Parked the car a week ago Saturday, it was running fine. Started it up the next Monday, there was a loud banging/rattling noise coming from the front (right) side of the engine. The sound was concurrent with the engine revs. Needless to say, I shut it off right away. Started it up for a few seconds a couple more times to try to pinpoint the sound more. Total running time with this sound was less than a minute, although it was the kind of sound that could have done damage right away, like a spinning part beating on something that shouldn’t be in its way.
Ran the engine briefly without the accessory belts, sound was still there. Looking at the top of the engine, there is a steel bracket holding the alternator bracket to the block. One of the bracket bolts was missing. It location was right above the timing belt cover, which does not seem to completely seal the timing belt area from the rest of the engine bay. So, a dropped bolt into a pulley seemed reasonable.
So it just took me a week to get to get the timing belt cover off, thanks in no part to many difficult-to-reach bolts, and the crankshaft bolt discussed here:. I didn’t hear any bolt fall out, and I can’t find one on the floor.
Turning the engine with a ratchet doesn’t reproduce the sound, either because the noisemaker is now gone, or it’s too slow to make the impact noise. I can’t see anything hitting anything in there.
1. You have to take out an engine mount to get at the timing cover. Is it safe to start and run the engine for a few seconds with it still supported by a jack and the two other mounts?
2. Close inspection of the timing belt shows a distinct rounding of the ribs on the outside edge. Is this normal, or is foreign object damage the likely explanation?
3. The back side of the belt appears shiny behind each rib, and sort of longitudinally scratched behind each valley. Also, the outer 1/8" of the belt is a more uniform scratched texture across both ribs and valleys. Note, the scratch texture in both cases is more like not-shiny than deeply scratched. I’ve never inspected a timing belt before - what’s normal here? What’s not?
4. How tolerant is the assembly to the inevitable dirt that has fallen is as I removed the covers?
I’ll put some photos below.
The photos:
More photos:
The timing belt, even worn, should not show signs of damage. Since you see them, chances are there is a misalignment or foreign object that caused the damage.
Check to see if the timing belt jumped time. The engine is an interference fit, meaning a timing belt snapped or out of time could lead to damaged valves and pistons.
If the timing is off, set the timing correctly to see if the engine will start without any noises. If it runs OK, replace that belt before putting it back together.
Replace the belt in any case. This belt has been damaged and will total the engine if it fails.
You should be able to run the engine at it’s current state for a short time period. But put the beveled washer back on the cranksaft and the crank bolt/pulley before doing so. But I notice the timing belt drives the water pump. You might want to remove the timing belt, and try turning the water pump by hand to see if that’s where the noise is coming from.
Tester
Thanks.
Are you sure it’s an interference engine? There’s no mention of it on the Gates website.
What do you mean the beveled washer? The small shield that fits the crankshaft key? If I’m not reinstalling the harmonic balancer and accessory pulley, why do I need to put the bolt back?
(edit: The 2nd sentence now makes more sense.)
When you removed the bottom timing cover, there was a beveled washer/shield in front of the timing belt. This is the timing belt guide. The crank pulley has a collar that pushes against this washer/shield to hold it in place on the crankshaft. Without this washer/shield in place and held by the crank pulley, the timing belt can come flying off when the engine is started because the timing belt guide is missing. And without the bolt, the pulley can come flying off.
You’re at the point where the timing belt is going to be replaced. Because it doesn’t look that good. And if you’re doing the timing belt, you’re also doing the water pump because you’re there. If you look at the last image you posted, there’s a little seepage of coolant below the water pump.
Tester
Ah, yes, we’re talking about the same thing then. Flying belt hazard noted.
Too bad I won’t be able to try this until tomorrow - I don’t know if I’ve (inadvertently) fixed the original problem yet or not.
What else can suddenly start going bang bang bang? Broken valve spring?
Re coolant leak: Are you referring to the blacker-looking bit immediately below the pump? Any chance that that is oil? This engine leaks oil from every seal.
I’ve seen water pumps fail where they sieze and break a timing belt or cause the drive belt to burn up. I’ve also seen water pumps fail at the bearing and cause one hell of a knocking noise. And I think that’s what’s happened.
I want to refer you to the last image you posted. The pulley with the red ring is the timing belt tensioner. Above that, between the cam shaft sprockets, is the water pump pulley. If you look below the water pump pulley in the water pump casting you’ll see a boss sticking out with a hole. This is probably for one of the timing cover bolts. Just to the left of this boss, you’ll see a tube in the water pump casting running from the water pump pulley down. This is the water pump weep hole. And if you look, the coolant leak below the water pump is from this weep hole. So this can mean the bearing in the water pump has failed causing the impeller blades to hit within the water pump causing the noise.
Tester
using a ratchet on the main crank bolt, rotate the engine until the timing marks line up with their respective reference marks on the block. if they line up, then do the waterpump, and tensioner replacement. if the timing marks are off, i personally would realign them re assemble and run the engine, just to check the noise. once you dissemble it, you get pretty good at opening it back up again!
you are correct about the non interference engine, so the noise is coming from elsewhere. the waterpump is the most likely, but a tensioner can chatter too; although not so noisy as you described.
think of the oil leaks as a slow speed oil change! you just have to keep the reservoir full! 
Sadly, it doesn’t seem to be the water pump:
Started the engine, the noise was still there. Took off the timing belt. The water pump pulley is not loose at all. I can’t rock it back and forth. It spins very smoothly. The tensioner pulley is slightly loose - I can rock it back and forth, say, half a millimeter.
For kicks I stuck a ratchet on each of the camshaft bolts. The front shaft (2-4-6) sprung from the timing mark to 120 degrees, then 240 degrees, and back to the timing mark. The rear (1-3-5) shaft sprang from the timing mark to 60 degrees, 180 degrees, and 300 degrees. I guess the timing mark is right between the cam high points on one of the cylinders. The force needed to turn the shafts was the same for all of them - does that mean anything?
So, what else could be causing the noise? Broken valve spring? Or did I just rule that out? Anybody have an ordered list of things to look at?
Well? I think you’ve reached the end of the rope. (no pun intended)
If the noise is still there running the engine, and the water pump shows no problem, stick a fork in it, the engine is done.
Tester
I bent my fork.
You’re assuming a main bearing or something? I’m still trying to understand how it can be running fine one day, and immediately be bad on startup another day.