Crankshaft Pulleys....and what happens when they come loose

[RedRacer]

The Prelude may have died a premature death.

The bolt holding the crankshaft pulley worked it's way out. Had been working it's way loose every day, apparently since the last timing belt and water pump install, and it finally came almost completely out while I was interstate driving Saturday morning. The belt started wobbling with the pulley and slapping up against something next to it as it spun/wobbled crazily, and began making a terrible noise in doing so, which immediately caused me to pull the car off the road, into a parking space and shut the engine down.

Cranked the engine again and opened the hood. Looked down into the area where the noise was coming from and immediately could see the crank pulley wobbling like a child's spinning top toy. Shut it down again and called for a tow. Thank God for AAA Roadside service! Had to tow it home as my mech is garaged downtown and no way was I leaving the Prelude outside on a downtown city street for two nights! Had to tow it from home to the shop Monday morning. W/out my AAA towing, it would have cost me over 300 bucks for the two tows!

Broke it down Monday morning and found that the pulley is totally worn out or, as we say down here in the south, "wollered" out.... crankshaft and timing gear alignment notches are somewhat out of align.....not a lot, but enough. Going to put a new pulley on and tighten it to Hell and back and hope that the crankshaft isn't worn or beat down. IF it is........ new engine time.

[RedRacer]

Originally stated by SpiffyGuido:


Start praying that your main crank bearings aren't rattled flat.

For those reading who are wondering why RedRacer is rabbiting on about his crankshaft pulley being loose, a seemingly trivial problem, allow me to explain:

The crankshaft pulley on a Honda engine also acts as one of the harmonic balancers for the crankshaft (which despite being quite small as far as crankshafts go, is VERY heavy due to the high grade steel Honda fashioned them out of). This is a simple enough system, but should the pulley ever get loose, as Red's has, the balancing function of the pulley will go away. If the pulley is roaming back and forth on its shaft while spinning at high rpm the crankshaft is going to be dancing all about, likely transferring some pretty profound vibrations into his main bearings. Simple though it may sound, this can very quickly spell certain death for an engine, and a potentially violent death at that.

RedRacer has noticed this problem and has wisely decided to re-tighten the bolt. Two scenarios will now unfold:

Scenario A: Red's engine will prove to be surprisingly resilient to the added vibrations and live out its natural life. This is the happy ending, and the one we're all hoping for.

Scenario B: Red's engine is damaged. Even though the pulley is now tight, the bearings have already developed flat spots. While running, the engine could spin a bearing, which could cause total destruction of the rest of the engine. Bent valves, shattered pistons, rods coming through the side of the block, and little pieces of debris finding their way into the fragile vanes of the turbo turbine. All bad news.

I've got my fingers cross for scenario A. With luck, this issue has been identified early enough.

While we're on this topic, I'd like to draw attention to two other things that are indicative of Honda's commitment to engineering.

First is the fact that although RedRacer's pulley bolt was loose, it didn't actually come off, and nor did the pulley. A big part of this good fortune is likely due to the fact that the crank pulley shaft on a Honda engine is equipped with a Woodruff key. Without the woodruff key, Red's pulley would be more likely to continue its little holiday right off the crankshaft and brought his car to a stop leaving him sobbing on the side of the interstate.

Second is the crankshaft pulley itself. These are a very important part of the engine, due to the reasons described above. I often hear of Honda drivers buying lightweight crank pulleys hoping to reduce rotational mass. Reducing rotational mass is a good thing. Don't you think that Honda knows that? Don't you think that Honda would have put a lighter crankshaft pulley on the engine if they thought it was a good idea? Trust me, they would have, but the engine needs a heavy one to keep the vibrations down. I've read way too many posts about people putting lightweight crank pulleys on their engines and then coming back a week later to report that their crankshaft has snapped or their engine had spun a bearing.

[RedRacer]

As for right now, we got a new crankshaft pulley and bolt installed (Honda ONLY) and tightened it up using the giant tool, the socket, the bar, and then the pipe cheater bar that's about 6 feet long that allows you to literally put your whole body into it for tightening.

The grooves on the inside of the pulley were rounded smooth pretty bad in a few places. None of it was completely smooth metal yet though. Well on its way though, had it not been caught when it was. Had to really push hard to get the new pulley on, and it wasn't loose or spinning freely... so that gives me some hope that things are not as bad as they could have been.

Cranked up, sounds good, runs fine. Big sigh of relief at that point.

Drove home fine. I was paranoid at every odd sound I heard though! A dump truck rattled by on a cross street, and I didn't see it but I heard it and I immediately stiffened up and thought OH MY GOD I DIDN'T EVEN MAKE IT A BLOCK FROM THE SHOP AND THE WHOLE ENGINE JUST TORE ITSELF APART!! ... but then I saw the dump truck and heard the noise again..... phew! I felt a lot better.

Brought it home and parked it in the garage. Will drive it this afternoon while on some errands, etc.
We'll see in a few days or a few weeks if anything bad is going to happen. Fingers crossed.

Anyway -- good information given Spiffy. Very good indeed! And you're right .... I would have been sobbing on the side of the interstate..... no doubt about that.

And some more sage advice ...... LOC-TITE!! ANY time you remove a crank bolt, it should ALWAYS go back on with LOC-TITE spread around the threads....especially if you're not going to install and re-tighten the bolt to spec and not use the right tools to do so.

We suspect that this whole bad incident happened because of the last guy who did my timing belt and water pump. My regular mechanic (the guy who built the engine) was out of the country at the time I needed the work done, so instead of waiting, I took it to someone else. BIG mistake. Can't prove they didn't do the job right, but if they had, and if they had used Loc-Tite (which Honda shop mechanics do) it most likely wouldn't have happened.

[RedRacer]

Pulley pics - not the best in the world.

You can see where the inside of the notches are worn flat.

Also you can see where the keypath is well mis-shaped and chewed. NOT GOOD.

[spiffyguido]

It looks pretty ravaged. Tough break.

Lets hope that a similar story hasn't played out inside the engine. No sign of trouble yet I assume. Here's hoping you've seen the end of your troubles.

[RedRacer]

So far so good, 'knock on aluminum'.

I did have a good go of speed and duration Saturday afternoon. We'll just call it a closed circuit....... Ran a constant between 95 - 120 mph for a little over 5 miles. No ill or adverse affects so far. Pulls just as strong, boost is good, noises are familiar. Smelled a little oil burning after I closed it down, but that's due to a leak off the back of the valve cover /distributor area.

My mech told me to drive it every day for the next couple of weeks and we'll know yes or no by the end of that window.