A few days ago i was returning to work and I heard a funny noise and the engine shut off. I luckily had my tools and i popped off the valve cover and noticed my Timing belt slipped off and sitting on my cam gears..... leading me to bend a few valves.

This weekend I swapped out the Valves for Omni power hi-comp valves and reassembled the motor and started it up.... after a few mins of idle the noise came back and there again the belt slipped off . but i was able to save it this time. i replace the timing belt and tensioner....

Today i gave the car a good once over and checked the belt and took it for a drive. it drove fine and idled great, but i turned onto my street and acceled the car and lo and behold the noise came back. i got it in my garage and poped the bonnet, remover the timing guard and touched the belt and the belt had well over 2 inches of slack on the exhaust side.


I want to know if the tensioner blot would get rounded up inside on the threads and maybe be backing it self off ( however the bolt "feel" tight if i put the ratchet on it to loosen it) . Or could it be the spring that is shot and causing the tensioner to slip and not work well.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eg6madness &raquo;</TD></TR><TR><TD CLASS="quote">I want to know if the tensioner blot would get rounded up inside on the threads and maybe be backing it self off ( however the bolt "feel" tight if i put the ratchet on it to loosen it) .</TD></TR></TABLE>


The soft aluminum threads in the block would rip out long before the threads on the bolt stripped off. As long as you're torquing the bolt to spec, that should never be a problem. The torque spec for that bolt is rather low.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">Or could it be the spring that is shot and causing the tensioner to slip and not work well.</TD></TR></TABLE>

No, the spring only serves a purpose while you're tensioning the belt. Once you tighten the tensioner pulley bolt, the spring does absolutely nothing.

To be honest, it sounds like you just aren't setting the belt tension properly. Not to insult your ability, but you know there's a very specific procedure, right? You turn the crank counter-clockwise until the cam(s) are slightly (about 3 teeth) past TDC, then tighten the tensioner bolt. This is very important, because the belt tension fluctuates depending on the cam position.

There is an ever-present slack in the timing belt that constantly fluctuates between the intake and exhaust side of the cylinder head. This is a direct result of the valve-spring pressure pushing back on the cam lobes when the valves are open/opening. That's also why the belt felt so much looser on the exhaust side when you inspected it.

 

Yeh I know there is a procedure and i do it. Yesterday i used a screw driver to apply a bit of tension to the belt then i thightened down. should i never use a screw drive to apply some thension?

 

Some people do that, but I never have. I'd be worried about belt fatigue and premature belt failure (i.e. the belt suddenly snapping...). But other people have done it successfully, so what do I know. It just kind of seems like a band-aid on the real issue. After all, on a healthy running motor, the tensioner spring does just what it's supposed to - applies correct tension. If the belt is still coming off, it seems that there is a problem elsewhere.

Unfortunately, I don't know what to tell you. The timing belt makes a simple path, so it doesn't seem like there are that many things to go wrong. All I can think of:

1. Belt is bad
2. Tensioner pulley bearings are bad
3. Water pump is bad/siezed
4. Timing belt guide plate is on backwards
5. Tensioner pulley bolt is backing out

Other than that, I'm stumped. Does the belt show any signs of unusual wear?

 

^ second all of that. Have you checked your water pump? Or is the belt showing unusual signs of wear? If not, then it must be the tensioner bolt backing out. Was it tight after the first Tbelt broke? How about after the noise came back a second time?
Good Luck man, Davey

 

Hey,

1. I know the belt is good since it is a new belt
2. I know the tensioner is good since that is also new
3. Water pump is fine since i replaced that when I rebuilt the motor and it turns once i turn it by hand
4. What exactly is the timing belt guide? do you mean the plastic covering?
5. and number5 i can only assume is the problem

We put on the belt today and started the car. we reved it out 3-4 times to like 6000rpm and after the 4th time the belt was slack adn flapping all over the place. we shut off but i had to go to work.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eg6madness &raquo;</TD></TR><TR><TD CLASS="quote">
4. What exactly is the timing belt guide?</TD></TR></TABLE>

It's a thin piece of metal located behind the timing belt cog gear on the crankshaft. But if it was backwards, I believe you'd see unusual wear marks on the sides of the timing belt.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">We put on the belt today and started the car. we reved it out 3-4 times to like 6000rpm and after the 4th time the belt was slack adn flapping all over the place.</TD></TR></TABLE>

Eh, you're sure you're following the correct tightening procedure??? What are you torquing the bolt to? That bolt should NOT back out if properly torqued.