Knocking on 4.2 in RR Classic Help!!!!!!!

AR018 · Post by **AR018** » Sat Aug 28, 2010 2:44 pm

Hi All

Hoping someone here has some more ideas as we are running out fast...

We have a knocking sound very much like top end noise probably more evident on the nearside of the car than the offside.

We have so far: changed the cam (for new standard cam), cam followers for new hydraulic ones, changed the timing chain and gears. swapped in second hand pushrods and rocker shafts from a (before total loss of compression following overheating) working engine. swapped all the ignition, HT leads, plugs, cap, etc. Taken the heads off and opened up the pushrod holes in the head (there is some marking on the removed pushrods to suggest that they may have been hitting the head). and done one hell of a lot of head scratching (ours not the cars?)

And yet the noise is still there!

We have also been over the whole engine, bellhousing and front end of the gearbox with the stethoscope, and still come back to the nearside head area as the most evident.

I have also bought new pushrods, but these seem to be the heavy duty rods and are fatter than the standard ones.

Gut feeling is that the pushrods are still hitting the heads, we have thought about putting the new pushrods in, but are concerned that if the ordinary pushrods hit the head, the fatter ones are going to hit much more severely and may do damage.

There is little difference on load or off load, but the noise is only present once the engine has warmed up. The noise is more noticeable behind the engine than in front.

We have not changed the cam bearings, but there is no obvious signs of excessive wear on the bearings,as far as I can see, on the removed camshaft. (the lobes have definitely seen better days)

We even suspected the flex plate as this engine is mounted to an autobox and there were reports that this could be a similar type of noise. but we have removed the bell housing cover and, as best we can without as yet removing the engine, inspected the flexplate, torque converter and flywheel.

If anyone has any thoughts about this, they would be very much appreciated.

Thanks
Andy

ian.stewart · Post by **ian.stewart** » Sat Aug 28, 2010 3:22 pm

Checked your exhaust gaskets, thar can make a horrible tapping noise

AR018 · Post by **AR018** » Sat Aug 28, 2010 3:48 pm

Hi Ian

Sorry should have mentioned that one. Yep new exhaust gaskets manifold to head. we do have slight manifold to down pipe leak, but our noise is a knock rather than a blow (although there is obviously a blow as well!

Thanks
Andy

ian.stewart · Post by **ian.stewart** » Sat Aug 28, 2010 4:40 pm

whein I blow a exhaust/head gasket it sounds terminal, got to a point where I never know if engine has a problem or the gasket has gone again
It sometimes sounds like a bottom end tap or sometimes a knock,
How far is your engine modified, Piston slap can be a problem with some rovers too

AR018 · Post by **AR018** » Sat Aug 28, 2010 4:45 pm

Engine is totally stock, RR is my dad's run around. 4.2 has been perfectly enough power despite us all doing a lot of towing.

Definitely agree with the noises from the gaskets, but we have replaced these ones and tightened to specified torque. also checked with hand for blowing.

The noise we are getting is possibly best described as like dropping a spanner on the floor.

Thanks
Andy

ian.stewart · Post by **ian.stewart** » Sat Aug 28, 2010 5:52 pm

If its that sort of noise, I would be thinking flex plate too, starter jamming in may produce a ringing noise, but flex plates do work harden and crackCould be a bolt screwing out and clipping something

jrv8 · Post by **jrv8** » Sat Aug 28, 2010 7:31 pm

Try to prove the noise to a particular cylinder by taking off the plug leads one at a time.
If you take a lead off and the noise goes away, it rules out the flexplate etc.

Jim

AR018 · Post by **AR018** » Sun Aug 29, 2010 7:52 am

Hi Jim

We have done the HT lead removal trick, even done the injector plug removal trick, and there is no difference when disconnecting any cylinder. I am hoping this rules out: big ends, little ends and piston slap, unless anyone thinks different.

Thoughts welcomed...

Has anyone ever had pushrods hitting the locating holes in the heads?

Thanks
Andy

CastleMGBV8 · Post by **CastleMGBV8** » Sun Aug 29, 2010 9:40 am

Andy,

Worst case scenario would be a slipped liner, possibly 6 or 8, has the engine suffered from overheating and or loss of coolant at some time?

What actually happens is that once the engine warms up, expansion allows the liner to move up and down with the piston and makes contact with the head face causing a knock.

Try using a long screwdriver as a crude stethoscope and put the end on the block by the head joint around cylinders 6 & 8 and see if you can hear where the noise is coming from.

Kevin.

DEVONMAN · Post by **DEVONMAN** » Sun Aug 29, 2010 10:17 am

I'd agree with the slipped liner possibility except if it's a nearside noise then it would be an odd number cylinder.
Out of interest, did the noise get worse over time or did it happen suddenly?
Regards Denis

AR018 · Post by **AR018** » Sun Aug 29, 2010 1:07 pm

Hi All

Thanks for responses.

The noise is probably more nearside than offside. having gone over the whole engine with a stethoscope, the noise appears to be more pronounced around cylinders 3 and 5.

Having taken the heads off, I didn't see any obvious signs of a slipped liner, but don't really know what I would be looking for. It was something we looked into from a relatively uneducated point of view, as we did consider these issues once the heads were off. (Had a 4.6 decide to do the slipped liner business!)

The strangest thing for me is how much more noticeable the noise is from behind the engine than in front. That is without stethoscope, just standing / walking around the car.

How do you tell if you have got a slipped liner?

Not sure about how the noise developed, we had got a noisy cat, an inlet trumpet that had worked loose and was rattling around (now replaced the whole set and casting) all at the same time. So the car was noisy and we needed to fix it!

Thanks for all the thoughts so far.

Andy

DEVONMAN · Post by **DEVONMAN** » Sun Aug 29, 2010 4:18 pm

AR018 wrote:

How do you tell if you have got a slipped liner?

The top of a slipped liner will be below the surface of the block and could be just a few thou down or alot more. A slipped liner usually does not make a noise unless it is so bad that it is contacting the crank counterweights.
However, if it's a loose liner it could move up and down with the piston and make a knocking noise when it comes into contact with the head. When the heads were off you would have probably noticed some marks on the head if the liner had been contacting the head.
Regards Denis

AR018 · Post by **AR018** » Wed Sep 01, 2010 3:42 pm

Hi Dennis

Thanks for the info.

It doesn't sound like a slipped or slipping liner then to be honest. there were no marks on the heads and i don't think any were noticeably low.

This leaves me still totally perplexed

Anybody got any other thoughts?

Thanks
Andy

kiwicar · Post by **kiwicar** » Wed Sep 01, 2010 3:52 pm

Hi
I think this was mentioned above, but is it piston slap? if so I would live with it, just ask a ducati owner, they don't loose any sleep over it

. does it occour at engine revs or half engine revs?
Mike

ian.stewart · Post by **ian.stewart** » Wed Sep 01, 2010 4:08 pm

kiwicar wrote:Hi
I think this was mentioned above, but is it piston slap? if so I would live with it, just ask a ducati owner, they don't loose any sleep over it . does it occour at engine revs or half engine revs?
Mike

Dont need to ask a ducati owner, Just ask a Rover owner who runs a loose engine about slap

mine sounds like a bag of nails,