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At this point, I've done TCTs on two very low mileage AP2's. One had 9500 miles, the other had about 10k and both cars are not driven hard regularly. One is due for a 2nd TCT.
Greenlight....I will take a meticulous depth measurement of the next noisy car. It shouldn't be long, I'm doing them every few weeks. Paypal 20 bucks to Billman250@optonline.net, and I'll send you two
I've measured the OD of the piston on about 10 units. They are, by calibrated Central mic, at 50 degrees, .6298. I'll pick up an inside snap guage to get the ID of the housings between these two TCTs.
I believe the TCT maintains tension by a combination of spring/hyd pressure.
The next test I'd like to do is to remove a bad TCT, clean ONLY the friction surfaces of the worm gear, coat them with moly engine assy lube, and put it back in the car. Maybe this can rule out the worm/friction theory by fperra. Thank you for that.
I also have a customer with 80k on a MY2000 with no issues. He also runs Mobil1 15W50, and is SC'ed. his car is here now.
What I think what we really need is a pressure test of the TCT. I can tap a guage into the top cap of the TCT on the next noisy car.
There is another factor we all may have overlooked...THE O-RINGS. O-rings flatten out over time. If pressure gets past them, the internal pressure of the TCT will drop.
I have been adjusting the allen to close the bleed hole and intern raise the pressure . It is adjustable . I think this is what you are talking about trying .
On cars I shaved the heads to raise compression without building a motor . I take 2 tensioners cut a 1/4 inch off the end of one piston and Tig weld it to the piston of the tensioner we are going to use . Works pretty good . I have been telling Glenn that if I had a spare I would have sent you one . But since I use 2 to make one that does not leave many spares .
I can add length to the piston myself. But I'd really like to root the cause, not mask it. If we come to a conclusion that the tensioner design is hopeless, I'll start to install lengthened tensioners.
I think you guys are on the right track with the Hydraulic theory, the change or leakage of pressure would be my guess. The most likely suspect may be the o-rings given that the check valve is staked. Variation is operating oil pressure may be another but too many cars are involved for that. Also very low mileage cars have had this occur so I would not suspect the bore or piston? Threads like this are why I like to lurk hear .
Ok, here's a close up of the check valve in question. The valve is removed and standing on top of the tensioner. It is through this ball/spring valve that the oil makes one of it's exits out of the TCT, through the small hole pictured in the TCT.
The bottom of this valve bottoms out in the TCT, which seals it to the housing. Should you crack it loose, pressure would bleed around it's edge and through the exit hole, dropping the TCT pressure.
Twisted...what makes you think this is adjustable? In my book, it is in no way adjustable, aside from changing the spring pressure inside the valve itself. In a tight state, oil pushes past the ball seat. In any other position it would render the valve useless.
TCT oil use/flow:
Oil goes through the VTEC screen. It exits the VTEC valve, into the head.
Oil enters the TCT through the small hole in between the two O-rings on the side of the TCT.
from there, it goes to the top of the TCT, under the two bolt cap.
from there, it splits. some oil goes through the screwdriver headed nozzle, into the inside of the piston and worm gear.
some of the oil flows out of a pin hole in the TCT housing, to lubrcate the contact point between the TCT piston tip and the chain guide boss.
back to the first split: from the inside of the piston and worm gear it flows back up to an internal cavity in the housing (NOT the top cap), and heads for the check valve.
Since I've never heard one of these go "bad", I'm just speculating here. But from the descriptions, the sound seems to be caused by the chain slapping against the face ot the TCT piston. This would lead me to believe that, for whatever reason, the piston is sticking in its bore and not providing any tension on the chain. From Greenlight's analysis, oil pressure being the greater of the two forces, low oil pressure could be the culprit. So could leaking o-rings. The easy solution seems to be to find a stronger spring.
This is what the TCT piston sits against, the chain guide. Note the steel boss sticking out. I have a feeling the noise itself is resonating from this piece, due to it's distinct loud plastic clicking noise. Perhaps a series of untaught chain links hitting the top of it, which would colaborate with the speed of the click.
01-17-2007, 03:08 PM
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