Timing Belt Tension Trick For 5S-FE

[Digger1]

I did a search on this topic and did not see this trick mentioned. I apologize if it is common knowledge.

I just put a new timing belt on my Camry (see signature block for specifics on the car).

As per the instructions in the FSM and Haynes manual, I positioned the crank at TDC and positioned the camshaft at the TDC position. However, when installing the belt, I could not get rid of some excess slack in the front of the belt (the part that runs forward from the top of the camshaft pulley to the waterpump pulley). I could not pull the belt any tighter, since the most I could pull it toward the camshaft pulley was only about half a tooth of belt length.

So, here is what I did to remedy the situation:

I pulled the belt back off of the camshaft pulley. Note that the tensioner pulley was temporarily fixed in the "loose" position, as per earlier instructions in the repair manuals. I then turned the crankshaft 5 degrees counterclockwise. It was now at 5 degrees BTDC. I then put the belt back on the camshaft pulley. The camshaft pulley was still at the TDC position.

I then rotated the crankshaft 5 degrees clockwise to TDC and checked my alignment. Voila! Spot on! The small rotation of the crankshaft had merely taken up slack in the timing belt and did not move the camshaft pulley. Just to be sure, I rotated the crank through 720 degrees and checked my alignment again. Spot on! Ever skeptical, I cranked 'er up (after setting the tensioner pulley as per the instructions) and ran the engine for a few minutes without the upper timing belt cover in place. I shut 'er down and checked the alignment again. Spot on!

Best of all, the forward portion of the timing belt was now properly tight.

Comments?

I hope this helps some other shadetree mechanic out there.

[WhiteRabbit]

i will def come back to this when i do my timing belt, thanks!

[sr20de2]

Good write up i could have used this a few weeks ago when i did mine


archie

[noodlerooney]

At last, a solution to the 5S-FE timing belt flutter! Great piece of deductive reasoning Digger1, congratulations! I recently acquired a 94 Camry LE 5S-FE and immediately noticed what I describe as the "timing belt flutter", also noticed it on all other 5S-FE Camry’s I have heard running. The timing belt was changed at the stealership by the previous owner 20K miles/2 years ago. After removing the upper cover, I noticed the excessive slack in the belt on the rearward side (without the tension adjuster, water pump side), and also noticed that the belt tensioner on the other side was very nearly at the extreme "loose" position, but I had no idea that there was a solution. I've read many threads where the timing belt actually hits the cover and would imagine this is where it would hit after the belt stretches with age, mine comes very close to hitting now. I plan on readjusting my existing belt as soon as possible. This information should qualify as a "sticky", great solution to a common 5S-FE problem that even the stealership "pros" are not aware of. I'm dying to see if there is an increase in responsiveness due to this mod. I will also recheck base timing to be sure it has not changed from 10 degrees BTDC, I wouldn't think it would but I have been wrong before.

[Ken4]

There may appear to be slack in the 'front', but once the crank pulley starts turnnig clockwise, all slack on the 'front' side is gone. So all slack goes to the 'rear' side, this is where the tension spring is supposed to work. If you have a weak spring, it is not going to take up the slack sufficiently on the rear side. And if you tighten the tensioner on a weak spring, you will forever have a loosey timing belt. So the moral of the story is, change your tension spring when you change your timing belt. But the good news is, the timing will not be out even with a loosely adjusted tensioner. Timing depends on the whether the teeth spacing is out or not.

[noodlerooney]

If you turn the crank clockwise from TDC to take up the slack, isn't the crank now at about 5 degrees ATDC?

[Digger1]

Originally Posted by noodlerooney

If you turn the crank clockwise from TDC to take up the slack, isn't the crank now at about 5 degrees ATDC?

Noodle,

You are correct, as far as I can tell. That is why I was concerned about getting the slack out of the belt on the water pump (front) side of the belt.

[noodlerooney]

Digger1,
Was an adjustment to base timing required after replacing the belt? It seems that the belt was moved counterclockwise 1 tooth on the cam sproket as compared to before. Or, since you have an OBD2 99 as compared to my OBD1 94, did the computer automatically adjust base timing? My 94 has a distributor and rotor to adjust base timing, I'm pretty sure you don't.

[Digger1]

Noodle,

On my car, the ECU automatically adjusts the ignition timing.