Friday, April 7, 2017

Different Flywheel - Still Vibrates!!

In the previous post, I'd gone to the mammoth effort of removing the flywheel to see if could nail down the reason for the unpleasant vibration that was coming through the car ever since the new engine had been fitted.

First on the agenda today then is to measure the nose of the crank for any deviations that could be causing the flywheel to wobble. Even though this is very unlikely to be the case, (unless I'm very unlucky) it's worth checking while I can for peace of mind. Second task is to fit the flywheel from my old engine, fire it up and see what the result is...

Crank Nose Measurement
I confess now that this is something that really should have been checked out while I was building the engine, which to be honest I would have done if I'd known about it, but I didn't, so I didn't! Anyway, that was then and this is now and I need to find a way to securely attach the base of my DTI gauge to something so that the needle can rest against the crank nose.

Unfortunatly this is easier said than done as the base is magnetic and there is nothing but aluminium alloy within range! Curses Batman! So some creative thinking had to be devised and after a few failed attempts, I finally found a solution which was a crude as it was effective.

As you can see below, best I could manage was to use a G-clamp to simply grip the base against the bit of the housing that the covers the starter motor pinion. As this was the only place I could find, it had to do.

Now to turn the engine... after a quick look around it quickly became apparent that the only means I had at my disposal of rotating the engine was to stick a socket on the whopping big flywheel nut attached to the end of crank nose and rotate that.

As I've gone on about on other posts, the engine rotates 'up the front and down the back', which from this end of the engine is anticlockwise. This posses a bit of an issue though as when you rotate a nut anticlockwise, it loosens it which is no good at all. So the only solution was to rotate the engine the wrong way which I can't imagine will wreak too much havoc after 3 turns.

What would wreak havoc though would be the engine starting by me rotating the crank. Even though it was in the wrong direction, I didn't want to risk it, so I took the HT leads off the spark plugs to avoid this tiny risk.

After three rotations of the crank, the needle on the dial gauge hardly deviated at all which means that the crank nose is nice and straight.

Alternate Flywheel
So now onto the main course which is swapping over the flywheel with my good old tried and tested one to see if it makes any difference... and here it is in all it's glory...

Once it was mounted into place, I torqued it up to the required 152Nm (big torque wrench required) and nipped one of the locking tabs over as the last thing I wanted was for it to come loose and tear the housing to bits. Oh what fun that wouldn't be!! Anyway, once the engine was fired up it soon became apparent that all my efforts hadn't made that much difference as I could still feel that damned annoying engine vibration coming through the body of the car. - Pooh!

Fan Check
While I was at it, I thought I might as well rule out the fan as the source of the problem. Although I knew it was highly unlikely, I checked it out anyway. With the fan belt detached from the lower pulley, I fired up the engine and sure enough it was still wibbley-wobbley. Well at least I know now.

Well apart from concluding that this has been a mahoosive waste of my time and energy, I'm beginning to run out of simple options and am worried that I'll end up having to pull the engine apart again.

There is one last thing however left to check, which I would have never thought about at all until a friend suggested it and that's the engine mounts. Not only am I pinning my hopes on this as it's my last hope, but also because the mounts that are on the car a the moment are not the mounts that were on the old engine, so there's a chance that the new ones are too harsh.

Thankfully the 'old' mounts are still in excellent condition as they are not that old, so the plan is to dig them out of storage, bang them on and cross my fingers!!! That is of course just as soon as I've swapped the flywheels back over and got this side of the engine back together; which given the space I have to work with and how difficult it was to get off, is no mean feat!!!

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  1. Maybe fit a harmonic balancer to the front of the engine??

  2. I might look into it, although I don't think the 998 has a harmonic balancer. I could be wrong though.