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Timing belt falling off, need permanent fix idea's

19K views 43 replies 14 participants last post by  amc49 
#1 · (Edited)
I've been dealing with this problem for too damn long and I'm finally sick and tired of it. I don't mind replacing belts, I hate it because I have to retime my cams every time and it takes me (on average) 4 tries to get them correct, and this is going by notes I take each time. I'm sick and tired of this crap; every ~10,000 I put a new belt on and have to dick with this timing crap. Car has 185,xxx (first new belt was @ ~90,000). so you get the idea of why I'm pissed at it.


I've had the GC idler on the car for the last little over year and for the most part it did what I bought it to do; help slow the eating of my belt. Unfortunately the pulley shit the bed. I had to replace the bearing the second week I had the thing. It was then I'd noticed the fit to be loose, but I went with it. Well that loose fit finally did the pulley in, galvanic corrosion and the loose has become measurable gap.

I don't want to hear anything about belt tension. It's perfect. And even if it wasn't I think I've tried adjusting things enough over the years that I should have found a sweet spot at least once. Nope. Also there is no difference I can tell in how fast or slow it eats away.

I don't want to hear anything about pulley alignment or ware. The last belt was installed with every pulley (minus the GC one) brand new,,, CFM cam gears, new Ford tensioner, new Ford drive pulley, new Ford lower idler. Alignment was checked with a laser and everything was true.


I'm pretty good at figuring most things out, but this one just has me utterly baffled. Nothing I've tried has stopped it or slowed it down, and nothing I can find explains why the belt is walking off. It's like the car just wants me to burn it down.


Only idea I have is to get custom pulleys made like the GC one. But add more of a lip to it. But I know that just 1 won't make much difference. I'll have to, or really should, have 3 of them,,, that means I'll have to have a custom tensioner made (awesome [mad]).

Or, is there any way to swap it over to a chain?
I could rig up a oil spray for the chain pretty easily, just a oil jet in one of the plugs in the head outta work sorta. Bridge when there deal though.


*edit

k, so I'm sitting here thinking about this and I think I've come up with a reasonable and viable solution:
Have a 'shim' made to fit the drive gear. If it tapers up to the crank dampener and fits over the drive gear ~1/16" it should move the entire belt over enough so that it rides true again.
Near as I'm figuring I have to attack this from the bottom up. If I get and keep the bottom true then everything thereafter should follow suit.
Plus this should be the quickest and cheapest fix, being it's essentially a big tapered bushing.
I'll try and get it drawn up tomorrow and off to my neighbors shop to be CNC'd. It'll be steel simply because then I don't have to worry about the belt eating it if it does rub.

**edit

Well that idea died real fast.
Just went out and test fit a brand new belt to an old drive gear. There is no side play, or not enough for any type of 'shim' to fit.
So now I'm wondering if my drive gear is back far enough. Just did the belt a day ago and checked it and it sure looked like it fit back far enough, least it wouldn't go back any further than it did (crank dampener reads "front" on the back side, meaning it fits the drive gear nice and tight). Maybe the key isn't quite straight or something ... have to pull it apart and see I guess. Kinda doubting I find anything wrong though. Wasn't any play so i can't imagine anything's FUBAR.
And i guess long as I have to get back in there I may as well flip the DG so the washer fits the outside and see what happens. That outta push it in 1/16". Just hope to hell it doesn't dive in or shit's really gonna go wrong, buh-bye crank seal/oil pump.
 
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#3 ·
Also check your crank for crank walk, check the end play. If you have excessive crank walk that will throw a timing belt and i had it once knock out my front oil pump seal. If there is excessive crank walk, you may need a thrust bearing at a minimum or a crank kit at a max. One way to check and see if the crank is walking, is pull the crank sensor and see if the flywheel has been rubbing it.
 
#4 ·
Crank walk isnt going to do anything but move the crank pulley forward or backwards .060 to .100 wore slap out ( that bad would be eating the crank sensor) it isnt like the belt would be off the end of the gear , why do you feel otherwise ?

There is something wrong with your set up , no one else is having this issues , I have found a few with the idler and or tensioner to where they let the belt drift off this allows the belt to move to the block ot to the mount , I have only seen the bolt hole off in 2 blocks causing this , have you checked the pulleys to be square with the block ?

Tom
 
#5 ·
I've checked and rechecked everything. It's as square as can be. It just doesn't make any sense.
Also used 2 different Ford belts (same PN but different MFG's), a Dayco belt, a Cloytes belt, a cheap O'Reilly's belt (can't recall the brand),,, all do the exact same thing. To rule out MFG error in a belt.

Drive gear = gear on the crank snout, btw.


I do have a new block being built but I'm not sure when it'll be done and I do need the car running up until I do the swap. Really hope I don't have the same issue with the new one; and just in case I want to solve this so I can quickly fix the new engine.


For reference,
I can set the belt to the very inside of the gears and on the 3rd full rotation it's to the outside already. From there it'll ride as much as the back of the crank gear allows, which is very little but just enough to rub and ware the belt down.
You don't even want to know how far it's dug into my Aluminum pulley.
 
#8 ·
After changing out all of the replaceable parts (I assume that means new bolts to rule out a bent bolt) that leaves one part not replaced-the head.
You say you checked alignment with a laser but really a variance of only a few thousandths of an inch will cause belt walk. I don't think the laser has that kind of accuracy.
I am going out on a limb here but I would bet there is either dirt (not likely due to your diligence) or a mis-aligned mounting surface on the head, either at the tensioner or idler pulley mount point.
 
#10 · (Edited)
Head has been replaced ... remember I'm running a milled SVT head. But I had this same problem on the stock untouched head.
So IMO that rules out anything head related. But I guess it could have been milled at a slight angle, I never checked it,,, but I also have extreme confidence in the guy how milled the head to do accurate work (I've known him almost all my life and never heard a bad thing about his work).

I figure it has to be something in the bottom end. But the only thing it could be there is the crank, and that just doesn't make sense. I'd have to see the dampener move if the snout is bent at all, and it doesn't.

I'm gonna check endplay in a bit here and see what it is.



*edit

Endplay looks to be 0.003". Nowhere near enough to even worry about.
But that's assuming I measured the correct way,,, difference from clutch in to clutch out. I can see loading the clutch measuring slightly different than stationary, but even still, not enough to make any difference.
Crankwalk/endplay is not the problem.
 
#11 ·
This is gonna sound really dumb but, do you have a warped cam?
 
#12 ·
Every zetec belt I've ever seen walk had too much tension, they really do not require nearly what one would think. On used engines at end of belt life you can pull the belt off without loosening anything, they are loose yet stay in place all day long. Too much tension is what gives enough bite/traction to start walking, they can do it with all parts 100% dead straight.

Having said that, I have no SVT experience.

One can use pulleys with a high crown in the center of the width, the middle is slightly higher than the ends. I used parts like that on long runs of belt with absolutely no side guides at all to prevent walking. The high crown keeps belt running centered on pulley. That was on high speed printing equipment and belt runs 10 feet tall.

I notice the words 'lower idler' used once, if using the one next to the crank drive pulley on the right I'd be dropping that one. Once slightly worn it can induce walking at the crank from pulley tilt. The close angle lead-in allows the tilt to give belt edge some bite into crank pulley and subsequent walk.
 
#13 ·
iminhell,
I'm in the same boat as you. I installed the VCT delete kit from Tom about 6 months ago. With new belt, idler, tensioner and AEM cam gears. Could never get the belt to ride center. I read as many forums as I could find and did what they all recomended, loosen tension. Lossened it so much that at 3500 rpm the belt would flap like crazy on top of the gears, still would not move back to the block/head.

I then ordered the GC idler. Thinking everything was fine I sold the car. I'm Senior Master Tech at a Ford dealer here and told the guy I would help with any issues with the car. He brings it back to me and even with GC, the belt was comming apart. So I tore the front of the engine apart. Replaced the belt and tensioner new (thinking the tensioner was at fault). Reassembled vehicle, belt looked about 2-3 mm from the timing cover by the mount, I thought it looked better. Adjusted the tension with the arrow on the very outside of the square, still loose.

He called me yesterday and said the belt is wearing again, only about 30 miles on the repair. I also installed underdrive pullies a while back, really don't think that would affect anything.

But I am stumped on this as well man. Everyone at my dealer says they've never even seen a belt walk issue on zetecs (they also never done cam gears)
 
#14 · (Edited)
Well, I had a local CnC shop make me a modified copy of the GC idler. I've got about 200 miles on it now and it's perfect.
I had them make the lips square instead of tapered and they are slightly taller. If you had to clearance for the GC idler you'll have to clearance just a tad more for mine.

If you want me to have one made for ya just let me know.

Here's how I sit right now:



 
#15 ·
Yes please! I just looked at the car right now, I found a small bur on the GC pullie... I swore I checked it for anything of the sort this weekend, filed it out and loosened the hell out of the tensioner (belt was 1 mm off the cam gears). Belt looks like it's in your spot in the pictures now. But I still don't trust it, at idle the belt walks back and forth about a half mm.

Can you send the price info and everything to zteben@gmail.com and I'll forward it to the owner. I appreciate it and hope this is the final fix for our problem!
 
#16 ·
Could you pm me info as well iminhell? I know with GC idler there was an issue some had with the bearings not lasting. Does the one you had made correct this as well by using better bearing? Info much appreciated.
 
#18 ·
One other trick that can work is to machine the gear teeth so that the center is slightly taller than the edges. Across the width front to rear. The high center steers belt to center of gear.
 
#20 ·
That idea has to been done from the get-go, simply trimming down the outside OD at the edges ain't gonna cut it. The GROOVE itself must be curved. Used the idea on flat belts that ran several feet in length with no side guiding on pulleys at all. On highspeed printing equipment running at 1000 ft./min. with 3 side cutting going on in there. 3 sets of belt holding product, the individual belts had eccentric pulleys that could be moved to change the effective length of each belt on 1/2 of the belt run so could overdrive or underdrive one side of product in relation to the other to fine tune straight cutting at variable speeds. Could have no raised side edge on pulleys since the product actually driven by the center high spot of the pulley. As many as 6 pulleys and belts tracked super straight but once the high center crown wore off pulleys watch the troubles begin.

A tip. When guiding with a raised edge the belt cannot be tracked by bumping it HARD with the raised edge. If so the belt will slightly fray and the fray whisker getting caught in between the gear and belt and raised edge will steer the belt in erratic ways even if the belt looks fairly clean edged. You want to kiss it as softly as possible to get your effect. A frayed edge is thicker and if tensioning on the backside of it (as a zetec does) you WILL get steering away from straight running.
 
#22 ·
iminhell: Awesome fix.

I have noticed on my normal Zetec, that the belt naturally sits forward on the cam gears a little. When I rebuilt it, I pushed the belt back a little on the cams gears, and turned it twice by hand, and it went back to the edge. But It never falls off.

But this has me thinking "why did it do this for you"?

There has to be some scientific reason for this?
 
#23 ·
would there be any reason, in your case, for tensioner (as a whole) not sitting close enough to the engine block? i mean 0,5mm further away from the block than it should be and belt can start walking over the edge.

would you say for sure that the bolt which holds tensioner is getting in all the way, and you used torque wrench to tighten it?

would you try not to go after perfect tension, but set the tensioner adjustment pin off, but on intention, and see if ti would keep belt where it should be?


edit: ok nevermind, was reading on phone, didn't notice there is a second page to this thread with a solution ready :)
 
#24 ·
I'd look close at the second pic. At the new idler, belt run seems to show a slight fray of the belt on the rear edge on like 6 teeth in a row. The little mark there repeated on several teeth. Maybe nothing, but could be a pulley dent or ding that digging into belt could steer it.
 
#26 ·
Working just fine. Is squeaking when cold. Warm and it's quite. Come warmer weather I'm going to pull it and swap in my other one. Then look at how it's been doing.
Haven't put a ton of miles on it, but a fair amount of RPM.

Now that I have a good drafting program, I'll make a drawing and try to get G code for it. Then I'll post it all so anyone can go to a machine shop and have one built.


And I'm not sure if I mentioned it but, I'm also running the lower idler from the Zx2. It's taking up the little extra slack in my belt and has helped me.
 
#27 ·
That's cool. Figured since my timing belt will need to be changed in the next 4-6 months I might as well plan now. I know my old Gold Coast pulley worked good until I totaled my Kona. Think I put about 10k miles on it. Only started squeaking when cold from when my coolant tube cracked and sprayed fluid ALL OVER the engine bay and soaked the billet idler.
 
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