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[chrisp]

I've just bought a Gates kit (K015453XS) to replace the timing belt and pulleys on my 1993 Cavalier 2.5litre V6. I've noticed two issues and I hope that someone here can help me resolve them (I've tried the Cavalier forum but there are so few Cavalier V6s now on the road that there is no expertise to draw on).
1. The kit-supplied backplate/bracket that holds the tensioner and upper idler pulleys is different from the one on my V6. The backplate is a slightly different shape where it holds the tensioner pulley and this pulley has a flange on both sides, while mine is flangeless on its outer edge. I'm aware that the double flanged tensioner pulley requires timing belt fitment in a clockwise direction instead of the original anticlockwise, but can I fit the new backplate to my engine or should I keep my original backplate and tensioner pulley and just change the 2 idler pulleys?
2. The timing belt has two sets of markings for lining up with the crankshaft and camshaft sprocket timing marks during initial fitment - one set in white, one set in yellow. I suspect that one set is for use with the older backplate and flangeless tensioner pulley, while the other is for the newer backplate and flanged tensioner pulley. But which is which? The Gates kit online fitting instructions don't even mention the markings and they have failed to respond to my email enquiry.
Thanks in advance to anyone who can help.

[Doctor Gollum]

Firstly, swap the new pullies onto your backing plate.

Secondly, don't worry too much about the belt markings.

Thirdly, do use the complete locking kit.

Lastly http://www.omegaowners.com/forum/index.php?topic=90518.0

I would highly recommend the dvd, but you may need to PM TheBoy as I believe that the shop is temporarily unavailable. It is only a couple of quid, but worth its weight and helps keep the lights on 

[chrisp]

Thanks for the reply and i have PMed Theboy to see about the DVD.
I do now have a set of locking tools, though I have not used them yet. I first did this job quite a few years ago, without using the locking tools and without using the markings on the timing belt. At that time I just replaced the belt, leaving all the pulleys in place, and I must have got it right because I've since done some 40,000 miles on the car without a problem, taking the total mileage to 114,000. So I thought it about time to replace both belt and pulleys.
From your knowledge will there be any issues if I do replace the existing flangeless tensioner pulley with the new flanged one on the existing backplate?

[Doctor Gollum]

I've no Cav experience, so wouldn't want to guess...

But it may be that the flanged pulley is an update from the flangeless one... Only obvious issue would be a clearance one on either the cover or backplate, but again, that's a guess
Doubtless someone else will be along in due course to assist 

[Enceladus]

The revised flanged tensioner superseded the flangeless version for model year '97 on. The flangeless tensioner being implicated in the premature timing belt failures on early V6s. I believe that's true for all applications of the C25XE, X25XE and X30XE engines. The revised tensioner design, which came in the Gates kit, was a standard retrofit for these engines. This also meant that the belt now had to be installed clockwise and not anti-clockwise as with the old tensioner.

I'm surprised you have an flangeless tensioner still in service. The engine should have been upgraded on it's first or second scheduled timing belt renewal.

Your existing backplate should be stamped with the letter D. The revised backplate should be stamped EA or EB. According to Haynes anyway.

Since the backplate with revised tensioner and upper idler assembly was intended to be a retrofit to fix a problem, I would expect it would be a drop-in replacement on your engine. I believe you should replace the whole assembly. IE please do not not swap the new tensioner and upper idler onto the old backplate. Please check but you may also need to use the new backplate fixing bolts that should be in the Gates kit, rather than your existing bolts. Also you probably also need to use the new spacer washer with the new lower idler and probably a new bolt from the kit. The new spacer  might be a different thickness.

If you can't get the forum DVD there's a useful ContiTech video here.

I suspect your belt has white and yellow marks. Might be wrong but I think it's the white set you need. However use the timing gauge from the timing kit to make sure.

[chrisp]

Many thanks for this informative reply. It seems that I may have been lucky having no problems with the flangeless tensioner over 114,000 miles and some 3 or 3 cambelt only changes, and each time fitting it without the locking tool kit!
If the new backplate and flanged tensioner assembly can be retrofitted to pre 1997 V6 engines that would explain why Gates only offer one kit part number for all V6 engines.
Regarding the white and yellow cambelt markings, the yellow ones only cover the crankshaft and cam sprockets 1 & 2 (Driver's side for the Omega, rear of the engine for the Cavalier). There are only white markings for cam sprockets 3 & 4. This would suggest to me that the yellow markings are there for the clockwise fitting of the cambelt required with the flanged tensioner, but of course I can't be sure about this.
Anyway, as you say, I can check the timing with the gauge in the tools kit that I've now aquired.

[chrisp]

Well, I asked Gates (the suppliers of the timing belt kit K015453XS for clarification on the timing mark white and yellow colours, and I’ve now received a reply from them:

“For models till ’99 (with idler just above crankshaft),
•   Use the TM’s on each side of the direction of rotation arrows to line up the left camshaft sprockets.
•   Use the 3 remaining WHITE TM’s to line up crank- and right camshaft sprockets.
For models from ’99 onwards (with idler in the middle between left camshaft and crankshaft),
•   Use the TM’s on each side of the direction of rotation arrows to line up the left camshaft sprockets.
•   Use the 3 remaining YELLOW TM’s to line up crank- and right camshaft sprockets.”

The belt supplied in my kit has only white TMs around the direction arrows so this advice effectively means that only the white TMs should be used on pre-1999 models, while a mix of white and yellow TMs should be used on post 1999 models.

However, the reply is confusing in two areas:
1.   The reference to LH and RH camshaft sprockets does not define whether this is as you look directly at the timing belt from the side of the car (or from the front on a Vauxhall Omega), or whether it refers to an Omega, sitting in the driver’s seat looking forward. I suspect the latter because of the way the white and yellow TMs are arranged on the belt, and because this is the way LH and RH are conventionally used.
2.   The reference to an idler just above the crankshaft for pre 1999 models, and between the left camshaft and crankshaft for post 1999 models is very confusing. As far as I’m aware ALL V6 engines have two idlers – one just above the crankshaft and the other between the two camshaft pairs.

I’ve replied to Gates asking for some further clarification, but I’m getting a bit pessimistic about getting it!

[deviator]

I'm sure there are exceptions to the rule, but generally the front of the engine is side with the timing belt on it. So left/right apply as normal. It doesn't matter if the engine is inline (Omega) or transverse (Cav/Vec/Sig). EDIT It's pretty much always looking the front of the engine from outside, certainly is for VX's. I don't know of any car (although I bet there are some) that look it at as if you are inside the engine looking out (for want of a better expression).

With regards the timing marks, turn the crankshaft pulley until it's on it's on its timing marks. Look at the camshaft marks. If it lines up with either the white or yellow marks, then you know which ones to use. If they are no-where near either mark, turn the crankshaft pulley another 360 degrees and they should then line up. As long as everything is the same after you are done, you should be golden.

I will add, save yourself the headache next time and write down which timing marks are used. On the inside of the timing cover or the manual or even on the lid of the timing kit - even all three if you can.

[Nick W]

Don't make it any more complicated than it needs to be, GM already did that for you!


If your belt kit has the wrong backing plate, fit the new rollers to yours
Route the belt clockwise from the bottom unless the final adjuster isn't adjustable. Then you do it anti-clockwise.
Ensure the belt is tight when the adjusters are in the centre of their travel.
Remove the locks, and start the turn through/check/adjust/repeat procedure until you're satisfied.


It's more work trying to use the marks on the belt than ignoring them and relying on the locking kit.


If you don't have the locking kit, GET ONE


You will find it's easier to do in an Omega than a FWD application....

[chrisp]

Gates, who supplied the kit K015453XS for replacement of the timing belt and pulleys on my 1993 Cavalier V6 have, despite my initial pessimism, been very helpful in sorting out the use of the white and yellow timing marks on the belt and the issue of flangeless and flanged tensioner pulleys.
The changeover from a tensioner pulley with no front flange to one with flanges at both front and back occurred in 1997, so my 1993 V6 engine came with the flangeless pulley. Gates has confirmed that the flanged tensioner pulley, together with its mounting backplate and top idler pulley, as supplied in their kit, is a direct replacement for my flangeless version, and that this change has nothing to do with the use of the white or yellow timing marks on the belt. Since the flangeless pulley has been associated with the belt riding forward and scuffing the plastic cover, changing over to the flanged design is a good move (though I’ve never had a problem with my flangeless design in 114,000 miles).
The white and yellow timing marks relate to a later change which occurred in 1999 and is illustrated in the diagram. The left hand diagram shows the pre 1999 arrangement, while the right hand diagram shows the post 1999 arrangement. The only difference is that the idler pulley up from the crankshaft in an anti-clockwise direction in the diagram has been moved higher up. For the pre 1999 engines, solely the white timing markings on the belt are used. For post 1999 engines the yellow marks are used for the crankshaft and cam sprockets 1 & 2 (the pair on the left in the diagram), while the white marks are used for cam sprockets 3 & 4 (the pair on the right in the diagram), there being no yellow marks for these two positions.
So, with Cavalier Mk3 manufacture ending in 1995, and Calibra manufacture ending in 1997, the yellow timing marks only apply to later Omegas – and of course subsequent Vectras and other GM cars that used the V6 engine.
This has taken significant effort to sort out – I wish the timing belt kits would come with a simple printed sheet with this explanation and diagram.
And yes, I know that people have successfully changed timing belts without using the timing marks on the belt. I have done this several times also, and without a locking tool kit either, but now I have a locking kit I want to do the job “by the book”.

https://i.postimg.cc/65Lvtwnq/V6-engine-timing-belt-diagram.jpg[/img]

[chrisp]

Addendum: I’ve just been able to look at the excellent DVD from the Omega Owners Forum showing V6 timing belt replacement. This states that the different backplates for the tensioner and upper idler pulleys are NOT interchangeable. This is in opposition to Gates’s advice that the later backplate is a direct replacement for the earlier one and, having taken another look at my original backplate and the new one in the Gates kit, I can see that they do differ significantly in the position of the tensioner pulley. So I think the best advice is, if the kit supplies a different backplate to the one on your vehicle, just swap the older tensioner and upper idler pulleys for the new ones in the kit and keep the original backplate. It appears that you can still swap a flangeless tensioner for the newer flanged type when doing this. The advice on which colour timing marks to use is unaffected by this new information.  Ho hum – why is this so complicated?

[Enceladus]

Check the existing backplate that has the flangeless tensioner. If it's never been updated then the backplate will be embossed with the letter "D" in between the tensioner roller and the idler. This tensioner assembly was re-designed and introduced 1997 due to premature cam belt failures. The improvements are to the backplate, the tensioner and it's roller and the bearing in the idler. And also to the thickness of the cambelt, this cambelt is unchanged till end of production.

For C25XE (in your case) engines and early X25XE & X30XE the tensioner assembly was updated and that includes the backplate. The revised backplates are embossed "E*" (usually EA or EB). The mounting bolt pattern is the same albeit the mounting bolt lengths might be different and the effective positions of the rollers slightly different.

"E*" was eventually changed for "01" for 1999 on. There is another newer revision but I don't know the code offhand.

Your Gates kit is listed for C25XE so it should contain an "E*" series backplate. In that case you bolt the whole tensioner assembly onto your engine. The Gates K015453XS is equivalent to GM 93188674 which is the GM kit for a C25XE Cavalier or Calibra.

The upper idler and the flanged tensioners are all the same from 1997 onwards so they can be freely swapped onto any 1997 onwards backplates.

[chrisp]

Thank you for this reply and information. The new backplate in the Gates kit is indeed marked EB, but the existing old backplate has no discernible markings at all. My V6 engine was, I think, one of the first made in late 1992 –early 1993, so that may explain the lack of markings. From what you say, the Gates advice that I can replace this early backplate with the EB one they have supplied in the kit is correct, despite my reservations and the comment in the DVD. New mounting bolts are supplied with the kit, which will obviate any issues with different bolt lengths for old and new backplates. The slightly different position of the tensioner pulley may also explain the slightly different tensioning procedures that I have noted in the differing Autodata timing belt installation instructions for older and newer engines.
With all the uncertainty on both backplates and timing mark colours leading to delay, it’s a good job my Cavalier V6 has now become a bit of a hobby car rather than a daily driver!