# Broken Upper Timing Chain



## Boughtabadone (May 12, 2005)

I just bought a dead 1993 Nissan Altima for a few hundred bucks. The car appears to be in great shape with lots of amenities. I confirmed that the upper timing chain is shot by removing the timing cover and simply pulling out the old chain. The chain no longer forms an endless circle but instead it now just forms a line. My question is this... Is it necessary to go through the whole timing chain replacement procedure of dropping the oil pan and engine just to replace the upper timing chain? Will I have to pull the head? I probably will anyway just to confirm that there is no valve damage but If I can just take my chances, I would love to get off easy! Anyway, If anyone has performed an Upper Only replacement I would like to pick your brain. The lower timing chain appears to be in great shape and is not sloppy.

Thank You In Advance!


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## Asleep (Jan 19, 2003)

Boughtabadone said:


> I just bought a dead 1993 Nissan Altima for a few hundred bucks. The car appears to be in great shape with lots of amenities. I confirmed that the upper timing chain is shot by removing the timing cover and simply pulling out the old chain. The chain no longer forms an endless circle but instead it now just forms a line. My question is this... Is it necessary to go through the whole timing chain replacement procedure of dropping the oil pan and engine just to replace the upper timing chain? Will I have to pull the head? I probably will anyway just to confirm that there is no valve damage but If I can just take my chances, I would love to get off easy! Anyway, If anyone has performed an Upper Only replacement I would like to pick your brain. The lower timing chain appears to be in great shape and is not sloppy.
> 
> Thank You In Advance!


pull the cams and check to see if the valves are still all the same height. if you have any that are lower than the rest, chances are that valve is bent. id like to know what caused the chain to break... thats an extremely rare occurrence... is it possible for you to take some pics?


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## I'm3rd (Dec 24, 2003)

AsleepAltima said:


> pull the cams and check to see if the valves are still all the same height. if you have any that are lower than the rest, chances are that valve is bent. id like to know what caused the chain to break... thats an extremely rare occurrence... is it possible for you to take some pics?




I was under the impression that the Altima engine is not an interference engine. IOW, if the timing chain breaks there is clearance between the pistons and any open valves. Right or wrong?


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## Boughtabadone (May 12, 2005)

*Upper Timing Chain (ONLY) replacement DONE*



AsleepAltima said:


> pull the cams and check to see if the valves are still all the same height. if you have any that are lower than the rest, chances are that valve is bent. id like to know what caused the chain to break... thats an extremely rare occurrence... is it possible for you to take some pics?


Well, I replaced the upper timing chain ONLY, started the engine and it purrs like a kitten. Now that I have a running car, I have discovered LOTS of rattles around the engine and around the exhaust system. Stuff like loose brackets or other supporting linkages. The whole procedure only took me about 15 hours and $85, including new oil, filter and Bosch Platinum spark plugs. I reused the old valve cover gasket to test everything and make sure that the engine ran before I finished the whole re-assembly process using a new VC gasket. 
Here is what I discovered:
1) I didn’t need to pull the right wheel. Although it makes it easier to access the crank pulley bolt to turn the engine over by hand, it is not necessary contrary to what the service manual indicates.
2) I definitely did not need to pull the head. I think that I could even skip this if replacing the lower chain also.
3) There is no need to pull the oil pan/pump. If the bottom chain needs to be replaced, then it looks like you will have to do this though.
4) I could have skipped draining the radiator. The only reason that it makes sense to drain it is to get the upper radiator hose out of the way. 
5) The cams do not need to be pulled unless you feel like checking them out anyway. If your valve clearances are still acceptable then I would leave the cam alone. You only have to remove one of the cam sprockets to get the new timing chain on.
6) The timing sprocket bolt is a bear to break loose. I used a big wrench on each of the camshaft hexes and had my sons hold on to them with all that they were worth. When this didn't work, I cut a piece of 2x4 to the desired length and placed it between the wrench closest to the timing sprocket and the firewall. This way, when I pushed on the breaker bar to loosen the timing sprocket bolt, the wrench that was holding the cam pressed into the block of wood which pressed into the firewall. This gave me the immobility that I needed to break that thing loose.
7) Putting it all back together was a walk in the park. The next time that I have to do this (God forbid that from ever happening), it should only take about 6 hours. 
8) I don't like timing chains!!! I would rather do a belt. What was Nissan thinking?!?


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## Asleep (Jan 19, 2003)

Boughtabadone said:


> Well, I replaced the upper timing chain ONLY, started the engine and it purrs like a kitten. Now that I have a running car, I have discovered LOTS of rattles around the engine and around the exhaust system. Stuff like loose brackets or other supporting linkages. The whole procedure only took me about 15 hours and $85, including new oil, filter and Bosch Platinum spark plugs. I reused the old valve cover gasket to test everything and make sure that the engine ran before I finished the whole re-assembly process using a new VC gasket.
> Here is what I discovered:
> 1) I didn’t need to pull the right wheel. Although it makes it easier to access the crank pulley bolt to turn the engine over by hand, it is not necessary contrary to what the service manual indicates.
> 2) I definitely did not need to pull the head. I think that I could even skip this if replacing the lower chain also.
> ...


very nice that you got it all fixed - pretty cheaply too i might add. sounds like you gained some valuable experience as well. my only comment is that i actually like the chain instead of a belt. breaking a chain is not a very common thing to happen. high mileage engines barely show any stretch and its not considered a maintenance item. time interval or otherwise. nissan was looking for reliability and longevity. sounds like you got it all worked out though.


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## DgF (Dec 20, 2005)

*Is the 1995 altima an interference engine?*

Is the 1995 altima gxe 2.4L an interference engine?

The chain is making noise, i believe its the issue with it getting lose and hitting the upper guide. I am deciding if i should replace it soon or let it slide til i have the money. Is $1100 to replace both chains alot?


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## tm_94altima (Aug 12, 2005)

Timing chain tick is very common on the KA24DE. There was a tutorial a while back on altimas.net about how to get rid of it. Also after so many miles, it is common for vehicles with timing chain to have this ticking.


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## thevern44 (Feb 4, 2006)

*94 Altima timing chain noise*

I bought this car about 7 months ago and it had a little noise but lately I noticed it has gotten louder. The symptoms are as follows, when cold there is no noise, as it warms up the noise starts. The sound is there when idling. At higher RPMs it goes away. Currently it is more of a gentle grinding noise at idle. The sound seems to be amplified through the valve cover. From what I have read in this forum it sounds like a guide. Do I remove the guide? Any suggestions?


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## KA24Tech (Feb 2, 2004)

Pull the valve cover to look but it is the old style timing chain and guides. The noise is the chain for sure though.

Troy


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## thevern44 (Feb 4, 2006)

*More Info*



KA24Tech said:


> Pull the valve cover to look but it is the old style timing chain and guides. The noise is the chain for sure though.
> 
> Troy


Thanks, but should I worry about it breaking now? Will it break? Is it just an annoying noise, or is it a precursor of bigger problems. I'm an old chevy guy and not familiar with nissan or this type of motor. It is winter up here and I do not have a good location to dissassemble at this time. Any details will be greatly appreciated.


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## KA24Tech (Feb 2, 2004)

Inspect it but it is a rare occurence for either chain to break. Save some money up and with the aid of the factory service manual or a Haynes manual decide whether you can or cannot do the repair yourself.

Troy


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## DgF (Dec 20, 2005)

*Removed top guide*

I removed the top guide on the upper chain a couple weeks ago, but it didnt reduce the noise. I didnt have the time to get to the side guide on the upper chain and assume it is still rubbing.

The chain showed little wear, and there was a small groove being worked into the top guide. It didnt seem like there was excessive slack in the chain but i dont have any experience with them.

In the service bulletin for this engine it says to remove both guides on the upper chain and replace the lower chain guide with an updated guide.

Does anyone know if the noise originates from the lower or upper chain, or both? Thanks


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## miss_my_altima (Oct 6, 2006)

Apparently my 94 altima does not have a "non interference engine". My upper timing chain broke at 260,000 miles and I replaced it. This thread helped a lot! Of course I didn't notice until I was almost ready to put the valve cover back on that none of the intake valves/lifters or followers (not sure what they are called) were touching the cam! I set the valve cover back on the engine and sure enough it turned over very fast and never tried to crank. That means the valves weren't all closing so it could produce compression. The car is cheap but it is in pretty decent shape. I hate to let it go but I am not sure I have any viable options. I am open to suggestions.


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## phill (Oct 22, 2006)

DgF said:


> I removed the top guide on the upper chain a couple weeks ago, but it didnt reduce the noise. I didnt have the time to get to the side guide on the upper chain and assume it is still rubbing.
> 
> The chain showed little wear, and there was a small groove being worked into the top guide. It didnt seem like there was excessive slack in the chain but i dont have any experience with them.
> 
> ...




Alright sorry to bring up an old thread but this is where I'm at.......


I have removed the top guide for the upper chain.....the noise went down quite a bit but is still there....louder at lower rpm..... How much slack should be in the chain? Can someone please tell me about the service bulletin that says to remove the othe guides?.....where might I find this info? 


Also what about the chain tensioner....does it wear out? Should it be replaced?


Thanks for the help!


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## Asleep (Jan 19, 2003)

the tensioner can wear out or it can also be plugged. regular oil changes help to keep this from happening, but if its plugged now, youll have to unplug it or replace it.


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## phill (Oct 22, 2006)

Thanks!!


I pull it apart tonight and take a closer look at it.


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