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Old 03-08-2004, 09:05 PM   #1
Jon [in CT]
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Default Parking Uphill Can Cause Timing Belt to Jump Teeth?

This is an excerpt of a "tech tips" story from Australia (http://www.fueltech.com.au/vehicletips.htm):
Quote:
SUBARU IN TROUBLE.
Here's a doozey for you! Subaru 2.5ltr drives fine. Pull up at Claudia's place on the hill — being careful to select first or reverse gear and pull hand brake on hard. In the morning, engine won't go. Eventually get the vehicle towed to a repairer and discover the cam belt has slipped a couple of teeth. What has happened is the engine has been left in gear, and as the hand-brake has crept overnight with the weight of the car, the engine has rotated backwards taking all the tension out of the hydraulic tensioner. As soon as you wind it over in the morning, there is initially no tension on the belt, and bingo — 2 or 3 teeth jump on the crankshaft before the tension is taken up again. Hopefully it hasn't popped any valves in the process. Any manual cam belted engine (or chain for that matter) that uses a hydraulic tensioner and is parked in gear where the weight of the vehicle could turn the engine backwards, is at risk of this sort of problem. Got to be worth sharing with your customers.
Strange but true?
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Old 03-08-2004, 11:04 PM   #2
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hmmm, first i've heard anything like this.....can any disspelled or confirm this?
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Old 03-09-2004, 12:02 AM   #3
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.....mmmm....I never park in gear....no hills in florida to worry about...but....

Once again, thanks to Jon for another interesting tidbit
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Old 03-09-2004, 09:24 AM   #4
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Seems like a fluke or it would be happening all the time in San Francisco.
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Old 03-10-2004, 09:32 PM   #5
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It's probably one of those really rare things...like human spontaneous combustion or winning the lottery.
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Old 03-11-2004, 12:55 PM   #6
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The tensioner is hydraulic, and it never lets tension off of the belt. I for one cannot see this happening.


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Old 03-11-2004, 01:50 PM   #7
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Quote:
Originally posted by Mike Wevrick
Seems like a fluke or it would be happening all the time in San Francisco.
That was my first thought, as well. Granted, I keep my parking brake adjusted and curb my wheels, but I've never had a problem any of the hundreds of times I've left my car parked in the City for extended periods of time.
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Old 03-11-2004, 03:43 PM   #8
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i've never seen one in my two years in the shop.
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Old 03-14-2004, 12:30 AM   #9
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This is common on other makes.

Always:

1) put car in 1st gear if nose of car is pointing down.

2) put car in reverse if nose of car is pointing up.

This will make sure that the engine never rotates backwards, unless there is an earthquake (don't laugh, I know of someone who bent valves in an earthquake).

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Old 05-05-2004, 01:03 PM   #10
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although i do believe you guys my brain tells me that if the car nose is pointing up to put the car in first, if i were to put it in reverse couldnt it still roll? and doesnt it not matter if the car is off either direction is backwards pressure? maybe im a little slow today studying for history finals and all, and my physics is a bit out of whack... but thats what my brain tells me would happen. lol correct me if im wrong
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Old 05-05-2004, 03:51 PM   #11
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The issue is that the timing belt tensioner is engineered to provide the proper tension on the belt when the engine is turning in the normal direction. If the engine is forced to turn backwards, some types of tensioners release tension which allows slack in the belt and can cause the belt to skip a few teeth with possibly horrible consequences.

Thus the admonition not to allow the car to roll backwards in a forward gear. This is also part of the reason for the saying "in a spin, both feet in".

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Old 05-05-2004, 04:14 PM   #12
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The tensioner in the Subaru is hydraulic, and the direction the belt spins will have no effect on it giving pressure to the belt at all times though.


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Old 05-05-2004, 04:18 PM   #13
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Sounds like a fluck that your belt tensioner was faulty. Ed
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Old 05-05-2004, 06:43 PM   #14
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Where does the hydraulic pressure for the tensioner come from, anyway? Obviously there must be some residual pressure to maintain tension when the engine isn't running. The question is, can a weird orientation (like being parked on a really steep hill, upside down, etc.) somehow disrupt the engine-off pressure?
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Old 05-05-2004, 07:48 PM   #15
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The pressure in the tensioner does not come from the engine. It is kind of like a strut- it is a pressurized cylinder with a piston in it. The piston pushes on the arm that the idler pulley is attached to, thus tightening the belt. When they leak, they lose pressure and you get that characteristic 'fwap' sound of the belt hitting the timing belt covers.


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Old 05-06-2004, 01:36 AM   #16
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neverless wouldnt putting your car in the gear that is accompanying the slope of the hill allow a possibility of rolling? i mean if im facing downhill and i put the car in first, and the Ebrake comes off wouldnt the car still roll forward if its in first, i mean thats what its supposed to do... or once the engine is turned off does it stop motion completely
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Old 05-06-2004, 10:20 AM   #17
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The tensoners pressure is supplied by a spring which is controled by a hydralic piston.
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Old 05-06-2004, 01:54 PM   #18
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Quote:
Originally posted by Hayes
The tensoners pressure is supplied by a spring which is controled by a hydralic piston.
I've got two dozen of them of both styles sitting on the shelf here, and I guarantee you there is no spring involved in a Subaru timing belt tensioner. It is a pressurized cylinder, much like a strut .


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Old 05-06-2004, 03:46 PM   #19
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The pressure is supplied from something and I think it's a spring as most are.
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Old 05-06-2004, 10:10 PM   #20
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Maybe for those who live in mountain area like SF, you should a wooden or metal rod (stick) and depress the foot brake and hold it to your seats maybe so that foot brake will still be applied.



- Charles
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Old 05-10-2004, 12:00 PM   #21
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Quote:
Originally posted by chaddeus
Maybe for those who live in mountain area like SF, you should a wooden or metal rod (stick) and depress the foot brake and hold it to your seats maybe so that foot brake will still be applied.
...and then your battery dies because the brake lights are on all night.

Just get some parking blocks (wedges).
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Old 05-11-2004, 08:48 AM   #22
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Quote:
Originally posted by Hayes
The pressure is supplied from something and I think it's a spring as most are.

Again, no spring on a Subaru tb tensioner.
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Old 04-23-2012, 12:52 AM   #23
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Old thread I know, but this happened to me. I was parked noise up the hill, fairly steep and I left it in 1st gear. I didnt have the hand brake on strong enough (when I put the clutch in to start it, it rolled backwards). When I initially turned it over, it fired once but then nothing... Pulled the timing covers off and sure enough, drivers side intake cam gear has jumped a tooth.
Motor has 15,000km on it, built EJ257, EJ207 heads, old style/2 piece tensioner. I have yet to disassemble and check the tensioner but I couldnt hear any symptoms prior.
I've been told that this isn't that uncommon and usually happens when the car is hauled in a tailor while in gear.
Anybody else have this happen?
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Old 04-23-2012, 04:24 AM   #24
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god bless ya for searchin

and I have not seen this one posted since the original thread.

id suggest replacing the timing belt tensioner
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Old 04-23-2012, 09:44 PM   #25
gold rush
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I went to the local Subaru dealership to pick up an new tensioner today. They no longer offer the old one and the parts guy wasn't certain about what I would need to convert to the new style. They had the tensioner and the little idler (between the tensioner and driver side intake gear), but they needed to order a bracket.
So should those 3 items be all I will need to convert from the old style tensioner to the new one?
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