Rapping engine sound

Up to you. if the car keep running, then why not. My car kept going , with nothing worse that slight noisy tappet, and had been given numerous engine 'tune-ups' by he previous owner. I was fooled into buying it, thinking nothing worse than tappets needed adjusting. (I was used to a noisy A series engine).Cam wear was such that 2 or 3 lobes had no significant lift, but the car kept going, and seemed to run well.
I cannot see that you will be doing your engine any more harm by not changing the cam, but I am sure that someone will disagree.
Do you want perfection? Are you prepared to pay for it?
 
I would change the cam myself. But for now, I just want to drive the car this winter. Perhaps next summer. But I also have thought of simply installing a Turner or Atlantic British new / rebuilt V8
 
Well after a marathon work day, everything is back together and car runs. The good news? The misfire is gone. The bad news? It overheated driving it just a mile away and puked coolant out the overflow. I believe I have either a stuck thermostat or major air bubble. The thermostat is plastic at the bottom of the radiator in its own housing on these. The engine is running smoothly. The rapping was gone until my last drive it slowly returned. I’m wondering if it’s not the engine and instead the AC compressor? It seems to be quieter overall though. So I guess some good news and some bad.
 
troverman said:
Well after a marathon work day, everything is back together and car runs. The good news? The misfire is gone. The bad news? It overheated driving it just a mile away and puked coolant out the overflow. I believe I have either a stuck thermostat or major air bubble. The thermostat is plastic at the bottom of the radiator in its own housing on these. The engine is running smoothly. The rapping was gone until my last drive it slowly returned. I’m wondering if it’s not the engine and instead the AC compressor? It seems to be quieter overall though. So I guess some good news and some bad.
Click to expand...

From memory the P38 Range Rovers run with a 96-degree thermostat, and as you say reside in a plastic housing located in the bottom radiator hose.
Have you sourced another housing with integrated thermostat?

Sounds like an improvement, and that has to be good.

Ron.
 
Update: the cooling system had an air pocket in it and just needed to be bled. The overheat is solved. However, the engine rapping sound continues just like it was before I did any of this work. I drove it over 30 miles last night including a run on the interstate where I was driving at 70-80mph. The car ran perfectly the entire time. I scanned for codes at the end and there are none. Two more drive monitors remain, but one is evap and one is secondary air. Both work fine so I believe the misfire problem is truly cured. The rapping sounds like a lifter not pumped all the way up! With the hood / bonnet raised, the noise appears to be coming from the right hand cylinder bank. With it shut you can clearly hear the sound loudly from behind either front wheel. After the drive it seemed to get lighter. I have no idea if I still have a valve or lifter or cam problem, or con rod knock or something else. My thought is that if a cam lobe was worn to the point the lifter could not make up the gap fully, then the valve would not fully open and a misfire would occur.
 
Hi, Check that the torque converter bolts aren't loose or that the flex/drive plate isn't cracked.

Colin
 
When I installed the engine, I did use thread locker on the torque converter bolts, plus the transmission is very smooth.
The strange thing is, when the engine cold starts, the idle is totally quiet. No rapping sound. Only when it warms up does it make the noise. The engine oil will get thinner as it warms, I guess that could be it? We had a very cold morning today - about 9F - and I started it and let it warm up for 10 minutes or so. It was idling smooth with zero rapping sound. Strange.
 
Have you considered an exhaust manifold leak?
Obviously they usually tick when cold and quieten down once warm but perhaps a strange anomaly worth a quick investigation.
Jim
 
I did consider it, especially since the thin-wall stainless steel header style exhaust manifolds on the P38 are known to crack. I've tig-welded one in the past, but not this Rover. Since I had the head off, I carefully inspected the manifolds and of course they received new gaskets and were properly torqued.
 
Any more thoughts on what could cause this rapping sound once the engine warms up? All I can suspect is that oil pressure drops when the oil is warm. Revving seems to cause the noise to stop, but its hard to hear with the mechanical fan.
 
Slipped liner? I believe that could cause your symptoms, worse when warm and the revving to quieten..
Crankshaft Sensor loose and colliding with flex plate, but engine temp wouldn’t affect that surely?
Jim
 
Thanks for suggestions. Liners were all good when the head was off and no pressurizing of the cooling system. For now, I’m just driving it.
 
Hi, A thought has occurred to me that it could be little end or gudgeon pin worn. It's not a commonly heard noise because when an engine is getting on it's not usually the first thing that starts making a noise. I do realise this may not be what you want to hear however but something to get confirmed from elsewhere.

Incidently I first had it pointed out to me by an old school mechanic back in the early 70s and I've only heard it a couple of times since.

Colin
 
Thanks Colin. In the US I believe we call that the wrist pin. It’s running great but clattering all the time. Kind of disappointing.
 
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