Question during the timing belt change.
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Audiworld Junior Member
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Question during the timing belt change.
So my buddy and I are doing the timing belt on my 1995 90 and when it came to stretch the belt over the cam sprockets the passenger side sprocket let loose and turned between 45-90* (the tension of the springs spun it). I knew exactly which direction it turned so the question isn't about getting it back into proper alignment, but my question revolved around the status of the valves after the slippage. Yes, I know we should've had the bracket back on while pulling the belt on, but hey 20/20 hindsight right?
Is it possible to bend a valve under this circumstance? It wasn't a huge amount of force, but I know anything is possible. I haven't started the car yet, it's actually been sitting waiting for the job to be done for almost two months. What do you guys think? Thanks
Is it possible to bend a valve under this circumstance? It wasn't a huge amount of force, but I know anything is possible. I haven't started the car yet, it's actually been sitting waiting for the job to be done for almost two months. What do you guys think? Thanks
Audiworld Junior Member
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One way to to tell is to remove the cylinder head and looking to see if a valve is damaged, i would just put it back together and see how it runs. If you have the valve timing correct no other damage will occur but if a valve is slightly bent it wont seat properly against the cylinder head and the engine will have symptoms like a miss. My guess is the engine prob ok and just go ahead and try it.
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From: Tucson, AZ
You should be fine. It is usually the piston hitting the valves with a lot of force that bends them. With the piston already at the top of the cylinder I doubt the valve springs are strong enough to force the valve into the piston hard enough to bend it.
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From: Charlotte, NC
I second that. You are OK. Assuming that you lined up the timing mark for TDC, the middle piston on the passenger side is all the way up and the valves are closed. The other two pistons are down. Regardless, just rotate the cam back into position. My question is, with out the camshaft holding tool, how do you plan to keep the camshafts in position while you torque the bolt? Further, if you didn't do it, the cam sprokets need to be broken free so that you can properly take up the slack with the tensioner. Otherwise, you can have a tight belt on the passenger side and a sloppy belt on the drivers side of the water pump pulley. I guess it is doable without it, but it's gotta be tough. But, to address your concerns, pull the plugs and hand crank the crankshaft a couple of revolutions to ease your mind.
Last edited by hubturn; Sep 20, 2011 at 05:30 AM.
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I second that. You are OK. Assuming that you lined up the timing mark for TDC, the middle piston on the passenger side is all the way up and the valves are closed. The other two pistons are down. Regardless, just rotate the cam back into position. My question is, with out the camshaft holding tool, how do you plan to keep the camshafts in position while you torque the bolt? Further, if you didn't do it, the cam sprokets need to be broken free so that you can properly take up the slack with the tensioner. Otherwise, you can have a tight belt on the passenger side and a sloppy belt on the drivers side of the water pump pulley. I guess it is doable without it, but it's gotta be tough. But, to address your concerns, pull the plugs and hand crank the crankshaft a couple of revolutions to ease your mind.
good luck
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Thanks for the tips guys, I appreciate it.
My question though, is why would I need to crack the sprocket bolts to adjust the tension? I already said I had the cam holding tool, but I had to take it off to allow the belt in. The cam turned before we could put the tool back on, but we made sure to turn the cam back and reattach the tool before we proceeded to route the belt back on. Could you guys clarify?
My question though, is why would I need to crack the sprocket bolts to adjust the tension? I already said I had the cam holding tool, but I had to take it off to allow the belt in. The cam turned before we could put the tool back on, but we made sure to turn the cam back and reattach the tool before we proceeded to route the belt back on. Could you guys clarify?
AudiWorld Senior Member
Joined: Sep 2010
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From: Cincinnati OH
Here's why...
The order this is done in is as follows...
replace belt
route it properly
put cam lock tool back
tension the timing belt properly
tighten the cam sprocket bolts
remove cam lock tool.
if you have the cam sprocket bolts tightened and the cam lock tool on when you try to tension the belt you will only tension the portion from the crank bolt to the one cam sprocket
the part in orange here...
make sense? the sprockets need to be able to rotate on the shafts while you are tensioning or they can't tension the belt evenly.
The order this is done in is as follows...
replace belt
route it properly
put cam lock tool back
tension the timing belt properly
tighten the cam sprocket bolts
remove cam lock tool.
if you have the cam sprocket bolts tightened and the cam lock tool on when you try to tension the belt you will only tension the portion from the crank bolt to the one cam sprocket
the part in orange here...
make sense? the sprockets need to be able to rotate on the shafts while you are tensioning or they can't tension the belt evenly.
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Thread Starter
Audiworld Junior Member
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It makes a fair amount of sense, but I guess I'd like to understand conceptually how the sprockets can turn freely with the camshafts still where they are. Does the bolt sandwich the torque into the sprocket and there's no alignment key on the sprocket itself? I want to make sure I do it right. What's the torque on those bolts too? Thanks.
Here's why...
The order this is done in is as follows...
replace belt
route it properly
put cam lock tool back
tension the timing belt properly
tighten the cam sprocket bolts
remove cam lock tool.
if you have the cam sprocket bolts tightened and the cam lock tool on when you try to tension the belt you will only tension the portion from the crank bolt to the one cam sprocket
the part in orange here...
make sense? the sprockets need to be able to rotate on the shafts while you are tensioning or they can't tension the belt evenly.
The order this is done in is as follows...
replace belt
route it properly
put cam lock tool back
tension the timing belt properly
tighten the cam sprocket bolts
remove cam lock tool.
if you have the cam sprocket bolts tightened and the cam lock tool on when you try to tension the belt you will only tension the portion from the crank bolt to the one cam sprocket
the part in orange here...
make sense? the sprockets need to be able to rotate on the shafts while you are tensioning or they can't tension the belt evenly.
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AudiWorld Senior Member
Joined: Sep 2010
Posts: 623
Likes: 5
From: Cincinnati OH
Yeah, the cams have tapered ends you can get the sprockets on and route the belt and tension it. When you are tensioning with the sprockets not torqued down they'll still rotate on the camshaft though the camshaft is locked by the tool. Then when the belt is tensioned you tighten the sprocket bolt and that tightens the sprockets down onto the camshafts and locks them in place.
It doesn't really matter where the sprockets are relative to anything.
It only matters that the camshafts are in the position that the tool holds them and the timing belt is tensioned properly while the engine is locked at TDC.
It doesn't really matter where the sprockets are relative to anything.
It only matters that the camshafts are in the position that the tool holds them and the timing belt is tensioned properly while the engine is locked at TDC.
AudiWorld Member
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Posts: 541
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From: Charlotte, NC
Go Here
http://www.12v.org/maintenance/repairs/tbelt.php We should have sent you to 12v.org right off the bat. When pulling the cam sprockets off the taper, the cam bolts and locking plates stay on, but loosened, while you use the gear puller to break them free. When it lets go, it is loud and sudden. The sprockets are not keyed.
Last edited by hubturn; Sep 22, 2011 at 05:37 PM.