# Engine knocking



## Ejay07 (Feb 1, 2018)

Hello everyone. I am new to this Forum and in need of help. A close friend has handed me his 06 Nissan Altima 2.5S with 170000 miles on it due to him joining military. Unfortunately vehicle is making a knocking sound when you start the vehicle. So a quick run down to the major work that has been done to vehicle in 2017. All 4 wheal bearings replaced, all 4 engine mounts replaced. Vehicle overheated on him and toasted head gasket, so it has new head gasket and resurfaced head. New water pump. New radiator. According to my buddy on an evening drive when getting on a freeway he punched the accelerator Nd everything seemed fine, but on his way back home he noticed a slight loss of power and oil light turned on which he found weird due to recent work done to vehicle. Following day he decided to take vehicle to work oil light still on. 20min into drive vehicle completely loses power and seemed to go on safe mode. Would not go over 2500rpm and only 1st gear. He said he got a check engine light but I don’t know what codes were given. When checking his oil it was black. Engine light has been erased and vehicle will drive but not to its full potential. Vehicle is now in my hands and these are symptoms. When starting vehicle it knocks LOUD. When vehicle warms up knock is barely heard. When in gear knock is Barely heard. Before handed to me he had recently done an oil change so oil is full and clean, any ideas? What should I start checking?


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## smj999smj (Jan 1, 2006)

If it sounds like a rod knock, you'll need to drop the pan and inspect the rod (and mains, while you are there) bearings for damage. Previously blown head gasket followed by the oil light coming on and still driving the vehicle with the knock doesn't sound promising!


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## RJ64 (Jul 23, 2017)

Ouch! Those lights are there for a reason, and red lights mean danger ahead. Oil light on means oil pressure is so low that you will damage parts if left running. You may be able to limp it along and get some more use out of it, but in all honesty going by your post, it's time to replace the engine. You will find that trying to change bearings, which I have done before in a similar situation, is no substitute for a properly matched crankshaft and bearing set. Plus there are other parts in the top of the engine, like cam(s), that will be scored badly from no oil pressure. And you have a bunch of miles on it anyway. From past experience, which for me isn't always good experience (lol), It comes down the $$. You can probably find a good used engine, and get a ton more miles out of the car, or spend many $$ playing around with the engine in the car now. Or you could rebuild the one you have now if certain parts aren't damaged too badly. Like smj999smj said, it doesn't sound promising. Only you can decide what course of action to take, but I wanted to share some of my experience with you. Good luck.


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## Ejay07 (Feb 1, 2018)

Thanks! I’m going to take oil pan off today and see if there is damage in there.


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## Ejay07 (Feb 1, 2018)

Ok so oil pan is off, I see no metal pieces but there is ALOT of oil sludge!!! So as soon as this happened the vehicle has not been driven. Should I buy an engine sludge remover? If so any specific brand?


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## rogoman (Dec 16, 2004)

It looks like the previous owner was very negligent in doing oil changes. If there is a LOT of sludge, the oil pickup screen most likely got plugged up which probably shut off most of the oil going to the rest of the engine, hence the oil light and engine knocking. Clean the oil pickup screen thoroughly. Remove the valve cover and clean that area also. Any brand of sludge remover will work OK, just apply a small amount at a time with *very frequent* oil/filter changes. Most sludge cleaners call for just idling the engine for about 10 minutes between oil changes. 

De-sludging may be a waste of time/effort. First inspect the condition of the rod/main bearings as well as the cam shaft bearings. The rod/main bearings, crankshaft journals, cam shaft bearings may all be shot. That would require a major overhaul or engine replacement.


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## matthias (Jun 11, 2018)

Great information. . . . .


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## christanwilley (Oct 10, 2018)

Thanks all folks.


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