24V whats the story on chain breakages?

[man of kent]

There is an interesting article on 24V chain breakages on the Autobarnstormers website. http://www.autobahnstormers.org/ (Peter harrisons strengthened timing chains).

There are now very strong chains available that dont break like some of the originals. It mentions that Vauxhall introduced stronger chains at some stage. Was this during the build life of the car or only as an after market chain when the Carlton/Senator had gone out of production? i.e. are the later cars ok? Apparently Lotus carlton chains break quite easily! No doubt automatics do not put as much stress on the chain as manuals due to the softening of the drive take up with the fluid auto drive, unless the auto box is in lock up on a motorway.

If you need to change the main chain, Haynes says its an engine out job. Can you just disconnect a link, connect to the new chain, get somebody to turn the engine over, plugs out, and feed the new chain round the crank sprocket whilst the crank is turned, and pull it up and reconnect to the other end after removing the old chain?

Can you get the tappet cover off to inspect the chains without taking the manifolds off?

[Murph]

I can be done with the engine in situ.

The radiator would need to be out to improve access and the rocker cover would need to come off along with the front timing cover, so no small job even so.

The main cause of chain failure in the guides though so as long as these are inspected regularly you should be OK.

It's generally thought that if a car was going to suffer chain failure due to a problem with the chain itself it would have done so by now.

[Winky]

There is an interesting article on 24V chain breakages on the Autobarnstormers website. http://www.autobahnstormers.org/ (Peter harrisons strengthened timing chains).

There are now very strong chains available that dont break like some of the originals. It mentions that Vauxhall introduced stronger chains at some stage. Was this during the build life of the car or only as an after market chain when the Carlton/Senator had gone out of production? i.e. are the later cars ok?

Vx uprated the chain during the life of the car to what was known as the Blue link chain. These in themselves still aren't as strong as the Peter Harrisons ones. My '93 Senny had the blue link fitted as can be seen in the pic of the chain after doing the CHG & changing to the PH chain.

I agree with Murph that a lot of chains break because of the guides breaking down & the chain getting caught but the originals were made of chocolate.  

[Pedro]

The main cause of chain failure in the guides though so as long as these are inspected regularly you should be OK.

Playing my favourite game - Devil's advocate. 

So by merely checking to see that the guides are OK, all will be well?

I mean, if the guides are found to be FUBAR one day - then what?

New guides - but from where?

OK, seriously - can anyone tell me what the guides are made from - acetal perhaps?
Reason I ask is that there must be a company somewhere with a CNC machine who could reproduce the guides at a not-too-exhorbitant price..........current commercial climate etc.
Combine that with duplex chains and you'd be looking at another 100,000 miles wear from them.
I swear now that if I blow the current engine (due to timing chain issues or otherwise), in goes a 3.0 V6 from an Omega........with no smog stuff! as the 24V is getting harder and harder to maintain when it comes to essentials.....................like chain guides.

[kevinfourlegs]

I seem to recall a brand new timing chain guide still in the bag sell for £410 a short while ago on eBay. What are they made from, gold?

[man of kent]

If its the guides that go first, how do you tell if they are going? Noise - screech or rattle or clatter? Possibly noise on the over run thats not there in drive?

If its the guides, presumably there is some sort of slack and it is the snatch on full throttle that breaks the chains?

Is the auto less likely to cause this snatch having a fluid drive cushion? i.e. you dont get the sudden load from the manual transmission.

Murph mentioned that you needed to take the rocker cover and front timing case off to inspect. If you only want to inspect the chain ONLY, the photos in Haynes suggest that you only need to take the rocker cover off and slowly turn the engine to inspect the chain. Is this correct? I would have thought whilst doing this, you could poke around down inside to see if there is too much slack indicating that the guides were on their way out.

In Haynes 4B.13 illustration 15.45b, the photo does suggest that you might be able to  take the throttle housing off leaving the manifolds on and get the rocker cover off ?? A bit of poor design if the manifolds have to come off. Would have thought it would be better to have designed the throttle body a bit longer with the manifolds clear.

[Winky]

IMO If you're that concerned about it & are prepared to take the rocker cover off to then just feel for some slack & leave it at that is a waste of time. Get the front cover off & inspect it properly or leave it alone.

These were my guides. Judge for yourself if you think you would have been able to feel what they were like from any slack in the chain there may have been.






Engine was on approx 170k & on the basis of having the blue link chain fitted I reckon these were the original guides.

[man of kent]

Sounds like the later 24V engines are much better than the earlier ones and were fitted with the blue chain during the engine build lifespan.

Looking at the wear on the guides makes me think that the 24V engine would do better with molyslip (molybdenum disulphide) which is proven to be a very good friction reducer. To show how good molyslip is, many years ago they tested an engine which had lost all its oil but had molyslip in it. The molyslip kept the engine running for many many miles before it seized.

Is it known how much damage is done when the chain fails? Presumably lots of bent valves or do the pistons get seriously damaged as well? I remember my Rover SD1 2.6 belt going and there were just some bent valves with no piston damage. i suppose it depends on how deep the combustion chamber is and the overlap between the piston and valve open.

I notice from the specs that the GSi 24V is more powerful than the 24V fitted to the standard Senator/Carlton so assume the GSi is more prone to guide & chain failure.

[Winky]

Is it known how much damage is done when the chain fails? Presumably lots of bent valves or do the pistons get seriously damaged as well? I remember my Rover SD1 2.6 belt going and there were just some bent valves with no piston damage. i suppose it depends on how deep the combustion chamber is and the overlap between the piston and valve open.

Depends what revs you're doing & how quickly you pull over/stop the engine. Have a look at 24vmans thread about the Lotus Senator he bought with chain failure (that for a change appears to be chain NOT guide failure)

http://totalcarlton.com/forums/index.php/topic,12941.0.html

I notice from the specs that the GSi 24V is more powerful than the 24V fitted to the standard Senator/Carlton so assume the GSi is more prone to guide & chain failure.

Yes the Diplomat is a slightly downgraded engine (4bhp) but the other 24v C30SE engines are 204 bhp for Carlton or Senny. Manual is quicker than auto & Carlton quicker than Senny but thats down to gearbox & weight. Same chains fitted across the range (same engine). If you're looking at the specs of each on the ABS website bear in mind it doesn't list figures for the 24v Senator (177bhp is a standard 12v, the gold top I believe was mid 180s with the 24v 204)

[man of kent]

This picture of the chain torn apart shows the same type of failure as the ABS site. I think it confirms sudden acceleration of the engine under load like revs right up and then letting the clutch out. No doubt if you drive them gently they will last but then whats the point of having a 24V.

The 24V is definitely an engine you have to be careful of when buying. The question unanswered is, if the engine sounds nice and quiet with no rattles, is it actually ok or could it fail at any time?

The old Peugeot/Volvo six cylinder was known for similar problems but you could hear the chains rattling around before any terminal failure. Is this the case for the 24V?

[chris]

You can inspect the main chain by simply removing the front cover, no need to remove the rocker cover.
Its quick and easy to do although visibility isnt great so you need a good light.

Ive never heard a 24v with a rattling chain, then again Ive never had a failed chain in 12 years and many cars. I do change the oil a lot though which some say makes a big difference.


On the subject of accelerator on then off etc, it doesnt matter much to the chains, they are pulling the cams round no matter what the revs are, the cams are being constantly braked by the valves so no matter whether accelerating or decelerating the tension is still there on the same side of the chain.
If that wasnt the case you would need a tensioner on both sides for when the slack swaps sides, but it doesnt.

[Cosmo D]

I'm on my second engine. When the car had reached approx. 150000 km, the chain decided to snap and say goodbye! It got a new engine, which had done the same milage, approx. 150k km when it was fitted. The car has now done 10-20 k km after the engine swap.

I'll probably be having an engine overhaul when the summer arrives.

[man of kent]

I'm on my second engine. When the car had reached approx. 150000 km, the chain decided to snap and say goodbye! It got a new engine, which had done the same milage, approx. 150k km when it was fitted. The car has now done 10-20 k km after the engine swap.

I'll probably be having an engine overhaul when the summer arrives.

Was your first engine that blew fitted with an early chain or the later blue chain?

Was there any warning that it would snap such as a rattle? Somebody suggested that the tensioner stops any rattle and then somebody else said that the chain broke because the tensioner wore out allowing the chain to be loose. The ABS site mentions that somebodies chain tried to get off the sprocket and then broke which suggests no tension in the chain because of no tensioner.

The old Peugeot/Volvo V6 was prone to front end chain problems but you could tell because there was a rattle before the chain gave up.

[nightmare]

The old Peugeot/Volvo V6 was prone to front end chain problems but you could tell because there was a rattle before the chain gave up.
[/quote]

RATTLE they sounded like an old clapped out chieftan tank on my old peugeot.

[man of kent]

Does the Carlton/Senator 24V chain rattle before it breaks? Or can it be silent and still break? Thats what I'm trying to find out.

[Cosmo D]

Was your first engine that blew fitted with an early chain or the later blue chain?

Was there any warning that it would snap such as a rattle? Somebody suggested that the tensioner stops any rattle and then somebody else said that the chain broke because the tensioner wore out allowing the chain to be loose. The ABS site mentions that somebodies chain tried to get off the sprocket and then broke which suggests no tension in the chain because of no tensioner.

The old Peugeot/Volvo V6 was prone to front end chain problems but you could tell because there was a rattle before the chain gave up.

Dunno, it's a 1993 model though, so probably, but why would it go after only 150k km then? I wasn't the owner of the car when the first engine broke, so I don't know if there were any warnings like rattles and so. I've also heard that when the tensioners lost tension, the chain could jump off.

[man of kent]

The ABS site shows some broken chains where one of the rollers has pulled out of the side plates completely. I would suggest that the damage to the chain is not sudden as the side plates gradually give with cracks appearing and the chain becomes longer and thus the chain could jump a tooth on the sprocket as well as jumping because of the tensioner not working.

If the tensioner stops working and the chain jumps a tooth on the sprocket it would suggest that there is a rattle before this happens.

Without knowing the full facts it would seem there are two failure modes causing breakage. Inoperative tensioner allowing slack and tooth jumping and the failure of the chain side plates.

Not sure that comments about the load on the chain being the same all the time is correct. If you gently accelerate there is less load on the chain from the crank than if you floor the throttle. When you floor the throttle there is more acceleration of the crank and thus the chain with an increase in load. The load from the valve train will also be higher as again the valves accelerate faster when under full throttle load. If you then have a slack chain with the higher accelerative loads you reach the peak of the failure mode.

It would be interesting to look at some failed chains and tensioner components.

[kevinfourlegs]

It would give you a clearer picture if you could see the failed components. There may be a common link, no pun intended, or not.

I take it the 12v models don't suffer the same issue(s)?

[The Duke]

I take it the 12v models don't suffer the same issue(s)?

12v's have duplex (i.e double row) chains so they're stronger. Supposedly Lotus wanted to change the 24v engine to a duplex setup but Vx wouldn't allow it on cost grounds.

[melinx]

If you have ever had the head off an engine and attempted to turn the camshaft (as I have) during the valve clearance setting procedure, you would have some idea of the force required.

That was on a 4 cylinder 8 valve: A 6 cylinder 24 valve needs either a bloody strong or a duplex chain

[man of kent]

I agree. Not using a Duplex chain was a big mistake but there may be a problem with packaging one. Maybe there wasn't room? A cost save?

One of the problems that all designers face is that the test team will set up a series of prototype tests on a test bench that is supposed to represent an owners use of a component. Trouble is it passes all the tests and then fails in service.

I'll give you an example from many years ago and will not mention the manufacturer as its quite embarrassing...............

A door and hinges was designed and prototypes to production standards were assembled on a test bed. A hydraulic ram slammed the door shut hundreds of times into a body without failure. The vehicles were built with the same components and sold to the customer. On many vehicles the hinge broke when the customer slammed the door!

Almost certainly the 24V tests on the chain passed all the tests on the engine test bed in GM Germany. As soon as they saw the failures they introduced a stronger chain. A cost save using a weaker chain could also have been forced on the design engineer.

[chris]

Not sure that comments about the load on the chain being the same all the time is correct. If you gently accelerate there is less load on the chain from the crank than if you floor the throttle. When you floor the throttle there is more acceleration of the crank and thus the chain with an increase in load. The load from the valve train will also be higher as again the valves accelerate faster when under full throttle load. If you then have a slack chain with the higher accelerative loads you reach the peak of the failure mode.

Yes very true, I agree that the engine will accelerate and decelerate and the camshafts must follow meaning the force will increase and decrease, what I meant was that the force is always in the same direction so the chain is always tensioned naturally on one side and always needs the tensioner on the other. I don’t think I explained my thought very well and probably still am not.

Why I wanted to make the comment is that I think people often think that when you decelerate the naturally tensioned side of the chain becomes all slack like the chain of a motorbike along the top run and this allows it to jump.
Im my opinion it doesn’t as it is still making the cams turn which is quite hard work.

On the motorbike the engine is pulling the wheel sometimes but then the wheel is pulling the engine during deceleration, in an engine the crank is always pulling the cams round no matter what.

That’s what I think anyway.

[melinx]

I reckon that's spot on

[man of kent]

Yep. Chain failure is thus affected by how hard you boot the throttle. You will get a lot more miles driving it gentley and also if an automatic as the fluid drive acts like a sponge.

Reading the ABS site the chains on the lotus carlton dont last long! Nice car to have if you can afford to repair the engine frequently or drive it gently in which case there is no point in having the Lotus!

I've no doubt that the design is flawed with the original chains.

[kevinfourlegs]

If anyone knows, then its you, Keith. Have you ever thought of publishing your knowledge?