Phssthpok

So I'm toolin' along on the freeway, heading home from work (with yet ANOTHER load of fire wood ) and I'm hangin' out in the slow lane because I'm keeping it mellow with this massive load in the back. About halfway home the traffic seems to open up, so I start to creep the speed up a bit. Right about the time I hit 60, I hear this..NOISE. Sounds kinda like a cross between a whoopie cushion, and an oversized duck call thats out of tune (too loose).

On a reactive impulse I push the clutch in and the sound goes away. Let the clutch out, and it's still gone. At this point I'm thinking mabye I heard a reverberated 'jake brake' from the freeway sound barrier walls (I had my window down which is rare for me) and I resume my drive home. As the speed creeps up again towards 60 the sound comes on again. (note: the sound does not ramp up.. it happens suddenly) Clutch.. release.. no noise. So now I've isolated it to MY vehicle and either clutch, exhaust, or engine.

So I decide to keep it down to 50 and baby it home.... Not a problem as traffic is now stacking up to get accross the bridge. 3/4 of the way home I come to a small downhill run towards my exit, so I downshift to fourth in preparation to leave the freeway. As soon as I released the clutch the noise came back....AH-HA!.. It's RPM sensetive, not road speed sensetive (confirmed this while pulling away from a stop light), and it seems to be coming from the engine bay, not the tranny. (Loose belt? I know I have one in there)

I get home with no further incidents, and I pop the hood with the engine running. Placing my finger on the throttle linkage ( and standing WELL out to the way of any parts that may fly ) I rev the engine up slowly till it makes the noise. DEFINATELY something 'flatulating' (rappidly flapping), and it SEEMS to be coming from the carb/aircleaner area. Now I'm because I cant think of anything that would make that kind of noise. I haven't torn into it yet... I wanted to post here to see if anyone else has run into this sort of thing before.

Engine- 20r
Platform- 77 2WD Pickup


Anyone?

Phssthpok

Curiouser and Curiouser....

I pulled the lid off the air cleaner and was unable to reproduce the sound. Put the lid back on and the sound is back. SOMETHING is vibrating at about 3K RPM.

I pulled the whole air cleaner off......no noise. I put the aircleaner back on sans the center nut on the lid...no noise.

I figure whatever was loose and rattling got moved just enought to fix the noise, add the last little center nut on the aircleaner lid and.........THE NOISE IS BACK!

I figure it has something to do with vaccum/airflow, and covering/sealing the hole where the center stud is, is JUST enough to trip teh noise. BUT I CAN'T FIGGER OUT WHATS MAKIN NOISE IF I CANT SEE IT!!!! :cry:

PirateFins

My uneducated guess. At 3k flapping rattle type sound. I would have to sya timing chain. The guides have become toast and the chain is hitting the cover.

Phssthpok

Why then the sensetivity to the center nut on the airfilter assembly being on or off?

Phssthpok

Assuming the worst, and it is indeed teh timing chain, am I safe for a week or so, babying it to and from work if I keep it under 3K?

I have a spare head I want to get rebuilt and it's going to take a few days for parts and machining, but I figure as long as I'm yarding off the head for a timing chain job I might as well put a fresh head on.

Phssthpok

A second set of ears has confirmed the source to be a 'rubber flapping noise' eminating from teh Carb/Aircleaner area.

Any ideas? Anyone?

Beuhler?....Beuhler...?

Yamaha+Toyota=Fun

Pull off the valve cover and take a look at the timing chain. You will be able to see if the guides are broken or not.

Phssthpok

Anyone have any ideas that DON'T involve the timing chain?

kyle_22r

i've never heard of a 20R or '81-82 22R timing chain guide breaking. both guides are STEEL with rubber padding, unlike the plastic ones the later engines got.

maybe try something to isolate the air cleaner nut from the air cleaner itself(maybe also the lid), like a rubber washer or a bead of RTV around it? there might be a little imbalance or resonance that's causing the nut to rattle

timing chain is more of a low speed noise, kind of a spooky rattle.

Phssthpok

Got it licked!

Apparently Toyota, in it's infinate wisdom, decided to put a gasket under the air-filter. This gasket had swelled due to petroleum product influences, and was not sealing properly at a point where the floor of the aircleaner assembly was inconsistant, allowing it to 'flap' at higher vacuum/airflow levels.

Solution was to cut about 3" of the gasket to reduce its overall diameter, and butt the ends together away from the 'flat-spot' in the air cleaner floor. Once the lid was anchored in place the noise was completely eliminated.