Interesting way of changing a cambelt

[rainagain]

Whenever I change a cambelt where the cam/crank pulleys aren’t keyed I always do it the proper way, i.e. use a locking kit to lock the engine up and then loosen the pulleys. I was talking to someone recently and they said what they did was use a sharp knife to cut the existing cambelt in half lengthways all the way around. So basically you have a cambelt that is still going round all the pulleys but is half as wide, he then said you loosen the tensioner and slip on the new belt halfway on the pulleys whilst the old belt is still there, before cutting the old belt off.

 

He said it was a great way to change belts as you can never get the timing wrong and you don't have to bother buying locking kits or checking timing marks. As all cambelts are slightly different could this method result in the timing being slightly out or would it be so small as not to matter? I need to change the belt on my OH’s Hyundai and according to the manual you have to take the valve cover off to hold the cams so you can loosening both of their pulleys, so if I could use this method it would save messing about.

[Timewaster]

How sharp is his Stanley knife? Cambelts are as tough as they can make them and I would have thought the brute force needed to cut one up could potentially damage plastic pulleys, bearings etc.

Does he hold the knife in the belt and spin the engine over?

I suppose they are weaker around than they are across of that makes sense.

[dollywobbler]

A technique I've heard of, but never tried. Problem is, how do you check the health of tensioners and the water pump if you can't turn them by hand?

[HillmanImp]

Someone else suggested doing this the other day on here oddly enough.

[HillmanImp]

I had just come on here to edit my post to say that DW, not realising you had said something just before me.

[Split_Pin]

Since tensioners go just as often as the belt itself, I'd say that was s lazy bodge

[Rusty_Rocket]

It's a great idea in theory and probably works on the odd (old) engine. But the problem is, almost all belt pulleys/ tensioners/ idlers have a shouldered edge that prevents you simply sliding the belt on.

[RichardMoss]

I used the technique on a mk2 Golf some time back. It worked.

[rainagain]

Thanks for the replies guy, as it's our own car I think I'll do it properly, so as DW says I can check the tensioners, etc. 

[Ratdat]

So you cut the belt in half length-ways by holding a blade against it whilst it's running... then the remaining half of the old tired cambelt snaps as it's no longer strong enough, lunching your engine in the process. Doesn't seem like it's the worth the risk to me! 

[overrun]

I wouldn't do it.

 

I also don't worry too much about the timing marks. Stop engine, mark the pulleys and belt, transfer marks to new belt (count the teeth), make sure engine is still on your marks and fit the new belt.

 

This allows you to change water pump, tensioners etc and not have to piss about with sometimes invisible or missing timing marks.

 

The only car I have had an issue with keeping everything lined up, was my dads dci Clio.

The fuel pump pulley kept on rotating and that time I used the proper timing marks.

 

There's a shit-load of B.S. surrounding timing belts, imo.

 

Mind, I also used to remove the head from my SR20 and cable tie the cam sprockets to the timing chain and hang the chain from the underside of the bonnet with mig wire and that worked.

[rainagain]

I always wondered why they moved to this new system where you have to lock the cams and then move the pulleys to suit the new belt. The first car I saw this on was a 1.2 16V Fiat, where you had to turn the engine till you could insert the locking tool into the cams and make sure one of the cylinders (I can't remember which one) was at TDC. You fitted the new belt and working from the crank to the cam,  then you loosened the cam pulley so it aligned with the teeth on the new belt.

[sporty-shite]

I always wondered why they moved to this new system where you have to lock the cams and then move the pulleys to suit the new belt. The first car I saw this on was a 1.2 16V Fiat, where you had to turn the engine till you could insert the locking tool into the cams and make sure one of the cylinders (I can't remember which one) was at TDC. You fitted the new belt and working from the crank to the cam,  then you loosened the cam pulley so it aligned with the teeth on the new belt.

 

It effectively gives the accuracy of a vernier pulley. If you have woodruff keys, your timing is only accurate to one tooth of the belt, with the locking system, it is infinitely adjustable. I did the belt on an Alfa 147 a while ao, and bought the tools pretty cheaply on ebay. To be honest, it was easier wioth the cams locked than it has been on other cars where you're arsing about with marks. 

 

Really, if you're doing the job, it isn't worth attempting a bodge for the sake of a few quid on the proper kit.

[lisbon_road]

I agree with all the above comments.

 

The only time you'd want to do that is if you want to be able to say to someone 'I've changed the cambelt'.  Any other time, you at least want to check the pulleys and water pump.

 

I can think of one occasion when I changed a belt without changing anything else.  The car had done six thousand miles from new and was about six years old.  Logic was that the belt might have deteriorated but the rest should not have.  Still nice to check them though.

[Split_Pin]

My mate did the belt on the astra in '10 and he used tippex to mark up the timing. I suggested using the locking tools buy I guess once you've done a hundered or so belts you don't need your nappy changed over it.

[Mr_Bo11ox]

Presumably you wouldnt do it with the engin running incase the stanley picked up and flicked itself into your gonads, forehead, neigbour's handicapped child etc? Why not turn the engine over with a spanner on the crankshaft? Seems like a good idea on the whole if youre not arsed about swapping the tensioners and theres no retaining lip on the pulleys.

[mat_the_cat]

I've done this 'bodge' before, obviously only on vehicles without a flange on the sprockets. Couple of times it's been for cars that I was selling, and the buyers wanted a belt fitted but also on my own fleet occasionally. I never do it with the engine running, just turn it over by hand and then slip half the belt off whilst stationary so I don't see an extra risk of breakage - all the time it's being turned it has the full width of belt on it. You can still feel gross play in tensioners and pumps once you release belt tension, although obviously not roughness.

 

Personally I've not found the need to change tensioners at the same time if using decent parts - the BX for example I've had the longest and done 4 belt changes on it in 130k miles, but only one pump and tensioner change. Seeing as that was the time before last, I slit the belt on the most recent change to save removing the starter motor to lock the crank. (Next time I'll do it properly though).

 

Some might think I'm cutting corners by not changing the lot, but I check tensioners/pump for play while the belt is off or slack. I would only replace if play was felt or if it sounded noisy - my logic is when I do a belt myself I'm not paying for labour so the cost of a decent quality pump and tensioner is significant in relation to the belt cost. Secondly, neither is likely IMO (but anything's possible!) to suddenly fail without any warning. If you are used to how your engine sounds then you can usually pick up on small changes and act accordingly to prevent breakdowns. If it was a job for someone else though, I'd recommend replacing the lot as you can't rely on them to spot warning signs, and when things come down to a question of judgement then sooner or later I'm bound to get it wrong! And if you're paying for labour anyway then it's less of a difference.

[twosmoke300]

Bottle of "timex" is what you need.(like tipex but has oily fingerprints on it.

Also if you need to stop cams moving without special tools just take one cam cap off and CAREFULLY put a bit of card under it and nip it up.

 

Incidently I read today that some cars (ford ecoboost) have a cambelt that runs in the oil.!!!!

[Conrad D. Conelrad]

Incidently I read today that some cars (ford ecoboost) have a cambelt that runs in the oil.!!!!

 

Cambelts running in oil should, in theory, last as long as a chain. I don't know what Ford's change interval is for the wet belt engines. Obviously the belts themselves are not susceptible to oil contamination!

[Station]

I could change a K-series headgasket (so that includes the cam belt) in an MGF in two hours from start to finish.

That's how often I did the K-series HG. I think that's quite incredible, and worthy of raising Norris McWhirter and Roy Castle from the dead to invigilate. Also on an MGF, where you can only see the cams and the crank pulley.

I found it difficult to get the belt on even with the tensioner slack. I think I'd just mark everything up and just do it the normal way tbh.

[New POD]

Cambelts running in oil should, in theory, last as long as a chain. I don't know what Ford's change interval is for the wet belt engines. Obviously the belts themselves are not susceptible to oil contamination!

You have to compare the functional requirements of the 2 alternatives.

 

Dry cambelt, has to cope with every fluid that could be thrown at it, including unknown cleaning chemicals, brake and pas fluid, gearbox oil and engine oil.  With 2 cams, you have 3 dynamic shaft seals with all the tolerances and speciality rubbers that requires, plus there's always sand and dust, and stones, that might find their way in.

 

Or put the cambelt in a known chemical, at a known maximum temp, design one big seal around the cover, that NEVER has to move again, and you can make it last 'forever' and it's cheaper.