Snapped cambelt, next step?

[saintjamesy89]

Hi all, if you haven't seen me moping about the blog section the you'll not know that the GT's cambelt has snapped at some point since it was last running (last October). As I am an engine virgin, I have a few questions. All I have tackled before on engines are some ancillaries, servicing and gaskets.

How does the starter drive the engine, cambelt or other means? Before I knew the cambelt was buggered I was turning it over after swapping ignition parts over etc to see if I could get it running, so if the starter rotates the engine by a non-cambelt means, then each time i've been turning it over I would be doing more damage, yes?

So really, what's the next step? Take the head off and see what's what? What's worse case scenario, busted rockers/valves/pistons/rods/cam. Or more or less most engine internals that bear stress.

Although I was quite upset, and it means the GT will be off the road for that much longer, I've always wanted to do some proper engine work, to understand more how they work. And if the head is busted, I fancy the idea of a flowed one

[mat_fenwick]

I've replied on your blog, but I'd be inclined to put a belt on it and check the compressions. Or borrow/hire a leak-down tester which would pressurise each cylinder in turn. You would then rotate the cam until both valves are closed on the cylinder you're testing, and assuming they aren't damaged, you would get a good seal. If you get air coming out of the inlet manifold for example, you know that the inlet valve is no longer seating properly.

[ghaddon1701]

Worse case scenario is eight bent valves. All eight is unlikely. Snapped camshaft, damaged pistons on a petrol is highly unlikely.

[RxBX]

Oh dear Tom !

Personally before you start spending any money on compression testers etc. !

IMHO the first port of call would be to lift off the camshaft cover on the top of the engine to see if the camshaft is still in one piece and also to check if any of the 'Cam caps' haven't cracked/burst open ?

the above items are not damaged !

Good luck and report back with those findings first.


.

[JayW]

Worse case scenario is eight bent valves. All eight is unlikely. Snapped camshaft, damaged pistons on a petrol is highly unlikely.

Actually, damage is highly likely, all the XU's are of the "interference" type. Particularly if it's been repeatedly spun over on the starter.

Having had 2 snap their belts (one at speed and one at idle) they were both damaged. Unfortunately the latter paqssed a compression test and was reassembled. But despite it's good compression a slight kink in 2 of the valve stems caused it to snap the replacement belt 4000 miles later.

You should also weigh up the benefits of refreshing all your gaskets, pulleys & belts.

[saintjamesy89]

You should also weigh up the benefits of refreshing all your gaskets, pulleys & belts.

I was very gradually doing so, but wanted to get it running before I did anything else so it could be moved or lowered/risen to make jacking easier, using the sills as jacking points makes me cringe, and when it's low you have to, to get a bigger jack on a sturdier point.

[Mothman]

Ime so sorry you have this problem Tom, must be very frustrating.
Actually, it must make all of us looking at and trying to resore MK 1s very wary of the age of the cambelts and how fragile they can become and make it a priority that these are changed as soon as possible to prevent such events.
I hope you can sort it bud. Be a terrible shame if you had to sell her as i know you have had such high hopes of her.

Good luck bud.

Andy

[mat_fenwick]

Actually, damage is highly likely

There's obviously a lower compression ratio on the petrol, but the glimmer of hope (more info on Tom's blog) is that it seems like it wasn't running when it snapped, so at the worst it snapped at cranking speeds. From the description of the sound when last cranked it appears like it hasn't even been turned over since the belt snapped - in which case why it has failed is a mystery, unless it has been eaten through by mice (they took a real shine to all my injector leak off pipes on the van one winter!)

Personally before you start spending any money on compression testers etc. !

IMHO the first port of call would be to lift off the camshaft cover on the top of the engine to see if the camshaft is still in one piece

On his blog I made the offer to loan my compression tester (as I'm hopefully down for the Bristol show), so no expense required! A very quick way of checking the cam is intact is simply to put a spanner on the belt end of the cam, rock it slightly and see whether the rotor arm moves correspondingly...

[saintjamesy89]

I'll wander over there this week sometime and look to see how the cam is. Thanks very much for the offer Mat, if you do make it down we'll sort some suitable renumeration out for you. Acommodation offer is still open for you, Sandre has bagsied the spare bed though unfortunately!

As you say Mat, from what other have posted it sounds like the belt snapped moments after I stopped cranking the engine, as the cranking sounded normal. It does look nibbled, or torn as if it's caught on something and gradually worn through. If it did snap whilst the engine was rotating, then it was at cranking speed.

[Jayboy]

Snapped the belt on Visa GTi years ago, engine just stopped driving along at 30mph. Thought I'd ran out of fuel as i was limping it to the petrol station at the time. Like you, I replaced lots of bits before realising the belt had snapped.

All I did was replace the belt and all was well, you may be lucky! However, as said above, maybe we should be wary of future problems following a belt failure but it will be a longtime before the Visa covers thousands of miles!