# Cam Gear Bolt and Pin Sheared 98 Toyota 3.4 Engine



## 47_47 (Sep 11, 2007)

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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## BigJim (Sep 2, 2008)

47_47 said:


> 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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## 47_47 (Sep 11, 2007)

BigJim said:


> 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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## BigJim (Sep 2, 2008)

47_47 said:


> 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.
> 
> ...


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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## Brainbucket (Mar 30, 2015)

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!:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> 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!:vs_cool:


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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## Brainbucket (Mar 30, 2015)

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.:vs_cool:


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## BigJim (Sep 2, 2008)

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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## BigJim (Sep 2, 2008)

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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## crash525 (Apr 3, 2013)

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.

Sent from my Nexus 6P using Tapatalk


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## Brainbucket (Mar 30, 2015)

Toyota engines are NOT valve interference engines. Throw a cam in it and go.:vs_cool:


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## crash525 (Apr 3, 2013)

Brainbucket said:


> Toyota engines are NOT valve interference engines. Throw a cam in it and go.:vs_cool:


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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## Brainbucket (Mar 30, 2015)

More than likely was improper install.:vs_cool:


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## crash525 (Apr 3, 2013)

Brainbucket said:


> More than likely was improper install.:vs_cool:


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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## Brainbucket (Mar 30, 2015)

If they didn't torque it correctly it could back out over time and do the death wobble and break the pin and bolt.:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> If they didn't torque it correctly it could back out over time and do the death wobble and break the pin and bolt.:vs_cool:


That I didn't think about, very possible. I checked out the timing belt and it looks new, I know it isn't new but no teeth are missing. I am going to go as far as removing the heads to see what is going on in the cylinders, I have a feeling there is a blown head gasket or a cracked head also, it keeps loosing water. 

By loosing water it could have over heated and locked down and popped the bolt. If that is the case the heads may be warped. The way I know it was loosing water, it has a new radiator and there was some copper stop leak in the top of it and there was no water when I popped off the top hose. I will let y'all know what I find. Thanks again for helping me out on this one.


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## Brainbucket (Mar 30, 2015)

If it's been overheated, you can take off the oil fill cap and smell the engine. If it has been overheated, it will smell bad, kinda burnt. If not, it should smell like oil. If a blown head gasket is suspected, fill radiator with water and crank the engine and watch the water. If it blows out then yep, it's blown. If not, pull the spark plugs, as a head gasket leak will 'wash' the cylinder as it is turning into steam and it will be clean. If you have a radiator pressure tester, pump it up with the plugs removed to see if the cylinder is filling up. Also a tell tail sign is murky (gray or yellow) oil. But your leak may not be a head gasket. I would pressure it up and see where it is coming from before I would remove the head for inspection. It may just be a hidden bypass hose.:vs_cool:


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## BigJim (Sep 2, 2008)

Bb, there was no way to fire the engine up as the cam gear was laying down inside the cover, it sheared the bolt the second time because of the play in the gear. I have not heard this engine run at all. I tore into the engine today until it rained me out. I have the timing belt/water pump off and half the intake so far. If all goes well I hope to be inside the valve cover tomorrow. 

I did notice the cam gear on the other side had a little play in the cam gear, are the gears supposed to fit a little tight or have some play? 

I have another question, are the cams on each head interchangeable between heads?


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## Brainbucket (Mar 30, 2015)

Each cam is different. You have intake and exhaust cam on each head which are NOT interchangeable. The pulley is torqued to 81 foot pounds. No play what so ever. Seems like you need 2 cams and 2 pulleys and 2 bolts and another t-belt. Spin the idler and tesioner pulleys and if you hear anything, change them. Look at the oil seals and if you see any evidence of oil leakage, now is the time to change them. Change 1, change all in the front as the rest are right there in age with the 1 that is leaking. No evidence of oil leakage, leave it alone unless you want to do it anyway. If you want the removal and installation procedures, I can post them.:vs_cool:


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## BigJim (Sep 2, 2008)

Bb, I am going to strip it down to the block to see how much wear there is on the cylinders and to see if I have a cracked head. I found a place who rebuilds heads for this engine, they are $325 each with manufactured cams, that is pretty good compaired to some I have seen. I will need new cam gears also.

I am an old 60s mechanic, there is an awful lot to remember on these newer engines. I have to take the intake and head bolts off in a sequence or it will warp them. I miss the days of the old 327 and 427 Chevy engines, they were soooooo easy to work on.


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## BigJim (Sep 2, 2008)

Well it is down to the block now, has been for a couple days. I found a blown head gasket on the opposite side from the busted cam gear bolt. All I can think of now is what Bb said, that someone didn't torque the gear bolt right and the play sheared the pin and over tightened the bolt and popped the head off.

I was amazed at how much pressure it takes to turn the cams over, that timing belt has got to be one tough piece of equipment.

Once I had the heads and all off the block I was also amazed that there is zero ring groove at the top of the cylinders, I can still see the hone cross thatches in the cylinder walls. 

I did find one busted head bolt, which was caused by someone not knowing the back head bolt, which is an allen head, was there and pried the head up from the front and snapped the bolt off even with the block. You can see the spot on the head where the pressure from busting the bolt is. I wonder if that is the reason for the blown head gasket? The place the gasket was blown is in the center cylinder.

I have kicked it around a lot these last couple of days trying to decide to rebuild or just buy another used engine. I can buy one with very low mileage cheaper than I can rebuild.

This is kinda wierd, when I took the first cam out on the driver's side all was fine, I took the one with the loaded spring loose and was placing the caps in a safe place so not to get them out of order, the blame cam just popped right out of the head all by itself, I mean it jumped completely out of the head and landed on the frame of the car. These new engines are something else.

Well that is where I am with this deal right now. When I jerk the block out, I am going get a plasti gauge and check the mains and rod bearings to see how they are, if they are within tolerance, I may just go on and rebuild instead of buying a used engine. Although the engine I am looking at has only 64,000 miles whis is barely broken in.

I can sure tell this person who owned this car didn't take care of the oil changes or use good oil. The heads are really gunked up almost like they had used Quaker State oil, (or cheaper) which I wouldn't use in a lawn mower. 

I have seen engines with Quaker State Oil that I had to literally use a chisel to get the stuff out of the heads and valley, bad stuff.


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## Brainbucket (Mar 30, 2015)

Not changing oil and/or overheating it and not changing oil will cause the oil build up. Since you said that, I would get the other engine and slap it in there. The reason you don't see a ridge in there is because of the fuel injection systems now a days. Carburetors are not as efficient as fuel injection systems maintaining 14:7 fuel to air ratio which is the sweet spot. Carb runs rich and thus wash the oil off the cylinder walls and rings wear into the cylinder more that fuel injection. With carbs back in the day, you was doing good if you got 70,000 mile on it before it took a dump. Now a days 300,000 - 400,000 miles with fuel injection. But the way the previous owner treated the engine, I would get that other engine and slam it in there because you are inviting trouble if you keep the old one unless you go through it. Use synthetic if the other engine is clean inside. Synthetic 'washes' the engine and protect the hell out of it.:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> Not changing oil and/or overheating it and not changing oil will cause the oil build up. Since you said that, I would get the other engine and slap it in there. The reason you don't see a ridge in there is because of the fuel injection systems now a days. Carburetors are not as efficient as fuel injection systems maintaining 14:7 fuel to air ratio which is the sweet spot. Carb runs rich and thus wash the oil off the cylinder walls and rings wear into the cylinder more that fuel injection. With carbs back in the day, you was doing good if you got 70,000 mile on it before it took a dump. Now a days 300,000 - 400,000 miles with fuel injection. But the way the previous owner treated the engine, I would get that other engine and slam it in there because you are inviting trouble if you keep the old one unless you go through it. Use synthetic if the other engine is clean inside. Synthetic 'washes' the engine and protect the hell out of it.:vs_cool:


Buddy I appreciate that more than you know. Like I said earlier, I am an old timey 60s mechanic and working on the new engines now days is just about like starting learning all over again. I didn't know that the injectors is the reason an engine last so long, I always thought it was about the lower compression now days. If this is the orignal engine in this 4Runner and I can still see the hone marks in the cylinders, that is really amazing.


I will go ahead and buy the other engine for sure.


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## Brainbucket (Mar 30, 2015)

No problem my friend. Here to help. Check the timing belt on the other engine while you have it out. It's easier to install and check your timing marks. After you install it, rotate the crank 2 revolutions and see if the timing marks line up. Make sure you don't hear any noise coming from the pulleys.:vs_cool:


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## BigJim (Sep 2, 2008)

Thanks Bb, I do plan to check the timing belt while it is out. Got a question for you just out of curiosity, what kind of oil do you use today to break an engine in. We used to use non-detergent 30 weight oil for 500 miles.


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## Brainbucket (Mar 30, 2015)

You could use 30W in the older engines but not the modern engines. I use dino oil and what ever the engine calls for. Some engines take 5W-20 so if you use 30 weight, it's to much. After 500 miles, I switch to synthetic. Your engine takes 5W-30 unless the temps outside reach 100 degrees, then it's 10W-30. Engines of old aren't like modern engines. I work on both. The oil passages are a lot different and smaller so if you put say 20W-50, over time it will blow up. Especially VVT (variable valve timing ) engines. It's critical in modern engines to put the right weight as that's what it's designed for. Engines of old, you could put 20W-50 in there and be ok. I would do that when I thought the engine is about wore out and the thicker oil helped with the slack. But you do that with modern engines and it's a receipt for disaster.:vs_cool:


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## BigJim (Sep 2, 2008)

Bb, that is good to know, sometimes it does hit a 100 degrees up this way but not for weeks on end. I never really had a lot of faith in the synthetic oils but I will now, I appreciate you taking your time to explain this to me. I am going to look locally so I can do a compression check on the engine before buying, I am too old to jerk another engine out. LOL

Have a great day buddy.


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## Brainbucket (Mar 30, 2015)

You too.:vs_karate:


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