1998 2.4 = interference engine?

[J-Ri]

I started driving down the highway at 75 MPH with the air on and the radio cranked up, 15 miles later when I turned off the air and turned the radio down before my offramp, my engine was making a horrible ticking/taping/pinging/slapping/screaching sound (I just hope it wasn't doing that for the entire 15 miles ). Anyway, I had it towed to the shop I work at. I havn't had a chance to look at it yet (other than a quick "Well, nothing important's missing or on fire" while I was waiting on the tow truck) because I work the first of two shifts , which leaves me SOL until Saturday when I can finally tear it apart (and home is about 15 miles from the shop, so I'm not towing it there for a 2 day head start)

Anyway, back to the car. I think what happened is the plastic came off the chain tensioner, which is letting the timing jump around. My first question, then, is if the engine is interference; and my second question is, if it is, would the plastic coming off the tensioner loosen the chain enough that a piston could hit a valve? (or, rather, all of the pistons hit all of the valves?)

[skibum1111]

It's an interference motor. If you jumped more than a tooth, you had a collision between valves and pistons. Which way depends on which cam jumped. I doubt there is enough play with just the guides toasted for anything to hit, but that also depends on how much carbon is built up inside the heads. More than likely the noise was the timing chain bouncing off the housing. Take a good look at the housing when you take it all apart to make sure its not cracked.

[inafogg]

i agree but you could tell if you heard it run, besides the noise did it idle ok??
how many miles on engine,i have the same car only 70K but like to see whats coming.Good Luck & let us no!!

[J-Ri]

It idles decent, so I wouldn't have thought there was any valve damage... of course that depends on how far the valves overlap the pistons, if they just barely touch, I was thinking there may be some damage that isn't bad enough to lower the compression.

Thanks for the input. I'm pretty good at telling customers when they absolutely need to fix something before they drive it any further, I just need to work on it myself

I'm tearing into it tomorrow morning, so I'll let y'all know sometime after that

[J-Ri]

I got it tore apart, the tensioner plastic and all the other guides are still in place, but the tensioner gave out completely. The noise I was hearing was the timing chain. It was so loose that the chain was resting on the outter part of the sprocket teeth and snaping back into the grooves as the pulley turned (it sounds awful even turning it by hand). I'm on a lunch break right now, and was about to check to see if the chain jumped a tooth when I left. I'm replacing all the plastic guides, the tensioner, all the sprockets and the timing chain. They should be here by Tuesday... why I didn't order the parts Wednesday night, I don't know

I'll take some pictures before I push it out into the lot... I can't believe it didn't sound worse than it did, and that nothing else broke. I pulled the spark plugs and the tops of the pistons are pitch black, so I think I got lucky there.

[doctorhrdware]

Sounds that you got very lucky.

I had an old GMC pickup. I don't remember what size the engine was think it might have been like a 305. It has the fiber main large gear. Had like 6 theeth break off. Boy did the truck shake rattle and roll. It was also running hot. Did the timming chain and gear myself. Had to drop the oil pan to pull the timming chain cover. The cover had a lip that was part of the oil pan gasket.

[J-Ri]

I ran into a slight setback

The good news, however, is that I noticed the greenish tint on the head gasket while everything's apart.

Here's the pics I took:

Notice how much slack there is in the chain, I was able to move the chain links 1/2 a tooth by hand.



The timing chain jumped a tooth, notice the timing mark at the top of the crank sprocket. The cam sprockets are both lined up with a 1/4" bolt through the alignment holes.



There was a 1/4" to 3/8" gap between the tensioner and the tensioner shoe.

[xeroinfinity]

yeah it does sound like you got lucky J-Ri. The way my luck runs, I would have bent every valve.

Teeth breaking off was an issue on many older vehicles because of those fiber gears, they were/are crap and broke easily.
Thankfuly all these newer model engines use steal gears.

So J-Ri did all the gears look ok ?

[J-Ri]

The sprockets were questionable... I meant to take some pics of the stuff I took off that I have laying on my toolbox today... but those electrical gremlins were out to get me and I ended up staying an hour late as it was . The sprockets have feelable grooves in them worn by the chain, so I'm replacing the crank sprocket, both cam sprockets and the chain.

[inafogg]

Hello J-Ri, never did say the miles i'd like to no for my own g/am Thanks

[xeroinfinity]

Probley a good idea to change out everything while its open. You consider changing the main seal ?

I'm still thinking on what to do on my GT... right now the heads are needing a valve job, so things are moving slow(er).

Good luck with those electrical gremlins.

[J-Ri]

inafogg - 194,xxx miles

Xero - I considered changing the rear main seal, front is done already. I actually considered rebuilding the entire engine but decided against it because I'm driving my '86 Chevy pickup while my G/A's apart and discovered I am getting less than 2 miles per gallon... or someone is syphoning gas out, I actually hope it's the latter because that's real easy to fix with a 12 guage rocksalt shell

[xeroinfinity]

I've seen a few 2.4's with over 200k and never been opened before.

Not that many people take care of thier automobiles, I know you pay to play in the Grand ams.

2 mpg is terrible!! I'd call a cab , ride a bike or walk. hope you dont live far from work. lol

[J-Ri]

I don't think mine was taken care of at all, but as I just said in my "head work?" thread, the car was too cheap to care.

I'd be supprised if I'm actually getting 2 MPG. Before I started building it up, I got 12 (yeah, lots better ) pretty consistently, so with all the heavy off-road stuff I don't see getting less than 8. I also had a 5 gallon gas can (almost empty) stolen from in front of my garage, which is why I was wondering if someone was borrowing some out of the tank. If some was taken, it was over the weekend, so next weekend I'm running 220v to the gas cap and sitting in the garage with my shotgun until I hear a yell (or BOOM!), then I'm beating the SOB with a tire iron (don't worry about the truck, it's essentially a chassis cab right now and the fuel tank is straped down on top of the frame rails, and the rear windows and windshield are already shattered... seeing it kindda makes ya wonder why anyone would think there's more than fumes in the tank!

[skibum1111]

Fill a gas can with a nice mix of sugar, salt and gas and wait for the sob to take it again. Then drive around looking for the broken down car and run him/her over. Repeatedly.