[12GLS3.5]

Bad news indeed. I believe these are "interference" engines, which basically means that if the timing belt breaks any number of the valves can remain open and when the piston comes up, it will hit the valves causing severe damage to the valves and potentially the pistons.

When I was still turning wrenches we had a Hyundai Elantra (90's model) come into the shop with a failed timing belt and that's exactly what happened, but luckily the pistons weren't damaged so we were able to install a reman. head and send the customer on their way happy they didn't have to junk their car or install a new engine.

 

[rjsilva]

Bad news indeed. I believe these are "interference" engines, which basically means that if the timing belt breaks any number of the valves can remain open and when the piston comes up, it will hit the valves causing severe damage to the valves and potentially the pistons.

When I was still turning wrenches we had a Hyundai Elantra (90's model) come into the shop with a failed timing belt and that's exactly what happened, but luckily the pistons weren't damaged so we were able to install a reman. head and send the customer on their way happy they didn't have to junk their car or install a new engine.

Does the belt appear broken in the video? It seems to have tension.

I’m really curious what’s going on in that video. How can the crank pulley spin the belts but the timing belt not spin. Is the timing belt gear on the crank removable? Could it possibly have come loose or disconnected from the crank?

 

[Car guy]

Is the timing belt gear on the crank removable?

Yes.

Could it possibly have come loose or disconnected from the crank?

(single) Woodruff key and/or crank pulley wear/failure and/or thrust washer.

How can the crank pulley spin the belts but the timing belt not spin.

The crank pulley is turning due to its long bolt, driven into the end of the CS.

 

[nemotheboss]

Yeah the pistons coming up and fuckin the valves is what I've been reading too, like a 500 dollar fix without labor. The belt still has tension. I am not trying to basically take my entire engine apart just to get this hunk of **** back on the road.

 

[Oleg S.]

Yes, it is definitely bad news, sorry...
Your timing belt is fail. Teeth on your timing belt around the bottom (crankshaft) pulley are broken - so the belt
(and upper pulley) does not move when you crank the engine.
Anyway, you can find a lot of information about the timing belt on the Internet - how it work, what happens when
it fail etc.

This engine is an interference engine. This means that valves it your engine may (or may not) hit pistons when belt failure occurs - it all depends on the position of the camshaft at the moment of failure.
If you are lucky - and pistons did not "meet" with valves - then you can simply replace the timing belt with a new one and your car will be ready to go...
If you are unlucky and piston(s)/valves(s) contact happen... Repair can cost you from a few hundred bucks up to the whole engine replacement...

To be honest, the second scenario is more common: I seen both, but perhaps only 1 out of 5 of these engines will survive from belt failure without internal damage...

You can test how lucky you are and just replace timing belt... Timing belt kit will cost you 70-100 $ plus labor...

There is another way to check for possible internal damage: some mechanics (and experienced DIY users) use bore scope and can inspect combustion chamber (pistons, valves and cylinder walls) through spark plug hole.

 

[nemotheboss]

There is another way to check for possible internal damage

When I was doing research I was seeing compression tests being done in the spark plug holes to see if the valves got hit, could I do that as well before the belt swap just to make sure?

 

[Oleg S.]

No, you can't. For compression test you need to install new timing belt first, then you can crank engine and do compression test. But with installed timing belt you can just start the engine and see how it work.

 

[rjsilva]

Before getting another timing belt, you may want to take the lower timing cover off just to see if it’s the belt teeth which are broken or if the timing gear on the crankshaft is not spinning. I suppose if you’ll go to that effort then you may as well get another timing belt anyway

If there is damage, perhaps this is an opportunity for you to learn about the guts of the engine? It’s not as scary as it may seem. You appear to be mechanically inclined, and that engine is not hard to work on.

 

[nemotheboss]

Before getting another timing belt, you may want to take the lower timing cover off just to see if it’s the belt teeth which are broken or if the timing gear on the crankshaft is not spinning

That's a really good idea and I will check as soon as I'm home, dmv day today. I did get one anyway since most of the parts on this car are from the factory and it was manufactured in the first month these elantras were being made. Id really like to learn all that I just don't have the tools for this job (ie: jack, jack stands), and I have a mechanic who didn't solve the problem so I'm gonna have him do it once I figure it out. As long as I can without said tools

 

[Oleg S.]

... since most of the parts on this car are from the factory and it was manufactured in the first month these elantras were being made. Id really like to learn all that I just don't have the tools for this job (ie: jack, jack stands), and I have a mechanic who didn't solve the problem so I'm gonna have him do it once I figure it out. As long as I can without said tools

Does it mean that timing belt is original too? If not, when it have been changed last time? How many miles you have on your Elantra?
I can't believe that professional mechanic can't diagnose timing belt failure, and would strongly recommend you to found another one...

 

[nemotheboss]

Does it mean that timing belt is original too? If not, when it have been changed last time?
[/QUOTE
I don't think the timing belt is original if they aren't supposed to last longer than 100k. I've driven it like 25-32k so I was going to change it so I didn't have to later if it wasn't it. Cars got just under 250,000. Idk if he considers himself professional, I see him more as a diyer. Basically a me just with cars, I'd rather support a friend and not have to learn something if I can get it done cheap. Though you're right on it being odd him and every other diyer around here I know didn't even think about the starter belt or ignition system. Do I need a jack and stands to remove the bottom cover of the starter belt? If I do then I'll just get the belt replaced and see if the timing gear is spinning as well then

 

[nemotheboss]

Does it mean that timing belt is original too? If not, when it have been changed last time?

I don't think the timing belt is original if they aren't supposed to last longer than 100k. I've driven it like 25-32k so I was going to change it so I didn't have to later if it wasn't it. Cars got just under 250,000. Idk if he considers himself professional, I see him more as a diyer. Basically a me just with cars, I'd rather support a friend and not have to learn something if I can get it done cheap. Though you're right on it being odd him and every other diyer around here I know didn't even think about the starter belt or ignition system. Do I need a jack and stands to remove the bottom cover of the starter belt? If I do then I'll just get the belt replaced and see if the timing gear is spinning as well then.
(Must've erased a bracket on accident)

 

[Oleg S.]

I do not think that there is any problem with lower (crankshaft) timing belt pulley itself. But if you really want to see it, you not need to remove lower plastic timing belt cover. You will need to remove crankshaft belt and both belt pulleys - as you can see on this video at 4.42 - 5.08 time mark:

But it may be tricky to remove crankshaft bolt without impact gun (air or electric)...
Actually this video (all three parts) have pretty good and straightforward description for timing belt replacement procedure. And of course you'll need not only jack and stands, but also other tools too - wrenches, sockets, torque wrench etc...

 

[nemotheboss]

And of course you'll need not only jack and stands, but also other tools too - wrenches, sockets, torque wrench etc

Yeah I guess I'll just have him do it😂 I probably could've made do with just a jack, I simply don't have nor have easier access to them than just having someone who still owes work and has the tools to do it instead.

 

[Oleg S.]

It's up to you at this moment, it depends on overall car condition and how much money, time and effort you willing to spend on repair.
Good luck and let us know about results...

 

[nemotheboss]

UPDATE: We got the timing belt swapped and we got it started! But there's a knocking in the engine that wasn't there before. The belt's teeth were sheered off on the camshaft. My friend thinks its just a valve adjustment or better timing and not actual valve/ piston part replacement but either way its looking like a leakdown test. What do yall think?

 

[Oleg S.]

You can double check that belt was installed correctly. There is no "better timing" - belt may be installed correctly only one way. It is unlikely valve adjustment too because that noise was not present before. This noise is not a good sign, but to be sure you need to perform cylinder leak test...

 

[nemotheboss]

I will be sure to check if the belt is installed correctly, as long as it is in correctly then the next step would be getting an air compressor and performing a leakdown test correct? I also forgot to mention that turning the car off doesnt sound good either, sounds like it dies rather than stopping but I'm assuming it has something to do with the noise.

 

[Oleg S.]

Yes, do cylinder leak test and let us know about results. Compression test also would be informative and easy to do.

 

[nemotheboss]

I cant get my hands on an air compressor to do a leakdown test, but when doing a compression test cylinders 2 and 4 do not have any compression at all