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Serpentine belt change - is it easier from the top or bottom?

XK / XKR ( X150 ) 2006 - 2014

Serpentine belt change - is it easier from the top or bottom?

 
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Old 06-06-2019, 07:02 PM
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Default Serpentine belt change - is it easier from the top or bottom?

I looked at a few threads. Seems Cambo preferred removal from underneath, Ranchero from above. I have the base model, not the SC. I have a lift.

I read the manual and it indicates to remove the under scuttle below and air intake duct above. I don't get the point of doing both. I can barely see the belt from the top. I haven't put it on the lift to remove the deflector, but I would think it would be easier accessed from below. Any opinions?

Obviously I can just start on it this weekend and figure it out, but the fewer parts I remove to gain access would be my preference. But you DIY guys usually have some rationale for doing things a certain way.

Reason for changing fwiw, the belt has never been changed so it's 13 years old. Voltage started out at 14.3 on today's drive but as the engine heated up, the voltage started to drop. 13.4 volts by the time I was home. Logic is telling me the belt is just worn (stretched) and the tensioner pulley can't do its job.

So as always, your two cents is appreciated.
 
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Old 06-06-2019, 08:17 PM
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If the belt were slipping you would hear it.
 
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Old 06-06-2019, 08:28 PM
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Thanks JT. I assume the same. I guess generators can slowly fail. no codes are being thrown so I thought this would be a bit of maintenance that may solve a problem.
 
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Old 06-06-2019, 08:38 PM
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Originally Posted by Sean W View Post
Thanks JT. I assume the same. I guess generators can slowly fail. no codes are being thrown so I thought this would be a bit of maintenance that may solve a problem.
Just keep an eye on the voltages and you may want to check the battery connections. Usually the voltage regulator in the alternator will fail causing no charge and you'll see battery voltage while running. Different modules will start to shut down. You are only seeing a few tenths of a volt change so just keep an eye on it. If it goes under 13 volts then start to think about the alternator needing servicing.
 
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Old 06-06-2019, 10:19 PM
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With only 70K miles logged, the belt may not need changing. I have 86K miles on my 2007 and inspected the belt a few months ago. It was fine, no cracks in the ribbed area, no obvious wear on the ribs. When I bought the car two years ago I bought a bunch of parts including the engine coolant pump, serpentine belt, and tensioner pulley, but have not found any need to change those after inspection.

I was getting some belt noise during this past winter upon cold startup, with cold ambient air temps, so that was the reason for me to inspect the belt. Curiously, after exercising the tensioner pulley mechanism to slip the belt off that pulley so that I could get a good look, then reinstalling the belt, noise no longer was produced.

I think it would be easier to remove the belt from the top but you have to start by removing the intake air duct that runs across the front of the engine for access.

If you work from the bottom I think it would be harder to exercise leverage on the tensioner pulley to remove the belt.

Actually I think the service manual has it right by giving you access from both the top and bottom. You will probably need that to reach all of the pulleys.

13.4V does seem low. What has your prior experience been with the voltage being displayed? The range that I find to be customary is 14.5V to 14.2V. However I would attribute abnormal voltage more to the alternator than to the belt or tensioner pulley if unusual noise is not being produced.
 

Last edited by Patrick Wong; 06-06-2019 at 10:22 PM.
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Old 06-07-2019, 08:08 AM
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Do it from the top. Gravity is a much better friend versus enemy. Get the fender top about belt buckle high so you can lean over it. You'll also appreciate being able to tuck the extension pipe on the end of the ratchet holding the tensioner loose under your arm while feeding the belt through with both hands. You really don't need to see anything, just use your fingers and make sure the belt ribs are seated correctly.

Doing it from underneath, blood runs out of your arms and they fatigue quickly. Your neck will hurt from looking up. Stuff falls on you. You'll get stuff in your eyes because your safety glasses will fog up. You still need to deal with the tensioner somehow. The belt will flop around like a fish out of water and fall off the pulley's.

Don't fight gravity. Gravity always wins.
 
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Old 06-07-2019, 08:25 AM
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On my XKR, I didn't remove anything and it went fairly quick to change both belts at 11yo and 54k. I was getting noise on the belt drive, but none of any of the components had any resistance of made any noise when I spun them, so I did belts and it's been great since. They had a sheen and also had small cracks. A pair was I think like 30-40$ on RockAuto for continental belts. Obviously less for an XK with only one belt.

I think I had about an hour in it when all fiddling around was said and done. No jacking up, no removing anything other than that giant top plastic engine cover thing, just changing belts. There was this thin metal piece across the top of I recall that made it a little jabby into my arm but nbd.
 
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Old 06-07-2019, 12:24 PM
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I would agree with Ranchero. If you pop the hood in service mode you should be able to lean over and reach everything you need. I did both the S/C and main belt on mine and did it from the top. But then again I have an XKR and I had the supercharger and coolant manifold already out!

As for you voltage, i remember my x-type repair manual specified that was normal, its supposed to charge at a higher voltage initially due to startup. Then it gradually drops down below 14 volts. It also varies with battery temp, as the battery gets hotter the voltage from the generator drops off. I'm assuming its the same on the XKs.

Here is some detail from the XK manual:

 
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Old 06-07-2019, 12:47 PM
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What is "service mode"?
 
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Old 06-07-2019, 01:12 PM
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110 reef What is "service mode"?
unbolt the bonnet (hood) rams and it will lean further forwards giving you more working room to the front of the engine area
 
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Old 06-07-2019, 02:03 PM
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Thanks guys. I'll give it a go from the top then. It's $30 for peace of mind and I can check out the idler too. The last few days have been in the high 80's. Not hot for you southern guys but would explain normal behavior for the generator as noted in the service manual.

Besides, I need a break from life and turning wrenches = peace of mind. Prolly change the oil too and check for leaks....
 
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Old 06-07-2019, 02:35 PM
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Originally Posted by plc View Post
110 reef What is "service mode"?
unbolt the bonnet (hood) rams and it will lean further forwards giving you more working room to the front of the engine area

Don't unbolt the ball stud, use a thin flat blade screw driver to partially remove the black "C" spring that holds the socket on the ball stud. Takes five seconds and to go back on you just snap the "C" spring over the ball stud. Easy peasy.

I also want to say it's a pair of 6mm or 8mm holes that line up when the hood is fully upright to hold them in place. A long #2 Phillips screwdriver will work short term until you can put a bolt in the other side.
 
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Old 06-07-2019, 04:20 PM
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Thanks.

My old Mercedes had little latches that you could disengage to allow the hood to open further. I didn't see such a device on the Jag, but what you have described is the same effect. Great tip. Thanks!

(Hope I don't need to use it anytime soon)
 
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Old 06-09-2019, 01:32 PM
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I decided to take Patrick's advice. I pulled the under scuttle and the air intake, couldn't recall see much of anything so I grab the bore scope. The belt looks brand new. Tensioner appears to be working as it should. Initially I thought what the hell, it can't be much work but it's pretty much done by feel.

And I'll now follow JT's advice and just watch the voltage. BTW, Jagtoes is JT for me going forward because auto correct sucks.

Ranchero thanks for the service mode advice on the hood. That simplified everything.

Inspecting the engine from the underside and topside with vanity cover off, I found an oil leak. I'll put that information in another thread.
 
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