2001 Deville - Engine Noise

jdot1

2001 Cadillac DeVille owner looking for pre-mehcanic visit information on engine noise issue

Just looking for advice from anyone with experience on these cars, it's always nice to have an idea of what I might be looking at before seeing the mechanic.

I'm 71 with a very nice and comfortable black 91 deVille. I use the car frequently but have managed to maintain fairly low mileage at 51,000 or 86,000 km. OR at least that is what I believe to be true as I did get it used a few years ago.

The issue is there sounds like a rough noise coming from the engine, or at least under the hood, until now it has ran very quietly. Any idea's, is this common? I checked the boards but didn't see anything.

Joe

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sorry, I think I found other posts on rough engine sounds, if you have additional advice please add

bolivar

We could use some more info on the noise. Is it a lifter tap? Squeek? Squeel? Rattle?

jdot1

It starts with a high squeal for about 40 seconds. That fades and the motor sounds are just rough as opposed to running smoothly. It sounds like it is overworking itself and that creates a loud noise. Rough going sound compared to its usual smooth hum.

bolivar

Well a squeal - first thing might be a belt squeal. On a 2001, the belt might be 12/13 years old. Look at the inside of the belt, it is segmented with about 5 or so grooves. Get a good light to shine under there, you can't see anything without a good light. If it has cracks, especially if it has small chunks of missing material, this might be your problem. As it slips, it might heat up and then stop squealing.

A Northstar motor also has a separate, very small belt that drives the water pump. It is at the front of the motor on the drivers side at the front with most of it under a cover. It is driven off a pulley off the cam in the front head. It might also be bad. If it breaks, your motor will overheat very quickly.

Otherwise, it might be any one of the other driven accessories on the motor. AC compressor, alternator, PS pump, etc. with a bearing going out on one of them.

Only try the following if you are moderately handy with tools and can be very careful. If you get a dowel rod in your skull, don't come crying to me. Having a professional mechanics stethoscope would be nice. But here is something you can use that will work in many cases. Buy a dowel rod, about 1/2 inch one. You can then CAREFULLY put one end of the rod on the housing of an accessory behind the pulley. Getting it behind the pulley is better because this gets the rod closest to the bearing inside the housing. Again, be CAREFUL. If you get the dowel tangled up with a pulley or the belt, you might be holding an arrow, splinters, or watching a belt come apart. Now, you might not want to believe this. Put your thumb on the top of the rod and stick the end of your thumb in your ear! It works. You will be able to hear closely what is going on inside the accessory. A nice running one will give off a hum. If your hear grinding, thumping, etc this is probably the accessory that is going to fail.

The accessories on a Northstar are tough to get to. One of them, the AC or alternator is far down in the right side of the motor. Again, be careful. There also are probably 'idler' pulleys that keep tension on the belt. Check these also. An idler would be the cheapest thing to replace.

This is just a diagnosis. You are still going to have to replace whatever is causing the squeal and noise. But you might be able to know what it is before you turn it over to a mechanic. And if it is an idler and a mechanic tells you the alternator is failing, you can take it to a different mechanic.