96 3.4 slipped a timing belt

[montelover]

So this morning I was driving my 96 monte and the timing belt slipped at about 2000 rpm and the car died. I was wondering how many of you have had luck with it not bending the valves. I am not sure how much money I want to put into this just wanting to know what the odds of the valves surviving are.

[jmgtp]

I wouldn't write the motor off just yet.

I had a tensioner fail at about 3000 rpm which cause the belt to slip and the motor stalled. I lucked out and had no piston to valve contact. The 96-97 motors are rumored to be intereference, meaning if the belt goes the valves will hit the pistons. I'm not sure if it has ever been confirmed.

I think the fact that you were only turning 2000 rpm is to your benefit. I'd say, find the reason it slipped, replace the bad component, retime and see how it runs. If it runs well and doesn't make extra noises your probably OK. You could aslo perform a compression test but to do so you still need to replace the defective parts and retime.

Just curious, what brought you to the conclusion that it is in fact the timing belt that caused the motor to stall and not another issue?

[montelover]

I pulled the timing belt cover over the cam pullies. I and it also does not sound right when I turns over. I was supprised to see how bad the timing belt looked for only have 65K on it. I know you are supposed to change them ever 60k and I found out why.

[pocket-rocket]

It won't sound right at all until the cams are timed correctly.

Now if you mean you have a metallic smacking sound inside the engine when it turns over then there could be trouble brewing inside, but like jmgtp said, the 2k rpm breakdown I think is going to work to your advantage. I have a set of the 96 heads here, and barring the huge exhaust ports and clover leaf combustion chambers I don't see any major differences that would make the 96-97 engines interference (at least lets hope there aren't any I can't see).

You could also try to take the plugs out of the front bank and look down the holes with a flash light to see if you can see any shiny new indentations in the pistons.

[jman093]

Very small chance that you bent valves. When you replace the belt, install a new tensioner pulley and actuator. If this wasn't done when the other one was installed 60k ago, that's probably why it failed so soon. I had one fail with only 40-50k on it due to a bad tensioner.

[jmgtp]

Same, when my belt let loose it was caused by a failed tensioner. Only had 20-30k miles on it.

And I agree 100% that if you're changing the belt with the intention of it lasting, you should also change the tensioner actuator, tensioner pulley, and the two idlers as well. If you're doing the job the right way, you'll also need a plenum gasket and its a good time to inspect/replace spark plugs as well as leaking cam cover isolators. If you haven't bypassed the coolant hose to the throttlebody then you'll also be draining the coolant so its a good time for flushing that too.

Don't forget that the tensioners require to be filled with oil and I believe the service manual calls for Mobil 1 fill. Why there needs to be oil it it - well I just don't know! As far as I can tell the tensioner actuator itself is just spring loaded with no moving parts (other than the spring). I can't even count how many timing belts I've done timing belt jobs on the LQ1. I screwed around with a bunch of different cam timing options, did a few as side jobs on other peoples cars, etc etc.

At least you have a late LQ1 motor which means you have the easy to release lock rings on the cams. The 91-93 motors were a pain, even with the specialized tool to pull the cog.