BKD Timing belt loose tensioner nut

**galari377** · 27-04-2025,11:46 AM

Hi everyone, I'm hoping some of you seasoned can shed light on a problem I've hit.

I have a 2008 Seat Leon 2.0 16V (BKD) with about 190K km. Just last week I changed the timing belt kit (with water pump) – I know the kit came with a new tensioner and nut, but I kept the original tensioner (and its nut) because it looked more robust than the new one. Everything was great at first. A few days ago I was driving very slowly (around 20 km/h) and turning into a parking space when the engine suddenly died. After a fair bit of cranking it restarted, but it definitely sounded off time. I only drove another 50m at idle to a safe spot and then stopped again. On checking, I found the timing belt on the tensioner side had lost tension and the belt had shifted slightly outwards – although it wasn't completely slack. Strangely, I could spin the tensioner nut by hand; it was that loose. I haven't run the engine again since. I popped in the timing tools (crankshaft and camshaft locks) to check if a tooth had gone. They almost fit perfectly (maybe about 1mm out), and I can still see the timing holes, so I think the belt didn't actually skip a tooth. Still, the fact that the tensioner nut was finger-loose worries me. I’m guessing my mistake was reusing the old tensioner hardware. Looking ahead, I’ve got a brand-new tensioner, nut, and 8mm stud ready to fit (all OEM spec). My big question is: should I just replace the stud with the new 8mm one and torque it correctly, or is it worth doing a helicoil/insert and stepping up to a 10mm stud for safety? I’ve heard about tensioner studs failing on VAG engines and that some people drill the block out for a bigger stud and Helicoil in an M10 thread. On the one hand, a thicker stud might be stronger; on the other hand, I'm wary of messing up the alignment or introducing new problems. Has anyone here dealt with this on the BKD or similar engines? Is simply fitting the new 8mm stud and tensioner (torqued to spec) adequate, or should I bite the bullet and do a proper M10 repair? Any advice on the best and safest approach – or pitfalls I should watch for – would be hugely appreciated. Thanks in advance for your thoughts! cheers,

(P.S. I’m from Spain and wrote this post with the help of Translator to make sure it’s clear in English!)

**Crasher** · 27-04-2025,06:42 PM

We always fit a new M8/M8 stud as they come in the genuine kit. If the thread in the head looks poor so the new stud moves around until bottomed, then we TimeSert the thread. The M8/M10 stud is an option instead (the same thread size as an M8 TimeSert) but it MUST have the diameter change radius set lower than the mounting face of the tensioner centre so the tensioner does not sit on the radius.

**galari377** · 28-04-2025,09:33 AM

Alright, perfect, thanks for the clarification. The stud should be tightened to 15 Nm, right?

What about the damper bolts — do they also need to be replaced? When I did the timing a few days ago, I installed new ones because it was mentioned in ElsaWin.

And regarding the engine mount bolts, it also says they should be replaced, but since they are thicker, do they hold up, or is it better to replace them as well?

I also have another question: in the kit, there was a stud and nut for the other roller in the timing assembly. Should I replace that stud too and tighten it to 15 Nm, or is it not necessary?

Thanks a lot!

**Crasher** · 28-04-2025,10:10 AM

We replace EVERY nut, bolt and stud without exception, using genuine VW parts. The tensioner stud is 10Nm into the head with the tensioner nut being 20 Nm + 1/8 turn (45°) further. The lower roller can be a stud so 10Nm or a bolt which is 20Nm. Personally I don't like tensioning studs down, it is not what I am used to such as with the APR head and main studs I have just used on an S2 20v where the spec is hand tight only and I also use a medium strength thread lock on studs BUT ensure the fastener is brought to torque before the thread lock sets.

**galari377** · 30-04-2025,11:53 AM

Hi, I've already changed the stud and installed the new tensioner. I reused the same belt. When it came to tensioning the tensioner, I followed the workshop manual: held it with an Allen key, aligned the arrow between the marks, and tightened it to 20 Nm plus 45Â°. The manual mentions that it's possible for the arrow to move 5 mm to the right, but in my case, it stayed in the same position after tightening and turning the crankshaft twice. Why is that? Did I do something wrong?

**galari377** · 30-04-2025,12:19 PM

This is how the tensioner mark is currently; I will have turned the crankshaft 4 times.

**Crasher** · 03-05-2025,02:04 PM

What is the part number of the kit you used?

**galari377** · 03-05-2025,05:55 PM

Contitech ct1051 wp2

**Crasher** · 03-05-2025,11:50 PM

I get it as CT1051K2, in the past I have had problems with the tensioner is many kits slipping during adjustment.

**galari377** · 06-05-2025,09:12 AM

After doing 200km, I've checked it every 50km. Yesterday it was 5mm to the right, after 50km it was in the middle, and this morning before starting it, it completely loosened again. I don't understand. I did everything as the manual says. Could it be that my torque wrench is out of calibration? Should I buy a new tensioner?