Dogged by timing belt

Someone can correct me if I'm wrong, but once the tensioner pulley is torqued to 31 lbs. (iirc), the tension spring is irrelevant, since it's not going to move the pulley's position if that level of torque on it's mounting bolt is achieved. And if you inspected the belt's tension and found it rather snug around all the pulleys before torquing the tensioner pulley, the spring wouldn't be a factor imo.

I would be concerned with what nitonate33 said. The water pump, oil pump, tensioner pulley, and idler pulley should all spin easily by hand.

The crankshaft is generating the belt's movement, so that's not likely going to be the cause. The camshaft is turning because the engine is starting, albeit briefly, so it's definitely not frozen atleast. So I would probably make sure the other 4 items don't have any noticeable resistance when turning by hand.

(another thought would be making sure the belt is installed properly, over and under the pulleys in the proper sequence according to the diagram. There probably aren't many ways one could get it wrong and still get the right tension, but I almost did before I double checked it.)

In addition to what's been mentioned I'd also check each pulley to make sure there is no wiggle in them. Everything should be snug on it's axis and rotate like you mentioned your water pump does, but have no play side-to-side play at the same time. It's not something you'd expect from new parts, but new parts can be defective too.

Another [low-probability?] issue could be if the crankshaft key, which the crankshaft pulley is held into place by, could be damaged or worn down, or if the pulley's inner diameter slot is damaged, either or both allowing this pulley to slip when the motor is running.

The camshaft pulley has a hole that sits on a solid pin on the camshaft, so it would probably be hard to imagine that pulley slipping as long as the pin it sits on is still in place and not damaged.

Maybe others would have more insight on this one, but could the oil pump be so worn that the driven rotor doesn't rotate freely, or rubs against the housing quite a bit? I had a bit of housing-wear on mine, altho don't know if the parts could wear enough to cause enough resistance and make the timing belt slip.

A side note, I'm also wondering what precipitated the need to do this timing belt job in the first place, ie. if it's possible the thing you're trying to solve now is what created the problem in the very beginning, causing you to start this repair project.

71Corolla said:

I completely fail to see what difference it makes where the crank is when you tighten the tensioner, it doesn't matter at all, the belt has no idea where the cam and the crank is. This job should be simple, once you have the timing marks lined up, allow the spring to pull the tensioner pulley, then tighten down the bolt.

Rotate the engine clockwise a few times, then loosen the bolt so the spring will take up any remaining slack, then re-tighten the bolt. That should be all you need to do. Never rotate the engine with the tensioner bolt loose, that is a sure way for the belt to slip, rotating the engine causes pressure on the tensioner pulley, if it is loose it will move it down and you'll have to start all over again.

You'll know if you have the belt on correctly, there will be little to no slack from the camshaft gear and downward to your right. If there is, the belt is on wrong.

edit - to make the job even easier, I pull up on the tensioner myself with a hook which causes force above what the spring provides. It's not much more, but enough to ensure the belt is tight. BTW, I can see why you might want to rotate the engine at a certain angle so the valve springs don't cause a rotating force, but in practice I've never had a problem with this.

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That was my approach as well, but I guess I can see the logic since depending on where the crank is, the greatest tension in the belt can be either after the crank and before the cam, or after the cam and before the crank...? I would assume it's best to tighten the tensioner at a point that the tension is equalized as much as possible between both. I tried for this, but not based on crank position.

I was just doing seals, I didn't know if the spring was new, so I pushed the tensioner pulley by hand to make sure it was creating enough tension on the belt. I'm sure a hook would have been more effective.

Maybe someone can offer a rule of thumb for what the proper belt tension should be or look like...how far you can press the belt inward with your thumb between pulleys when it's tight...a 1/4" at the most? I just used instincts on this to make sure I was comfortable with the position of the tensioner pulley before tightening it. Too tight can cause faster wear, too loose can slip.

KarensCamry said:

Hi guys! I have significant progress to report. I put the timing belt on, got it tight and tensioned it with the new tensioner spring. I torqued down the pulley nuts to 31 pounds. It started right up, and I ran it for about 10 minutes until I shut it down. It idled a little rough and hestitated when I put the gas on -- but when I shut it down, the timing marks were perfect. I have the front end jacked up on the front passengers side and ran the engine that way.

Earlier, I removed the distributor out of a concern that the cam shaft had seized. I marked its exact position with a magic marker before I took it out and I put it back to those marks exactly. Nonetheless, could my timing be off and could that accoint for the rough idle and hesitation?

Thanks a million!!

Hugs and kisses!

Karen

:Bruce:

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Excellent to hear progress, that's great.

I've read lately a few people have inadvertently left off a vacuum hose and solved a similar rough idle issue. Also make sure the spark plug wires are attached properly and plugged in tight etc. Make sure the spark plugs are screwed in all the way, in case you loosened any to crank the engine or keeping it from starting earlier, etc. Make sure any disconnected wires are reconnected.

Overall, just try and make sure everything is plugged back in and restored to previous state. I know that when I've been involved in a project and it drags on, I tend to forget some little things that I did before or along the way.

If you removed the distributor, you still will want to use a timing gun to time the engine. Sounds like you were cautious marking it well and replacing it the same, but it's not a perfect science and tiny adjustments can account for a few degrees. It's not automatically a solution to the rough idle, but something that needs to be done (as a 'rule of thumb') now that you've got it running.

KarensCamry said:

Hi guys:

I think I do have a vacuum leak on the pc valve hose. So I am going to get two new clamps.

I ran the engine again today, and the timing belt slipped. I am at a loss to explain it. Before I started the engine again today, it was pretty tight. On the belt run between the water pump and cam -- I pressed the belt down with my thumb and moved the belt about a quarter of an inch. Does that sound like too much slack?

I put it on again, but this time, I moved the cam one notch toward the front of the engine. When I got the belt on, I then turned the cam to the left to TDC and then took the remaining slack out with the tensioner pulley. It is even tighter now. I will let you know what happens.

Thanks!

Karen

:Bruce:

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Wow, slipped again. If it were me, albeit with an 'asterisk' for being a camry newbie, I'd inspect the belt closer if you haven't already. Really make sure it hasn't been damaged. I don't know of teeth can break away on one side yet still be attached, but that's what I'd look for. I'm assuming all oil and grime has already been cleaned off of everything really well too...that's pretty much a first step.

The crankshaft key/keyway was mentioned earlier and am assuming they were checked and aren't an issue where the pulley could slip if the key/keyway was damaged or fell out.

So at this point, if this were happening to me that is, I would make every effort to make the belt 'too tight', since nothing I'm doing is making it tight enough. I don't know if that is sound advice, but that's what I'd do.

Turn the engine over a few times, tighten/torque the tensioner, turn the engine over a few more times, loosen tensioner, then retighten/retorque. Maybe even doing that again to make sure ALL play is out of the belt. I'd even push (or use a hook as someone mentioned earlier) to make sure that tensioner is pressured up against the belt before torquing. (and of course recheck timing marks after said and done, to double check you're still line up correctly before starting engine.)

I wouldn't make it stupid-tight, but at this point I've got to prove to myself that I can get it tight enough. While 1/4" sounds familiar to what mine was like, it's obviously not enough for yours. Once success is found, you can recheck the belt and at any time loosen the tensioner and give the belt just a little more play.

Anyone know if these pulleys can crack or wear, causing problems keeping the belt in place? I can't imagine that being very 'typical', but I think we're unfortunately beyond 'typical' already.

Good to hear the timing belt is staying on. Tightening the pump probably won't help your oil leak from this area, since the leak is usually from the o-ring aging and becoming brittle, and a tiny bit more pressure probably isn't going to stop a leak from here (it had no effect on mine.)

There is also the oil pump seal, camshaft seal, and crankshaft seal that are potential leak factors in that area, all relatively inexpensive replacements.

Timing being off can cause sputtering depending on which direction it's off and how much...one way tends to speed up the idle, the other way tends to slow it down. I've never used a tach with a timing gun and have just made sure the car is warmed up first and the rpm's have come down to the standard idle range. Admittedly it's not as scientific an approach as using a tach.

I'd be curious if the car runs fine maintaining it at higher rpms, or if it eventually sputters there too. Imo the timing would be a first thing to make sure is set properly since it's an easy way to eliminate a potential factor.

I don't see a timing light in Autozone's loan-a-tools section, but if you don't have one, a neighbor or friend might. Other than that I'm out of additional thoughts with little experience with an idle issues with this car, but I'm sure some veterans will offer some good suggestions.