Timing Chains - Retain or Renew?

On several occasions over the last year or so the subject of timing chains has cropped up. The question is, change them or leave them? 

The last occasion when this subject was discussed was prompted by a posting from Damian:

Hello Folks, below is the review of the 85-98 Granada/Scorpio from http://www.honestjohn.co.uk
Are the 24v timing chain system replacement every 60k miles and autobox problems from 60k correct generalisations for the Scorpio? And 900 quid for a TD alternator?
Damian

Quite how Scorpios autoboxes  'fail after only 60000 miles' and yet still manage to be one of the three manufacturers least likely to break down, and how 'clocking is rife' on cars which read the mileage from the PCM  - even if you plug a lower-mileage instrument panel into a high-mileage car the odometer will still display the higher number - is not explained. And has anyone heard of a 4X4 Scorpio - not! I think we've pretty well established that the journo is stuck in the Granada rut here. At least the Recalls were accurate - as is the mention of www.fordscorpio.co.uk ;)

However, I answered this one with the same points I had used before:

Damian,
Blimey, this old chestnut again. I had an argument which lasted for weeks with some nutcase on the old Granada site who reckoned that the timing chain had to be renewed after 60,000 miles. I argued that timing chains had been in existence and commonly used for racing engines since 1912, they were 'real engineering' and didn't need changing in normal service. They are not shown on the service scheduling written by Ford, either. Changing the timing chains is a big job, taking more than a days labour by a skilled mechanic and I argued that Ford would never have designed an engine to need that much work after only 60,000. I then asked for a poll of other Scorpio owners. I had the answers as 140K, 110K my own at 85K and several others well over 100K and none of them had had trouble with the timing chains. I think I won the argument.

Expecting trouble with the gearbox is another growing myth. The A4LDE is closely based on the A4LD, which regularly went through 150K miles without trouble. I used to buy my Granadas with about 85K on the clock - and then change the rear CV joints because they were so sloppy. I now notice that on my Scorpio the rear CV joints have no slackness at all at 95K genuine miles, so I suggest that my old Granadas had been clocked at least once before I got them. None of them gave any trouble, except the newest one, curiously.
The new A4LDE is much simplified because the gear changes are controlled by the PCM, so I would expect them to last longer than the previous one without giving trouble. Recent experience suggests that in almost every case where a gearbox problem has been diagnosed, it has turned out to be a wiring loom fault rather than the A4LDE and it might be this which started the myth.
My own Scorpio 24V has covered 94,500 miles being driven hard (if not thrashed) and the gearbox is still working flawlessly (touching wood as I write that.) As usual, here we have a motoring correspondent talking crap - just because someone is paying him to write doesn't mean he knows what he's talking about !

Chris Nickless, was sceptical too:

Ref Timing Chains etc.

I suspect the referenced article is using a bit of journalistic licence and leaning on some previous articles  - I have read of problems with the pre-1995 Cosworth engine timing chains - a single duplex chain (6ft long) which was prone to stretching. Having said that, I looked at a car (1993 Model) which had done 150K + miles and the engine sounded and ran like new - the car had been well serviced by one owner and mostly used for long runs.
The post 1995 Cosworth engines with the two shorter chains seem less of a problem (once the tensioner gets pumped up on cold mornings).

Also the earlier high pressure Teeves ABS system was more troublesome than the MK 4 onwards systems fitted to the later cars (from about 1988 I think)
Chris.
 

Fredrik Svensson then threw in a surprise:

In my (Swedish) service book, it states that the timing chain on the 16v 2ltr should be replaced at service every 120000 km (~74564,5 miles)...It actually was replaced some 18 months ago, before I owned the car.

Fredrik

This was curious, because I had checked twice with Ford and had them look at every service schedule for the UK Scorpio - nothing. The timing chain is never mentioned. Does Ford do something different in Sweden? Although it now appears that the timing items shown as needing changing were not chains but belts - for the CVH PTE engine and the Escort Zetec and Zetec-E engines - Ford engines in general, but not specific to the Scorpio.

Then Mike Walsh posted the same advice from his mechanic as I had received from mine:

I have recently sorted out all problems on my Cossie and asked meteor ford in Brum about the timing chain, Stan the master mechanic there made enquiries with his ford technical contacts, and not only did they say don't change the chain, they also said don't change the tensioner (that was noisy at start-up). the reason being that the chain and tensioner have got used to each other and bedded into each other and a new tensioner might put different strains on the chain and cause a problem. so basically a 'don't bother doing anything' what I do is try and park the car flat or downhill. This seems to make it a little quieter in the morning!!

cheers
mike w
 

Martin Stanjer then pointed out that he had had a gearbox failure -

My 96 16v scorpio gearbox died at about 85,000 due to burnt brake bands. I'm afraid perhaps this could have been something to do with my driving. My current 12V estate had the box replaced before I bought it at about 50,000 miles. My Auto box man said that people who fit extra fluid coolers on their automatics could put him out of business, as many failures are due to burnt brake bands. Perhaps this is worth doing?. It's worth remembering that auto box failure affects all makes sometimes, so perhaps it's not fair of Honest John to say this is a particular Scorpio problem.

Regards,
Martin.
PS. The rare manual Scorpios are sought after by taxi drivers for reliability more than fuel economy. 

Martin also thought that the reason my rear CV joints are quieter is that Ford had changed the seals on the joints to stop them drying out. Could be, although they look the same for me. Thanks for that, Martin. I'll have to have a closer look!

Now Colin posted a gearbox failure:

Hi Guys

My '95 24v estate has had a slight timing chain rattle at cold start since I purchased it 3 years ago.  So far no problems!!

However the gearbox gave up @ 80150!  I do thrash mine & tow a heavy caravan - I do have an external gearbox cooler- however all my previous autos have passed 150k with no attention.

Apparently these gearboxes seldom give trouble in the 12v motors but can be a little unreliable? in the 24v's.

Colin
 

Now Steve Mac posted a closely-reasoned argument for changing his timing chains - the point was that if it needed doing, do it before it broke and trashed the engine!

Like many of you I wondered if and when the timing chain should be changed on my 2.0  16v.  After asking many people including the so-called pro's I couldn't get a definitive answer. I have made the decision to change the chain in the very near future as the car has done 75000 miles.  I would agree with those of you that say chains generally last longer than timing belts and that years ago the timing chain was only changed when it began to rattle.  I take the view that years ago timing chains weren't turning twin cams and lifting sixteen or more valves with high load springs.  Also years ago if a chain snapped (very rare) it was unlikely to do an awful lot of damage as the pistons were unlikely to hit the valves on those relatively low performance engines.  My final deciding factors were 1/ When I lifted the cam cover the other day there was clear signs of wear and pitting on the chain rollers despite their life of luxury bathed in engine oil. 2/ There is a plastic sprocket on the tensioner which certainly isn't as strong as a steel sprocket and is a possible point of failure (Just like the plastic timing belt sprocket on the early diesel Mondeos)  3/ The cost of parts for the whole job is less than £100 whereas a snapped chain will cause in the region of £500 plus damage to a motor. Comments?
Regards SteveMac

As you might have gathered, I'm sceptical myself, but I understood Steve's viewpoint:

I had actually posted the last point before, that the use of synthetic high-lubricity oil had quietened the cam rattle, although slight - which I had on my 24V. This must have been before Mike joined, because he came back, obviously intrigued:

I was happy to confirm it - at least on my engine -
 

Meanwhile, the discussion went on. Colin voted for caution:

So there we have it. Two different views, and evidence for both. Checking has confirmed that the timing chains are not scheduled for renewal for Ford Scorpios. Meanwhile on the Message Board we heard from one owner that he had changed the chains on his 24V, and quite a job it was too.

Meanwhile, Steve Mac has changed his cam chain! He promises to write it up for the Site.

A Question of Timing - The Complete Timing Chain

Now let's look at the source of this controversy.

Granada Cosworth Timing Gear

How had the timing chain changed on the 24V Granada - which the HonestJohn journalist was thinking of - to the Scorpio Cosworth?

To the right is the printout of the Granada 24V engine. A duplex chain (1) rides the crankshaft pulley and then runs over the camshaft pulleys, dropping vertically to engage the auxillary drive shaft. (In the 12V Cologne engine, this shaft is the camshaft.)

In this design there is only one chain tensioner (5), while on the inner run there are two chain guides (3 & 4). Not numbered, on the nearside of the chain run there is a sprocket which runs on an idler shaft just above the outer chain guide (2)

On the lower figure the tensioner (9) is shown.  This is hydraulic in operation, receiving oil under pressure from an oil gallery. This presses against the tensioner blade (5) which uses the bolt and shaft (32 and 31) as a fulcrum.

A separate chain slider (34) is fitted to a mounting (35) between the cams on the cylinder heads.

A result of this arrangement is that the timing chain is almost 6' long, no doubt why a duplex type was used, with a chain tensioner arrangement on one side and an idler pulley on the other.

Scorpio Cosworth Timing Gear

 

Now we can look at the revised timing chain for the Scorpio 24V.

The figure on the right illustrates the two timing chains (1). Now simplex, they ride on a double pulley on the end of the crankshaft, the offside first, which engages one side of the auxillary drive pulley, and then the nearside. There are now two chain tensioners (15) operating on the tensioner blades, (2 & 4). These operate on a fulcrum provided by the sleeved bolt (9) and the collared bolt (12), while further support for each chain is provided by the guides (5 & 3 & 6)

The auxillary drive has now been reduced to driving the oil pump from a gear at its rearward end.

Look closer at the diagram shown on the bottom right of the figure. It is this tensioner that is the subject of a TSB, 142/97 which suggests that its design enables the tensioner to drain overnight, causing a chain rattle when cold. It is the threaded plug (14) which is removed from the tensioner (15) to gain access to the torx nut which retracts and locks the device before removal. A single bolt (13) can be reused, but it would perhaps be wise to change the tensioner gasket (16).

The effect of this arrangement has been to halve the load of four cams on a single duplex chain of the Granada and divide it between two simplex chains.

DOHC Timing Gear

The DOHC engines have many parts in common.

On the right the DOHC2000 is shown. Both the 8V and the 16V use this arrangement.

There are two simplex chains of unequal length, one for the cams and the other for the oil pump. The timing chain (4) rides the crankshaft pulley to run over a tensioner pulley (6) operated by the tensioner (8), then over the camshaft pulleys. An upper chain guide (10) is fitted between the cam pulleys.

It passes the chain guide (11) operating on a fulcrum provided by the collared bolt (21).

The oil pump drive chain runs on the forward pulley (1) passes a blade tensioner (19) using tension from the spring (9) and then over the oil pump drive pulley (3) and returns.

DOHC2300 Chains

For the DOHC 2.3 the parts for the timing chain remained unchanged, but the oil pump was revised to provide a drive for the balancer shafts.

The figure on the right shows the new arrangement. A tensioner blade (24) and tensioner (22) now replaces the spring tensioner. A chain guide (23) operates about the fulcrum provided by the collared bolt (26) while the chain (5) is now longer and drops to the balance shaft drive sprocket mounted in the sump (not shown).

2.9 Cologne V6 Timing Gear

As you would expect from such a longstanding design, little has changed with the 12V Cologne V6.

The camshaft runs in the engine block in the centre of the V. The timing chain runs round the crankshaft pulley (2) and past a chain tensioner mounted on the offside (4). It then passes over the camshaft pulley (1) and returns through a guide rail (5) operating about the fulcrum bolt (9).

2.5 TDI Diesel