Hello:
The car:
A 1998 P38 4.6 HSE full option with close to 200,000 miles on it. It has always been serviced to the letter by an official Land Rover dealer. I have it a few years and have driven it for about 35,000 miles. My foot is on the heavy side, I always drive in Sports mode and do not shy away from the occasionally flooring it. The engine runs fine, no oil burning or undue noises or smoke -- until now.
What happened:
While merging into a main road I put the throttle a bit more than 3/4 down. All of the sudden it makes a sort of rattling noise, a bit like the fanshroud hitting the fan. I immediately lift the throttle and the noise goes away. As soon as I load the enige however it returns. When I stop and open the hood, nothing seems amiss save a faint ticking sound which becomes louder when I rev it cautiously. I am able to limp home (about 10 miles). I have the impression that, by now, it is louder and more like a flappin or loud ticking. It is not a rod which is deeper in tone and originates from the bottom, it is not like a broken piston neither. It is more like a valve, a flat piece of steel acting as valve, which closes violently, slamming against its seat.
Symptoms:
The noise seems to come from somewhere under the inlet manifold. It does not seem to originate from within the valve covers. We are unable to locate it positively, even not with an automotive stethoscope. It is not directly related to the revs and is not synchronous with them neither. It is not constant even, it goes tak tak tak and then all of the sudden taketaketak, not always the same order. It becomes very loud when the engine is loaded however. The engine rocks very gently, almost inperceptly on idle in drive with the AC on indicating a pretty even combustion in all cylinders.
I took off the inlet plenium and did not see anything out of the ordinary save that the air "trumpet" of the 8th cylinder was a bit black with soot, the others were just the normal slightly oily black. with no soot.
Additional info:
Recently the engine was severely overfilled by an @#$%#@ of a mechanic. Depostits in the engine came loose and at one point the oil pressure light came on and the valves started ticking. The engine was immediately stopped and the car towed to the shop. The the pan was removed and the mesh on the oli pump cleaned, also the sump. New oil and a new filter were installed. This is alreay about a thousand of miles ago.
What could this be ??
One theory is that an hydraulic lifter got some dirt in it and did pump up too high, the valve got hit by the piston and is now bent. This could explain the soot on cylinder # 8. If the valve is very slightly bent then the engine would still run pretty evenly. BUT this does not explain what the noise is and certainly not why it is not synchrone with the revolutions. The noise defenitely does not originate from that corner, it would more be like in the center or towards the # 1 cylinder but then still under the manifold. (I know I first should measure the compression but had no time yet
).
About me:
I am a professional mechanic with 40 years experience on all sorts of cars, rebuild numerous engines from basic to Lotus 16 valve, Jaguar 6 es and Maserati DOC V8's. I mention this not to boast but to put my story in perspective, I know what I am talking about. This however is something I never heard of nor experienced, maybe somebody had a similar experience or a suggestion.
Any help/suggestion is more than welcome
Thank you
Andre
The car:
A 1998 P38 4.6 HSE full option with close to 200,000 miles on it. It has always been serviced to the letter by an official Land Rover dealer. I have it a few years and have driven it for about 35,000 miles. My foot is on the heavy side, I always drive in Sports mode and do not shy away from the occasionally flooring it. The engine runs fine, no oil burning or undue noises or smoke -- until now.
What happened:
While merging into a main road I put the throttle a bit more than 3/4 down. All of the sudden it makes a sort of rattling noise, a bit like the fanshroud hitting the fan. I immediately lift the throttle and the noise goes away. As soon as I load the enige however it returns. When I stop and open the hood, nothing seems amiss save a faint ticking sound which becomes louder when I rev it cautiously. I am able to limp home (about 10 miles). I have the impression that, by now, it is louder and more like a flappin or loud ticking. It is not a rod which is deeper in tone and originates from the bottom, it is not like a broken piston neither. It is more like a valve, a flat piece of steel acting as valve, which closes violently, slamming against its seat.
Symptoms:
The noise seems to come from somewhere under the inlet manifold. It does not seem to originate from within the valve covers. We are unable to locate it positively, even not with an automotive stethoscope. It is not directly related to the revs and is not synchronous with them neither. It is not constant even, it goes tak tak tak and then all of the sudden taketaketak, not always the same order. It becomes very loud when the engine is loaded however. The engine rocks very gently, almost inperceptly on idle in drive with the AC on indicating a pretty even combustion in all cylinders.
I took off the inlet plenium and did not see anything out of the ordinary save that the air "trumpet" of the 8th cylinder was a bit black with soot, the others were just the normal slightly oily black. with no soot.
Additional info:
Recently the engine was severely overfilled by an @#$%#@ of a mechanic. Depostits in the engine came loose and at one point the oil pressure light came on and the valves started ticking. The engine was immediately stopped and the car towed to the shop. The the pan was removed and the mesh on the oli pump cleaned, also the sump. New oil and a new filter were installed. This is alreay about a thousand of miles ago.
What could this be ??
One theory is that an hydraulic lifter got some dirt in it and did pump up too high, the valve got hit by the piston and is now bent. This could explain the soot on cylinder # 8. If the valve is very slightly bent then the engine would still run pretty evenly. BUT this does not explain what the noise is and certainly not why it is not synchrone with the revolutions. The noise defenitely does not originate from that corner, it would more be like in the center or towards the # 1 cylinder but then still under the manifold. (I know I first should measure the compression but had no time yet
About me:
I am a professional mechanic with 40 years experience on all sorts of cars, rebuild numerous engines from basic to Lotus 16 valve, Jaguar 6 es and Maserati DOC V8's. I mention this not to boast but to put my story in perspective, I know what I am talking about. This however is something I never heard of nor experienced, maybe somebody had a similar experience or a suggestion.
Any help/suggestion is more than welcome

Thank you
Andre
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