Timing is everything

My 1998 Ford Escort ZX2 with 153,000 miles quit running on the highway. The engine turned over but seemed to have no compression. I took the timing belt cover off thinking the belt had broken, but the belt looked fine and it turned over with the engine. A mechanic told me that the engine had spark and fuel, but the idler pulley had “grenaded”. Would this cause the no compression problem? Apparently, one of the valves was bent as this is an interference engine, so a new cylinder head was installed along with new pulleys and a belt. Then the mechanic said that the coil pack was bad and dropping two cylinders, so he installed that too. I’m wondering if the coil pack was the problem all along.

What the hell does it mean when he says the idler pulley “grenaded”?

The mechanic did not offer to show you the damaged cylinder head? this is a red flag.

It’s a plastic pulley, and supposedly it came apart. I’m not sure if that would cause damage to the valves.

I had to leave the car with him, as I live and work 160 miles away.

I suspect that since the engine had no significant compression after if stopped the valve timing really had slipped off. Yes, an exploding idler could do this. And yes, this cound cause internal damage in an interference engine.

If it were the coil pack all along you would have had normal compression after it stopped.

I’d guess that the coil pack problem is simple coincidence.

According to the Gates timing belt guide, the engine in your vehicle is NOT an interference type engine. So there should be no valve damage if the timing belt/tensioner let go.


There is no evidence of malfeasance. The timing belt could have jumper timing at 2,000 rpm, during cruise, and, later, turned the camshaft (apparently, normally) when cranking. If the crankshaft-to-camshaft timing were checked, before anything else were done, that would have shown whether the timing belt had jumped teeth (timing), or, not. Now, it’s ex post facto time…that is, unknowable.
A valve can bend, burn, crack, for any number of reasons. The valve may have been that way for a long time.

What gets my attention is the requirement for a NEW cylinder head,what was the reasoning here? What type of evidience is this,just the facts.