Jeebus, I'm completely baffled here. Hope someone's smarter than I am.

96 GSR, B18C1, about 90K miles. I just did the 90K timing belt change. Also did the water pump, the tensioner, the main seal and both cam seals. Put it all back together and started up. Nasty rattle in the top end. Yikes!

Went back and checked *everything* twice for correct torque, you name it. A-OK.

I did do the valve adjustment, properly. I did do the tensioning procedure, rotating three teeth CCW on the exhaust cam gear before torquing down the tensioner pulley. Still rattles.

Dealership guy said that an undertensioned belt can make the distributor rattle. Someone's comment on the site said the noise might be the bearing in the dizzy about to let go. I traced the noise along the head with a screwdriver to the ear. Yeah, the rattle is strong in the distributor casing.

Retensioned the belt aggressively, rotating five or six teeth CCW this time. No difference.

Bought a 30K mile Type-R distributor off of ebay. Installed it after verifying that the part number stamped on it was compatible with the engine. Instant start, rattle still present. Arrrrgh!

There is only one thing I can think of. The new timing belt was bought off of ebay -- Honda-labeled, in a sealed bag, with the correct inventory code on the bag label and the same part number printed on the new belt as the old belt. But the new belt was noticeably *longer* than the old one, like 3cm or so.

That struck me as weird. Shouldn't the old belt be a bit longer because of service stretch in the fibers? But I figured that the factory must know what they're doing, and the part numbers did all match.

Believe me, I am NOT in a big hurry to put the original belt back on to get a cross-check. But at this point, it might make sense to try, unless someone has a better idea.

 

My first impression is that the timing belt isn't on correctly...

Why would you buy a timing belt off of ebay? :thinking:

 

See if you can find someone local with an old (or new) belt to compare your old belt to.

I can't think of a good reason why a new belt would be longer on a b18c1. If you had a b16a and picked up a b18 belt then yeah, might be a smidge longer (anyone confirm?).

Did you bed the belt on the pulleys beforehand by rotating the crank counterclockwise 4-6 times?

 

Combining my replies here...

Just seemed like a decent deal, half of what it would have cost to order an OEM belt from acuraautomotiveparts.org. The seller advertised a new OEM belt, sealed, and that's what showed up, with all labels matching perfectly.

If this belt is a fake, it's an incredibly artful one. And I don't think a rebagged used belt could be made to look completely new.

What none of those comments rule out is that the new belt could be genuine OEM, but defective. I thought Honda had pretty tight quality control on any goods sold under their label, but mistakes still do happen.


I will probably just go ahead and bite the bullet and buy a third belt directly from the local stealership. If it comes to that, I will compare lengths of #1, #2 and #3 and report.

I did not bed the belt with four to six rotations -- probably did two or three. I installed by looping it around the pulleys and tensioner, with the tensioner bolt backed off, performed 2 or 3 crank turns CCW, back to TDC1 on crank, reconfirmed TDC1 on both cams, turned crank to produce three teeth CCW on the exhaust cam, tightened up the tensioner bolt.

Easy enough to re-bed it with more rotations. I will try that before I actually pull out the belt.

 

Here's the complete adjustment procedure from my helms.

 

Thanks, q. I'll follow this one to the letter and see what happens.

I definitely recall having backed off the tensioner bolt more than half a turn. Probably two full turns. Half a turn very much felt as though the tensioner was still tightly held and unable to move on its mount.

And when I first read through the instruction sequence above, on the last one, I thought that Helms was saying to torque the *tensioner* bolt to 177 Nm. Holy cow! Fortunately, I caught my error on a second, closer reading.

 

40 lbf-ft on the adjusting bolt.

 

Did you remove the cams to do the seals?

 

That's what I have in my notes here. But there's not enough room to get in there with the torque wrench that I have, unless I do something insane like mill off the front third of a short socket. Not well thought out for tool access!


I did. Reassembly was in the proper order on the cam holder bolts, quarter turns starting in the middle and working outward, torque double and triple checked with two different wrenches. Pretty sure it was done OK.

The thing that *might* have gotten effed up on the cam removal was my having to take the cam sprockets off. They have to be stopped from spinning in order to remove the sprocket bolt. I braced a box-end wrench under an arm on each sprocket, other end of the wrench in the motor mount cavity. In theory that might have bent a sprocket out of balance. But to the eye they are fine.

Certain older Honda motors had small holes in the sprocket arms designed to slip a key or a bit into, to hold the sprocket while removing its bolt. Noticed that when helping on a friend's car. But this helpful feature was left out on the B18C1 from what I can tell. Too bad.

 

OK, I have done the tensioning procedure as set out in the Helms manual provided by qtiger.

The instructions are slightly unclear on one point. They say, "Rotate the crankshaft 5-6 revolutions to set the belt," but they don't say if the tensioner bolt should be tight or loose while doing so.

However, since later on in the sequence they say to back the tensioner bolt out a half-turn, I assume that the bolt should be tight during the crank-turning step.

Anyway -- with tensioner bolt still tight, I pulled the valve cover and the plugs, got a socket on the crank pulley bolt, rotated the engine 6 full turns CCW, brought it to TDC1, backed off the tensioner bolt 1/2 turn, rotated the crank CCW to produce 3 teeth past TDC1 on the exhaust cam marks, stopped, tightened up the tensioner bolt, reinstalled plugs and valve cover, started engine.

Instant rattle. Gar.

So let's assume for the moment that I am doing the tensioning procedure properly but the belt may still be too loose. What could be the cause? I can think of three possible sources:

(a) New belt may be so far out of spec on length that the tensioning mechanism can't get it properly tight. The new belt *was* noticeably longer, as mentioned.

(b) The tensioner (which is also new, a fresh-box GMB unit) might be boogered up somehow. It felt fine and it was visually identical to the old unit. I did check to see if the tensioner spring was on tight. It seems to be.

(c) The water pump, also new GMB, might be the wrong unit. I do recall that I did a close visual comparo between that and the original pump. No difference to my eye.

So how loose is the belt? Let me run this by some more experienced eyes. I took some photos that illustrate the amount of slack in the belt system. Looking in between the cam sprockets, the belt varies from visibly tight to visibly loose at various points in the rotation of the crank. I have shot tight, loose, and the amount of deflection that a thumb can easily produce at both the tight and loose points. Sorry, these aren't 56K friendly.

http://home.pacbell.net/rteasdal/belt_at_taut_point.jpg

http://home.pacbell.net/rteasdal/def...taut_point.jpg

http://home.pacbell.net/rteasdal/bel...lack_point.jpg

http://home.pacbell.net/rteasdal/def...lack_point.jpg

This is a fairly large amount of variation, but I don't know how much is too much on a Honda engine. It seems reasonable that too much variation between taut and slack could be whipping the distributor drive and causing the rattle.