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Knock Knock Knocking on Engine's Door

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I have a loud knocking sound coming from the engine compartment (video clip with audio here).

This is what the mechanic has diagnosed so far; I am looking for additional insight:

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Yikes!

I had a cold knocking once that was due to a loose header flange, it would knock until it warmed up enough for things to expand a bit, and make a solid connection. But.........it was more of a click/knock sound.

Hope it's an easy fix.

Edited by Erzulis Boat

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Some things to check --

- valves need adjusting? That's a noise that could go away when warm because of metal parts expanding.

- is the 60ft-lb. nut on the crankshaft (holding the pulleys on) tight? That wouldn't make sense for going away when warm, but you never know, and it is known to cause a rod-knock-like sound. Worth checking.

- piston slap -- pistons worn just enough that they knock in the cylinders a little bit, but expand when heated and go away.

- my computer speakers suck, but that doesn't sound like a big, heavy crank/rod knock. That sounds more like a top end noise to me. I'd check things like valve guides and seats, valve stems for wear.

- I can't tell from the sound, but if the knock sounds slightly exhausty, it could be a burned intake valve, and a slight amount of exhaust is piffing out

- but if the noise is entirely metallic, then probably not

- being loudest at the bellhousing may or may not mean anything -- it could be coming from anywhere and just be amplified there . . . or it could be the throwout bearing? (that's a real stretch of a possibility, though)

Just some suggestions off of the top of my head. Hope it helps!

- T

Edited by Tony K

Tony K. :)

 

Esprit S1s #355H & 454H

Esprit S2.2  #324J

1991 Esprit SE

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Thank you for the input. These are all deeper suggestions than have initially been thought of (i.e. vacuum leak, vac pump, bolts attaching exhaust manifold to engine, etc.)

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Tricky one,I get a bit of piston slap when cold and I understand that its not unusual. This sounds different to that, more like valve running gear IMHO.

Mikey

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Had a noise like that which turned out to be an exhaust manifold gasket...but, by then, I had the whole thing in bits!! Would have sworn it was something serious...so check very carefully before you start to tear it apart.


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Had a noise like that which turned out to be an exhaust manifold gasket...but, by then, I had the whole thing in bits!! Would have sworn it was something serious...so check very carefully before you start to tear it apart.

Interesting. I just had the exhaust manifold replaced last May, although I don't remember this sound last year. How bad a job is it to replace the gasket?

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If it is an exhaust related issue, usually the fasteners are the source of the problem at the start.

Once the gasket has been banged around by a loose connection, then change out the gasket (cheap insurance), but the nuts on the studs are the usual culprit. Thread compounds (Loc-Tite etc.) are not the real solution, I would advise that bona-fide mechanical locking nuts are in order.

I have seen people utilize lock nuts with the nylon element and kind of survive, but there are aircraft application suitable nuts that are constructed entirely from heat resistant alloys.

I will not build a motor without aircraft level lock-nuts on every exhaust system connection/flange.

It might not be a fastener/gasket issue, but this is just a heads up.

I have to redo my exhaust flanges on my Range Rover (clicking/knocking when cold) because the factory used a thread compound, and after 9 years has finally crapped out. Lock nuts will be installed-no question, as well as new flange gaskets.

Your video sounds like it might be something else............but we can hope, can't we?

I listened to it again, it sounds like a reciprocating or up/down clicking with some criiingcruuung with the click. Does not sound like a exhaust system knock, an exhaust system knock is usually not so pronounced on idle, it gets quite loud on a 1st gear load in the morning, then backs down after about 5 minutes on the road. Good luck!

Edited by Erzulis Boat

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I agree with previous post, sounds a bit different from exhaust. In my experience blown manifold gaskets sound more like noisy tappets. You have about 20 seconds starting from cold to feel for leaks with your hand!

The noise sounds pronounced enough to locate with an engine stethescope. How many miles has the engine done, has it recently had anything done mechanically? Has your heater and cooling system been performing correctly recently?

Steve

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The latest in troubleshooting:

The sound seems to be influenced more by the accel/decel mode of the engine than anything else. The sound seems mechanical and in sync with the engine speed, whether it's half/same/double speed I'm not sure.

Next step: change the oil filter and add the new oil then run the engine again. An old timer at the NAPA store has heard a lot of engine noises over the years, but the fact that the noise is louder when accelerating and quiet when decelerating left him scratching his chin.

As for a broken Piston, another fellow had three broken pistons in his V8 and they didn't make any noise. From what I could see of your Pistons and Rods, they seem OK.

The next test I'll try is to check the valve lash, The noise doesn't seem to come from there, but... Depending on the result I'll remove the three V-belts and run the engine for a half a minute. That should eliminate the Vacuum Pump, etc.

The noise sounds pronounced enough to locate with an engine stethescope. How many miles has the engine done, has it recently had anything done mechanically? Has your heater and cooling system been performing correctly recently?

The engine has never had a full rebuild; it has 66k miles on it. It was out a few years back and the valves were reseeded, new piston rings, new timing belt (and a couple since then), probaly some other items I am forgetting. Last year the engine was out for a new exhaust manifold.

I replaced some of the AC pieces last year and have not noticed anything out of the ordinary regarding heating and cooling.

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You would be surprised where knocks come from...........but that doesn't sound too healthy.

Changing the oil will have a 99% chance of failure of eliminating that knock I fear.

I have listened to the video about 20 times, and do not get a good feeling.

There is a click and a slap sound, if all the external rotational stuff checks out (pulleys, belts etc.) then it is probably internal.

I do not like the fact that the knock gets louder towards the rear of the engine. About halfway through the video there is a distinct double knock.

I have my fingers crossed for you............please be a bucket/cam lobe issue.

Edited by Erzulis Boat

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I have heard one time a noise very very similar to that, in my opinion it seems like a bearing failure..probably main engine bearing.

;)

Not good sound anyway...

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It has a "tinny" sound, that sounds like cam cover harmonics, as Tony was saying, a main is deeper and "thuddy".

You were stating that the valves were re-seated? Lapped/ground existing seats, or an actual re-seat?

The sound leads me to believe it to be an internal top end problem.

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uhmm....

maybe I'm wrong but the sound I have heard was more "tinny" than this and was a main.

By the way, top end problems in valves area generally are confirmed by a burnt oil in the exhaust or I'm wrong?

;)

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Sounds very similar to my 83 with "piston slap" on cold start up. Engine had 46,000 on the odometer. Once warmed up the pistons expanded and noise decreased. If the engine has been overheated this problem only becomes louder. If you buy a engine stethoscope you will be able to pinpoint the origin.

Good luck,

Jeff


www.espritturbo.com

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I didn't really consider piston slap, that would be one slappy piston. It might very well be.

From the info- the noise is more pronounced under load, which might go hand in hand with piston slap.

Stethoscope time.

Keep us posted.

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I'm leaning toward piston slap or valve/top end noise.

In keeping hopeful about exhaust, an exhaust leak would also be louder on acceleration and quieter on decel . . .

Keeping my fingers crossed, too. . . .


Tony K. :)

 

Esprit S1s #355H & 454H

Esprit S2.2  #324J

1991 Esprit SE

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Thanks everyone for the replies. I also posted on the Turboesprit Listserv and some good ideas are coming back there. I will be sure to update this thread with the resolution if/when it happens.

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To expand further on the leaky manifold gasket idea...mine sounded exactly like a little end bearing; loud under acceleration, quiet on the overrun..driving with the window open past buildings the noise reflected from the walls and was truly godawful. The root cause of the problem turned out to be improper fitting of new exhaust studs, they seemed fine but two of the nuts on no.4 were bottoming on the stud threads and not compressing the gasket sufficiently..was OK until the engine had done some mileage and the gaskets had compressed a bit, resulting in a developing leak. Cure was simple:new gaskets and a couple of extra washers!! The gaskets are individual to each cylinder, not one overall exhaust gasket. Let's hope this proves to be your problem..since the manifold has been changed recently,I'd say you were in with a chance.


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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I'm not going to propose to answer this as my exposure to Lotus engines is nil. But, going on the video, the noise is far louder over the cam covers. That suggests top end pretty quickly. A lot of guys on here have suggested manifold leak. There is an easy way to listen for either vacuum or pressure leaks, even if the obvious sound dissappears after a short while. A length of 3mm vacuum hose or similar is the easiest way. Put one end in your ear and move the other end over suspect leak points and you will hear the leak as clear as a bell in your ear. If you can see the 'test' end of the hose and you change the way the hose end points, you can pinpoint pretty accurately where a leak is. Depending on the strength of the leak and experience, you can actually tell by the physical feel in your ear whether it's a vacuum or pressure leak. One feels like someone blowing in your ear (i.e. pressure leaks should be everyones favourite) and the other one sucks.

If you don't want to fork out for a stethoscope either, a screwdriver handle held to your ear and the other end at suspect points again on the engine is just as good as a stethoscope.

Edited by ramjet

All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

Opinions are like armpits. Everyone has them, some just stink more than others.

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It would be useful to hear the engine being slightly revved.

My S3 Turbo sounds exactly the same from cold and it has a fully rebuilt engine to HC spec.

The noise is definitely cam / valve noise, which may be improved by re-shimming the followers.

I personally have left mine alone as I know that my engine is effectively only a few thousand miles old.

To settle your mind, you may wish to lift the cam covers and just check the cam profiles etc for signs of wear or damage.

Kind Regards

Craig

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It would be useful to hear the engine being slightly revved.

To settle your mind, you may wish to lift the cam covers and just check the cam profiles etc for signs of wear or damage.

Craig -

Thank you. I will try to post a new video/sound clip with the engine revving (except I don't have the car anymore - it is in the mechanic's hands). But I passed along your suggestion.

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Hey guys,

I feel like it is just the valve lash is a out of wack. I too have an HC with about 4k on it and at start up I have a tapping noise fromt cam boxes. Once she is warm and running it goes away. I have checked the valve clearance and I have a couple on the bubble put still in spec. I figure at timing belt replacement I will re-shim. I have often read on this sight about noises at start up such as "mine sounds like a bag of spanners'. Check your valve lash, I will bet you are out of spec.

Cheers

Clay

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Check your valve lash, I will bet you are out of spec.

Update:

The wastegate was removed and reinstalled, removing a small gap that was down there. No change in the sound. (But the turbo lag is gone.) :devil: Valve lash was checked yesterday and everything looked ok. Still working through some of the other suggestions. Thanks again!

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