Noises on acceleration 3.5 V8

[Jer]

Folks I'm new to the forum and have been an enthusiast for some years. I've been fortunate enough to pick up an 88 3.5 V8 auto for zilch from Sydney with nothing but a starter motor needing to be fitted to get it running. Since then she's recieved a few mods courtesy of my old 77 2 door donations.

I'm having a problems with some awful noises coming on acceleration, not when cold but when warm at all speeds. The noise sounds like a fan catching on a peice of wire clacking loudly and sounding as if something is just about to give up the ghost. To date nothing has happened. I've checked all pulley belts, fan blades, engine mounts, anything loose interfering with blades or wheels. Nothing has revealed anything to cause alarm or consideration to tighten etc.

I've been reading some stuff on the Discovery where the inlet manifold has warped by a few mil next to the engine and is making somewhat the same noise. I have not as yet taken the manifold off to inspect it although I can tell you it's pretty rusty, not cracked and probably in need of replacement in years to come.

Anyhow I'm flummoxed with what it is and don't half **** myself when the noise comes. It does go when I back off on the pedal. However not always a solution when your trying to get somewhere and need some oooomph.

The engine is on 240000 kms so not necessarily worn as such. Tons of power now I've added a snorkel and new air filter. Not on gas just straight fuel.

Hope someone can help.

Cheers

[alfredenewman]

seems kike you might have a crankshaft problem ie big end bearings which is not good news. any decent mechanic or knowlegable enthusiast should be able to say yea or nay if its yea its rebuild time.

[patch1]

seems kike you might have a crankshaft problem ie big end bearings which is not good news. any decent mechanic or knowlegable enthusiast should be able to say yea or nay if its yea its rebuild time.

I agree

[Hybrid_From_Hell]

Big ends = deep knocking noise

Little ends = not as deep a noise but sort of as you describe as would a broken /worn pistons rings bore

Try a compression test on all 8 cyl

Nige

[steve_d]

So to recap.

Noise not present when just reving the engine?

Noise when under load?

I'm going to put a side bet on flex plate.

Steve

[landmannnn]

The engine is on 240000 kms so not necessarily worn as such.

Cheers

At 240,000kms a rover v8 engine will be very worn.

[RILEY]

150,000 miles Bit tired my friend will have plenty of power its a v8 serious investigation required

[Landowner]

Could be a front prop U/J , I had a similar noise on my 110

[Jer]

Could be a front prop U/J , I had a similar noise on my 110

240000 kms in AUSTRALIA is not considered a hard slog with a 3.5 V8, average road speed 60 miles an hour tops, great weather, little salt or silt on the roads and little need for waiting to heat the engines up prior to driving. Guys have ran rangies with GSH up to 500 k with no issues. However I do take the point it's getting on a bit. I know the history of the vehicle and it's been driven with care, no towing or off roading ever or usage in anger.

Noise is not present when just revving the engine although to be fair I have'nt flogged it when in neutral as my neighbours would not be impressed. It's present under load whilst towing a camper trailer when it goes into kick down, but equally comes in when not under load on a flat stop start. I need to emphasize that the sound does not continue as soon as I back off the pedal.

Sorry about this but I'm at loss as to how a crankshaft, big end bearing or UJ will sound like someone is whacking a length of wire off a tin can. I would expect these noises to either be more thumping or grinding and with the UJ would'nt the shaft balancing be evident with it reverberating through the vehicle. I had somewhat the same problem some years ago with my TDI disco and initially I thought it was a wheel out of balance until I found out it was the front UJ on the shaft.

I 'll check it anyhow and let a mechanic listen to the sound to see what comes up. Thanks folks.

[Landowner]

Sorry about this but I'm at loss as to how a crankshaft, big end bearing or UJ will sound like someone is whacking a length of wire off a tin can. I would expect these noises to either be more thumping or grinding and with the UJ would'nt the shaft balancing be evident with it reverberating through the vehicle. I had somewhat the same problem some years ago with my TDI disco and initially I thought it was a wheel out of balance until I found out it was the front UJ on the shaft.

The metalic noises, squeaks, ticks, etc., can be made by a dry uj bearing breaking up, mine sounded like two dry washers rubbing together and wearing each other away. The noise disappeared when cruising or decellerating and was only evedent starting off and sometimes only in first gear, very strange..

[SteveRK]

Couple of thoughts on this problem:

Is it engine RPM related? i.e. does it make the noise at the same frequency regardless which gear, first gear, second gear etc, ?

This would elliminate props-shafts, final drive and hubs.

If engine RPM related that leaves engine and gearbox; and by gearbox also flywheel/flex plate to torque converter bolts (I assume yours is an auto). I am not familiar with the Land Rover auto box setup but on other makes the flywheel is typically more of a steel disc with several mounting points for the torque converter. If these were loose this would cause flexing under load - possibly.

If yours is a manual box then the noise could be related to gears/bearings on the input shaft side?

[Jer]

Couple of thoughts on this problem:

Is it engine RPM related? i.e. does it make the noise at the same frequency regardless which gear, first gear, second gear etc, ?

This would elliminate props-shafts, final drive and hubs.

If engine RPM related that leaves engine and gearbox; and by gearbox also flywheel/flex plate to torque converter bolts (I assume yours is an auto). I am not familiar with the Land Rover auto box setup but on other makes the flywheel is typically more of a steel disc with several mounting points for the torque converter. If these were loose this would cause flexing under load - possibly.

If yours is a manual box then the noise could be related to gears/bearings on the input shaft side?

I've checked the props and UJ's. No play play and nothing untoward. I did rev it to bits and have found the sound in the top left region of the engine either at the manifold or actually inside the rocker cover. If the rocker cover would this be top end bearings???. I'm still of mind it could be the manifold metal gasket flapping given it could be warped, but then I'm not sure.

I suppose I need some indication of how long I can drive this thing without something catatrosphic happening. I have an 800 mile round trip planned at the end of the month and if it's top end bearings or flex plate what would the potential damage be if I continue to drive. Last thing I want is to be stranded in the outback- not a cheap place for a tow in Aus.

Another thing from memory with the installation of the starter motor was that the teeth on the old starter motor were broken- approximately three teeth were broken off and lying in the recepticle. I did give it a good clean out prior to placing the new one in. I don't know if this has any bearing on the flex plate though.

When you say flexing under load what exactly is the plate doing??.

I 'll take it to a specialist tomorrow as I'm now somewhat concerned. As you all know with these things taking it to a mechanic with someone like myself who's a self taught mechanic I'm very sceptical whether or not I'm being ripped off. I must not whinge though I got the truck for nothing.

Thanks again