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View Full Version : Probably (hopefully) nothing but I leave on a road trip tomorrow, so...



Pfunk
12-16-2013, 07:56 AM
Hey everyone,

Two days ago while starting the car (about 8ºC) it cranked as usual, then let out a quite loud metallic clank, then cranked a bit more (normally) and fired up, ran normally. I've started the car several times since then, cold and warm, and the sound was never repeated.

Yesterday, while cresting a sharp driveway I hit the butterfly brace on the road hard enough to make a pretty loud clang.

Today while driving, engine warmed up, as I came to a light and put the car into neutral and as the revs fell to 800~1000, I heard a loud, hollow knocking sound, tank-tank-tank-tank, that started with one somewhat muted 'tank' then increased in volume, then tapered off. It got my attention. It happened three times, at three lights. Each 'episode' was 30s at most, and as soon as I put it in 1st and released the clutch it went away. I stopped at the supermarket, got back in the car, and drove home, with the sound never coming back.

I got under the car when I got home and the Maruha free-flow cat and mid-pipe are really close to the butterfly brace, maybe 3mm. I can press on the pipe and make it contact the brace pretty easily.

The thing is, I am supposed to take my wife on a week-long drive down to another prefecture about 800km away tomorrow on a small holiday. We're due to leave around 7AM.

With my motor having been built a year ago, about 10,000km/6000 miles on the clock, and with me not abusing the motor, I'd like to think the odds of it being rod knock are very, very low. Oil level is normal, oil pressure is normal. Engine runs fine. Rev it, no knocking sound at all. At idle now, no knocking sound.

I'm hoping the brace got shifted a bit from the hit, and it's just the mid-pipe clanking against the brace. I hit the brace with a hammer and the noise does sound similar.

But.

But.

The last thing I want to do is head out on the road in winter with my wife and have motor trouble.

I called RS Aizawa upon getting home around 9PM and they said knock would not appear intermittently like that only at idle, and that it would not go from no sound to loud-ass clanking so quickly. They think it's the brace/pipe... probably.

So... I'm asking what you all think. I have to make the call, I know, but input would help.

Cheers,
P

kung fu jesus
12-16-2013, 10:23 AM
I would lay money on the brace, too. I am wondering too if the cooler temps plus a more aggressive motor mount that you may have installed is also causing this at idle, when the motor is moving around in a couple of directions a bit more than under acceleration.

Pfunk
12-16-2013, 02:48 PM
Keith at FM thinks this is the case as well. I did install stiffer motor mounts when all the work was done, and the other day, with the 'clank' at start-up, it was when the engine gave a lurch--I think the high compression give the motor a bit more kick, kind of like the old-kick-start bikes back in the day--could have been it smacking the brace.

Fingers crossed!

kung fu jesus
12-16-2013, 02:55 PM
You may be able to remove that butterfly pretty easily...

Good luck Paul! Hoping Kim doesn't notice. :)

theothersawyer
12-16-2013, 03:25 PM
I'd put money on the brace as well. I removed my motor to do my clutch and I have a few clunks and clanks now.

Pfunk
12-25-2013, 03:20 AM
Update: we made the trip without any issue other than the occasional noise. I noticed once that when idling ~900rpm the sound came back, though more softly than before, and when I touched the gas to bring idle up to 1000rpm the sound went away.

I took it to RSA today and we pulled the starter motor to look inside the bell housing with an endoscope just to make sure it wasn't the flywheel/clutch/etc. and every tooth is fine. We then went over the entire underside looking for signs of contact but couldn't see anything. We checked the motor mounts, the engine brace near the oil filter, etc., just to make sure, and it all looks OK.

I'll keep an ear open, but I am not too worried about it at this point.

One thing I noticed in cold weather: oil use increases, a lot. On the freeway oil temps never made it above 60ºC, and I lost 0.8L of oil: 0.4 to the catch can, 0.4 burnt, in 1600km of driving (that's just under a quart, in all, over 1000 miles for you folks in the US). When the motor heats up I don't lose nearly as much. According to RSA, of all aftermarket pistons they've seen: CP, Mahle, Wiseco, Toda, only Toda run as tight as stock and oil loss is lower. All the rest lose a fair bit due to clearances, when the engine is running cold. I think I may need to fab an aluminum cover for the oil cooler in winter months.

wannafbody
12-25-2013, 10:04 AM
Maybe step up to a thicker oil. Some people run 5w40 and 10 or 15W50

kung fu jesus
12-25-2013, 11:55 AM
Paul, what RSA is pretty accurate. Forged piston can slap and need time to expand. A simple cardboard or gatorboard cover ziptied over the cooler should help in the chillier weather for a quick solution

Tkblazer
12-26-2013, 10:27 AM
Does your oil cooler not run a thermostat?

Pfunk
12-26-2013, 04:39 PM
It does; I would still like to see temps higher than 60ºC.