Timing belt replacement & problem

[vic124]

Hi All

I have a problem and I'd like your help if possible.

A few days ago I replaced the timing belt in my brother's 124 Spider. When I rotated the crankshaft I realized that the camshafts didn't line up after the first rotation. I then rotated it once more and it got to a point I couldn't rotate it any more. I then pulled the belt off and attempted to align the camshafts and the crankshaft to top dead center. I was very careful not put any pressure to damage anything. I made sure the auxiliary valve was correctly aligned to and I fitted the new timing belt properly this time. I rotated the engine a number if times and it all aligned well and there seemed to be no problem. When I started the car there was this huge bang - like a gunshot. I switched the car off. When I restarted it, there was this fairly loud tinking noise while idling and so switched it off again and there was this strange hissing noise. I pulled the cam covers off and rotated the crank and nothing seemed visually unusual.

My question is, have I done some damage to the engine? Has anyone had this problem before? Any advice on what it could be and what I should do to diagnose the problem?

Your help will be much appreciated.

Cheers
Vick

[klweimer]

vic124,
Doesn't sound good. I'm guessing here, but I think the loud bang was your crank hitting the aux shaft. I suppose it could have been a piston hitting a valve, but I don't think it would make that kind of noise. I'd start by running a compression check on each cylinder. I would also turn the engine over by hand and watch the valve shim buckets in the head to see if any of the valves are not closing once the cam lobe lifts off the shim. This would indicate a bent valve.
Let's see what others think...
Kirk

[nelsonj]

Was the bang a backfire? That can sound like a gunshot.
Did you do anything to the distributor that would get the spark timing out of whack?

As for the "ticking" sound, make sure the timing belt hasn't sliped and that your cam timing is all aligning properly. Rotate by hand (removing the plugs makes it easier).

Let us know what the compression results are.

Good luck.

[Spider951]

Is the car fuel injected? On my 1981 FI Spider I have experienced backfire if the airflow rubber boot becomes detached from the Air Flow Meter (AFM). The boot is just held on with a standard hose clamp and sometimes has a tendency to loosen, allowing air to leak and bypass the AFM. The car may run, but very roughly and commonly with a loud backfire. Was the bang a metallic one or just a pop like a backfire? Steve

[narfire]

If it wasn't a back fire, usually no "tinking" noise afterward in my experience, as mentioned I'm thinking the #2 rod whacked the aux shaft. Perhaps consider taking the timing belt belt off and pull the aux shaft out. Careful when doing this as if it is broken, the broken end can fall into the oil pan. If it does, then you have a fishing expedition that could take a couple of hours. If the aux shaft comes out without the back end, I'm thinking using a strong magnet to carefully try and pull the remainder of the shaft out.

[vic124]

Hi All

You won't believe this.

On Monday night I had a helper and we checked the compression on each cylinder to check if I had damaged a valve and all the readings were positive and consistent at about 160psi.

I then removed the cam cover and started the car, played with the distributor and there was no noise. We put the cam cover back on and the noise came back. One of the wheels or something was obviously touching the metal cam cover as the engine turned. We fixed the problem by putting rubber washes in between the cam cover and the engine.

Conclusion is that I was being paranoid when I heard the rattling noise thinking it was something more serious.

Thank you everyone for your tips.

Cheers
Vick

[nelsonj]

Sounds like good news - no valve damage and the car is running smoothly without noise.
However, you need to have a good seal between the cam cover and the cam housing or you'll leak oil all over the place, and likely fill the spark plug wells with it.

I'm not sure what you did with "rubber washers", but make sure you have a good seal. You could look for thicker rubber seals for the covers, or you could "double up" two thinner ones and hope you can get a good seal that way.

Again the good news is this will be a cheap fix and there is not damage. Congrats.