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Timing Belt Tools

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XC92

Proven Member
1,563
356
Jul 22, 2020
Queens, New_York
So I ordered all the parts I need to do a complete TB job, i.e. both belts (no BSE for now), 3 pulleys, hydraulic tensioner, water pump, 5 front seals, all OEM except a Gates racing BSB and Aisin WP. But I have some questions about the tools you're supposed to use to do it properly.

There are three I believe, a long M8x1.25 threaded bolt, a 2-pin adapter, and a cam sprocket securing device. Complete sets sell for around $50, individual tools for $15-$20.

I'm wondering how important it is to have these actual tools compared to using "close enough" tools I might already have on hand, since I don't expect to have to do another TB job for years. Seems like a waste of money if it can be avoided and I don't want to have to sell them online when I'm done.

I already bought a 250mm M8x1.25 threaded bolt, for $6. Can I use it as is, if I weld, glue or otherwise secure a nut at one end to install and remove it? Or do I have to grind off some of the threads on the other end, for clearance, and if so how much, in mm?

What about using a set of right angle snap ring pliers instead of the adapter? I'd have to guess the torque, but I think I can manage that as it's not a high number.

And the FSM itself says to use ordinary binder metal clips. I've also heard of people using plastic zip ties. Does either work ok?

It's not so much that I'm cheap (although I am) as that it just seems silly to spend $50 of more for tools I'll use once every 5-10 years for 30-60 minutes.

Oh, and separate but related question. I'll also replace the thermostat and gasket. A while back, before I understood how important it was to get OEM parts for a DSM, I bought a Stant at RockAuto. Is that ok or am I just asking for trouble?

It's this one, from their "Heavy Duty" line:


Oddly, they don't sell an Aisin one.
 
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So I managed to get everything installed and (I think) properly tensioned using jerry-rigged tools. Basically, ordinary binder clips to hold the TB on the cam sprockets per the FSM, a long 8x1.25 threaded rod with a nut at one end to install and remove, and a really clunky but effective tensioner pulley tool consisting of 3 short flat metal brackets from an old-fashioned wall phone jack plate that had predrilled holes that were just about the right distance from each other, connected with short bolts of the right size.

Anyway, it worked, and I think I got the tension just right (and all the timing marks aligned after turning the crank 6 times, although I'll try it again today just to make sure. I totally agree though that if you're going to do this even semi-regularly, as in once every year or two, you need to get at least the pulley tool. But I don't drive that much and don't expect to redo the TB jobs for quite a few more years, so I couldn't justify it.

My only "concern" is that when I did the drill bit test, I was able to insert a 3.55mm bit easily in the space between the tensioner and arm, but a 3.95mm bit was pretty tight, and the only way to fit it was at a very slight angle, like 5-10 degrees. I know that the lower limit is 3.80mm, but I don't have anything handy of that thickness that would fit in the.

But I suspect that with the 3.95mm bit fitting in at just a slight angle, a 3.80mm bit would fit in perfectly, if a tad snug. And even if not, does going even a hair below 3.80mm mean trouble down the line, or would natural belt stretch bring it above 3.80mm in no time? This is a brand new OEM tensioner right out of the bag. I mean if you're going a tiny bit outside the 3.80-4.50mm range, isn't it better to be a tiny bit too low than too high?

In any case, I'm guessing that it's at 3.80mm or above, and I'll try to find something closer to 3.80mm or just above to see if this is a non-issue.

Btw I didn't really see the purpose of the threaded rod with a brand new tensioner with the pin still in. Or am I missing something?
 
I only spent $6 on it so no big deal there. I was just wondering if I even needed to use it. Looks like I didn't as all it did was push the tensioner rod in after I removed the pin, only to have the tensioner rod come back out when I removed the threaded rod.

But mainly I just wanted to know if that 3.80mm lower limit is hard, or if there's a bit of room there to go a hair lower. And the only thing I've found that's 3.80mm is several feeler gauge blades stacked together, but getting the whole gauge in there will be tough with the engine still in the car.
 
The tensioner pin piston that sticks out shouldn't be able to be pressed in by hand. It usually takes a vise to slowly compress it if it ever comes all the way out. It should have a lot of pressure behind it that is to much to "gorilla" it back in.
I have never used the drill bit method. If the grenade pin slips in and out with no effort after timing and spinning the engine 6 times, letting it sit for 15 mins AND all timing marks are on the money, you are done! Pretty easy really.
 
Oh, forgot about this other method of finding out if it's good. I'll try that. If it slips in and out but with an ever so SLIGHT amount of resistance, meaning the holes aren't 100% aligned but almost there, should I still be ok?

I can't imagine that whether or not the belt slips and kills your engine depends on not being off as little as 0.05mm here. But there's a lot I can't imagine!
 
While I try to be PERFECT at that spot, if it has a slight bit of tension, you will be ok. It has to slip in and out real easy or you need to retension it slightly.
 
I'm about to use 3 different methods to measure the gap. If any seem off then I'll just redo the tension. A pain but not that bad.

Btw I installed a new OEM Evo 9 Kevlar belt. Could that explain this if I did everything else right? They don't stretch much, especially initially, right?
 
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I'm about to use 3 different methods to measure the gap. If any seem off then I'll just redo the tension. A pain but not that bad.

Btw I installed a new OEM Evo 9 Kevlar belt. Could that explain this if I did everything else right? They don't stretch much, especially initially, right?
No that wouldn't explain it. The go no go measurements are very objective. All you have to do is hit the mark. Btw this is where the screw tool can come in handy. If you're slightly off and have to tighten it back up you can get the pon back in and be ready to reset.
 
Using the pin in the holes to set the tensioner only works with a flat tensioner arm.

If there is a divot, the clearance between the arm and the top of the tensioner is reduced by the extension of the pin into the divot. This can cause the arm to contact the tensioner body when the belt is under dynamic tension (like when the engine is accelerating). If you adjust to maintain the clearance between the auto tensioner body and the tensioner arm you won't overtighten the belt by hitting the body but you may hit the other limit, how far the pin can extend to keep the belt tensioned under deceleration.

There have been reports of the arm doing this when people over tension the belt and making noise and many reports of belts skipping teeth.
 
So, the pin went in and out with only the SLIGHTEST resistance, which I assume was due to the gap being ever so slightly less than 3.80mm. But given that there's a 0.25mm hole in the arm, I attribute the slightly too-tight gap to that, and if there were no hole, the gap would be above 3.80mm.

In fact I know this because I was able to insert a 3.55mm drill bit with room to spare, and 3.55 + 0.25 = 3.80. The hole is not ideal, but it's small enough to be tolerable, I think, and unless I'm not figuring this right, it also means that my gap is good, and towards the low end of the range, which I assume is even better.

Btw, this being a Kevlar belt, is there also somewhat less to worry about in terms of min and max tension depending on whether the car is accelerating or decelerating?

Using the pin in the holes to set the tensioner only works with a flat tensioner arm.

If there is a divot, the clearance between the arm and the top of the tensioner is reduced by the extension of the pin into the divot. This can cause the arm to contact the tensioner body when the belt is under dynamic tension (like when the engine is accelerating). If you adjust to maintain the clearance between the auto tensioner body and the tensioner arm you won't overtighten the belt by hitting the body but you may hit the other limit, how far the pin can extend to keep the belt tensioned under deceleration.

There have been reports of the arm doing this when people over tension the belt and making noise and many reports of belts skipping teeth.
Per my comment just above, what if the gap is about as much under the lower limit of 3.80mm as the hole is deep, so that if there were no hole, the gap would be 3.80?

Doesn't that give enough play under both hard acceleration and deceleration so there shouldn't be skipping or other issues, especially with a Kevlar belt which doesn't stretch as much from what I understand?

Although, in my situation I suspect that the amount that the gap is below 3.80mm is less than the depth of the hole, 0.25mm, probably more like 3.65-3.70mm, so allowing for the hole the gap is really more like 3.90-3.95mm.
 
Gates claims less than 0.1% change in length for a modern fiberglass timing belt. So stretch is pretty much a red herring. The hydraulic damper is there to address the harmonics of the dynamic loading. The tensioner pulley and arm move to do so. Not because the belt stretches but because the belt is longer than the distance around all the sprockets and the belt moves under load. If it didn't move, the tension in the belt would fluctuate widely. Now add in the changes in loading caused by the valve springs and it gets pretty noisy inside the belt.

While I still recommend filling the hole in the arm the adjustment spec is how much space there is between the bottom of the arm and the top of the hydraulic damper body. You don't want the arm hitting it. Like I said above you can't use the simple does the pin move freely in the holes when the arm is worn.

The total extension of the pin is 12mm so there is more play available on the extension side of the adjustment than the compression side. Just use your larger drill bit and make sure it lays flat across the top of hydraulic damper body. That will give you ~3.9mm, right?
 
The smallest drill bit I have that's 3.80mm or larger is around 3.94mm and it just barely doesn't fit. I'm guessing but I think it's too thick by around 0.15mm, which would make the gap 3.79mm, close enough to the 3.80mm threshold so it shouldn't be a problem, I'm assuming. It may be too thick by even less. I mean I just have to angle it just a tiny bit to get it to fit in the gap. But is that 3.80mm lower limit hard, or is there some wiggle room there? When you said you've heard or seen skipping for values out of this range, by how much?

I know I'm missing the point, that I shouldn't have to guess or hope that the real lower limit is somewhat lower. But I can't believe what a pain this whole TB job has been, and I just want to get it over with. Even getting the TB lower cover and water pump pulleys back on have been incredibly challenging. Everything is just so tight in there, and I'd rather not take the covers off and redo everything just to get another 0.02-0.03mm in the gap. With the gap being so close to if not in range, is there really a serious rick of a tooth skipping because the arm hits the tensioner, and if it does skip could one tooth skipping cause damage to the engine, or would it have to be multiple teeth? What if I keep checking to see if the timing marks are all aligned?
 
I wish I could reassure you that you'll be fine but I can't. I didn't design it and don't know the guys who did. I can only assume they did the math and came up with the specs. I'm sure they didn't spend any time on how much slop should we leave for people who reuse worn parts so they don't bounce the valves off the pistons.

As far as I know, your risk here is hitting the tensioner body and wearing out the belt and bearings early. This will make noise that you might notice before it gets bad.

If it is too loose you have the risk of skipping teeth. You might notice the belt flapping around or not.
 
What kinds of noise or visual signs should I listen and look for, especially if it's skipped teeth? Is it subtle or very obvious and loud? And does the arm hitting the tensioner due to the gap being too small tend to happen over a certain RPM or when driving very aggressively, or during normal driving and not be related to RPM or driving style?

I actually put everything back together today and ran the engine. Nothing horrible like valves smashing or gears grinding. Ran fine in fact. However a couple of somewhat unusual things that I'm guessing are unrelated.

One, the engine wouldn't idle below 1000, and it's supposed to be 700-800.

And two, when I revved the engine over 2000 there was this weird low pitched sporadic sound similar to the thud that fireworks make when they go off. Not the explosion but the shock wave. It was subtle but noticeable, several times a second and kind of random.

Not sure if either is related or just a sign that something else needs attention. Could either be due to the timing being a tooth or two off? I assume that if I replaced the spark plug wires in the wrong order there would be much worse noise, right?

I'm going to run it as is for a while and keep a close eye on things. Most likely I'll take everything off again at some point in the not too distant future and check the status, especially the gap, and maybe have that hole filled and leveled off, and make sure that I can fit a 5/32 drill bit in there.

But this experience was pretty draining, a lot harder than I expected, and I'd like to take a break now. Not because any particular part was especially complicated, just that with everything so tight in there with the engine in the car it was hard getting everything just right and then back on again. The lower TB cover itself took me over an hour to get back on as it was so tight. Then I struggled with the PS pulleys, then the 3 drive belts, and so on.

Of course having a bad cold and it being cold outside didn't help. And I made things even harder by cleaning up all the parts to remove grime and rust and painting the structural parts. I even cleaned the bolts!

Next time, though, there will be no cleaning, I won't have to replace the seals, water pump or BS belt or have to remove and replace the various sprockets and pulleys. Just the TB and arm, and maybe the tensioner if I need to compress the rod to get the pin back on, and of course all the parts that have to come off to get to them.
 
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With such a small dimple why have it filled? Just grind it flat. Anybody want to comment here? I doubt that arm is hardened or anything special.
 
I'll chime back in. If a divot is small, I don't fk with it. If it were more than "acceptable" I would either grind it just enough to be flat to the eye or fill it with a weld and then grind that down to the original edge. The 2nd one is the last ditch effort if you need to save one. I have a small stash of 6 bolt tensioner arms in various states for these times.
All the 4g's I have put together had SOME wear in that area but all of them have turned out fine and ran like striped ass apes. :)
Maybe I got lucky but I think you are just over concerned, and understandably, but you are going to be fine if the grenade pin was ok and all marks spot on.
I'm sure they are or it wouldnt be running right now. You did fine.
Marty
 
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