1966 Catalina possible bad main bearing

[pdecheine]

When first started cold I hear a noise from the front of the engine very much like a bad water pump bearing. When the engine is warm there is no noise. I replaced the water pump twice, 5 years ago when I first heard the noise and a few months ago when the noise returned. I have run the engine with both fan belts removed and the noise is still there. Also, when the engine is started cold, run for a minute or two, shut off and restarted the engine is quiet. Is this likely a loose main bearing cap or bad main bearing? Should I change the cam bearings if I go after the mains?

[Larry]

You don't mention what sort of noise. However, water pump noise would, I guess, be in the squealing range.

A main bearing noise is usually a heavy sort of thud noise because of the heavy load they carry. But that doesn't mean one starving for oil wouldn't squeal either. Bad or loose bearing caps don't repair themselves either when the engine warms up. If anything, the hot, thinner oil would make a main bearing worse. Unless, of course, you have a lot of oil blockage and the warm oil then manages to sneak into the restricted passageway and deliver some soothing relief.... but that is kinda far fetched.

Without knowing what sort of noise you are hearing, it is hard to guess at the problem. But, just as a shot in the dark, how many miles do you have on the engine? Pontiac is notorious for throwing timing chains at about 120,000 miles (almost like clockwork). While that doesn't usually give any telltale sound warnings, it could still be worth considering.

Noises have a way of sometimes appearing one place while originating from another. Have you thought about the fuel pump arm? I've heard fuel pumps squeak like crazy sometimes. Try removing the fuel pump and if it will run long enough on the fuel in the bowl to check for the noise.

Before tearing into it deeply, give me a yell and I'll run over and check it out with you. You're just down the road.

[pdecheine]

Hey Larry,
Thank you for your reply, The noise is kind of a continuous gong thump rattle! In other words, hard to describe. I had 2 opportunities to get a more informed opinion as to the cause of the noise and both times the engine was silent. I think she knows when someone else is listening. It it very generous of you to offer to have a listen, and I would greatly appreciate it. The engine was rebuilt about 60,000 miles ago and I would hate to have to dismantle it in vain. I live in the Lockwood and University Park area and usually have Monday and Tuesday off.

[Larry]

"gong thump rattle"... sounds like some of my wife's Caribbean music!

I sent you a private message for time and directions to check it out.

[pdecheine]

I'm going after it with a stethoscope today. Fuel pump will be the first stop.

[pdecheine]

I can only hear the noise when touching the upper oil pan about halfway between front and back. It is louder on the passenger side. I hear no noise near front and rear main bearing, oil filter housing, heads, or the engine block. Without the stethoscope the noise is loudest under the car at the front of the engine. Removing spark plug wires one at a time has no effect on the noise. I'm tempted to continue driving the car until it gets worse.

[Larry]

You did what I was going to suggest if you could get a hold of a stethoscope. That was all I could think of to try to isolate it somewhat.

It doesn't appear that something as severe as a bearing is going on. Especially since you say it goes away when it warms up. Did the noise stay all the while you checked this time? Did it then go away again?

The oil pan is pretty much like a bell when it comes to transmitting noise, but the problem remains what noise and from where.

The spark plug test helps for checking bearing knocks, and seems to have been negative. Do you have any vibrations? The heavy noise you describe along with a rattle also is puzzling. Can a harmonic balancer make noise? What's the age of the timing chain and gears? You say it is mostly toward the front.

Did you try the stethoscope on the timing cover?

[pdecheine]

Yes, I did try the timing cover. I have decided not to tear the engine down and will wait for the noise to appear "reliably" so I can have more educated ears listen. Thank you for your advice.

[Larry]

If anyone knows about what goes on inside a Pontiac engine, it's Bruce!

What he describes fits well for a noise that doesn't really seem to be there... if you know what I mean.

The idea of a loose rocker arm is still a possibility, and certainly worth checking. It might be a god time to even put on some of the locking nuts for the rockers.

[pdecheine]

Thank you Larry, I really appreciate your efforts to help. I will contact Bruce thru his website. I guess I will have the engine completely rebuilt. Are you familiar with Tampa Bay Engine Shop? They will completely rebuild my engine and provide a 3 year guarantee. I don't want to get stung again like I did when Yow's did the rebuild.

[Larry]

I used Yow's a long time ago but don't know who good they are now.

Have you thought about Ken's Speed & Machine Shop up in Brooksville? He is a big time Pontiac builder. (512 S. Main Street, Brooksville, FL 34601
352-796-8800 / Website: http://pontiacdude.cc)

They have promised our members a 10% discount on their machine services. It's probably no farther than the Tampa shop. Give them a call and discuss it with them. Remind them that they have promised this discount a long time ago. Have them call me if they are in doubt about it (or the person you talk with doesn't know).

[pdecheine]

Thanks Larry, I will give them a call.

[pdecheine]

Hi Larry,
I replaced the harmonic balancer and cured the problem. Thanks to you and Bruce for your input that slowed me down, made me think, and prevented me from spending thousands on a "worst case scenario." I have never trusted the rebuild so I jumped to conclusions when the balancer failed.
BTW, I met a guy (forgot his name, duh) who has a very nice 73 GTO with a 455 engine. He said he has ANOTHER one at home. One of the perks to living in Florida is retirees bring their cool cars with them when they relcate here!

[Larry]

WOWIE! ZOWIE!

Boy, is that some good news! I know I had asked about the harmonic balancer, but it was just a throw-out question.

I have seen bad ones... even chased an outer belt ring across the parking lot once! I've certainly seen the outer belt pulley ring slip on the inner hub too- that becomes obvious when the timing marks seem to magically disappear one day! By brother even had a loose balancer, so he tighten the crank bolt real tight-- and welded them together. Pity the poor next guy who got the car if he needed to do some work there.

Don't know how you found the problem, but sure are glad to hear that you did. Guess it's just one more of life's lessons about moving slowly.

Good news for a Monday! Thanks for letting us know.