Kevin's 200 20v

[Aktapod]

Whoa! That's app is pretty nifty! I'll give it a shot if I can catch a ride out to the car. I put a new Contitech belt (054 109 119A) on cause the old one had oil on it. I also have a Tommi's billet crank gear from EFI Ex, which I noticed has the teeth slightly offset to my factory cog.

The thing is, I had some trouble getting the timing lined up right when I put it all together. It seemed a half-tooth off. Either I set it forward a tooth and the idler side had waaaaaay too little tension in order to keep the timing right, or move it back a tooth and the tension is pretty high and cam timing slightly retarded. I opted for the second one, and got the cam timing as close as I could, and the tension not unreasonably high, but I wonder if that might be causing this.

Phil - Thanks for the vid! That sounds gnarly, and not in a good way. But it seems to be the same frequency as mine at idle, especially near the end of the video. I wonder if it'd do something similar with tension too high - or bearings failing. I'll pay more attention while revving it to see if it makes a difference.

[pilihp2]

Well that video was after I did a timing belt job. I had one side of the cam gear tight and the other pretty loose, if that makes sense. It was about a tooth off, making the tensioner side tight, but the side between the gear and the crank loose, causing that nasty noise.

AT least I think thats what it was. It might have been the reverse of that. I'm making dinner and about 4 beers deep at this point. Not totally certain.

[loxxrider]

AT least I think thats what it was. It might have been the reverse of that. I'm making dinner and about 4 beers deep at this point. Not totally certain.

That feeling... I know it

[alxdgr8]

FYI there is a continental app for your phone that can help determine if the belt is tensioned right. I don't think it's a tension issue, but you never know. Mine made a funky whirring noise from the idler when it wasn't tensioned properly. I think the app is tension2go

Sweet app! Great idea for a smartphone since frequency is very 'cheap' to measure. It's measuring amplitude that get's expensive.

[Aktapod]

School was cancelled today due to freezing rain, so I managed to get home to the car. Had to use a hair dryer to thaw the hood enough to open it, but I can now pull the timing cover off to take a look. The thing that perplexes me is that it always starts making the noise after running for two minutes. Never when it's first started.

[Berserker]

The thing is, I had some trouble getting the timing lined up right when I put it all together. It seemed a half-tooth off. Either I set it forward a tooth and the idler side had waaaaaay too little tension in order to keep the timing right, or move it back a tooth and the tension is pretty high and cam timing slightly retarded. I opted for the second one, and got the cam timing as close as I could, and the tension not unreasonably high, but I wonder if that might be causing this.

For what it's worth, the timing belt tension can be made to be tight/loose on the left or right side of the cam pulley just by turning the crank pulley a little clockwise or counterclockwise. If it's particularly loose on either side, it's time to tension it a little more and rotate the engine a little to make sure it has proper tension.

I'm not sure what your noise is, but I'd be checking timing again (possibly mechanically, as well, engine at TDC checked with screwdriver down spark plug hole, and valve cover off, cam lobe "O"s pointing at one another), along with belt tension. I'd hate to see a wrecked engine due to bent valves.

[pilihp2]

With mine the noise went away with more revs. If you watch the video youll see I give it some throttle and it goes away. It only did it at idle. So if it idles higher when cold, and then drops idle revs when warmer, that could cause it.

Just speculation here.

[Aktapod]

All speculation welcome and appreciated! I gave it some revs but, if anything, it got louder. After pulling the timing belt cover, I let it run and it took 5 minutes to come up this time. I stuck my stethoscope on the water pump and it was pretty quiet. But on the back timing cover near the idler, it was very distinct! I'm 95% sure that's what's making the noise. Just need to find out why.

I'd hate to see a wrecked engine due to bent valves.

You and me both! Haven't driven much farther than in/out of the garage because I'm worried I might cause expensive damage. If anything, my belt has too much tension. It's the only way I can keep it close to in-time, and the cams are still a hair retarded. I verified the new t-belt is the same part number as the old, so I'm not sure what's going on there.

Here's a terrifying thought: Is it possible that the t-belt is "bridging" across the crank cog? What I mean is that the tension from both the water pump and idler keep the belt from slipping on either side of the cog, but the bottom is not in contact with the belt. That would effectively make my timing belt a tooth shorter, which would explain why the belt is so hard to slip on even with the water pump as loose as it allows.

[pilihp2]

All speculation welcome and appreciated! I gave it some revs but, if anything, it got louder. After pulling the timing belt cover, I let it run and it took 5 minutes to come up this time. I stuck my stethoscope on the water pump and it was pretty quiet. But on the back timing cover near the idler, it was very distinct! I'm 95% sure that's what's making the noise. Just need to find out why.

I'd hate to see a wrecked engine due to bent valves.

You and me both! Haven't driven much farther than in/out of the garage because I'm worried I might cause expensive damage. If anything, my belt has too much tension. It's the only way I can keep it close to in-time, and the cams are still a hair retarded. I verified the new t-belt is the same part number as the old, so I'm not sure what's going on there.

Here's a terrifying thought: Is it possible that the t-belt is "bridging" across the crank cog? What I mean is that the tension from both the water pump and idler keep the belt from slipping on either side of the cog, but the bottom is not in contact with the belt. That would effectively make my timing belt a tooth shorter, which would explain why the belt is so hard to slip on even with the water pump as loose as it allows.

Your terrifying thought makes a shit load of sense at this point.
Is it loose on the... NOT water pump side of the cogs????

[Aktapod]

Your terrifying thought makes a shit load of sense at this point.
Is it loose on the... NOT water pump side of the cogs????

Nope! It's quite tight on both sides. In fact, I turned the engine backwards until it turned the cams before tensioning the water pump side. Even then, this the absolute best I can get @ flywheel TDC:

photo.JPG (152.11 KiB) Viewed 43083 times

But if I jump it forward a tooth and want to keep it in time, the water pump wouldn't be moved at all and the idler side would be flapping in the wind.

[pilihp2]

Well. You clearly have it tensioned enough. I'm so confused.
All speculation here. Homework right now and about 3 beers deep.
Is this a pattern?

I don't think your theory is possible very easily. With the 20v/mc1 style belts, maybe but I don't think you can with the 20v style belts. Not sure though.

[loxxrider]

This is the kind of thing that's really hard to grasp without being there and seeing it in person. Maybe it's best to just get a new belt and new idler and go from there? What did you change since the last time it ran as normal?

[Aktapod]

A few things, actually:
- Oil pan gasket
- Oil pump gasket
- Crank seal
- Timing belt
- Crank cog (replaced with this one)
- Associated hardware

My only other idea is that the new cog is slightly offset from the factory one (which it is; I noticed when it didn't line up with the imprint on the pulley), but it's not by much:

IMG_7807_lines.jpg (1.44 MiB) Viewed 43077 times

In any case, I really appreciate you guys helping out through the beers and all! Despite not knowing what to fix, it's nice not knowing together.

[loxxrider]

Hmm, if the crank cog was offset a bit, I think that actually would/could make the tension all out of wack... That may very well be your problem. I'd probably put a brand new stock one on there.

[AudiQuattros]

Terrible sound.
never met with such a noise from the timing belt. was similar to the noise from the camshaft.

[AudiSport4000]

My first thought was something rubbing, but that really cant be the case if its not consistent all the time, eh?

[Aktapod]

In a way, I'm glad it's inconsistent, because it confirms nothing has gone catastrophically wrong (yet). I think the noise is as a result of an over-tensioned belt, but, if I'm honest, I'm not really sure what to do about it.

I guess I could go to the stock pulley, though it'd be a shame to do a downgrade. I think the only logical step is to tear it apart again and see if I can isolate the cause first. I'll check that the t-belt is the same length as the old and, without fully torqueing the crank bolt yet, see if I can time the engine normally with some combination of the older/newer parts. Then order parts, if need be.

Other ideas 100% welcome, though! I'm not a fan of removing the pulley again, since I had to borrow the crank-lock tool from a mechanic.

[loxxrider]

I really think you should replace with OEM parts. It isn't a downgrade really unless you plan on making REALLY crazy power and/or install it improperly. The key for the stock crank cog is to make sure you torque it properly. DO NOT install with an impact, and you will be OK.

Also, just because a sound is intermittent doesn't mean there is no catastrophic failure. My buddy bought an E30 which idled somewhat normally, but it was just down a cylinder (could have been spark, fuel, whatever). However, when we revved it, it would make this horrible clatter. It turns out that piston number one wasn't even connected to it's rod anymore... I'm not saying this is the case with your issue now, but don't think an intermittent symptom/issue can't be catastrophic

[Aktapod]

Haha, excuse me. Given the intermittence of the sound and how capably the car made it up my driveway, I find it highly unlikely the engine is permanently or catastrophically incapacitated.

In any case, I was under the impression the OEM cog was prone to cracking the keyway? Is that not as big a concern as I thought? I'm a big proponent of "there's no kill like overkill," so I just sprung for the best I could find, so I won't have to upgrade in the future. I'm too broke for fancy impact tools, so I have to tighten it conventionally anyways. If that'd be cool with the OEM cog, I have no issue going back to OEM.

[PRY4SNO]

The sintered OEM crank cog is prone to fracturing with use of impact tools. You should be fine to run it, if need be. Just look for hairline fractures, especially in the bolt holes/threads and at the keyway.

You should be fine... however, the fact that the Tommis one (possibly) isn't working for you gives me pause. How many other people have them (myself included) and have had no issues? Are we talking install error, manufacturing defect, bad luck? Definitely weird.

[loxxrider]

If the indexing of the teeth is not the same on the two gears, then there is most definitely a problem. An adjustable cam gear may alleviate that though eh?

Anyway, the stock cogs are not an issue when installed properly and replaced with new each time they are removed. It's when you want to reuse the cog that having a hardened one is important.

[Aktapod]

It's a CNC piece, so I'd think it's close to impossible to have it produced inconsistently - at least without being noticed, and I can't see how I'd be the only one to have issues.

I considered an adjustable cam gear, but that seems a bit like masking some issue in the system, rather than fixing it. Happy to get one for other reasons, though.

This weekend, I'm hoping that reinstalling the old parts one-by-one will reveal what confounding variable is causing my timing issue (and hope that the over-tensioned belt was all that caused the noise, or that the cause will be otherwise revealed).

[loxxrider]

Why not use the app to see if it's over-tensioned?

[Aktapod]

I wasn't 100% certain what to enter for the belt info inputs, so I kinda guessed and it said it was okay between the water pump and cam pulley. I didn't think to check between the idler and cam pulley, though. I'll try that next! Do you happen to know where to find the inputs to give for the 3B belt?

[loxxrider]

Don't they have that information online if you look up the part number for it? I'm not sure because I haven't done that yet.