Quote:
Originally Posted by jbg
The large crank bolt, is it clamping both the harmonic damper and the crank timing belt gear onto the crank snout? The 4 6mm inhex bolts, they are screwed into the crank timing belt gear and also clamping the harmonic balancer to the crank timing belt gear?
It looks like if I removed the front crank bolt it would give me more room inside the harmonic balancer to work, and fit tools. The Green book says to first remove the 27mm bolt and then the 4 inhex bolts. If I did this would the crank timing belt gear become loose or fall off the crank? Or is there like a woodruff key on the crank snout and the timing gear to keep it all together? I don't want to disturb engine timing as I am not replacing the timing belt yet. I just want get to the 4 inhex bolts removable per preparation. Though replacing the timing belt is something I will do soon.
Here is the small parts list so far:
- Front timing belt
- Water pump o-ring
- From crankshaft oil seal
- 4 inhex bolts
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Quote:
Originally Posted by ngoma
Yes.
I think that's right (been a few years so not entirely sure-- hoping somebody else can double check).
No woodruff key, that's why sufficient torque on that bolt is imperative. Kind of a non-common method and the base cause for what is now probably the #1 reason for the D24 (arguably unfair) poor reputation of self destruction after TB maintenance by mechanics who do things the "normal" way.
The crank cog gear doesn't fall off so easily.
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Well there "kind of" is a woodruff key in there, in the sense that there is a fixed key inside the crankshaft timing gear that aligns the gear with a keyway on the crank snout. The issue of course is that the key does not have anywhere near the strength necessary to perform the task of keeping the running engine in time, hence the reason for the high required torque on the big center bolt. That torque is what keeps it all together for the long term with a running engine, by force and friction alone. The key and keyway are just there to aid assembly. And what's more, they don't fit especially tightly. So anytime you loosen the big center crankshaft bolt with the 27mm head, you risk timing drifting to some degree. But thanks to the keyed installation on the crank, it can't drift more than a relatively small distance.
Here's the setup you are working with.
- The big bolt with 27mm head holds the outer "balancer" tight to the crankshaft.
- The four small bolts with 6mm inhex heads hold the timing gear to the back of the balancer (they thread into the timing gear). So, the crank turns the balancer, which turns the timing gear, which turns the timing belt.
In other words, no, the timing gear is not sandwiched between the balancer and the end of the crank. The timing gear is like a donut and just floats behind the balancer on the outer perimeter of the crank snout, it has no internal flange. The big bolt exerts no force or contact on the timing gear -- only on the balancer.
Thus if you do as you say, jbg, and remove the big central bolt, then no there isn't any risk of the whole sandwich falling apart. But what WILL happen is that the key in the timing gear (which again does not fit very tight in the crank keyway) will be the only thing maintaining engine timing in position. So you'd get some timing drift. And worst case, the entire balancer and gear assembly could work loose from the crankshaft as you tried to work on the inhex bolts.
This is just $0.02 here, but I think if I were in your position, trying/preparing to deal with those mutilated inhex bolts, I would simply not worry about them for now. The good news is that they are in there and seem to be tight so they're not a functional threat, just an obstacle for service. It will be a battle to try to do anything with them in situ, with them on the engine down there in a hard to reach location.... but, you don't have to do anything with them there. Instead my move, whenever the time comes that you want to change the timing belt, would be this:
- Loosen and remove the big center bolt (this is after bringing engine to near TDC, other timing service preliminary steps etc as per greenbook)
- Use tool 5187 per greenbook to bring engine back to TDC with the center bolt removed
- Loosen timing belt using your preferred method
- REMOVE the entire balancer/timing gear assembly from the crankshaft as one combined unit, with the 4 inhex screws still in place and tight.
Now you have the assembly on the workbench where you can easily attack it with impact tools and/or heat.... or, most likely easiest of all, simply use a large drill bit and drill the heads off those bolts. Then separate the two parts, unscrew what remains of the bolts from the timing gear, and replace the hardware with new.
Fun to watch all the progress, cheers!
