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View Full Version : Broken 1.8t to rebuild 1.8t...



HumbleTurbo
04-28-2017, 04:03 AM
Well last week my 99 A4 1.8T bent its crankshaft, I can tell this because the crank pulley is crooked as shit and the bolt is still seated in the front.... The details on how this happened is still unclear but I am guessing it happened from revving the motor much.. much past redline. Anyone else seen this before? Not that it matters too much because its getting a new motor anyway, but finding out why what and how is half the fun.

There is a stage 1 tune (not sure which tune, but pushes 16psi boost) and the rev limiter is yet to be discovered, hence the bent crank. So, time for a new motor, I already have an AEB 1.8T in the garage that I rebuilt on a b5 Passat I had in past years, so that is going to be going in.

Never been this deep into an Audi before but I'm imagining its not going to be too different than the Passat. What I'm hoping from my AZ friends is for some advise on anything I might run into that I may not for see coming. Car has 227k on it, minimal rust, but if there is any that will be taken care of, debating new motor mounts, the stock turbo will be looked at and a rebuild kit will ordered if necessary, that is... unless someone on here can give me a better idea, which I'm open to. I don't mind throwing a little money at this job since I already have the motor, I'd really like a suggestions on a better/larger turbo but I'm not too keen on having to do a lot custom work to the structure of the car, but once again, open to suggestions. Its other supporting mods are Hyperboost DV and a turbo back exhaust, not sure its size, but has cat delete. Suspension has Koni adjustable coilovers and I just did an FCP Euro control arm kit this past fall, not that suspension has much to do with motor talk but oh well....

I'll try to get some pictures uploaded this weekend, any comment will be much appreciated!

Nollywood
04-28-2017, 04:11 AM
I've never heard of a crankshaft getting bent through over revving. Bent cranks are usually an attribute of hydro-locking, when the engine sucks up water through the intake, and the piston tries to compress it.

HumbleTurbo
04-28-2017, 04:20 AM
I've never heard of a crankshaft getting bent through over revving. Bent cranks are usually an attribute of hydro-locking, when the engine sucks up water through the intake, and the piston tries to compress it.

This logic makes very much sense to me yet there was not water around when this motor took its last breath

inc4203
04-28-2017, 04:29 AM
Is this an OEM crank pulley. Is it possible the rubber just failed and the pulley is junk making the crank to appear like there is a problem? I work for Fluidampr and have seen this before.

CoyneJ
04-28-2017, 06:54 AM
There is now way crank could bent from stage one tune

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Believer
04-28-2017, 07:49 AM
More than likely the bolts backed out of the pulley allowing it to develop play. The bolt in the middle of the crank pulley holds the crank timing gear in place and would have nothing to do with the crank pulley being loose.

HumbleTurbo
04-28-2017, 11:14 AM
I am going to have the car in service mode by the end of today so I will let everyone know what exactly is goin on with that pulley. Still likely that I bent some valves since its an interference motor though eh? I'm getting the feeling that you guys are saying the motor might not be shot, not a bad thing at all but I'm not getting my hopes up either.

Believer
04-28-2017, 08:36 PM
If there wasn't a timing belt failure or other timing component failure your valves wouldn't be bent.

Did the car stop running or something else drastic or did you just notice the loose pulley? The pulley on the front of the crank isn't involved with timing at all so i wouldn't worry about the motor unless there's a verified reason to. Let us know what you discover

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HumbleTurbo
04-29-2017, 07:18 PM
Got it into service mode, the pulley bolt had sure enough just backed out, it did not snap the bolt or the crank; Next time I will make sure to ask the AZ community before jumping to conclusions on diagnosis, the hardest part of mechanics in my opinion. unfortunately though I did bend valves, did a compression test not getting compression in any cylinder, bummer their, got my hopes up even though I said I wouldn't. At this point I'm wondering why the bolt backed out.. too much vibration? I haven't felt anything excessive, maybe wasn't torqued properly by whoever did a timing job before? not sure... I'm wondering so I can put the necessary work into the car before I put the next motor in, which at this point I'm back to my original plan of doing.

Also having trouble figuring out how to upload photos, this is my first thread if ya cant tell...

Believer
05-01-2017, 07:28 AM
When you refer to the pulley, of which below are you referring to? One is a pulley, one is a gear.

https://c1552172.ssl.cf0.rackcdn.com/139885_x600.jpg

https://c1552172.ssl.cf0.rackcdn.com/33512_x600.jpg

The former cannot cause your valves to bend, the latter however, will but isn't something that is normally touched during a t-belt change. At either rate, sorry to hear about the valves. I went through the head rebuild, it wasn't too bad other than not having all the parts I needed when I needed them. I didn't account for everything I was touching having 140k miles on it and ended up needs various gaskets, o rings, etc I didn't account for. Good luck!

HumbleTurbo
05-02-2017, 03:44 AM
The bolt ran through both the pulley and the timing gear, when it backed out both the pulley and the timing gear came loose, giving slack to the belts and causing valves to go bendy bend. Also it shaved the timing mark right off the pulley when all the chaos happened, pretty crazy. I don't plan on rebuilding this motor, at least not yet, I have one I rebuilt from my Passat a few years back.

Pulled the broken motor last night, fuckin 1.8's got a lot of hoses and shit, seemed like every time I thought I had everything I'd find another connecter or hose I missed. The turbo does have quite a bit of play in the shaft so I will be ordering a rebuild kit for the stock one, unless I can think of a better option. Everything else seems pretty good, there is almost no rust in the engine bay so I'm pleased with that. Id like to replace the motor mounts but I don't want to pay the 160 for the 034 mounts that I really want, along with their breather kit, id like that too. I digress

Thanks for the comments on figuring what actually happened with the carnage, I will be re-torqueing every bolt on the new motor going in to prevent this from happening again. Especially the damn crank pulley/timing gear bolt or whatever it needs to be called.

Believer
05-02-2017, 08:32 AM
The bolt ran through both the pulley and the timing gear, when it backed out both the pulley and the timing gear came loose, giving slack to the belts and causing valves to go bendy bend. Also it shaved the timing mark right off the pulley when all the chaos happened, pretty crazy. I don't plan on rebuilding this motor, at least not yet, I have one I rebuilt from my Passat a few years back.

Pulled the broken motor last night, fuckin 1.8's got a lot of hoses and shit, seemed like every time I thought I had everything I'd find another connecter or hose I missed. The turbo does have quite a bit of play in the shaft so I will be ordering a rebuild kit for the stock one, unless I can think of a better option. Everything else seems pretty good, there is almost no rust in the engine bay so I'm pleased with that. Id like to replace the motor mounts but I don't want to pay the 160 for the 034 mounts that I really want, along with their breather kit, id like that too. I digress

Thanks for the comments on figuring what actually happened with the carnage, I will be re-torquing every bolt on the new motor going in to prevent this from happening again. Especially the damn crank pulley/timing gear bolt or whatever it needs to be called.

Correct, the bolt runs through the pulley, however it does not hold the pulley on. The pulley is held on by 4 separate hex bolts. Just want to make sure you understand that large bolt does not hold the pulley in place so if both the gear and the pulley came loose someone really jacked up putting it all back together. Unfortunate situation. On the turbo front, probably a good idea to rebuild if you think you have the ability. It would be unfortunate to put it all back together to only have an issue with the turbo shortly thereafter. Good luck with getting the new motor installed and everything else!