For the last month or so I have noticed a noise coming from the motor I have not heard before. It is consistant with engine rpm and gets much louder as rpm increases. best way to describe it would be like loud gears, as if i had a gear drive timing set. Its a 4.2L with about 120k on it. Just had oil change today and no difference. Any ideas?

 

I should mention this hasnt cuased any actual problems, the engine still drives normally, and although it is very noticable in first and second gears once the rpms hit midrange, I cant really hear it once I am going 30mph or more since my tires are a bit loud (meaning the problem is really loud or anything like that, but definately noticable).

 

Does it make the noise in park if you just rev it up ? or only when moving?


Jeff

 

It goes with the rpms, regardless if the truck is moving. Like I said, it sounds very much like a gear drive (the less noisey kind!).

 

is the power stearing pump ok ?

 

If it's an auto trans,it could possibly be the fluid pump in the trans.
JL

 

It could possibly be the water pump impeller. In some 4.2l engines the bearing gets bad and the impeller scrapes against the timming chain cover eventually wearing a hole through the cover allowing coolant to enter the crank case..

 

Yikes... now I am wondering if this is relates to my recent problem with no coolant in my tank. But my oil looked good (no water or not milky lookin). BTW it is a manual, and no problems with power steering thats noticable to me. I'll have to get under the hood again and see if I can better locate the area the noise seems to be comming from.

 

You might try removing the belt and running it to see if the noise is still there. If the noise goes away, you can really narrow down the cause: water pump, PS pump, alt, A/C compressor.

 

If you catch it before the impeller wears through the timming chain cover your fine, only the part to replace the cover is quite expensive to buy new, used might be cheaper if you can find one...

 

Thanks for the good tips. I didnt get a chance to look at it on my 2 days off this week so it will have to wait till next monday. Just incase it is possibly serious, I am going to try and drive my bronco to work, but dang its going to be cold with no rear window, crappy heater, and a cold front comming through the next few days! I've been meaning to invest in one of those soft tops, atleast that would fix the no rear window problem I have.

 

i have a feeling it is your belt tensioner. that pulley is notorious for going bad...its a cheap part though. take the belt off and spin the tensioner pulley, if it isnt smooth and quite that may be your problem

 

about how much do they run?

 

for the 4.6 its $60.22. THis is With AC. Non Ac uses a different pulley.

 

from what u explained i had the same noise coming from my engine so i been paying attention to ur replies. ITs been goin on for a few weeks now, In the mean time, last week i passed someone on the way to work, and while in the passing gear ,the rpms went up to around 4500, thats when my battery light flashed 2 or 3 times, but i have been hearing that noise for several weeks, maybe a couple months, so i changed the alternator becuz of the battery light flashing, and Surprise ! the hum which made my truck sould like it was gear drivin, is fixed also. I dont know if u already fixed it so thought i would pass it on. When i took the old alternator off, I could spin it by hand and hear the grinding by just doing that !! Good luck