulley located just to the right of the tensioner pulley. As long as the belt is properly threaded around all pulleys you will be fine.
     
    Last edited: Jan 12, 2008
    Dave likes this.
  2. Dave

    Dave Administrator Administrator Moderator

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    Kevin, nice write up.

    Dave
     
  3. Paul M

    Paul M Full Access Member

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    Excellent

    Thanks for the post! For whatever reason the geniuses at Jeep decided NOT to place a belt routing diagram sticker or plaque on our 2007 KJ in the engine compartment or owners manual. (Our 1999 2500 Truck has one, the 1988 Commanche has one, but not the 2007 - Hmmm.) Certainly not a good decision considering those "Trail Rated" excursions into the backcountry when the old belt decides to fail. Thanks again.

    Paul...
     
  4. Paul M

    Paul M Full Access Member

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    Is this belt routing the same for ALL 3.7L engines or for a specific year? The dealer serviceman (who had to look it up by the way) gave me a slightly different routing for our 2007 model.

    Paul...
     
  5. tjkj2002

    tjkj2002 Full Access Member

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    It could be,in '07 the 3.7 was setup differently then the older years due to ESP and such.

    Most vehicles do not have belt routing stickers in the engine bay,it really sucks being a tech.
     
  6. Marlon_JB2

    Marlon_JB2 Kombat Edition Jeep

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    All of our 3.7Ls have looked the same to me... I'll check in the morning to see if there's any difference between mine and my sister's Jeep, which I think will need a new belt soon... but it looks great still.
     
  7. kb0nly

    kb0nly Full Access Member

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    Good writeup!

    When i went to test drive my Jeep and i popped the hood i knew i had to have it. Why?? The ease at which you can get to stuff. Trust me, live with doing maintenance on a Pontiac Montana minivan. The serpentine belt is a serious PITA. On the 3.7L KJ you pop the hood and you got tons of room in front of the motor to work on the belt.

    The AC compressor is right there on top, the alternator is right there too. I know if its one thing i have replaced a few times on vehicles, and cussed and sweared at it, was an alternator on a transverse mounted engine, this puppy has it right there in your face!

    I haven't read the how-to on spark plug replacement on the KJ but i bet its easier than it was on the Montana. The front three were easy enough, the back three required partial dissasembly of the intake to get behind the motor, or a lift to go up against the firewall from underneath.

    Keep up the good work guys! Love the How-To section on here!
     
  8. Paul M

    Paul M Full Access Member

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    Update

    Yes, this is the correct belt routing diagram for a 2007 3.7L w/ AC. I spoke with a dealer who confirmed it for me (he had to "locate" the diagram...took awhile which still surprises me). If - as I had done the first time - you accidentally route the belt from the AC across to the Alternator then down to the Water Pump then up to the Power Steering Pump, then as the diagram shows over the other pulley's, everything still rotates in the correct direction but the belt tension is not as much which causes the tensioner to rattle a little at idle. Who could have guessed this important install detail would be such a time waster to locate? The DIY'er can do the install in less than a few minutes, but I can imagine less savvy folks forking over a small fortune - let alone the time wasted - for a tow to a dealer then a re-install service call at $100/hr shop rates. One addition I'd add to the original post is you have to rotate the tensioner clockwise ALL THE WAY to the stop, fit the belt to the tensioner pulley, then release...easily done with a breaker bar, altho doable with a 3/8 socket wrench (takes a little effort tho).
     
    Last edited: Jun 9, 2009
  9. jarvis

    jarvis New Member

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    So, if I understand you right, the tensioner pulley should be under tension (on a spring-loaded arm or something similiar), so that it pulls back counter-clockwise automatically?

    Mine stopped doing that all the sudden tonight, resulting in an immediate loss of power steering, A/C, and alternator. :bangsheadonwall

    Any ideas on how to replace it?
     
  10. Corwyyn

    Corwyyn Full Access Member

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    Yes it is a spring-loaded assembly and you can't service it, it needs to be replaced. Looking at the FSM it shows one bolt holding the pulley assembly in place (Looks like both the tensioner pulley and the idler pulley next to it are part of the assembly):
    [​IMG]
    So you need to remove the tensioner, remove the pulley(s) and place them on the new unit, then install the new unit and replace the belt. Part number should be 53030958AD (still comes up good on an online parts search), runs around $80.

    Now to hope that my Jeep doesn't find out I typed this up and starts feeling left out ;)

    EDIT: Looking at the parts breakdown it seems that the assembly should come with both pulleys installed. Never hurts to keep the others around as spares in case one decides to go south :)
     
    Last edited: Jun 10, 2009
  11. Marlon_JB2

    Marlon_JB2 Kombat Edition Jeep

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    Checked today, belt routing is the same on my '08 WK with the 3.7L.
     
  12. whodat

    whodat New Member

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    Retrofitting serpentine belt to bypass A.C.

    Has anyone ever retrofitted the serpentine belt on an '02 3.7L bypassing the A.C.? Our A.C. unit if FUBAR and we want to be able to drive the Jeep until we can put the new unit on.
    It was sure a lot easier when Mopar used a separate belt to drive the A.C.
    Must be some real 4X4 enthusiasts back in R&D.
    Please advise.
     
  13. Uncle Krusty

    Uncle Krusty Full Access Member

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    I don't know about your bypass option, but unless your problem has to do with the AC clutch freezing up, you should be able to drive the vehicle by simply disconecting the wire that goes to the clutch on the AC unit. With the wire disconnected, the belt and pulley on the AC unit should rotate freely, allowing you to run around without turning the AC compressor.

    If the problem IS with the clutch being somehow frozen, it will continue to drive the AC compressor even after disconnecting the wire. If this is the case, more drastic measures (such as a bypass) would be needed.

    The big question is can you bypass it and still leave the compressor in place? If not, the first option would be to remove the pulley and clutch assembly from the front of the compressor. This would probably require some type of puller. Even with it removed, you still might not be able to run it as a "non AC equiped " vehicle if the shaft is in the way of the belt routing.

    Removing the compressor is even more fun. This requires propperly pulling the system charge down (we want to be eco-friendly) and then removing the compressor. You should also propperly cap the lines (not just a sandwich bag and some rubberbands) so that when repairs are made, the system is not full of the last x-miles/months of crud.
    Even with the compressor gone, it still might require a change in the idler/tensioner assembly to make it work right (I'm not sure on the 3.7, I haven't looked at the two different belt configurations)

    I understand your problem - AC REPAIRS COST $$$ :eek: To do it right (compressor, flush system, new dryer, re-charge system, labor) cost plenty. Unfortunately here in AZ, it's one of those things you almost have to fix this time of year.

    Hope the "wire trick" gets you by.

    Regards,
    UK
     
  14. kjweston

    kjweston Full Access Member

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    not if you have tow package :(
     
  15. JeepJeepster

    JeepJeepster Full Access Member

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    Or 2004 kj's. Mine doesnt have the tow pack but it has the bigger shroud. I like it though, easier to add the engine driven fan.
     
  16. AVR2

    AVR2 Full Access Member

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    Just FWIW, I just changed the belt and tensioner at the same time, and getting the new belt on was a two-person job. I had to use a T-bar handle on the tensioner pulley rather than a breaker bar, just so that I could pull with both hands. It literally took all my strength to move it far enough that my wife got enough slack on the new belt to slip it over the alternator pulley.

    Maybe I need to work out more, I dunno ;)
     
  17. MNBobster

    MNBobster New Member

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    Rattle from the front of engine

    At about 65K I noticed a rattle when I would put my 2005 Jeep Liberty Sport (3.7L V6) in reverse and begin to back up or start forward in drive-thrus when I had the window open. I noticed it came from the front of the engine near the AC compressor. It got pronounced so I went to the dealer and they told me my water pump was bad (again) and replaced it on warranty. It had been replaced at 55K, which I thought was unusual. Low and behold it was fine for about a month. Then I noticed it again and it got louder. I noticed that it did it when the AC clutch engaged and the tensioner shook. I was worried that the AC clutch might be going bad, but thought "what about that tensioner?". That shaking could be transmitted to the water pump and make it fail. I just replaced the tensioner (about $70 on eBay) and the rattle is gone. The belt shakes a tiny bit when the AC is running and you can hear the tensioner very, very faintly. I shook the old tensioner and it rattles. Thanks for the info on the serpentine belt. The service manual diagrams are rather hard to follow although the instructions are clear. This is an easy part to replace (1 bolt). If you hear the rattle (sounds like a spring or exhaust shield rattling), replace this part (Mopar 53030958AE).
     
    Last edited: Jul 15, 2011
  18. MNBobster

    MNBobster New Member

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    If you don't line up the belt almost perfectly on the inside (grooved) pulleys, you have to move the tensioner pulley further to get the belt on. I used a short 3/8" breaker bar and it was easy after I noticed that the belt wasn't all the way in. Your wife may not have noticed. I had just replaced the tensioner as well. I had to use a long 1/2" breaker bar with a 1/2" socket (same as a 13mm) to bust the tensioner bolt loose. I sprayed the bolt with WD40 before putting it back in and tightening it as it looked a bit corroded. The corrosion was mainly cosmetic, but if you replace the tensioner, you might want to replace it. The WD40 or a new bolt makes it screw in smoothly without binding.
     
  19. candpliberty

    candpliberty New Member

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    I just changed mine (06, 3.7, renegade). I used a ratchet/open combination wrench(the ratchet end) and used the A/C pulley as last as it was easier to work the belt over. I fed the new belt under the crank pulley, then worked the left and right sides over and under the pulleys until the belt was in position.
     
  20. PatriotBlue

    PatriotBlue New Member

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    Belt Replacement

    If you remove the belt from the smooth pulley first and over it last you do not have to move the tensioner as much since you don't have to get the belt over the lip of the grooved pulleys.:rockit: