TB Tension light
07-13-2005, 02:04 AM
#1
Three Wheelin'
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TB Tension light
Well it hit today. Of course in stopped traffic in the middle lane and on my 3rd change or the traffic signal. There was a friggen flag man F#$king everything up. I cut thru 3 cars and made my way in the other direction back to my carpoolers house so we could take his car. After work I picked up my car and that was the longest 1.5 miles I ever went. Weds night I am going to retension it. The light came on and stayed on. When I started the car after work it never came back on. Last checked was 6/04 10,949 miles ago. Is this common? The belt itself now has about 16.5k on it.
07-13-2005, 02:45 AM
#2
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thats why i drilled the small 1/4" hole in the cover so i can check the tension without removing the covers just to verify that the tension is correct and the sensor is just malfunctioning (which is has a history of doing)
MK
MK
Originally Posted by jserio
Well it hit today. Of course in stopped traffic in the middle lane and on my 3rd change or the traffic signal. There was a friggen flag man F#$king everything up. I cut thru 3 cars and made my way in the other direction back to my carpoolers house so we could take his car. After work I picked up my car and that was the longest 1.5 miles I ever went. Weds night I am going to retension it. The light came on and stayed on. When I started the car after work it never came back on. Last checked was 6/04 10,949 miles ago. Is this common? The belt itself now has about 16.5k on it.
07-13-2005, 03:37 AM
#3
Chronic Tool Dropper
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Joe:
The light is activated by a little spring/contact assembly that needs to stay compressed to keep the light out. Obviously, a belt that is genuinely loose will cause the contact to open and generate the light, per design. But... Inside the tensioner itself is a stack of cone washers (called Bellevue Washers after the guys who clean the mental hospital in NYC...). The movement inside th etensioner is damped by gear oil, so that there is less chance of belt flutter, and therefore less chance of a false tensioner light.
What to do:
Go ahead and verify that the tension is in fact correct. Check to see if th etensioner boot is intact. (they get brittle with age/heat/oil exposure). If it is still there intact, go ahead and charge the tensioner with a dose of 90wt gear oil. It doesn't hold mer than an ounce or two. Follow the WSM for which port to fill and which to bleed. Once that's done, you'll be able to sleep a little easier.
Hey, look at the bright side... You know that the tension light cicuit is OK!
-----------
I've got tensioner parts on the workbench now, and there's a sketch of it that will be redrawn in CAD to show how it's assembled, how it works, and what the oil does in there. It's really a sophisticated little assembly, with a lot of excess engineering effort spent on it. In normal operation, the movement of the piston causes the oil to be pumped through housing and back to the bottom of the piston. There's a really neat little check valve in the lower piston that makes the pump work. Cool stuff!
The light is activated by a little spring/contact assembly that needs to stay compressed to keep the light out. Obviously, a belt that is genuinely loose will cause the contact to open and generate the light, per design. But... Inside the tensioner itself is a stack of cone washers (called Bellevue Washers after the guys who clean the mental hospital in NYC...). The movement inside th etensioner is damped by gear oil, so that there is less chance of belt flutter, and therefore less chance of a false tensioner light.
What to do:
Go ahead and verify that the tension is in fact correct. Check to see if th etensioner boot is intact. (they get brittle with age/heat/oil exposure). If it is still there intact, go ahead and charge the tensioner with a dose of 90wt gear oil. It doesn't hold mer than an ounce or two. Follow the WSM for which port to fill and which to bleed. Once that's done, you'll be able to sleep a little easier.
Hey, look at the bright side... You know that the tension light cicuit is OK!
-----------
I've got tensioner parts on the workbench now, and there's a sketch of it that will be redrawn in CAD to show how it's assembled, how it works, and what the oil does in there. It's really a sophisticated little assembly, with a lot of excess engineering effort spent on it. In normal operation, the movement of the piston causes the oil to be pumped through housing and back to the bottom of the piston. There's a really neat little check valve in the lower piston that makes the pump work. Cool stuff!
07-13-2005, 05:57 AM
#6
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The tensioner mechanics may be clever, but the warning light was very much a poor add-on to the original design.
The path to ground through the tensioner contact parts is through a succession of disimilar metals and so on. A pretty poor piece of engineering.
On the Kempf gauage, the 32v motors need to be adjusted to the tight side of the window.
The oil is essential to help damp out tensioner "flutter" which can trigger the light, as others have pointed out.
Regards
The path to ground through the tensioner contact parts is through a succession of disimilar metals and so on. A pretty poor piece of engineering.
On the Kempf gauage, the 32v motors need to be adjusted to the tight side of the window.
The oil is essential to help damp out tensioner "flutter" which can trigger the light, as others have pointed out.
Regards
07-13-2005, 10:44 AM
#7
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The particular oil selected is pretty non-critical. The Workshop Manual instructions for the original 16-valve tensioner specified pouring gear oil into the tensioner prior to installation. There is a later tech bulletin that specifies using engine oil in the 32-valve tensioner.
Since there is not a huge difference in viscosity (the numbers are NOT in the same system, so 90 wt isn't three times as thick as 30 wt!), either will work. I just use the same synthetic that I use in the engine.
The pumping action that dr bob discussed is apparently intended to circulate the oil thru the recesses in the block to pick up engine heat more effectively.
The most common problem with the tension warning light is faulty connections between the warning computer and the switch - but it is NOT a good idea to ignore a warning!
Since there is not a huge difference in viscosity (the numbers are NOT in the same system, so 90 wt isn't three times as thick as 30 wt!), either will work. I just use the same synthetic that I use in the engine.
The pumping action that dr bob discussed is apparently intended to circulate the oil thru the recesses in the block to pick up engine heat more effectively.
The most common problem with the tension warning light is faulty connections between the warning computer and the switch - but it is NOT a good idea to ignore a warning!
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07-13-2005, 11:08 AM
#8
928 Engine Re-Re-Rebuild Specialist
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Joe:
I know that feeling. My light came one after the drive down the mountain at SITM....900 miles on the new belt (I'm sure the mountain driving accelerated the belt's break-in period
). I pulled it over 2 miles later, let it cool down and gave it a 1/4 turn. The next morning I checked the tension with the Kempf tool and it was in spec. I checked it again at 1,500 miles and it was just a hair outside of the "window", so I gave it another 1/4 turn to get the tension back in the middle.
Don't ignore warnings....and don't over-tighten!
I know that feeling. My light came one after the drive down the mountain at SITM....900 miles on the new belt (I'm sure the mountain driving accelerated the belt's break-in period
). I pulled it over 2 miles later, let it cool down and gave it a 1/4 turn. The next morning I checked the tension with the Kempf tool and it was in spec. I checked it again at 1,500 miles and it was just a hair outside of the "window", so I gave it another 1/4 turn to get the tension back in the middle.Don't ignore warnings....and don't over-tighten!
07-13-2005, 12:57 PM
#9
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the small hole in the timing belt cover can detect loosness at the edge of the window of the kempf tool vs at spec. the difference is putting a 3/16 drill bit (dull end) up the drilled hole in same position as where the kempf tool would measure tension, and seeing 1/4" less tension on the belt, thus more movement up into the belt with the drill bit.
i calabrated the drill bit tool timing belt measuring device (DBTTBMD) with my engine and scots engine when we did the timing belt tension.
mk
i calabrated the drill bit tool timing belt measuring device (DBTTBMD) with my engine and scots engine when we did the timing belt tension.
mk
Originally Posted by Big Dave
Joe:
I know that feeling. My light came one after the drive down the mountain at SITM....900 miles on the new belt (I'm sure the mountain driving accelerated the belt's break-in period). I pulled it over 2 miles later, let it cool down and gave it a 1/4 turn. The next morning I checked the tension with the Kempf tool and it was in spec. I checked it again at 1,500 miles and it was just a hair outside of the "window", so I gave it another 1/4 turn to get the tension back in the middle.
Don't ignore warnings....and don't over-tighten!
I know that feeling. My light came one after the drive down the mountain at SITM....900 miles on the new belt (I'm sure the mountain driving accelerated the belt's break-in period
). I pulled it over 2 miles later, let it cool down and gave it a 1/4 turn. The next morning I checked the tension with the Kempf tool and it was in spec. I checked it again at 1,500 miles and it was just a hair outside of the "window", so I gave it another 1/4 turn to get the tension back in the middle.Don't ignore warnings....and don't over-tighten!
07-13-2005, 02:23 PM
#12
928 Engine Re-Re-Rebuild Specialist
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Originally Posted by kraabel
I just got the Kempf gauage in the mail the other day and I'm planning my first "check."
How long should I set aside for the first time?
How long should I set aside for the first time?
Now that I know the bare minimum of items that need to be loosened and moved, I can complete the entire process in 20 minutes if the belt is already at proper tension. Adjustments will make it take longer since you have to keep rotating the engine by hand and re-checking the tension with each adjustment.
07-15-2005, 12:56 AM
#14
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Okay, The belt was kind of close to the loose end of the spectrum but not on it. I brought it up to the higher end with maybe a 1/4 turn. Just thought i'd share. Now @ 9pm I have to put it back together. BLAH!
07-15-2005, 08:05 AM
#15
Deer Slayer
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That's a cold and nasty feeling, all the way into your bowels, when you are hitting the gas and that light pops on.
I had trouble last year with a few false alarms, turned out the wire was right on the verge of coming unattached in the warning circuit and I was getting false ones. Each time my heart skipped a beat or 2.
'IDON'TWANNALOSETHEENGINE NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!'
I had trouble last year with a few false alarms, turned out the wire was right on the verge of coming unattached in the warning circuit and I was getting false ones. Each time my heart skipped a beat or 2.
'IDON'TWANNALOSETHEENGINE NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!'