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engine noise, very worried....

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RobSelina

RobSelina

Jedi Warrior
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Okay, this just started today as far as I know. I hadn't noticed it before. I started up the car and in about 20 seconds it started to make this grumbling rattle noise. Here are the details

- it's sitting in neutral around 1200RPM
- It's a rather deep sound. it's sort of a rattle and a grumble at the same time. It's what I would think a bad bearing may sound like.
- it goes for about 2 seconds then stops for about 2 seconds and then repeats
- it seems to do it at the same interval regardless of engine RPM.
- it sounds like it's comming from the lower front portion of the engine.

My first thought was crankshaft bearings but the fact that it doesn't seem tied to engine RPM makes me wonder. I'm getting 60 psi cold, so I don't think it's a rod bearing. Nothing seems loose except for the fan clutch which has some play in it. I can get it to rattle a little and move if I wiggle the fan. Could it be a worn fan clutch? The noise seems deeper than that when I hear it though so I'm a little skeptical there too, but the fact that it's not directly tied to engine RPM would kinda imply it's the clutch rattling...

Anyone got any ideas? where should I start on this? I'm tempted to have my mechanic look at it but I'm also not extatic about the idea of driving it over there if it's a crank bearing. I figure it's got to be crank bearings, trow out washer or the fan clutch.

It's a 75 with a 1500....

Any help appreciated.
 
Rob, pull the belt to isolate the fan, and see if that eliminates the noise. Hopefully it'll turn out to be the fan.
But,it could be timing chain rattle. These things only have a single row chain, and a funky blade type tensioner that is fairly weak.
Jeff
 
well, bit of an inconclusive test unfortunately.

I pulled the belt a few minutes ago and fired up the engine and it wasn't making a peep. I put it back on, and it's still not making a peep. LOL.

Guess I'll have to try it again next time it acts up. I'm going to be working on her again tomorrow evening and taking her for a spin so we'll see what she does then.
 
Rob, if it was the timing chain, the belt should have made no difference. I think you may have lucked out, and merely have a bad fan.
I'll keep my fingers crossed for you.
Jeff
 
I'm hoping that's the case and it's just quiet now because the tension on the belt isn't equal to before and it's dampening out the vibration (or something like that /ubbthreads/images/graemlins/smile.gif )

If the fan's the issue I'm considering an upgrade. Is an electric fan worthwhile? After looking at the stocker, it's about as light as it can get so I don't think an electric one would really be of much benefit. Any thoughts?

Also how much play should there be in the stock fan clutch?
 
From the "grumbling" description I would have gone for a fan or pulley too, rather than timing chain but the "rattling" noise is disconcerting. But how about water pump? My bet goes on a dodgy water pump. Without the belt it's not turning, so the noise would go away.
 
Rob, and Steve:
Not to throw crap in the fan, (pun intended,) but in my experience, if the bearings in the pump are wankered to the point where its making an audible noise, the seals are so far gone that it's leaking big time.
But, as always, pray for the cheap solution!
Jeff
 
It does sound like it might be the fan clutch.
To isolate it, take a 4 inch hose clamp and tighten it down between the fan clutch and the pulley. If the noise goes away, it is the fan clutch, if not, it is your water pump.
 
ordered a new waterpump with a new fan clutch. should be here in a couple of days.

Anyway, who knows what I've done this time, but I wired in my fog lights finally last night and I somehow managed to screw up spark. I used an existing ground near the coil for the 40A relay so I'm betting I upset something there...back in the garage tonight....

BTW - my uprated springs and suspension rebuild parts are arriving today /ubbthreads/images/graemlins/smile.gif Moss ships stuff out quick!
 
well, got her running again. Now if I can just get the carb tuned and the suspension finished....
 
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