Inlet Camshaft gear bolt Sheared!!! [update]

r055 · Post by **r055** » Sun Jul 29, 2007 3:41 pm

Sitting on the outskirts of new cumnock waiting for the flat bed to turn up.
RAC guy tells me the timing belt has snapped.
I know I won't know true extent of damage until head removed but what is likely cost of fix?
...And before anyone asks, Timing belt was changed 8 months ago...

Ross

Sanjøy · Post by **Sanjøy** » Sun Jul 29, 2007 4:56 pm

AA Parts & Labour ?

Sorry to hear it dude.

robin · Post by **robin** » Sun Jul 29, 2007 4:58 pm

Hmm - for it to snap seems unlikely then - perhaps the pulley came off or the pulley bolt snapped?

Anyway, assuming there has been valve to piston contact then you will need some new valves and probably valve guides. If the valves bent over enough to get stuck between piston and head you'll be looking for new pistons and possibly a new cylinder head. If you need new pistons/head and the car has >50K on it I would seriously be looking to swap for a lower mileage second hand engine rather than repairing the one you have - they come up quite a bit.

If it's just head repair and new valves I would get the head fixed and refit.

Either way, it's going to be expensive ...

Best of luck,

Robin

r055 · Post by **r055** » Sun Jul 29, 2007 5:50 pm

Nope sanjoy - RAC
I was going to see remainder of this cover then try to join AA.

Thanks Robin. The patr guy said its probably the pre-tensioner that's failed. Potentially not replaced at time of belt change?

In recovery truck just now.
What's the best thing to do first? Take cam belt cover off and survey damage or check head?

Ross

robin · Post by **robin** » Sun Jul 29, 2007 6:08 pm

Tensioner failure would make sense - again, not in 9 months of having a new one fitted, but perhaps it's a duff part.

You need to remove all the timing gubbins to remove the head, but you also should align the crankshaft to the timing mark before removing the head, which is going to be tricky if the belt has already come off/slipped.

TBH, where you are at, I would just leave the crank wherever it has ended up and remove the timing covers then cylinder head and inspect the damage.

You will then need to fashion some liner clamps to hold the liners in place while you rotate the crank to the correct position before refitting head etc. See the alcester racing sevens site for a homebrew liner clamp solution (it was somewhere in the great engine rebuild project).

If you've gubbed the pistons you're going to need to do an engine strip down or replace the bottom end, so the liner clamps will be the least of your worries!

Cheers,
Robin

BiggestNizzy · Post by **BiggestNizzy** » Sun Jul 29, 2007 6:35 pm

Sorry to hear that m8, wondered where you had gone

Hope it's not to serious

Had a look at the alcester racing sevens site if you need a plate made up I can get one made in 3mm Zintec I will need sizes or better a drawing and you will have to come get it as I am off the road too

ExigeKen · Post by **ExigeKen** » Mon Jul 30, 2007 11:18 am

Sorry to hear that Ross I hope you get it sorted soon.

Rich H · Post by **Rich H** » Mon Jul 30, 2007 11:40 am

Sh!t dude

Get the timing covers off and have a look at the belt. Take some photos.

r055 · Post by **r055** » Wed Aug 01, 2007 8:24 pm

Finally got time to take timing cover off tonight...

The front inlet camshaft timing gear bolt (no.3 below) that holds the gear onto the camshaft has sheared at the head meaning that the exhaust cam was turning but the inlet was not at the time

now i need to find someone thats brave enough to take the head off and inspect the damage - im not brave enough!

p.s. i did take photos, but left my card reader in the office

robin · Post by **robin** » Wed Aug 01, 2007 8:46 pm

I think you're in with a chance of there being no massive damage.

Do you know for sure there was valve-to-piston contact? The inlet cam can probably sit in a position where although two sets of inlet valves are not completely closed, they're also not completely open - I think there is 3mm or so of clearance from valve to piston.

If you think that there might not have been valve-to-piston contact you could consider removing the cam ladder, cams & spark plugs (in this state, all valves will be closed, but there is no compression due to spark plugs).

With the cams removed you can rotate the crank shaft to the proper timing mark (dimples on crank timing gear straddle the mark on the block). You need to do this slowly and stop if there is any resistance to rotation, as it means valve-to-piston contact.

If there is no contact at this stage, refit cams (having removed the broken bolt), cam ladder, pulleys and timing belt (obviously with all the timing marks aligned).

Repeat the turning over - this time the valves will open/close and there could still be valve-to-piston contact if one is bent and sticks. If not, refit spark plugs - now each half rotation should generate compression and a dump-valve like sound when the exhaust valves open one after the other. If you get compression on all four, you have got away with it I reckon. For good measure you could now use a compression tester and make sure you get good compression on each cylinder. (edit: but don't attempt to run the engine without resealing the cam ladder properly)

You can do all this without expense. If it looks good, you would need to split the head again, clean up and reseal properly with the anaerobic sealant, then fit new camshaft seals - total cost about 30 quid.

Again, if it looks ok, I would then fit a new belt and you might as well fit a new tensioner. I would not have thought the tensioner was damaged, but who knows!

Beyond the time, you're not wasting much going this way - if it turns out the valves are bent, you'll need to split the head anyway to remove the valves ...

I would love to help, but just don't have the time right now.

Cheers,
Robin

Rich H · Post by **Rich H** » Wed Aug 01, 2007 9:07 pm

I have a set of standard cams and pulleys you can have for nout if you need them.
(I also have a car cover that I still haven't managed to post

)

Post by **campbell** » Wed Aug 01, 2007 10:46 pm

Phshew, some job Ross. Rotten luck.

As ever, race engineer style diagnosis direct from the Jedi Temple

You probably got the message, but the detail of what can and can't be done and in what order is very important indeed. From my limited knowledge, dislodging the liners by moving the crank/pistons with head off is fairly terminal. Though I am *not* the best qualified to comment, I only have experience of my own head change under the tight supervision of Jedi Master Iddon.

If you can't muster the balls to have a go yourself, and I know I couldn't, then it's time to seek out a very, very trusted garage and go through the position with them step by step. I guess in theory they could cost you a lot of money yet claim it was "the damage" and not their fault...

We are a little short on recommendations right now, but maybe this is a chance for one of the independents to shine through.

Fingers crossed...but maybe it is indeed time to treat yourself to a low mileage K !!

Campbell
(2p worth non-tech faction)

r055 · Post by **r055** » Wed Aug 01, 2007 10:55 pm

thanks for the comments guys.
i know of a good independant local mechanic that works on race cars who im going to phone tomorrow.
I'll print off Robin's instructions and see if he would be prepared to follow.

unfortunately I could not bring myself to doing this in my driveway without cover, experience or the right tools so I'll leave it to the professionals I think

hope to be back on the road again soon!

scrossed

tenkfeet · Post by **tenkfeet** » Thu Aug 02, 2007 3:20 am

wonder if that is why they say you should not turn the cam belt using those bolts?

robin · Post by **robin** » Thu Aug 02, 2007 8:37 am

In the same way that the crank shaft bolt will eventually sheer if it was ever run loose, the cam shaft bolts will eventually sheer if they were ever run loose. Bolts aren't designed to be used in that orientation and the shock loadings on it will be high (the camshaft doesn't want to turn and will move in fits and starts - if the bolt is loose each fit and start will knock the pulley onto the side of the bolt, hammering away at it).

When ross recovers what's left of the old bolt it will be worth measuring it to see whether the bolt had unwound itself before breaking (my guess).

Cheers,
Robin