1.6 NA Timing belt slap

[Quantum TD]

Anyone ever get this?

At idle there is no noise, but you can see the TB moving vigorosously back and forth between the crank pulley and the idler pulley. When you rev the car up, the belt begins to slap the lower timing cover up to about 1900-2000 RPMS, beyond that, the belt is moving so fast, the slap goes away.

This is on a 1.6 NA Hydro motor that I bought some time ago. The motor has fantastic compression, starts right up and runs beautifully, aside from the slap. YOu can also see the lower crank V-belt pulley waver a bit.

I just did the following:

Camshaft (new)
Cam seal
Int shaft seal
front main seal
timing belt
resealed pump

When I took the crank pulley off, it looked fine, but when I slipped it onto the crank, there was a bit of rotational motion: a bit more than I normally see, if I can recall right.

I was just wondering if it was something simple: belt too tight, too loose, piece of dirt behind the crank pulley, etc. Maybe the AAZ guys can chime in. Did you ever hear a slapping before your crank gears let go, due to the harmonic balancer deal? I set the tension with my VW 210 tool, but it almost seems a bit loose now.

[rabbitman]

I know this is an old post but I figured I'd pull it up anyways.

Quantum TD what did you do to fix the slapping?

I just changed the t-belt on mine and due to all my IP bushing problems I set the tension looser than normal, now I get the same noises you described at 2100-2350rpm and I tracked it to the section between the crank and tensioner.

I read on this forum that some people are only turning the tensioner by hand and it's tight enough so that's how I had done it but to get the slapping to go away I needed the tool so I could turn harder on it, so now am I going to wear out the IP bushings for the 3rd time?
I'm wondering if it could be that my timing isn't perfect, you know so the harmonics cause the belt to vibrate .
Thanks

[arb]

I would have replaced the tensioner as well as the belt. I always use the tool to get get tension correctly tight. You don't want that slap. When off, you should only be able to rotate the belt by hand between the cam and IP pulley's no more than 45 degrees. I suspect you can go almost 90 degrees. The tool I use is a router tool. It does not take much force with tool to get the proper tension, but I don't think I could do it by hand. Some Popeye types might be able to ;-)

[lovinthedeez]

make sure that your cover has all three bolts securing it.  I had a noise coming from that area one time, and it turned the bolt that goes in the front of the cover rattle itself loose.  I know its not timing belt slap, but it did make the cover touch the spinning timing belt; a sound noone wants to hear with a brand new belt, or any age belt for that matter.

[rabbitman]

I just thought of something, if the frequency of the engine makes the belt slap between crank and tensioner, then can I change the distance and stop the harmonics from flaaping the belt by turning the tensioner counter clockwise?

I know the mk2 bentley says clockwise only but that is because it'll hit the belt cover.
This is an mk1 so assuming (I've never checked) there are no clearance issues with turning it the other way what other reasons are there to not do it?
I'm very sure the belt is too tight now but any looser and it slaps the cover. Thanks

[arb]

They say CW because when you tighten the nut, the pulley gets slightly tighter and is self limiting - the forces on the shaft will make it tighter. If you CCW, then when you tighten it, you NEED a tool to hold it tight while you tighten the nut. If that changes your harmonics and the belt is otherwise correctly tight, I see no reason not to do this. I think something else is going on, though. I've never had a properly tight belt slap, and I always get 80,000 miles out of a belt.

[Quantum TD]

Wow. This one got dug up from the grave.


Turns out, I hadn't tightened the belt enough. Truck runs fine now.

[rabbitman]

I'm gonna try loosening the belt some and see if it "happens" to not slap.

My IP timing was WAY out so I fixed it and maybe the vibrations changed enough so it won't make the belt slap .

[rabbitman]

Loosened it a bit, it's now as tight as I could get it with out the tool. The belt still flaps but it doesn't hit anything .

[92EcoDiesel Jetta]

I just installed a new timing belt and took this video. Is your slap more than mine? I've since tightened it a bit. A tensioning tool is easy to make. I made mine from a thin bar of aluminum and two 6-32 machine screws. A small 90 degree long nose pliers will work well also.

[rabbitman]

It's pretty hard to tell, video is kinda fuzzy. Got a better camera?

I think as long as it's not hitting anything it'll be ok though.

[92EcoDiesel Jetta]

Sorry for the quality. It's my phone cam and that's all I have.