Life of Uprated Timing Belt?

Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
The tooth pitch and count is what matters for keeping time. The tensioner is self-adjusting to temperature so there is no worries with it. As such, the extra 0.5mm, old belt and the 5622XS at 2.1 mm thickness and the Dayco 95242 is 2.6 mm, will be accounted for when you tension the tensioner. Recall that the tension markings/alignment are the mechanical equivalent to a feedback loop.
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
Those Dayco belts are pretty awesome. From experience with them on ALHs, they wear like steel. The toothed side is very hard.

Fwiw, ALH belts are the same width, just longer and with more teeth, of course. Otherwise, the construction of the Dayco belt appears identical.

Also, the CR motors came with Daycos from the factory pretty frequently, those are rated at 120k! Though I will say the Gen 1 CRs are wider, too. The CKRA/gen 2 is back down to about the width of the ALH/1Z/AHU belts, rating remains 120k, though.
 

Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
The CRs can do what, 7-9 injection events per combustion stroke though? That reduces the shock load quite significantly so that probably is partly why the longer life too, I imagine.
 

kooyajerms

grocery getter
Joined
May 5, 2004
Location
Pomona, Southern California
TDI
97 B4V (mine), 11 x5 35d (hers) 04 V10 (that one you want), 2014 Q7 (mom's) 74 Shasta 1400
Nice collabo guys! Too bad I did my TB 10k miles ago.

Now to find the harmonic differences in ALH and 1Z tensioners. Go!
:D

Good job.
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
Damn... I recently ordered 2 TB242s.

Dayco belts are nice. I've used their "Top Cog Golds" many times and recently installed one of their serpentine belts. Supposedly reinforced with Kevlar.

-Todd
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
The CRs can do what, 7-9 injection events per combustion stroke though? That reduces the shock load quite significantly so that probably is partly why the longer life too, I imagine.
Probably has less to do with injection events since the high pressure fuel pump does not control injection events at all. But the CR engines do have a fair bit less compression (16:1 instead of 19.5:1) and that alone makes for a reduction in the rapid accel/decel of the engine.
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
I have also read a lot of good things about the Dayco TB's. Most retailers in the US market Dayco v-belts as lower quality, which is fine because the price is often very reasonable. I've been very happy with the Dayco products I've used.

Steve
 

vanbcguy

Veteran Member
Joined
Feb 22, 2013
Location
Vancouver, BC
TDI
'93 Passat - AHU mTDI with GTB1756VK
Ohh super interested in this. Should page IBW and get this on the list at IDParts

Sent from my XT1097 using Tapatalk
 

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Dewey, AZ
TDI
Only the B4V left
Apropos since the wagon TB is 3k overdue.

Now that my back has mostly healed I can change it. Others have offered to change it for me but I like to give the cars a lot of extra attention during the swap since it makes a difference.
 

deecee

Veteran Member
Joined
Jun 26, 2012
Location
Black mtn NC
TDI
96 Passat Tornado Red, 99.5 Golf ALH, 2002 Jetta ALH
What are the thoughts on Dayco's tensioner? I am thinking of ordering the kit from rock auto which includes the belt and tensioner.
 

Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
From looking at the photos on Amazon, a lot of the tensioners are Litens with that brand's choice of bearings: SKF, NTN, NSK, etc...

From buying different brands recently, I can attest to this too.
 

Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
Can't say one way or another since their site photo of the tensioner, 85579, is unbadged and Google image search doesn't net anything else. Rock Auto is just as helpful. You can buy one and find out for us ;)
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
Pretty sure the Dayco kit has a Litens tensioner, not aure what the bearing is.

The upper roller tends to be GMB, though. I'd prefer sticking with INA rollers...
 

hughesjasonk

Veteran Member
Joined
Nov 8, 2013
Location
New York
TDI
2002 Jetta MK4;
So you think the Dayco will most likely be a Litens anyway?
Dayco uses litens for its roller assembly on its tensioner.

I personally always use the gates kit because those are all OEM Parts. you'll get ina litens for the rollers

Sent from my SM-G930V using Tapatalk
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
I dug this out because I had asked Gates (Europe) ages ago for a definitive answer on the belt situation and finally a few days ago I got a response.

Gates 'claims' they are not the same belt (5223XS and 5622XS) despite them both being applicable to the AHU. Here's what Gates says about that.

The belts are different length.



To which I say....really? 1/32" is different length? You can actually with confidence produce a belt (that does flex some) and say with a straight face that it's 1/32" different?

I mentioned in my response that I was reluctant to accept the answer, especially since their own catalog suggested that fitment for either on the AHU was acceptable.

Will be interesting to see if they get back to me, it took over three years to get the original request answered. Same with the lower radiator hose question I posed, about why they could get a B4 4 cylinder hose in Europe and we couldn't. The first response said that it wasn't a valid part number, after three go rounds about that I sent a pic with Gates watermark bearing the 4 digit part number I finally got the response that demand for the hose was too low in the US to offer it...finally, the truth.

Steve A
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
Unless the pitch of the teeth is different two belts with the same number of teeth will be the same length. Just like a chain where the length is determined by the pitch and number of links.

I don't have a calculator or napkin handy but .03" divided by 137 is going to be less than .0003". I don't see anyone designing a belt/sprocket with the pitch 3 tenths different from another existing belt.

Sounds like a rounding issue when converting from metrical units. I wonders why no one caught it and actually issued two P/N's for the same belt.
 

turbodieseldyke

Veteran Member
Joined
Jun 6, 2010
Location
Free Mustache Rides
TDI
98 jetta
Sounds like a rounding issue when converting from metrical units. I wonders why no one caught it and actually issued two P/N's for the same belt.
That's the most plausible explanation.

51 +3/8" = 130.493cm
51 +13/32" = 130.572cm

Someone might've gotten lazy and rounded 130.572cm down to 130.5cm, which is closer to 51 3/8.

Either way, it's the same. You'll get more variance due to stretching and tensioning.
 

jhax

Veteran Member
Joined
Jan 24, 2012
Location
Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
So has this concluded that we can use the 100k TB?
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
So has this concluded that we can use the 100k TB?
I don't believe that the 5622XS is a 100k mile timing belt. In fact I think Gates had said in their email to me to not deviate from the manufacturer mandated change intervals, so I would say no.

I'm in agreement with TDDyke, it's the same belt, you'll get more than the 1/32 difference in stretch etc...

BTW, Gates is no longer responding to my emails, I sent them a screen capture of the engines both belts work with since AHU is mentioned for both belts. I can hear them now, "we're done with this guy." hahahaha.

Steve
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
So has this concluded that we can use the 100k TB?
The Dayco? Probably would. Officially, Dayco says "follow manufacturer's recommended change interval," which is safe corporate speak for 60,000 mile in the case of these engines.

If I still owned a car with one of these engines in it, I'd be more than happy to play guinea pig with one and see how long it goes. I have confidence it would not have any issue getting to 100k miles, but you won't find any supporting documentation or official recommendations stating such.

If you're feeling adventurous and understand that it is expensive to repair and engine once a belt has failed, I'd love to see some data points on how long these last...

But not too many people are willing to shell out that kind of money and also risk being stranded on the side of the road just to create a data point.
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
FWIW, Franko6 can talk your ear off with his impressions of Dayco belts as a whole (not necessarily the 1Z/AHU version specifically, but I will note that the construction of their 1Z/AHU belt looks the same as it does their ALH and newer engine belts). He's also personally witnessed some very impressively high miles on those belts before they finally gave up the ghost... way past the interval.

Would I have confidence that the Dayco belt for the 1Z/AHU could make it to 100k miles? Yes. Would I want to risk pushing my luck much further beyond that? Not really, but it would be an interesting data point. As ever, there's a wide variance on where ultimate failure will occur given the wildly varying environmental conditions, driving styles and heat cycles along with age and how the belt was installed plus how much tension is applied to it etc.
 

turbodieseldyke

Veteran Member
Joined
Jun 6, 2010
Location
Free Mustache Rides
TDI
98 jetta
When I bought my B4, the belt had 80k, AND was shredded down to half-width, due to a slightly-rotated IP bracket. Unbroken. That was its 2nd belt. Its 1st belt lasted 115k before snapping, and leaving the PO with a very hefty repair bill.
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
When I bought my B4, the belt had 80k, AND was shredded down to half-width, due to a slightly-rotated IP bracket. Unbroken. That was its 2nd belt. Its 1st belt lasted 115k before snapping, and leaving the PO with a very hefty repair bill.
Yep. My first TDI, a 98 Jetta with the AHU in it (hence the username! Imagine that!) had a timing belt with about 80,000 mile on it when I changed it. Car was originally my dad's, I got it off him in 2004. I knew it had to be coming due sometime soon, I thought it was done about 20,000 miles later than it was. I searched through the old repair docs to find exactly when the last belt was done, only to realize it was now 20,000 miles overdue (60k rated belt at 80k miles).

So, I ordered the parts and I get around to doing the job and the belt had a tear starting in it, going about 1/3rd of the way through the belt.

But, as you can see from photos earlier in this thread, the Dayco belt is constructed MUCH more sturdily than any other 1Z/AHU belt available that I have encountered. And if you were to hold it upto the ALH Dayco belt (which is also a "follow manufacturer's change recommendations" which is 100k miles in the case of the ALH), you will notice the construction appears identical. Same thickness, same hard fibers on the toothed side, same texture on the back of the belt, whereas the 60k and 80k belts have a smooth back to them and are noticeably thinner from belt backing to toothed side compared to the Dayco.

Can 60k belts sometimes make it double their interval? Sometimes. But it seems with those belts, you're lucky if it goes much beyond 80k.
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.


Hah, found a photo of that belt. For some reason I left it in the trunk of my car for a couple months, as a memento I guess? Met up with Leicaman at Road America when the diesel Audis were running there in 2006 and I brought it out as we were talking TDIs.
 

garciapiano

Veteran Member
Joined
Feb 12, 2018
Location
Southern California
TDI
1997 Jetta TDI (1Z)
In my opinion the shorter interval of the AHU/1Z timing belt has to do with the engine’s roller design, not the belt itself. I’m all for operating TDIs economically, but this is a “stepping over dollars to pick up dimes” scenario.
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
In my opinion the shorter interval of the AHU/1Z timing belt has to do with the engine’s roller design, not the belt itself. I’m all for operating TDIs economically, but this is a “stepping over dollars to pick up dimes” scenario.
It's a problem that the AHU inherited from the ME/MF/1Y/AAZ engine and the old tech. It was partly resolved with the upper roller addition but not completely dealt with until the ALH engines...and then only some of them IIRC. But the ALH has its own issues after unwisely driving the WP with the TB...

TBH if a person can't mind the 60k mile belt change interval then a different car might be a better fit.

Steve
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
In my opinion the shorter interval of the AHU/1Z timing belt has to do with the engine’s roller design, not the belt itself. I’m all for operating TDIs economically, but this is a “stepping over dollars to pick up dimes” scenario.
The ALH has more rollers, yes, although one of them is really only there to ensure there's adequate teeth on the water pump due to the angle at which the belt gets to the water pump after the injection pump.

The upper roller is the same principle, just not the identical part, to what the ALH has. So, with that in mind, realistically the only additional roller the ALH has is the one between the crank and the tensioner. That's already the slack side of the belt, but the 1Z/AHU uses a nearly identical tensioner to the ALH. Both are spring loaded/auto compensating.

There is an obvious construction sturdiness difference between the standard 1Z/AHU belts and the "100k mile" ALH belts... and bear in mind the early ALHs that have the similar, thinner, smooth backed belts were also rated at similar 60k mile intervals. It wasn't until they got thicker belts with that textured backing did they up the interval to 80k, then when they updated the lower roller between the water pump and crank to be a double row ball bearing instead of single row, they upped it to 100k.

Being that the 1Z/AHU does not drive the water pump, but does drive an intermediate shaft to at least be an intermediary between pump and crank, it literally only leaves the belt and the absence of the small lower roller between the crank and tensioner as the most notable changes. And I'm not sure I see how the absence of that single small roller on the slack side of the belt would actually create a significant difference in rated belt life. The early ALHs were rated at 60k too... And once again, there were obvious similarities in belt construction between 60k ALH belt and standard 1Z/AHU belt.

So, to me, when you find a belt like that Dayco that obviously is of the same construction as the much higher mileage ALH belt, I think it would be very safe to assume you could get longer life out of it than the standard belt being that the primary thing that allowed the ALH to uprate belt intervals was the belt itself (at least to 80k), and then the large lower roller upgrade allowed it to go all the way to 100k, which is of no consequence to the 1Z/AHU setup since it doesn't have any of that water pump or extra roller nonsense anyway.

But yes, the 1Z/AHU belt is an easier one to change. No engine mount or mount bracket to deal with, less parts to swap out when doing the belt as well, so all in all, it's not a difficult service to just keep doing at 60k regardless of belt used. Though for guys who've boosted performance of their early TDIs, I'd definitely feel a lot more secure having that much more durable and aggressive tooth design of the Dayco belt.
 
Top