Front cam sprocket bolts sheared off

[myotis1134]

Hello people, I need your help.

My uncle allowed me to use his SHO this summer, so I could work on some issues on my car. Sometime in May, the passenger side wheel bearing died, which led to a total cluster-****. During the process, I determined the brakes had to be replaced, the control arms... I discovered the driver side strut rod was missing the bolt that fastened it to the control arm. Lots of little fun things that made me cringe when found. Everything finally worked out, new control arm, new poly bushings all around, new struts, etc. The car handled like a champ.

Drove it for about another month problem-free, when all of a sudden, it would start bogging down around 3000 - 4000 rpm. Did my homework and found it could be caused by several things - tps, crank sensor, cam sensor, etc. Got the tps and cam sensor locally, had to order the crank sensor from SHO source. Tps and cam sensor didn't fix it, so I started pulling things apart - following SHO Phoenix Project's front and upper maintenance guides.

To make a long story short, it turned out to be the rear valve cover gaskets leaking into all three spark plug wells. New plugs, wires, and gaskets from SHOsource fixed that, but I had torn the serpentine system down so I went ahead and replaced the cam seals and belts as well.

One of the largest (of many) problems I ran into was getting a straight answer on how much tension to place the belts under, especially the timing belt. the SHOPP guide was vague, and google was worse. I ended up making it as tight as I dared, with probably a little less than 1/8 inch defelection on the tensioner side. Got everything back together (finally), and it ran like a badass.

This time I drove it around for less than two weeks, had just left my new job and was waiting to pull into traffic, when I heard an awful grinding noise, and the engine died. Stupidly, I immediately tried to turn it over and heard another horrible noise, so I pushed it over to the curb and called for a ride. While waiting for my ride, I looked everything over, checked my fluids and tried to spot any leaks. Nothing looked or smelled wrong, so I figured I must have tightened the timing belt too much and it broke... so close yet so far off.

I finally got back to the car tonight, and pulled the belt system off to get at the upper timing cover. Got it opened up, and discovered that all three bolts on the front cam sprocket were sheared off - one of them fairly deep and the other two poking out a little. Needless to say, this sucks! I was very careful not to over torque the sprocket bolts during reassembly, so I must have over-tightened the timing belt. The only other explanation is that the 20+ year old cam-sprocket bolts on the vehicle that apparently lacked serious maintenance until I came along decided to give up the ghost.

Tomorrow I'm going to pull the crank pulley, remove the mid and lower timing cover, and see if I can find the rest of the bolts and the pin. I pulled the other cam sprocket to use those bolts for reference if I can't find anything. I picked up a bolt extractor and drill bit, and found a hose-to-pipe fitting that should make a decent guide for drilling into the chunk of bolt inside the cam, and I'll hit up home depot to find another guide that I can slip over the two protruding bolts.

My main worry at this point, is that the whole affair may have tweaked the entire camshaft, as the new seal is now leaking a very small amount of oil. Is this scenario possible, or is there no way that enough force could have been placed on the cam to necessitate replacing the bearings?

I just don't want to waste time and effort digging out the bolts if the now-leaking seal is an indication of a tweaked cam. I'll throw up some pics tomorrow, but right now I'm going to put up some of happier times.

Thanks in advance for any help/advice.


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[Irish Pride]

I would replace the cam and do a valve adjustment afterward.

The only time I have ever seen or heard of the cam sprocket bolts breaking is when they were not torqued properly. I would check the rear sprocket while you are in there. Chances are those will be loose too.

 

[rubydist]

I would also replace the cam.

The cam bolts will break for 2 reasons. As IrishPride said, if they are overtorqued, they can break as they are not that big. Also, if the cam sprocket is put on without the dowel pin, the bolts will break from that as well. Given the others not so high quality work you have discovered, I would not be surprised at either of those causes. btw, I do not believe those bolts will break due to overtightening the belt - I have seen a cam break from that cause though.

I have atx cams in my for-sale thread, but no mtx (you didn't tell us which did you?) I may also be able to find a dowel if you are in need of that.

 

[kevinspann]

I would also replace the cam.

The cam bolts will break for 2 reasons. As IrishPride said, if they are overtorqued, they can break as they are not that big. Also, if the cam sprocket is put on without the dowel pin, the bolts will break from that as well. Given the others not so high quality work you have discovered, I would not be surprised at either of those causes. btw, I do not believe those bolts will break due to overtightening the belt - I have seen a cam break from that cause though.

I have atx cams in my for-sale thread, but no mtx (you didn't tell us which did you?) I may also be able to find a dowel if you are in need of that.

Looks like it's an MTX based on his pictures. I've got the MTX cams, gears, dowel pins, bolts, etc as well...

 

[myotis1134]

Thanks for the responses guys. Sorry for the delay, I'm heading up to the slope tomorrow, and I've been running around trying to get my gear together.

The vehicle is indeed an MTX, and I sort of expected to have to replace the cam. I just got it back to the house, and am about to finish pulling the crank pulley and timing cover. Hopefully I will find the dowel somewhere in the bottom.

Probably won't find out exactly what happened, but I'll admit it's totally possible I screwed up somewhere during reinstallation.

I'm flying out to Thompson Point tomorrow, so I won't be dealing with the car for a while, but I'm going to try to get a friend who mechanics at a local dealership to start the repairs.

Thanks for the offer kevinspann, it will probably become necessary to hit you up for some parts in the near future.

I'm putting up pics of the cam and sprocket.

 

[myotis1134]

Out of curiosity, is there a reliable method of determining if the cam is bent, or is it more of an if-then scenario:

if a sudden eccentric axial force is applied to a camshaft, then you replace the sucker!

 

[kevinspann]

I'd personally try to just replace the pulley, bolts, and dowels, before replacing the cam.

There have been instances of the ends of the cam breaking off however....

The only tension the timing belt should have, would be from the spring on the tensioner assembly. Install the belt, let the spring provide tension, rotate the engine 2x, then tighten the nut on the tensioner. Job done.

 

[rubydist]

I like the easy way out, but there is no way I would try to use a cam that looked like that one. it needs replaced.