Bear with me here...timing belt failure revisited

[swapdip]

OK, so after replacing my timing belt I experienced a failure roughly 2000 miles later. At the moment of failure the engine simply cut off, no noise of metal smashing or anything like that, and subsequent efforts to start the truck resulted in that "freewheeling" sound which indicated to me that the crank is no longer connected to the cams, hence no compression. I did not hear any sound of pinging or knocking, and I know what an engine sounds like when a spark plug is inserted that is too long, and I expected to hear something like that if there was significant valve contact. So I took it all apart today and I noticed that the tensioner retaining bolt had completely sheared off, skewing the angle of the tensioner and disintegrating the belt. Well, that ought to do it. Not sure how that happened, the bolt, altho old, was inserted by hand to make sure no stripping occurred, and then torqued to 38 ft lb or whatever the Haynes manual said, and then it was good for almost 2000 miles. The tension was correct with the allen hole at 5 oclock, but whatever, on to more important things.

 

I turned the crank by hand, and it turns about as freely as you would expect with the plugs removed. The passenger side cam also turned as freely as I remember, with the indicative "clunking" into place every 15 degrees or so. So I took the valve cover off and everything basically looked like it should, no damage perceived up there. Valve guides and rockers moved as they ought to when I rotated the cam, everything operated symmetrically and freely.

 

I am wary to remove the head to check the condition of the pistons, so I looked around in the spark plug hole and felt in there with a magnet, resulting in nothing I could perceive, altho you all know how recessed those holes are and difficult it is to look inside. Removing the head is something I'm not sure I can do at this moment without some help, never done it before except on little motorcycles, so my question is, does this information so far indicate to you fellows that perhaps I lucked out and all my truck needs is a new belt? Should I do any further diagnostic work at the present moment, or should I proceed now to drilling out that retainer bolt, slapping on a new belt and checking compression? I know I may be grasping at straws here, and believe me I am considering the idea that I am kidding myself about ever running this engine again, however karma does favor the meek and I am meek as a motherf#cker.

 

Thanks guys

[87pathy]

I wouldn't bet on it.

 

I've had the heads off, and belive it or nt, its prett easy.

biggest problem are the exhaust manifold bolts / Studs.

 

PUll the plenum off in 1 piece, mark every wire and hose,

 

unbolt, pull away.

[Cuong Nguyen]

Removing the heads is easy. The only problem that gave me a hell of a time were the exhaust studs and manifolds. I also broke off my EGR. Other than that, everything is easy. Just keep track of what bolts go where.

 

You're most likely to have bent valves although everything looks right so far.

Edited June 4, 2010 by Cuong Nguyen

[GrimGreg]

I would install the new belt and then do a compression test on it (before assembling everything else back), the compression test will show if any of the valves are bent and "leaking". Then if you find a low compression cylinder, you know which head needs to come off, if at all. You might have gotten lucky and it broke with the valves in just the right spot to not make contact, but I would guess you hit at least one with it breaking while running.

[Precise1]

should I proceed now to drilling out that retainer bolt, slapping on a new belt and checking compression?

 

This. I have known of a few people who have gotten lucky and did no real damage so it is not impossible. My view is that you will have to fix the tensioner/replace the belt anyway so do that, just put on the lower cover and do a compression check. If you have to pull the heads you haven't wasted much time at all.

 

I know of a few people who have had the same failure; k9sar and someone else. It isn't normal and the only reasons I can think of is over torque of the stud, over tensioning the belt and/or weak studs.

 

HEY!! Does anyone know if the tensioner stud is the same as the exhaust manifold studs?? That would explain a lot...

 

B

[swapdip]

Well hell I might just toss in the towel then. Trying to extract that broken bolt I snapped off my extractor inside the engine block, now I'm kicking myself and wishing I had either more experience or more money to do the job right. I might hang around craigslist and look for a pathy with a bad tranny or something to grab on the cheap, but failing that you might see me parting out my poor truck on this forum sooner or later. Feeling super goddamm frustrated.

 

For the time being however, Ive got the Suzuki to get around on, and I am courting my neighbor to let go of a super grown in 2 door for a handful of quarters. Who knows what will happen...

 

Thanks anyways guys

Edited June 4, 2010 by swapdip

[Precise1]

Dripp or grind it out, it's not impossible or expensive, just tedius. Don't rush you you'll be fine...

 

B