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Yes I did end up swapping out the SFK pump for a Hepu Pump and another belt. I forgot I hadn’t updated that here. Everything has been charged twice at this point. As far as I’m aware, the 7a doesn’t use the diamond washer on the crank stack according to ETKA
I did think that but someone posted recently on the Facebook group that they were having belt alignment issues on a 7a and resolved it by fitting the diamond washer.
Nothelle S2 Avant
Black Ur project
Silver Rs2 Project gone
Ocianic Ur project gone
S2 Coupe project gone
Urs6 plus project gone
Yeah I think I spoke to that person too. There were two people who had some input when I mentioned this on Facebook. One said about the diamond washer, but I think it turned out he was actually talking about this diamond washer from 5inline Motorsport.
It’s not the same as the other diamond washer. This is 0.1mm thick and is only used to ‘increase friction’ as a preventative measure against the bolt coming loose.
This is the more common diamond washer that’s used to space the stack with it being 3mm thick. I understand this also has the same function of increasing friction, but the 0.1mm is obviously so thin so it can be used on vehicles that don’t use the 3mm one.
Looking at the position of the belt on the cam sprocket, it sits where most people historically have said it’s supposed to about 1mm from the back edge. If a 3mm washer was used on the crank stack the belt would be hanging off the idler and water pump. All that to say, I’m confident going by the documentation online and ETKA that there isn’t supposed to be a washer on the 7a.
The thing I always keep coming back to is what happened at the start. Although the belt originally was pretty loose, the distributor gears didn’t lash and the belt was stable. I changed the cam belt, water pump, crank pulley and oil seal, then the issue occurred. I know the dynamics will have changed with a new belt, different tension etc, but I can’t get my head around a possible cause if you think about that very first job.
........... the belt originally was pretty loose, the distributor gears didn’t lash and the belt was stable.
My thoughts were have you slackened the belt but then re-read your post and you have yes ?
If you're happy and confident with the work you've done , maybe just go with it for now? You've said the car runs beautifully and it isn't as bad as it was .......... how many miles done since it started to make the noise ?
BTW when I replaced the belt, pump and idler on mine, the (new) belt was in line with the outer edge of the cam pulley ?........ from memory I didn't replace the crank pulley, if I did it was with a stock Audi one.
Yes I did try to slacken the belt off to what I’d consider the lower safe limit as a test but the belt was slapping way too much.
I’d say I am confident with the work. I’ve done this job so many times now. I did get to a point where I thought let’s just live with it, but when I’d take the car out and hear it, or sitting in traffic and it idles abit higher and it would sit right on the spot where it’s rattling around, I know that the cam belt is slapping around. Knowing that it shouldn’t be doing it, and that if that belt did happen to fly off, skip a tooth etc then that’s it finished, it would just play on my mind every time I drove it and took all the fun out of it. Now I’ve also discovered the gears clattering has created more end float in the distributor shaft, it’s actually causing ‘damage’ rather than just being an annoying noise.
I couldn’t tell you exactly how many miles I’ve done, maybe 100 - 150 at this point. It’s hard to say because I haven’t been out for any drives for pleasure, I’ve pretty much been reassembling and then test driving. The longest single run I’ve done is probably 20 - 30 miles as a long test drive.
That’s interesting. So just to confirm, your belt sat at the edge towards the front of the car and not the back edge of the cam pulley? Mine sits towards the back. It also sat in the exact same spot as the original belt setup, confirmed by the wear on the idler. The only thing I haven’t done is put the OEM crank pulley back on, although I’ve used two of Chef’s billet pulleys and compared the OEM to it with a set of callipers to confirm the spec matches. With so many people documenting them using Chef’s I kind of ruled that out as a possibility of being an issue.
I know there’s bigger things to worry about than a car, but my god it’s taken over. I struggle to let things go once it’s got in my head and it’s an open loop that needs closing. I do appreciate everyone’s input so far.
As a quick side note, I tested it yesterday after reassembling and the PAS pump made a clunk and I saw the pulley move forward. Turned the car off and I measured there’s now 0.6mm end float in the shaft (although it feels like more but I did measure it) that wasn’t there before. Is that a cause for concern or is that acceptable and just let that get worse. It does whine a lot all of a sudden on full lock. Any thoughts on that would be great rather than me starting a whole new thread.
That’s interesting that your belt sits towards the front edge. Everyone else I’ve spoken to or setups that I’ve seen seem to sit towards the back.
Yeah anything else I’d live with it, but with it being cam belt related I just can’t let it be without concern. I do wonder if I’ve uncovered an issue or created an issue.
Every suggestion online related to the ‘classic 7a distributor rattle’, which I assume this is the same or similar, is typically shim it and change the plastic gear to metal. This seems to be the fix for every thread I’ve read through. There’s a handful of other threads I’ve read that do suggest the cam belt might be too loose, but as I mentioned, getting it to a spot where the noise and belt slap is minimised is around 80 degree twist. I’m pretty much at the end of the water pump travel there too so it just doesn’t seem right. It feels like an impossible situation!
As I’ve said already, I don’t know what else there is to check or test. I can’t imagine I’ve been that unlucky to have done the cam belt install incorrectly every single time. I’ve followed the Bentley manual, Haynes manual and any other forum resource where this job has been discussed to ensure it’s done correctly. I’ve tried various pre-loading and other forum members techniques and the result is the same every time.
Realistically, what would your next move be?
Regarding the PAS pump end float, the only mention of this after searching was a reply to someone from Tractor Dave. The reply being that ‘both of his have play’. I just don’t like how suddenly it seemed to happen. To be honest this is low priority compared to the other issue, but it would be useful to know if this is considered within spec.
Feel for you mate.
The only time i ever had a strange noise after doing a timing belt was on an Rs2 replica i fixed after catastrophic failure following bottom and top sprocket keyways shearing. I eventually discovered that the timing belt rear cover was damaged ( presumably when the belt flew off) causing the bottom cover to contact the vibration damper and make a strange intermittent rattle.
Yes, both of my cars here have some float on the pas pulley and i remember it on some of my previous projects.
If your belt is too tight, these engines normally make a goose noise when revving.
Good luck with it.
Nothelle S2 Avant
Black Ur project
Silver Rs2 Project gone
Ocianic Ur project gone
S2 Coupe project gone
Urs6 plus project gone
Feel for you mate.
The only time i ever had a strange noise after doing a timing belt was on an Rs2 replica i fixed after catastrophic failure following bottom and top sprocket keyways shearing. I eventually discovered that the timing belt rear cover was damaged ( presumably when the belt flew off) causing the bottom cover to contact the vibration damper and make a strange intermittent rattle.
Yes, both of my cars here have some float on the pas pulley and i remember it on some of my previous projects.
If your belt is too tight, these engines normally make a goose noise when revving.
Good luck with it.
Thanks Dave.
Just a sort of update. I've been picking away at this throughout the week and think I've got to a sort of middle ground. I've finessed the hell out of the position of the water pump. I set the belt's tension to a twist that felt right and I'd be happy with. Obviously, at this tension, the backlash in the distributor gear is present along with the belt slap. From there, I mounted the DTI above the water pump and adjusted it in increments. After each adjustment, I started the engine and repeated the process until the backlash was reduced to a minimum and any further adjustment had no effect.
I can hear an ever so faint 'turkey gobble' or 'goose noise' (might be what I'm hearing), but it's only at idle, doesn't increase with revs and doesn't sound like it's coming from the water pump. It actually sounds like it's behind the head. I'll investigate that further. The belt can still twist 90 degrees with some persuasion and delusion thrown in there. I think this is the best I'm going to get, backlash is minimal, and I know the belt isn't cranked all the way to the pump's stop in the adjustment, although it is relatively close.
I'm going to monitor the PAS pump. It's not groaning under load or knocking, so hopefully I'm ok for a bit there. I just wanted to give an update because it's unbelievably frustrating when you read a thread and it just goes dead at the end. Although this isn't the end of it, I'm somewhat happy to run it as it is and see how things progress.
While i am certain you are quite over dealing with this, i would have one question/suggestion. Get one of those mechanic's stethoscopes, it should really help narrow down the source of the noise.
I was having a nightmare similar to this when trying to figure out clunkiness in my s6 suspension post diy coilover install. Instantly traced it to flexing upper strut mounts.
While i am certain you are quite over dealing with this, i would have one question/suggestion. Get one of those mechanic's stethoscopes, it should really help narrow down the source of the noise.
I was having a nightmare similar to this when trying to figure out clunkiness in my s6 suspension post diy coilover install. Instantly traced it to flexing upper strut mounts.
Thanks for the input. I haven't got a proper mechanics stethoscope, but I have been round all the components with a pry bar and listened. I've 100% located the backlash (rattle) at the distributor gear where it meshes with the cam gear. Regarding the turkey gobble, I had another look yesterday and managed to get the pry bar on the water pump, difficult with everything reassembled, and I've confirmed the gobble is actually coming from the water pump. I'm assuming it's being amplified and reflected now that the cam belt cover is on, which could also explain why I thought it wasn't coming from the front of the engine. Frustrating.
It seems it's one or the other: the belt is slightly too tight (subjectively), but with audible feedback from the pump, so it's clearly putting strain on it and likely the other components. Alternatively, slackening it off to relieve the strain on the pump but reintroduces belt slap and distributor gear backlash. I took it out for a drive again last night with my partner, and I was saying to her that this just isn't fun to drive while I'm stuck in testing and diagnosis mode.
One observation that I thought back to was that I originally installed an SFK pump, then, as part of the elimination of components, I swapped that out for the Hepu pump (both pumps brand new). I don't recall the exact tension I applied to the belt during the initial test of that pump, but I do recall it being noisier than the SKF one in general. As much as it pains me to say this, I might swap the SKF one back in, set the tension as I have done and see if I can finesse that to a spot where there's no backlash or belt slap and the pump isn't giving me feedback. If I can get it to that spot, I'll monitor the pump as I put more miles on and see if it starts making any noises or signs of accelerated wear. I fear this will be another waste of time though. Technically, I've already had this exact set-up, so I'm not expecting anything to magically change by reverting back.
I realise I am going around in circles with this and probably will have to let it go or settle for one of the two issues. I know I said I'm happy to run it as is for now, but knowing it isn't right won't let me enjoy driving it. It's also frustrating to keep thinking back to the original set-up where the belt was loose and it didn't have this issue, and now I've set it up 'properly', I have an issue I can't resolve!
I've had a weird noise on my 3B, kind of a rattle, maybe more a chuckle, was convinced at one point it was coming from the distributor drive or somewhere up top. Lately I've been thinking it's actually coming from the gearbox. It happens when warmed and idling but can come and go, when blipped as RPMs settle, going slow in traffic in second gear it's quite obvious inside the car. Incidentally it's an ABY six speed box, not the original helical five speed..
It's been a while since I last posted in this thread, but unfortunately, I've made no progress in figuring out the issue. I had a theory, which unfortunately didn't solve it, which I will explain, but first, to address some of the most recent members' posts; I did get hold of a mechanics stephascope, and it didn't help in narrowing this down any further or help in finding the origin of the problem.
So the two sides of this problem are
Belt looser = belt slap/backlash (excitement through the belt, through the system to the distributor)
OR Belt tighther = minimal to no belt slap or excitement through the belt, but the water pump is audibly under strain.
The middle-ground between the two, where you'd think you've got perfect belt tension, gives you both belt excitement and waterpump feedback!
I bought another SKF water pump, fearing that the first one wasn't genuine, and to avoid what would be extremely bad luck of having bought an SKF and a Hepu pump and both being faulty. I'm confident at this point that the pump itself isn't at fault. I verified its authenticity using the SKF app. The stephescope did help confirm that the water pump is resonating when the belt is on the tighter side by probing the housing. The water pump feedback does get slightly worse when the engine/ coolant gets warmer. I haven't made a direct link between the thermostat opening and the water pump's feedback changing or getting worse, but it does appear to be linear over time/temp and in audible feedback. Going down the cavitation theory route, I did various tests like squeezing the coolant hoses when hot and cold, removing the reservoir lid, etc., with no audible change with any variation of test. So, in my mind, I can rule out cavitation as the problem with the water pump side of this issue and focus back on the forces applied to it.
Taking an overview of what I've replaced (several times over), you've got water pumps, idle pulleys, timing belts, crank pulleys. I changed back to the OEM crank pulley to test, and it didn't change the result at all, so I then reinstalled the billet one from Chef.
The final theory I had was that the damper, being 35 years old, and the rubber being dried and cracked (not slipping), possibly the damper isn't damping the resonant frequency or torsional twist of the crank, so that excitation isn't being absorbed by the damper and it is being absorbed by the belt instead. In my head, this makes sense as a real possibility. This also took me down a very expensive route of purchasing a damper from 5inline. Just as a footnote, and please don't take this any other way than me relaying my findings, but the damper that 5inline says fits the 7A does not. It has too much material on the surface where the crank pulley contacts. I triple-checked before I purchased with part numbers, and it's impossible for this to be bolted straight onto a 7A engine (at least my 7A engine with the OEM damper part number 034 105 251C); the belts do not line up. There was talk about the diamond washer, but I know the 7A never used it. It's almost as if the damper was made with 3mm of extra material to eliminate the need for it on the ABY, so you can use the 0.1mm friction washer that they supply instead. Here's an illustration I made to show the issue. Make of it what you will. This isn't an attempt to badmouth 5inline in the slightest, just part of this story and my findings.
*Pink is the 3mm diamond washer illustrated for argument's sake.
**Green dashed line is a fixed point where the damper's nose meets the crank's nose
So to make this damper work, I had Alex at Ultra Performance machine the 3mm off the back surface to make all of the belts and crank pulley line through to match the spec of my OEM damper. Upon delivery from 5inline, I noticed there weren't any holes drilled to offset the keyway. I asked whether it had been dynamically balanced, and I was told it was, but I had my doubts, so once I received it back from Alex, I thought it'd be best to have it checked, especially since I've also had it machined. So I sent it to Vibrartion Free along with my OEM damper to spin up as a reference. Turns out it was within spec. Waste of money, probably, but at least I have peace of mind that it's balanced, so I can rule out that possibility if there were any issues once installed.
So I received it back from balancing and installed it. No change. Nothing. Genineuly at a loss here. There's nothing else I can possibly think of doing to figure this out. I think I've said before that I've seen a handful of YouTube videos of a 7A being revved, and you can hear the same backlash as the revs drop, but the majority don't seem to have this issue.
I'm just getting sick of taking the front end off and doing this over and over to try to get a different outcome. This, paired with the hot start issue, makes the nearly 1.5 years of ownership so frustrating, as I haven't really been able to enjoy it yet. As the title says, I'm out of options. The only thing I can think of now is to pull the engine and rebuild, but I fear I won't find anything that's wrong, because it runs absolutely fine. Although it wouldn't necessarily be a waste of time and money, as it'll be a fresh rebuild, I fear that after all that effort, this issue will still be present. I just thought I'd share an update.
If anyone has any other thoughts on this, please chime in. As I said, I still need to get to the bottom of the hot start issue, but this really needs resolving, too. It would be great to meet up with another 7A owner just to compare and hear another one running in the flesh, so if anyone is nearish to Stafford, let me know!
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