Broken camshaft and #1 bearing cap

calebc3 · Post by **calebc3** » Tue May 22, 2007 5:12 pm

Decided to test drive my ecodiesel project. Seemed to be running pretty good, pretty peppy. It locked up at a pretty slow speed and I thought it would be odd that the timing belt broke because it was pretty new. Popped the hood and saw the belt loose (I had the cover off since I had been working on the vehicle), tensioner pulley off and cam sprocket kind of dangling. The camshaft broke. After getting it home and removing the valve cover the camshaft was broken in 2 places: right next to the inner edges of both the #1 and #2 bearing cap. The #1 bearing cap was broken as well. While in there I also noticed that the tensioner wasn't bolted to the head.

So, in trying to figure out why this happened I remembered installing an extra camshaft I had, since the keyway was broken on the one in the car. Maybe that camshaft was from a mechanical head? If the tensioner nut came off and I lost belt tension could that cause the camshaft to break? I remember tightening the belt tension and I would have had to tighten that nut, I couldn't have left it off. Maybe camshaft was out of balance and the wobble loosened the tensioner nut? I remember watching how the belt tracked on all sprockets with the car running and it stayed centered. Hmm.

While thinking about if it will be worth trying to repair this I remembered reading that bearing caps aren't interchageable. If this is the case then I will have to look for a new head, right? Or, is it possible to have a different cap machined to work on my head and then look for a camshaft?

tawney · Post by **tawney** » Tue May 22, 2007 9:07 pm

Seems like you're thinking the cam vibrated/broke and caused the other problems; not sure, but sounds to me like it could be the other way around: tensioner got loose, then the belt got so loose that the cam was no longer in sync with the crank, and then the pistons hit some valves, and the valves broke the cam. If so, I would suggest removing the head; your pistons might be okay, but you'll have some bent valves.

libbybapa · Post by **libbybapa** » Tue May 22, 2007 9:37 pm

Even a wobbly camshaft wouldn't be able to loosen the tensioner nut. Hate to say it, but probably the tensioner wasn't torqued properly and as mentioned, the belt jumped time and the pistons hitting the vales broke the cam. You should pull the head.

Andrew

calebc3 · Post by **calebc3** » Tue May 22, 2007 9:51 pm

The more I thought about it the more that seemed like the only option. Easier to try to blame it on something else than on your own mistake.

However, I saw this question asked before without an answer so I will try again: What will happen if you run a camshaft from a mech. head on a hydraulic head?

tylernt · Post by **tylernt** » Tue May 22, 2007 9:57 pm

A broken cam cap is not the end of the head. A machine shop can mill the flat bottom of the remaining caps to make them all a bit shorter, then install a new cap and line bore them all to the correct size. Then you're good to go.