Engine Whine (if that's the right word)

[Matt]

OK, I'm posting for a friend of mine... he has a 92SHO. I think he bought it about 3.5 years ago with 80,000 miles on it. It now has just over 150,000 miles. When he bought it there was always a whine at idle that would increase in loudness and pitch as the revs went up. This got louder until it hit where the second cam kicks in, around 4200rpm's. Anyway this got more and more pronounced until a week ago when the whine was really loud. It would get louder until 3500rpms when it would go away completely. Now, to our surprise the whine is gone completely, even at idle.

But now there is a knocking sound coming from around the timing belt side of the engine where all the accessory drive belts are. The knocking increases with revs, but I don't think it's an internal knock (I had an old 4runner that had a bearing go and it sounded nothing like this. I also stuck a screw driver on the block and there was no vibration.

The only think that I noticed is it looks like the crank pully is not true when it is spinning, like it may be warped or something. There seems to be plenty of tention on the belts and all of the other accesory pullies seem to be fine.

This engine looks a bit complicated to me, so I didn't want to mess with it too much.

Thanks for any help you can offer!!

Matt

 

[sdpatt]

Here we go. Has the timing belt ever been replaced on that car? On the 3.0L (manual transmission) SHO engine, the timing belt is scheduled to be replaced every 60,000 miles. Even if the previous owner had done this, it is again long overdue. I'll bet the timing belt is so loose that it is vibrating. The 3.0L SHO engine is also scheduled to have its valves gapped every 60,000 miles. My guess is that the first owner sold the car at 80,000 miles because he didn't want to pay for the timing belt change or valve gapping maintenance.

The crank pulley may be loose because the crankshaft damper bolt has come loose. It is very important that this 19mm bolt be checked for tightness. It should have been torqued to 133-126 lb-ft by either Ford or the shop that may have replaced the first timing belt. If the damper is loose, it has probably worn the crankshaft and possibly damaged the keyway. Hope that none of this has happened and that the damper just isn't true, but that shouldn't have happened. There is also a chance that it is an underdrive pulley from an after market manufacturer that just isn't up to spec. I'd have to see it to know.

The change that happens to the engine at 4,000 rpms is that the butterfly valves to the secondary intake runners (larger diameter, shorter length) open and allow the engine to breathe through both the long, narrow low rpm runners and the greater flowing secondary runners. The engine has four camshafts and they are always working. There is no variable cam timing or high rpm cam profile like some of the newer engines. The SHO changes its tune with the staged intake manifold.

 

[Matt]

Has the timing belt ever been replaced on that car?

That's a good question... I doubt that it has since my friend has had it, although I know it was at a Ford dealership for sometime, but I don't know what was done with it. Same goes with the valve adjustment, I'm not sure, but I doubt it. How much money do these usually cost to have completed?

Could the previous whining have been the timing belt beginning to come loose? Now its just to the point of vibrating, like you say? It's just strange that a noise the car has always made just goes away and leaves him with a knocking sound...

As for the crank pully, my friend never replaced it with aftermarket, so I'm going to assume it's stock. I'll check the torque on that one tomorrow.

I noticed your car has over 250,000 miles on it, what kind of miles can one generally expect out of one of these? To be honest, I'm surprised it has made it to 150,000 with minimal problems (the engine anyway)...

Thanks for all the info, you learn something new everyday.

Later,
Matt

 

[RStalveyARFF]

Matt,

If your friend in fact needs a new crank pulley, I have a used one right now in my stock, and I also run my own shop if you're baffled and it isn't too far of a drive for you. What Scott said definitely sounds right, he is the SHOForum guru.