squeege

I recently got an 85 2.4L with 100k on a remanufactured engine. I don’t know if it’s the single or double row yet but assuming I pop the valve cover off and find it’s single row with a plastic guide would it be wise to replace it preemptively or could I possibly get away with running it until it fails? I’ve heard it gives a pretty discerning knock when it goes but don’t know if it causes damage right away or if I could just pull over and tow it from there.

5 Fists

It is a pretty noticeable "chain slapping against metal" sound. In my experience you can drive it like that for awhile, but it's a bit of a gamble how long it will take for the chain to eat through the timing cover and cause some damage.

If it were me I'd drive it until I heard the chain slapping.

thefishguy77

iTrader: (1)

Drive it until it starts slapping or you have the truck down for another reason. Get a good set and have it on hand along with gaskets. They run for 100's of thousands or miles with the factory plastic one. You should be good for a bit as long as they used even decent parts.

13Swords

I'm for getting the timing set replaced NOW. A remaned engine with 100K on it, it's about due to have the timing set replaced anyway. If the guide does break, that chain can & will eat into the inside of the timing cover, possibly into a coolant passage, dumping coolant into your oil. The timing cover is aluminum & the chain is steel; it doesn't take too long for this to happen when the guide breaks. Did you really want to also buy a new timing cover?

At least get that valve cover off & have a look, especially to see how much slack/stretch the chain has in it. Even if has the plastic guide and it doesn't break, a slack chain can cause the the old "jumped tooth" syndrome, which will not be good for your engine. 22R's & 22RE's are interference engines, and when the chain jumps a tooth, you will bend some valves & maybe cause other damage. This can even happen if you have the steel-backed guide in there. The overly-slack chain happened on my '78 20R, which had the steel backed guides. Fortunately the 20R is NOT an interference engine so no valves got hurt; it would just crank & refuse to start.

squeege

Is there a rule of thumb for checking chain slack with the valve cover off? Manual just shows checking with the chain out of the engine.

13Swords

My personal rules for evaluating slack in a timing chain on 20Rs, 22Rs & 22REs:
If there is any slack in the chain it's usually (but not always) going to be on the driver's side, even if the chain guides are still intact.. I personally do not like to see anything more than 1/4" of slack in the chain between the top of the guide and the cam sprocket gear.
That is using a flat-blade screwdriver to put some sideways tension on the chain in that spot, using finger pressure on the screwdriver handle.
I have seen more slack than that on a still running engine but I don't like to push it that far. When I tore down my 20R, the chain could be deflected to ONE side 3/4 of an inch(!) That was 1 & 1/2' inches of total "slack"!

You can also use a flat-blade screwdriver to see how far off the cam sprocket gear teeth you can push the chain. I don't want to see anything more than half the height of a gear tooth exposed doing this.
The chain on my 20R was stretched enough that I could push the chain off the cam sprocket teeth entirely. This is what led to it jumping a tooth in timing. Never again!

I also use a strong light source to have a look down into the timing cover, to see the guides & tensioner. The tensioner is located on the passenger side below the chain guide; it can be a little hard to see, but you should be able to see enough of it for this..
It is operated by am internal spring and oil pressure, and as the chain stretches over time from use and wear, it will continue to extend out further, taking up any chain slack.
But even with the engine not running (no oil pressure) the tensioner can give you an indication on whether the timing chain is stretched or not, thanks to the spring inside it.

On a brand new timing chain, you should see about 1'4" or so of the tensioner shaft extended, between the tensioner body and the black "rub pad" on the end of the shaft. If the tensioner is near or fully extended and you have slack in the chain, the chain needs replacing.

Here is a pic of a new tensioner, in the fully extended position, for reference:

20R, 22R, 22RE Timing Chain Tensioner, in fully extended position.

I do not recall the exact measurement on a fully extended tensioner & I don't have one on hand to measure, but it should be around an inch or so.

Final rules of thumb - If the engine sounds anything like a diesel, especially on deceleration, the chain is slack enough to be replaced. If the engine has a noticeably hard "clacking" sound at idle, it's probably a stretched chain, a broken guide, or both.
I also sometimes use a 3 foot length of garden hose as a stethoscope to isolate the location of sounds like that, so I can be sure where on the engine it's coming from. R Series engines always have some valve noise so it's always a good idea to not confuse that with possible timing chain noises.

Hope this helps.

5 Fists

That's a tonne of great info 13Swords, thanks! Will be bookmarking for future use for sure.

13Swords

No problem. Experience gained is nothing if it isn't shared.