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  1. #1
    Senior Member Three Rings
    Join Date
    May 24 2008
    AZ Member #
    29149
    Location
    cornish,me

    2004 1.8 Timing belt

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    I've been looking over the 2004 Avant that I just bought and I removed the upper timing belt cover. I found that the timing belt from the cam sprocket to the water pump sprocket is loose and has no tension on it at all about an inch of deflection. The belt from the crank sprocket up to the cam sprocket is tight. I have done a couple of timing belt replacements on the 1.8's and they are tight when put on even before putting tension on the belt. The previous owns stated that the timing belt was replaced last year and I find a receipt for that. The engine ran fine but I'm concerned about the slack in the timing belt. I don't think that I will start it a gain until I sort this out. So if I'm over reacting and this condition is acceptable I'm open to explanations for this thank for any input.

  2. #2
    Veteran Member Four Rings walky_talky20's Avatar
    Join Date
    Jun 30 2008
    AZ Member #
    30427
    Location
    Erie, Pennsylvania

    Sounds like you are having some slack on the "front" side of the belt. That is, the side opposite the tensioner mechanism. As soon as you touch the key (or otherwise roll the engine forward), the front side of the belt will become tight and all the slack will move to the back side, where the tensioner will take it up.

    Slack being on the front side can come from the crankshaft being rotated backward. This can happen when parking on a slight grade, nose uphill, in 1st gear (manual trans) and the weight of the car rotates the engine opposite its normal direction. When the engine is asked to rotate backwards it will try to pull against the tensioning mechanism, which can result in slack being deposited on the front side run of the belt.

    It can also come from the engine shutting down in a specific position where the camshaft is loaded by the valve springs such that it wants to "spring forward" a bit. This constant pressure from the cam will pull against the hydraulic tensioner. It can give up some slack and allow the cam to roll forward slightly, leaving some measurable slack on the front side.

    Both of these events are normal. It is not necessary to be alarmed about this finding. Since you are a little worried about it, I would advise the following:

    - Make sure the t-belt receipt shows all parts were replaced: belt, main roller, hydraulic tensioner/damper, and water pump. (If it is the very new Litens type, it will not be hydraulic and the parts list will be slightly different)
    - If you are unsure about the above, you can post a picture of your receipt or post the part numbers/prices and we can determine if anything was skipped
    - Make sure the "eccentric adjustment" looks good. This is possibly a little difficult, but on the hydraulic setup, there is an important adjustment on the main roller. If the adjustment is left at the maximum "I don't know what I'm doing so I'mma just let it do whatever" position, you can be left with inadequate tension on the belt.
    - Basically you want to check the "tensioner gap" (the protrusion of the hydro piston) at TDC. You can kind of eyeball this by just removing the front cover. A mirror or smartphone camera might be helpful here.

    Pic of tensioner gap and eccentric adjuster:

    Tensioner gap should be 6-10mm after a slow, clockwise approach to TDC.



    If both of those things look good (all parts replaced, roller is adjusted within reason to achieve an adequate tensioner gap), then I wouldn't worry. You're good to go.
    ^Don't listen to this guy, he's not even a mechanic.
    2001 Laser Red A4 1.8TQM, 5-Speed Swapped, 4.11 Final Drive, APR 93, R8 coil packs, Labree HFC & DP, 2.5" Exhaust, ST Coilovers, 034 RSB, A8 Brakes Front & Rear, 18" RS4 Reps
    2006 Passion Red Volvo V50 T5 AWD 6MT
    "You need to know what you are doing...Its like a rainbow jungle in there." - Redline380

  3. #3
    Senior Member Three Rings
    Join Date
    May 24 2008
    AZ Member #
    29149
    Location
    cornish,me

    Thanks walky! The car is parked in the garage and has been up on the lift. The tires do turn a little when landing as it is a scissor lift. I hadn't thought that the belt tensioner could give up tension on the belt and create slack in the belt. I will try bumping the starter to see if there is any change in the belt tension. I've looked at the tensioner and the pointer seems to be pointing in the right direction. I thought that the tensioner gap by eye looks a little small. Thanks again!

  4. #4
    Senior Member Three Rings
    Join Date
    May 24 2008
    AZ Member #
    29149
    Location
    cornish,me

    Went out turned the engine over and when I checked the belt it was tight. I had an issue with no heat and pushing coolant out of the expansion tank. I hoped that the shop that flushed the heater core had left air trapped in the cooling system so I drained the system and vacuum filled it. I decided to put the covers back on and go for a ride around the neighborhood until I got heat. I decided to go for a ride the heat went away after about 5 miles. I'm not sure if the climate control did it or not I turned around and went home. When I got home I popped the hood was looking at the engine it didn't seem to be overly hot and the temp gauge was reading normal. The only thing the level in the expansion had risen about 3/8". I decided to let it cool down a little before I took the expansion tank cover off. After 20 min or so I slowly loosened the cap when it depressurized coolant began to fill the expansion tank. This indicates to me that somehow air or exhaust gasses are getting into the cooling system. That is what my thinking is I guess its time to start eliminating possibility's. My first couple of ideas are find an exhaust gas detection kit to see if there are any exhaust gasses in the coolant, or maybe pressure test the cooling system. If anyone has any alternative ideas I would be interested in hearing them. Thank you!

  5. #5
    Senior Member Three Rings
    Join Date
    May 24 2008
    AZ Member #
    29149
    Location
    cornish,me

    I did a compression test and all 4 cylinders are 120 psi. I'm sure its not good but does the fact that all four cylinders are the same indicate what the problem is.

  6. #6
    Veteran Member Four Rings walky_talky20's Avatar
    Join Date
    Jun 30 2008
    AZ Member #
    30427
    Location
    Erie, Pennsylvania

    I'd start with a pressure test and maybe a casual sniff of the coolant tank. Unless it's been overheated, it's not that common to have exhaust pushing into the coolant. At this point, my money is on it just needs some more air bled out. Hopefully that's it. Good luck.
    ^Don't listen to this guy, he's not even a mechanic.
    2001 Laser Red A4 1.8TQM, 5-Speed Swapped, 4.11 Final Drive, APR 93, R8 coil packs, Labree HFC & DP, 2.5" Exhaust, ST Coilovers, 034 RSB, A8 Brakes Front & Rear, 18" RS4 Reps
    2006 Passion Red Volvo V50 T5 AWD 6MT
    "You need to know what you are doing...Its like a rainbow jungle in there." - Redline380



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