piston slap (I think) - live with it?

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dlb
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My tercel:: '87 sr5, '83 dlx parts car
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piston slap (I think) - live with it?

Post by dlb »

*Although this question pertains to my '97 F-250, I put this in the t4 section since it's a general question about piston slap which applies to any vehicle, including t4's. But that said, feel free to move it if you would be happier with it in the non-t4 section, fellow mods.*

We bought a truck several months ago and never noticed any slapping, knocking, or ticking noises in the engine. But the temperatures around here dropped a lot in the last few days, and the other day I noticed a slapping sound. It only occurs when these three elements are combined:

- when ambient temps are close to freezing
- for the first 2 mins while the engine is cold
- and when giving it substantial throttle (no slap on idle or very gentle throttle)

I don't have any experience with piston slap, rod knock, or any other mysterious engine noise but from what I've read it sounds like a minor case of piston slap, and it doesn't sound like there's anything that can be done about it besides an engine rebuild which seems silly until the problem gets much worse. I imagine that as long as I either let it warm up or at least drive it very gently for the first few minutes on cold mornings, it may not ever require me doing anything about it (we rarely use this vehicle).

Any thoughts from the experienced wizards here? Does that sound like piston slap, and does my "live with it for now" approach sound reasonable?
xirdneh
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My tercel:: 87 tercel 4x4 wagon w/reringed engine, 83 tercel 4x4 wagon w/salvaged engine and 4.1 Diff's
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Re: piston slap (I think) - live with it?

Post by xirdneh »

I have had two Tercel's that had piston slap. Both had same symptoms. Knock when engine was cold. Quiet when engine was hot. Drove the first one for 6 years before curiosity had me take it apart. #3 piston was cracked and had noticeable wear pattern on skirt.
The second one had an engine with new pistons, rings and bearings. It ran fine for two years then started doing same as first engine. I took it apart right away and #3 piston had same wear pattern as first engine. I replaced that piston with a new one. Should have known better. Anyway it slapped right from the start but it was a quiet slap and also went away when engine warmed up. Drove it about 60,000 miles like that. A month ago the engine started knocking on a trip to town and kept getting louder. I plan to remove engine and remove oil pan so i can check the rod bearings. If they are good i will assume the #3 piston is cracked or worse. I have taken several Tercel engines apart that knocked badly on hot engines and they all had #3 pistons with the skirts broken off.
Love those Tercell 4x4 wagons but they sure suffer from road noise.
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Petros
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Re: piston slap (I think) - live with it?

Post by Petros »

those symptoms are typical early cylinder wear, first noticeable piston slap will occur when it is cold engine (aluminum piston shrinks/expands more with temp than steel/cast iron), it could go for years without issue. I ran an engine with bad piston slap for a number of months and than had the piston skirt fail, that allowed the piston to badly rattle around in the bore, smoked like crazy (remarkably still ran on 3 cylinders). t he only permanent fix is to rebuild with oversized piston and bored to correct clearance, and than always run with clean motor oil (the grit in old oil will cause bore to wear out faster).

it does not sound like this is bad enough to worry about it, add motor honey or STP oil treatment should make it go away, fills the gap with thicker oil when cold. if it eventually gets noticeable in all driving conditions, particularly in warm summer weather, best plan on rebuilding it.

Good luck.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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