loading...

What would cause a camshaft pulley (#12 in the pic below) to come loose TWICE, even after being properly torqued to 27 lb. ft? Car is a 96 Civic Ex with a D16Y8, timing belt is new and was working fine for a year before this took place.

Driving on the freeway, engine shuts off randomly, get the car towed home, pull the VC and the upper timing belt cover and I see the pulley bolt (#20 in the pic below) like halfway out and the little nub on the inside of the pulley is snapped off.

Inspected camshaft and rockers, installed a new pulley to 33 lb.ft. just to be safe and re-tightened the timing belt, checked compression and got 180 across the board, car drives fine for ten miles and then the pulley snaps again, same exact problem!!!

WHAT'S GOING ON :taz:



HOW IT LOOKED AFTER THE SECOND TIME



THIS PIC SHOWS THE NUB THAT KEEPS SNAPPING OFF

BlueEM2

iTrader: (1)

Probably excessive camshaft play causing vibration... Either that or improper installation. Any check engine lights before it went? OEM Pulley I assume?

ezone

2 things come to mind.

One, is the pulley bolt was simply too loose: Have you checked the accuracy of your torque wrench lately? If it is out of calibration, (torquing too loose) that might explain it.

Two, is maybe the cam is locking up or in a bind: Have you ever had this overheated? Head ever been milled?
My thoughts here would be to pull the rockers and cam journal caps and inspect journal area surfaces for galling and other signs of the cam locking up, and then reinstall only the journal caps without the valvetrain and see if the cam spins freely in its journals. A head that has been significantly warped (even if it was milled flat again) will still have the journals out of alignment, and not allow the cam to spin freely.

loading...

The journal shown below in the middle has a small ridge sticking up and I found some tiny metal shavings in this area so I'm pretty sure this is the problem. (If you look closely you can see how it looks rounded near the exhaust valve spring.) Also the camshaft has a hairline crack that goes all the way down the threads, but I'm not sure if that was there before or if it happened when the camshaft jammed this last time. What do I do about this? New camshaft and pulley for sure, can I get the journals redone or something or do I have to replace the whole head?



Also there are these weird cracked areas next to the valve springs that don't make sense to me because the valves don't move that way haha.

ezone

For the moment, I'm going to assume this is not a lubrication-starvation issue (are the cam journals blued or darkened?)
Unless you know if this engine has eaten any bearings in the past.
Or overheated.

===========


Heavy wear visible in the middle journals, but very little in the outer ends?

Observe wear marks on the upper journal halves. Are the caps on the ends showing wear, but the middles are not?

Kinda makes me think this head has been warped. Probably severely.



The cylinder head will typically lift up in the center when severely overheated.

That would put upward pressure on the middle cam journals, and probably cause your journal issue shown here.

A warped head that was only milled flat on the head gasket surface-- is still warped on the other surfaces.
That includes the cam journals.

I've read about cams breaking and seizing due to warped heads and journals being out of alignment.

(This is what makes "Baking and Straightening" a warped cylinder head a good thing.)

The sharp-cornered gouge marks around some of the valve springs makes me think someone has done a valve job, and wasn't very careful about it..... I don't think it left the factory with all those ***** marks.


=========================

How to fix it?
Really depends on what the cause of the problem is....

If my guess about the overheating and the head being warped at some point is accurate, then you need to replace the head and cam. There really isn't any way to straighten it out now that it has been milled.

A machine whop MIGHT be able to line bore it and machine it to fit a set of bearing inserts, but I'd think the expense would be higher than a replacement head (used?) and gasket set.



====


If this engine ate a bearing in the past, say like a connecting rod bearing, then metal could have been sent throughout every oil passage in the engine, including the head. If it wasn't thoroughly cleaned out at that time, then this might explain if this failure happens to be caused by oil starvation. Play this by ear.

BlueEM2

iTrader: (1)

Ouch!

loading...

Thank you sir, new head and cam it is. There were no bearing issues or any other issues for that matter. Would I be able to reuse the rocker arm assembly?

ezone

Ok,
Do you mean it's never been overheated, or just not that you know about?

A used head from a running engine would likely have everything on it, but I suppose you can use your rockers and shafts if need be on a rebuilt. If no uneven wear patterns at any of the contact areas, then go for it.


If you go with an unknown head, it might be in your best interest to figure out if it has been warped and milled. Most machinists would number stamp a head if it
Wait wait wait.....Make sure the new cam spins freely. Torque just the caps on without any of the rockers and make sure it spins freely.

Fliptard

1. Make sure the cam caps are FROM THE HEAD, you can not switch cam caps from one head to another, they are made specifically to each head.

2. you could have the cam journals line bored, which may work, but if the heads warped, it may make the journals too big.

3. Cam caps were over tightened, causing the cam to bind and eventually break.

4. To Be safe, I would get a new head (if used, have a machine shop check it) and make sure it has the cam caps the came with the head from factory. This is almost impossible to actually confirm, but if it at least comes with ALL of them, you should be safe.

loading...

To avoid problems with the cam caps I'm just gonna buy a new cylinder head with everything attached. Should I do a piston ring job and hone just because everything is taken apart or see if I get good compression numbers first?

ezone

Parts like this are machined together as a whole when new, than they are matched to that spot for the rest of their natural lives.

I kinda figured this just goes without saying. Anyone with any time in this trade should already know this.
Any used or reman head should arrive to you as stated.



Compression check cannot tell you about the oil rings at all.

How many miles on it now?
How long do you plan to keep it?
Does it consume oil?
WILL it consume oil?

Now would be the time to do rings, if you are going to do them.
I probably would not hone anything if the block is still in the car, just clean the ring grooves in the pistons really good before replacing the rings.

loading...

225,000

Until it dies

Nope, not when it was running.

I dunno lol.

ezone

That's a lot of miles (to me).


If I thought the rest of the car will last that long, and actually planned on keeping it that long, then I'd probably do the rings.

JMO. YMMV.