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Old 04-13-2017, 03:09 PM   #1
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Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


I am in the process of buying a 1998 Toyota 4runner 3.4 engine, 2wd limited addition, in good shape except for one thing, (I hope), the bolt holding the cam gear and pin on sheared. I haven't been in the engine yet as I haven't bought it yet. I know something had to seize the cam in some way to cause it to shear, any thoughts.

The reason I want an older car is I hate the looks of the newer ones.
This isn't mine but it is just like it.
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Old 04-13-2017, 04:23 PM   #2
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


Does it run? If not, remove rocker covers and look at the valves / springs. Probably belt jumped and valves hit a piston.

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Old 04-13-2017, 04:47 PM   #3
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


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Does it run? If not, remove rocker covers and look at the valves / springs. Probably belt jumped and valves hit a piston.
It did run after they put a new bolt and pin in but the lady parked it at work and it wouldn't start. That is where I am at right now. They said after replacing the bolt and pin the engine had a chirping sound to it. I guess I will have to wait until I have it here and can get into the cams to see what is going on. I was just wanting some info what others thought might cause the bolt and pin to shear.

My thoughts are the cam had to seize some way, or something jammed the cam to have that much force to break a bolt like that. I don't think the cam locked up because it started after they replaced the bolt and pin. I am chompin at the bits to get in that engine. LOL I know the belt didn't break, I saw it when they had it torn down, but not the cams.
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Old 04-13-2017, 05:34 PM   #4
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


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It did run after they put a new bolt and pin in but the lady parked it at work and it wouldn't start. That is where I am at right now. They said after replacing the bolt and pin the engine had a chirping sound to it. I guess I will have to wait until I have it here and can get into the cams to see what is going on. I was just wanting some info what others thought might cause the bolt and pin to shear.

My thoughts are the cam had to seize some way, or something jammed the cam to have that much force to break a bolt like that. I don't think the cam locked up because it started after they replaced the bolt and pin. I am chompin at the bits to get in that engine. LOL I know the belt didn't break, I saw it when they had it torn down, but not the cams.
Belt doesn't have to break to wreck an engine.

Was this the original cam bolt? Someone may have previously removed bolt and didn't properly reinstall.

Chirping noise sound like a contaminated belt. Either timing or accessory.

Try not to rip and tear into the engine. Careful examination on disassembly should reveal the root cause.
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Old 04-13-2017, 09:46 PM   #5
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


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Belt doesn't have to break to wreck an engine.

Was this the original cam bolt? Someone may have previously removed bolt and didn't properly reinstall.

Chirping noise sound like a contaminated belt. Either timing or accessory.

Try not to rip and tear into the engine. Careful examination on disassembly should reveal the root cause.
Believe me, I'm not going any further into the engine than I have too. LOL I had the same thought about someone putting a softer bolt in the cam than is supposed to be, but I don't know.

I checked and the 3.4 is a non-interference engine like some are. You can turn the cams and not be worried about a valve hitting a piston. Our daughter had a KIA that had an interference engine, two or three teeth off the timing belt and her engine was shot.
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Old 04-14-2017, 07:55 AM   #6
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


I would pull the valve cover off to see the cam journals. If you have a cam locking up, you will see a 'burnt' journal. One journal is a darker color that the others. It might be a improperly torqued cam bolt. Hard to say from an arm chair. I would buy the car assuming it needed an engine and if you save it, BONUS!
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Old 04-14-2017, 10:08 AM   #7
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


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I would pull the valve cover off to see the cam journals. If you have a cam locking up, you will see a 'burnt' journal. One journal is a darker color that the others. It might be a improperly torqued cam bolt. Hard to say from an arm chair. I would buy the car assuming it needed an engine and if you save it, BONUS!
If the lady can find the title I will buy it. I have priced several engines, this car is well worth replacing the engine and even with replacing the engine I would come out way ahead. Like you said, if I can save this engine, that is just icing on the cake.

What has surprised me is, there are no cam bearings, sorta like the old 50s engines with babbit bearings, when the journal is worn, the head is shot. I will check the cams the first thing I do, if I ever do get the car. Thanks Bb
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Old 04-15-2017, 11:52 AM   #8
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


What I would do is get the bolt out with reverse drill bit and get the pin out. If I could do that, then I would get a pulley and belt, install, and see if it ran ok. If it does, then a new cam comes into play as I can't see the end to see if it's damaged. I have save cams before but the end has to be true for the pulley to ride correctly. Or used engine.
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Old 04-15-2017, 12:06 PM   #9
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


Thanks Bb, so far the lady hasn't found the title so it may be all for nothing anyway. I will make a post if she does come across. Thanks again.
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Old 04-17-2017, 08:42 PM   #10
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


I pulled the trigger and bought the 4Runner, she let me have it for $500, I still can't believe it. I tore into it today and the cam gear bolt and pin was broken again. I did notice one thing, the gear is supposed to fit on the end of the cam snugly, it doesn't, it is really loose, way too much play.

My opinion is with all that slop in the gear, it sheared the pin then continued to tighten the bolt until it snapped the head of the bolt off. That is as far as I got so far. A couple pictures of the car, the inside has some wear but not that bad.
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Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine-4runner1.jpg   Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine-4runner-4-4-17-17.jpg   Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine-4runner2-4-17-17.jpg   Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine-4runner-3-4-17-17.jpg  
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Old 04-18-2017, 07:11 AM   #11
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


It probably jumped timing and sheared the cam pin and bolt. The free play is from the pulley spinning on the cam. As another person said scheck the valves see if any look bent or broken. Get a bore scope for a laptop or cell phones. There cheap. Check the cylinders out. But for 500 bucks you cant beat that.

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Old 04-18-2017, 07:51 AM   #12
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


Toyota engines are NOT valve interference engines. Throw a cam in it and go.
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Old 04-18-2017, 08:10 AM   #13
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


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Toyota engines are NOT valve interference engines. Throw a cam in it and go.
I heard that but have no experience with it. But what would cause the bolt and pin to shear? Bad oil pressure and locked up the cam? Clocked up an oil passage?

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Old 04-18-2017, 08:16 AM   #14
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


More than likely was improper install.
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Old 04-18-2017, 08:28 AM   #15
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Re: Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine


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More than likely was improper install.
You just dont shear a cam pin by installing it wrong. More so why was it intially replaced? Not trying to argue btw.

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