PLEASE HELP - Engine Knocking Sound - Video Inside

[Guvnor]

Please watch the video below. I'm not sure what to make of this knocking/rattle sound but it does not sound good. You can only hear it when the engine is warm and runs fine otherwise. The motor is stock but does have the upgraded cam tensioners.

It sounds like it is coming from the top or front of the motor and in the second half of the video I take the fan belt off. I'm finding it really hard to isolate the sound.

Any advice or additional things to check would be greatly appreciated.

Here is the video:
https://www.youtube.com/watch?v=f7i6XxU5Mtg&feature=youtu.be

Thanks!

Steve

[Quicksilver]

Rod knock would be a 'slower' sound. Really hard to tell from the video but it might be the chain.

You can use a long screwdriver as an engine stethoscope. Just hold the tip to the place you are checking and the handle to your ear. (Watch your hair and loose clothes around the fan and belt...) I'd start by checking the chain housings to see if that is the issue. If it is a tensioner/chain-guide issue you will want to get it handled before it skips a tooth and becomes an expensive "let's replace bent valves" issue.

[Justin@Athens]

That almost certainly sounds like chain rattle. I wouldn't run the car at all until you pull the chain covers and I bet you will find broken rails and or failed tensioners.

[Bob Kontak]

Originally Posted by Justin@Athens

That almost certainly sounds like chain rattle. I wouldn't run the car at all until you pull the chain covers and I bet you will find broken rails and or failed tensioners.

Yep.

You dodged a big bullet. A PITA but not terminal.

Bruce Anderson says (said - RIP) in his 911 Performance Handbook that failed tensioners will sound like a chain being pulled over a metal garbage can.

The video sounds exactly like that.

[DRACO A5OG]

Remove fan belt and try again. If it repeats it is chain tensioners if gone it will be the alternator.

Couple of minutes only, no longer.

[356911930]

^^^ This! Same thing I was thinking.

Rahl

[DRACO A5OG]

2nd Half of video, he removed the belt. It sure sounds like failed tensioners. Time for tensioner locks or update to Carrera tensioners but that will require addition of oil lines maybe new covers???

Fudge, sorry Brother.

[Guvnor]

Thanks everyone, the knowledge base lurking in here is amazing. It looks like I'm going to focus on removing the chain covers to take a better look.

I've dropped the motor to replace the air box before and it was a fairly painless process. Is this one of those jobs that is much easier to have the engine out? When replacing the tensioners, do I need to replace the chain too?

Thanks again!

[DRACO A5OG]

You can do a partial drop for better access. no need to drop her completely. No need to replace the chain. it should be fine but take a close look at it and the sprockets.

Have to remove the tin.

[jason2guy]

you can tell which side its coming from when youre in front of the engine. you dont have to drop or partially drop the motor- remove the muffler and the rear sheet metal and youll have plenty of access. most nerve racking part of job is securing the chain while the replacement takes place. there is the proper tool and if i were you id buy it. last time i did this job i got a pretty stout zip tie and i was able to get the chain real tight that way- it worked fine.

[Guvnor]

I'll try and dive into it this weekend. I'll post my findings here in the event it could help someone else diagnose a bad tensioner... Although is sounds like I was pretty lucky since the chain didn't break too.

[DRACO A5OG]

Exactly :-)

If you replace the tensioner, just make sure you compress it slowly as not to blow the inner oil seal. Some of us do it too fast and will blow the seal then it will fail.

[Guvnor]

So I pulled the chain covers off of both banks and everything looks pretty good. I did notice that the tensioner on the left moved relatively easily compared with the right side. You can see in the video clip below that it was moving easily then made a clicking sound and became harder to move.

How can I tell if the tensioners are bad?

Video Clip of left tensioner
http://vid1313.photobucket.com/albums/t560/Guvnor311/File_005_zpsbuys4vkx.mp4

Left Side


Right Side

[911obgyn]

Look at the little cups on the end of the tensioner, they have a spring and a ball under them, i had a tensioner fail because the cup came unseated and the spring was not holding the ball tight. I was lucky the thing didnt fly off and get lost in the sump. While I was in there I replaced my chain ramps, they were pretty used up and they were cheap.

[Guvnor]

Originally Posted by 911obgyn

Look at the little cups on the end of the tensioner, they have a spring and a ball under them, i had a tensioner fail because the cup came unseated and the spring was not holding the ball tight. I was lucky the thing didnt fly off and get lost in the sump. While I was in there I replaced my chain ramps, they were pretty used up and they were cheap.

Looks like the same thing happened to me. You can see a hole in the top where the other looks like it has a plug.

Do you think I should replace both or just the one tensioner?



notice the plug in the top of this one

[kyngfish]

Great thread, thanks for keeping us posted through the process and taking great pictures.

[DRACO A5OG]

OP, just the one that is missing the bleeder valve.

Get yourself a HF oil can and prime both tensioners after re-install. You will notice allot of air coming out those bleeders. Do it twice each after install.

The torque is 18-23 ft lbs on that chain tensioner 13MM nut. Make absolutely certain all moves freely and remove any rust of corrosion and apply some assembly lube or moly kote.

Oh yeah, dump the oil, that missing bleeder is probably in the engine now

While you are there, replace the orings, those get tired fast and will cause an annoying leak the torque value for that banjo bolt is 7.4 ft/lbs, no more or you will over squash the seal rings ( yes you need new ones ) and create a leak.

[Guvnor]

Originally Posted by DRACO A5OG

Get yourself a HF oil can and prime both tensioners after re-install. You will notice allot of air coming out those bleeders. Do it twice each after install.

The torque is 18-23 ft lbs on that chain tensioner 13MM nut. Make absolutely certain all moves freely and remove any rust of corrosion and apply some assembly lube or moly kote.

Oh yeah, dump the oil, that missing bleeder is probably in the engine now

While you are there, replace the orings, those get tired fast and will cause an annoying leak the torque value for that banjo bolt is 7.4 ft/lbs, no more or you will over squash the seal rings ( yes you need new ones ) and create a leak.

Thanks for the advice. New gasket set, along with o-rings and seal rings arrived today and hopefully the tensioners from our host tomorrow. I'm going to do both and keep the good used one as a spare.

I didn't think about the oil but that is a good call. I should probably pull the sump plate so I can check the screen too. Guess I'll need another gasket for that.

[DRACO A5OG]

Outstanding and break a leg Brother, Keep us posted

[Guvnor]

Quick update: New tensioners are in and she now sounds as smooth as silk feels. Thanks again for all the help and advice along the way

Old versus new. You can clearly see the missing check valve on the old tensioner


Don't try this at home. I opted not to buy the $18 special tool and use zip ties to keep tension on the chain while the tensioners were out