QuestionI have 1991 Nissan Pathfinder VG30E Engine. After resolving several issues associated with an engine replacemant, it seems to be running pretty good with the exception of a couple of noises.
The first one is a weird intermittent combination of whine/whistle/grind (bearing noise???) that seems to be coming from the front of the engine. It doesn't seem to affect the engine performance at all and the volume varies from non-existent to sometimes abrasive.If it weren't for the additional grinding part I wouldn't worry about it the below stated explanation would cover the whistle/whine.
My mechanic has said he thinks it just that the timing belt is a liitle tight and it will break in. (All new timing components were installed including tensioner and the installation was done by a Nissan mechanic.)
The second one I am somewhat more concerned about because I seem to be the only one who can hear it.
When I start the engine and I am sitting in neutral (M/T) with the
engine running there is an irregular thumping sound. It is not a knock, ping, or tap. It is a thump...... thump, thump...
The engine idles smooth and quiet and isn't missing or anything; it just has this wierd thump.
Thank You so much for your time and answering the peoples questions!!!!
AnswerHi Rachel -
I will try my best to assist you in finding these noises. Not physically being there obviously makes it difficult to diagnose, so please bear with me.
There might be a chance that the 2 sounds may be related, as I am assuming both can be heard when the engine is idling in neutral correct?
Have the engine mounts been checked? There are 3, left and right, and center, which is actually the transmission mount. To check the mounts yourself, apply the emergency brake firmly. Rev the engine while slowly releasing the clutch. As you feel the clutch engaging, watch the engine. If it rises abruptly, then the motor mounts need replacing. Do this both in reverse and 1st gear. As for the transmission mount, the only way you can check it is to go under the car and jack the transmission up slowly while watching the mount.
Since this noise is happening when the engine is just idling, we can rule out any linkage or suspension components.
I usually find noises successfully by using a very long screwdriver and use it like a stethoscope. Place the end of the handle against your ear and with the blade end touch various components such as the alternator, power steering pump, all idler pulleys, water pump, and A/C compressor.
If you still are unsure, then I would remove each drive belt, one by one and see if the noise is still there. If the noise is still there, then it will be internal, meaning, timing belt idler, tensioner, or camshaft.
Hope this helps -
aloha
calvin
