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Today I had a 740T in for a broken timing belt. A very routine job.
When I took off the upper timing belt cover, I saw what amounted to an intact and new-looking belt. That raised a big red flag. I turned the crankshaft and the cam didn't turn. The teeth on the belt were stripped at the crank gear. The question was, WHY?
First, the car sat for 18 months or so. We fired it up a few weeks ago after replacing the computer, and it ran perfectly. I had it running most of the afternoon last Thursday, and shut it off like normal. Yesterday it wouldn't start, and the sound clearly indicated a broken belt.
That said, the answer was right in front of my eyes. The #1 exhaust valve was stuck closed, holding the camshaft from turning past it. When I rotated the cam the other way, three of four intake valves were stuck open. The upper engine was full of oil, and the camshaft was clean, not scored or oil starved in any way whatsoever.
The cause? Rotten reformulated gas. I yanked the intake manifold, and it looked as if someone had poured brown epoxy all over everything.
Also, this was the SECOND car in two weeks to fall victim to bad reformulated gasoline. The first one was a Trooper that totally gummed up.
Having seen 2 of them in rapid succession, the cause is obviously bad fuel. The remedy is to treat the gas with stabilizer when you store it. No exceptions--if you're using the reformulated gas. Idling causes a buildup of varnish and gluelike substance on the intake and exhaust valve stems. When the car is shut off, it cooks onto the valves in whatever position they come to rest in, and the next time, the crank gear just strips out the timing belt against the frozen camshaft. It is that severe of an issue, or it can be.
I was NOT able to correct the problem. Tomorrow the head has to come off.
If you are storing a car for over a few weeks, stabilize the gas. It shouldn't suffer this kind of fate without long idling with bad gas in the tank, but it could do it. Don't chance it. This is especially crucial for multi-valve engines, which would face certain damage from valves stuck in the open position.
Unfortunately this is just one of the many ills of reformulated gas. Make sure you plan ahead if you are storing your car. I'll provide more details and hopefully pictures. I was amazed, and apparently the shop has had a couple others like this before.
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