Main Bearing Question

[mmulcahy1]

My Dad has an '03 4Runner with just under 90,000 miles on it. He's been experiencing a tapping sound for the last few weeks. Since it was almost due for the timing belt/water pump change, he took it in to the stealership to get the work done and have them check out the source of the tapping sound. They told him that it was the "main bearing."

What is the "main bearing?" Iv'e heard of it before but have no idea what it is.

Any help would be greatly appreciated.

[mmulcahy1]

My Dad has an '03 4Runner with just under 90,000 miles on it. He's been experiencing a tapping sound for the last few weeks. Since it was almost due for the timing belt/water pump change, he took it in to the stealership to get the work done and have them check out the source of the tapping sound. They told him that it was the "main bearing."

What is the "main bearing?" Iv'e heard of it before but have no idea what it is.

Any help would be greatly appreciated.

[kathyricks]

The engine crankshaft rides in a bunch of "main bearings". About the only way these bearings can become damaged is from insufficient lubrication; e.g. running the engine very low on oil.

I'd take the truck to another dealer for a second opinion (if you are sure the engine never ran severely low on engine oil).

[Hi Volt]

Definately get a second opinion, unless they pulled the oil pan for inspection, I can't see then calling a main bearing ( short of them knowing of a common problem with these vehicles). A tapping noise is more likely a rod bearing or wrist pin bushing as opposed to a failed main bearing. To produce a tapping noise from a main bearing I would certainly think more than one would have to be worn to allow that much movement of the crank to actually make noise against the mains. A worn thrust washer can also do it, as well as a loose crank pully or worn keyway. Is there any loss of oil pressure to indicate a badly worn bearing ? To diagnose the problem it would be very important to know when it happens such as hot, cold, idle, high load, acceleration, deceleration, does the pitch or volume change ? if so when ? How long has the noise been around and has it gotten worse over time ?

I am sure that we can offer some opinions on what the issue may be with a liitle more information on the noise.

[mmulcahy1]

The tapping noise gets louder when the engine is at optimal temp. The tapping is loudest in reverse and probably the lowest volume is in drive.

My Dad is very faithful about changing the oil. It's done about every 4,000 to 5,000 miles. As a matter of fact, the day he got the oil changed last (about 3 - 4 weeks ago) is when the tapping noise appeared. He took it directly back to the place that changed the oil (a Mom & Pop joint close to his house - first time there, too) and they told him that they had no idea what is causing the sound. Said they didn't get into anything that could have broken, anyway.

MOre info is always apeciated!!!!

[Hi Volt]

Does the tapping noise increase proportional to engine rpm and/or is it present only in motion ?

[Burger Steak & Eggs]

How about the engine mounts? Maybe there is intermittent physical contact between something on the engine block and a frame member.

[Hi Volt]

That could be, I am guessing it has more to do with the effect of what gear it is in and the relative engine movement (torque).

Just a thought, if this happened just after someone worked on the vehicle, check for a dropped tool or something, that may have wedged in the frame rail and be close enough to hit the engine block or exhaust manifold. As the engine torques it can vibrate up against the object and make noise. There is different movement between drive and reverse so that may account for the difference in loudness you hear. As things heat up they expand and that can close the tolerance and make it sound louder 'hot" as well. Just a guess, but maybe it will be lucky.

[mmulcahy1]

I don't think it can be a tool that has been dropped or lodged within the engine [compartment]. The tapping noise happens at idle (when fully warmed up), drive and as stated in my last post, in reverse - where it's the loudest.

My Dad had the timing belt and water pump replaced last week at the dealership. They thought it was the fan that was causing the noise and replaced it as well. When they finished and got the engine up to operating temperature guess what, the tapping was still there.

That's when they came up with the diagnosis of the Main Bearing.

[reelmagic]

Its the bearing at the front,middle and rear of the crankshaft that supports all the piston rods.
Usually its the rear bearing/seal that goes bad and leaks oil on your driveway.
Very expensive repair!

[Hi Volt]

The plot thickens, however I doubt it is main bearing for the reasons in my earlier post. Really difficult to call unless tha pan is dropped.

[Eddie]

Originally Posted by Hi Volt

The plot thickens, however I doubt it is main bearing for the reasons in my earlier post. Really difficult to call unless tha pan is dropped.

Agreed,I can't believe they're saying it's a bearing when the oil pan was never removed.
Did you check the oil level? Why do I get this feeling the mom 'n pop might not have put oil in then filled it when his dad went back to the shop?

[mmulcahy1]

Absolutely no sign of any oil leak - if that's what's needed to help with diagnosis.

The Mom and Pop shop didn't do anything like add more oil - the level is fine.

[HOGWILD]

Quality maintainers even at dealerships are hard to find, good luck! Is Rich at American the one that told you main bearings?

[mmulcahy1]

I have no idea who my Dad spoke with at the dealership. He plans on taking it in to get it fixed (under warranty) after the holidays.

BTW, why do you ask if it was Rich?