Camshaft Sprocket Bolt Broken While Driving 91 Ls400

[_mach_]

Ok, I have a very puzzling problem and wanted to see if anyone else has had a similar experience. I was driving my 1991 LS 400 (which has about 175k miles) when it randomly died on the highway. I tried to re-start it after i pulled over, but it was like it was running on 4 cylinders. I ended up having it towed home and tore into it last night. I found the driver side Ignition rotor was completely destroyed. When i removed the 2 screws holding what was left onto the cam sprocket, the head of the bolt that holds the sprocket to the cam was sitting inside the rotor. This bolt is about the size of a tube of chap stick (so VERY strong) and it had simply broken off. I was able to remove the rest of the bolt very easily and have a new one on order. it's just that I've never heard of anything like this happening before. I would think the timing belt would break before a bolt this big would? The cam still turns, nothing is bound up, everything else seems fine, it's like the bolt just decided to fail. I do know that it was a little over filled with oil (maybe 1.5-2 qts) but don't think that would cause anything like this. Anything i should check before replacing the bolt, ignition cap and rotor? The timing belt was replaced about 40k miles ago. I know that this motor is a non-interference motor, so even if the cam has moved inside the sprocket i won't break anything....correct? Thanks for the help guys!!

[curiousB]

Very strange as you rightly point out. Not sure how such a large bolt would fracture like that. I have heard of water pumps seizing and causing the timing belt to break. I wonder if that happened in the car's past and that event weakened the bolt that just recently snapped. Other than that maybe a defect bolt from the start and it just took a while to get the right torque scenario to snap it.

[_mach_]

Very strange as you rightly point out. Not sure how such a large bolt would fracture like that. I have heard of water pumps seizing and causing the timing belt to break. I wonder if that happened in the car's past and that event weakened the bolt that just recently snapped. Other than that maybe a defect bolt from the start and it just took a while to get the right torque scenario to snap it.

So I ordered a bolt, cap and rotor for it today, and should have it in tomorrow. Any suggestions on what else i should look for? Anything i should check before putting it back together?

[_mach_]

I ordered a new bolt for the cam, it'll be here some time in the next few days....So I decided to find a grade 8 bolt of similar size to see if that would work. It holds just fine, the car starts now, but it is still running very rough. Any suggestions? Is it possible for the belt to jump time? if so, is there an easy way to check for that? I have a feeling that it is out of time. The car was to be sold this Sunday, and I really want it up and running so I can get rid of it. Any and all suggestions are very appreciated!

[_mach_]

Well, i tore it apart and even the guide pin that holds the cam gear to the cam was broken. I had to drill it out, replace, put a new gear and bolt on, then replaced the cap and rotor...after all that the front main seal is gone and it's pouring oil out of the timing cover...at this point im thinking i just sell it for 1500 to 2000 bucks and cut my losses. It looks like the front main seal is bad, but not 100% sure. It's one of those situations in which I could tear into it, replace the seal, but what else could be wrong. Has anyone ever heard of anything like this happening before?? I'm baffled as to why this all happened at the same time...the car drove from Texas to Massachusetts no problem, and then was parked for 3 months, upon first crank...bam, down goes the lexus.

[RDM]

The crank seal isn't related to the cam/belt issues and it's unlikely it began leaking suddenly, it's probably been on it's way for some time. You're now noticing it more since it's finally given up completely. It's an easy seal to replace while in the front end but you might as well do cam seals too, plus anything else like the timing belt, water pump, etc. If you're not feeling taking it all on, sell it or have someone else do the job for you.