: Still making engine noise
12-05-09, 02:29 PM
95 SLS: After replacing the tensioners (both sides), the serpentine belt and its idler, the alternator and the A/C compressor I still have a noise from the front end of the engine. This is not to say the other parts weren't bad. They were, especially the A/C compressor. Anyway, two candidates that I can think of--the power steering pump and the harmonic balancer. I don't think it's the psp (doesn't whine louder when turning), but how can I tell if it's the harmonic balancer? Does the balancer on the 4.6 have an internal clutch that goes out? What's the typical noise you get with beginning failure of the balancer? The noise I hear is like a gear whine and it fades away as you get up above 25mph (or is masked by road/wind noise). It's not very loud, but you can definitely hear it.
12-05-09, 03:57 PM
I bet you a chain guide wore through.
The harmonic balancer is bolted straight up to the crankshaft. There is no clutch involved. I have seen Honda harmonic balancers fail, they sound like a belt squealing. The rubber middle separates from the metal part of the pulley so only the rubber is spinning. I have never heard of a cadillac harmonic balancer failing.
But anyways, here's a good thread (with pictures) with what I think you're experiencing: http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/173459-lifter-starting-tap-needs-replacing-8.html
12-05-09, 07:11 PM
Thanks. It does sound like a camshaft chain tensioner/guide (is there a difference?) might be the problem. Since that thread is focusing on the lifters and cams, it isn't real specific on how to replace the tensioner or guide if you're not doing anything else. The pictures are too fuzzy to make much out--I can't really tell where they are even located. In any case, it sounds like it's a real PITA. Are there specific instructions somewhere on this site or do I need the factory manual?
12-05-09, 07:43 PM
There are 3 cam drive chains: one from the crank sprocket to an intermediate drive sprocket, then 2 others to the heads. The cam drive chains use nylon tensioner and guide slippers to insure true run geometry and to keep a preset tension on the unloaded side of the chain. Unfortunately, slippers wear out, even back in the 60's for other engines. It's the nature of the beast. Everything is inside the front chaincase cover (timing cover) and you need to get the car up on jackstands and remove the wheel, fender liner, and literally remove the front of the engine. There are specific procedures that need to be followed, so you'll need a Helm/GM service manual or a subscription to www.alldatadiy.com.
The diagrams are for the 2000+ Northstar, but the basic procedure is the same for earlier engines.
#'s 1, 12, and 13 are the hydraulically loaded tensioners, and that's what wears through to the metal backing. Replace everything made of nylon........
12-07-09, 01:26 PM
This link to a Fiero website seems to have pretty good details.
Isn't AJxtcman one of the main contributors to this website?
How much, guesstimate, would it cost to have a mechanic replace the chain guides??
12-20-09, 05:32 PM
Here's a follow-up to this problem:
After getting estimates to replace the cam chain guides/tensioners etc., I decided to do a little more diagnostics myself (it's about $1500 to do the cam chain repairs). I removed the serpentine belt and started the car. No problems there, since it doesn't drive the water pump--just running on the battery instead of off the alternator which is no big deal for a short time. Guess what? No noise. So the noise has to be from something driven by the serpentine belt or the belt itself. Most of the stuff is new, but, being made in China, its quality is, in my mind, suspect. Also... when the shop replaced the A/C compressor, they also replaced the receiver/dryer... After installing the new dryer, the silver metal pipe that runs towards the front of the car to the condensor, was in close proximity--like touching--to the engine-side bolt on the passenger side dogbone (front engine brace). When the engine was running the two parts bounced off each other. I discovered this when checking the oil. I saw that there were a lot of tiny metal bits all over the place and the pipe was worn partly through. I investigated the serpentine belt surface and it had a lot of little metal bits embedded in it. I tried to clean it and the pulleys with some success, but the belt was nicked in several places so I put on a new belt. The moan I was getting went down in volume--a lot. (I also bent the A/C pipe away from the dogbone and strapped a piece of black heater hose around it to prevent any more contact wear.) Obviously the issue was never the cam chains and related gear or the noise would have continued when the serpentine belt was removed. It has to be somewhere in the pulleys and stuff still and I'm afraid the little metal shavings may have gotten inside some of the new stuff I put on there, thus causing the remaining noise. Ah well, onward we go.
12-20-09, 06:40 PM
Thanks for posting the follow-up. :thumbsup:
So many times people will post problems asking for help/recommendations on how to proceed and then never report back what worked or what the real issue was.
12-20-09, 11:03 PM
i put on a used alternator and the next day i got a belt whine. checked pulleys and found a noisy tensioner pulley. changed it and still had whine. changed serp belt and noise went away. i used a scope on tensioner pulley and it really howls but its brand new?
12-22-09, 07:32 AM
All that mechanical stuff makes noise... the question is, is it abnormal--that is, do you hear something different? It's amazing how much noise can be caused by the serpentine belt itself. Almost (but I emphasize "almost") all my engine noise went away with the new serpentine belt and the cleaning of the pulleys. But I still have an abnormal noise that bothers me. Using the stethoscope I can't narrow it down, because, as I said, everything makes some noise.