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1989 Range Rover Classic
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Discussion Starter #1
I recently had a top-hatted custom 4.6L built for my range rover classic, and while it runs great, tons more power and good oil pressure, I've noticed this knocking sound that appeared after about 500 miles, and has steadily gotten louder (now at about 800 miles). I don't think it's the bottom end (rod bearing or something), since the oil pressure is 50psi when cold, 30psi when hot at idle, so is it piston slap perhaps? Or something else? I took it back to my engine builder and he says he can't hear anything wrong, and my dad says he can barely hear anything, but I swear I certainly can, can any of you? What is it??? The motor is under warranty and the shop that built it is very accommodating/willing to help, but they say they can't hear anything wrong. The first video is at idle, the second is while driving (phone taped under the hood, bad sound starts at the 30 second mark).


 

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1970-1995 Range Rover Classic
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341 Posts
sounds valvetrain speed to me, probably loud lifter or rocker arm
 

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sounds valvetrain speed to me, probably loud lifter or rocker arm
I agree...
I hear it... kinda sounds like a lifter...
Might be the motor just smoothing itself out.... I would change the oil and filter
Just for kicks...
 

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1970-1995 Range Rover Classic
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136 Posts
doesn't sound rod knock or piston slap as much as valve. use a stick or stethoscope
 

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1989 Range Rover Classic
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147 Posts
Discussion Starter #5
sounds valvetrain speed to me, probably loud lifter or rocker arm
You think top end over bottom end? It sounded more low pitched to me than the usual tick tick tick of lifter clatter, which is why I thought it might be something else.
 

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1989 Range Rover Classic
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Discussion Starter #6
Also lately I've noticed it start to go away at idle (the idle video is from 3 weeks ago, the second longer video is from a couple days ago), but I noticed it sounds louder when under load, but goes away when I lift off.
 

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It definitely sounds like a lower end rod/main journal knock. I work for a major auto manufacturer and am very familiar with an issue we have with main bearing knocking in our V6 engines. Sounds very similar to this. Does the noise change as engine temp changes? Can you duplicate it by brake-torquing the engine? Since it's still under warranty I'd strongly suggest dropping the pan and inspecting the bearings to either confirm or rule them out. At that time they could look at the lower cylinder liners to see if there's any evidence of excess wear.
 

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1970-1995 Range Rover Classic
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It sounds more like valve/lifter chatter in the second video. The first video has more of a bottom end sound. I would at least send the oil to be analyzed out. If you have the space, then drop the pan.
 

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But, if it's under warranty, just hand it back. There is something wrong with that engine and they need to work it out, not you.
 

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1995-2002 Range Rover P38A
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It's unlikely to be bottom end due to the oil pressure, 50psi cold and 30 hot if very good for one of these old lumps, and if it was indeed main or big ends, oil pressure would suffer.

Sounds top end to me, akin to a stuck NRV in one or more of the lifters.

not too uncommon to have a dead batch of lifters/tappets when building one of these.

However as above if it is under warranty send it back...
 

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1989 Range Rover Classic
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Discussion Starter #12
It definitely sounds like a lower end rod/main journal knock. I work for a major auto manufacturer and am very familiar with an issue we have with main bearing knocking in our V6 engines. Sounds very similar to this. Does the noise change as engine temp changes? Can you duplicate it by brake-torquing the engine? Since it's still under warranty I'd strongly suggest dropping the pan and inspecting the bearings to either confirm or rule them out. At that time they could look at the lower cylinder liners to see if there's any evidence of excess wear.
The noise is worst when cold, but doesn't disappear. I usually let it warm up for a minute when completely cold before I drive it somewhere, but if I just jump in and go it's significantly noisier. It's not as loud as it was about a month ago (the first video), but I can definitely still hear it (longer video). I think the higher pitch sound then the second video is due to listening from outside vs in the wheel well. What do you mean by brake-torquing the engine? I haven't tried that.
 

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1989 Range Rover Classic
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Discussion Starter #13
It's unlikely to be bottom end due to the oil pressure, 50psi cold and 30 hot if very good for one of these old lumps, and if it was indeed main or big ends, oil pressure would suffer.

Sounds top end to me, akin to a stuck NRV in one or more of the lifters.

not too uncommon to have a dead batch of lifters/tappets when building one of these.

However as above if it is under warranty send it back...
Would a stuck NRV cause a lifter to collapse or not pump up?
 

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1989 Range Rover Classic
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Discussion Starter #15
Here is another short video from outside the car (only decent for a couple seconds before the wind noise ruins it) from just the other day. It's most audible on speakers with little/no bass, it gets drowned out.

 

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1970-1995 Range Rover Classic
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I have listened to the videos several times - to me: it sounds like a rebuilt engine that is wearing in with an exhaust leak.
 

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The noise is worst when cold, but doesn't disappear. I usually let it warm up for a minute when completely cold before I drive it somewhere, but if I just jump in and go it's significantly noisier. It's not as loud as it was about a month ago (the first video), but I can definitely still hear it (longer video). I think the higher pitch sound then the second video is due to listening from outside vs in the wheel well. What do you mean by brake-torquing the engine? I haven't tried that.
Brake torqueing is where you throttle up while holding the brake with the trans in DRIVE. Gently bringing the engine speed up replicates a light load on the engine. I think this would help to get a video of the noise without the wind noise. That's how we diagnose the issue on our vehicles at dealers. You don't want to do this for more than 5-10 seconds at a time to keep from damaging your torque converter and keep RPMs below 2000. You'll be good!
 

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1989 Range Rover Classic
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Discussion Starter #19
Brake torqueing is where you throttle up while holding the brake with the trans in DRIVE. Gently bringing the engine speed up replicates a light load on the engine. I think this would help to get a video of the noise without the wind noise. That's how we diagnose the issue on our vehicles at dealers. You don't want to do this for more than 5-10 seconds at a time to keep from damaging your torque converter and keep RPMs below 2000. You'll be good!
If the noise appears or increases when brake torquing it, what would that indicate? Is piston slap not a possibility?
 

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Piston sap is totally possible but usually goes away after the engine warms up unless the cylinder bore is way out of spec. Brake torqueing would allow you to get a good sound clip and possibly isolate the noise better with the vehicle stationary. If the noise is present it could indicate a possible issue that should be looked into. A freshly rebuilt engine should not exhibit that sort of knocking noise. The next level of investigation would be to pull the oil pan and removing bearing caps and inspecting bearings.

Were your pistons reused when the engine was rebuilt? Did the engine builder hone each cylinder to match a specific piston?

Have you drained the oil to see if there is debris present?

Your other option is to just drive the truck and hope it fails within the warranty.
 
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