View Full Version : 4.6L Northstar Rattle

11-06-08, 07:15 PM
I have a 94 Concours I have owned for one week that had a slight rattle on the front top of the engine. Other than that is ran great. Last night when I went to start it the rattle got very loud and then it would not start. Now the starter wont even turn it over; even after putting in a fully charged battery.:ill: Give it to me straight. Should I have a shop look at it, start looking for a reman, or put a chain on my new boat anchor? :banghead:

11-06-08, 08:02 PM
Pull all the spark plugs and see which one is wet with antifreeze. See if the motor will turn with them out. Worst case, is headgasket failure. You might could run on 7 plugs if in a jam and need to move the car. Not recommended, but if you're in a jam, what the hay?

11-07-08, 10:58 AM
That you for your reply. I think I need to be more detailed. When I said it would not turn over, I meant it just goes clunk now. The starter will no longer physically turn the engine. My only guess is that it is siezed somehow.

11-07-08, 12:34 PM
Yes, it's posssibly hydro-locked, like antifreeze in one cylinder. Water does not compress. Pull all the sparkplugs and try the key to turn the motor over. This is the only way to tell if your problem is upper or lower(like bearings) related.
If there's water/antifreeze in there, this will remove it. The longer water stays in there, the worse the damage will be...It the problem is unchanged with the plugs out, then we'll deal with that later.

11-07-08, 12:58 PM
I will look into that. I did not think of anything like that because of the loud metalic clatter that immediately preceded the engine problem. I assumed it was something in the cam or valve train letting loose.

11-07-08, 05:07 PM
Turned the engine some using a wrench on the crankshaft pulley. It will only go so far either direction while doing that then stops. We heard something that sounded like a chain moving against the casing sound coming from the rear overhead cams. Like the chain may have been loose in there and only going so far then binding. Tell me what you think of my theory. I think maybe the tensioner was bad on that side and was the low level clatter that I was hearing up there before. Then, the chain either came off or broke and jammed. I think this because before it froze the clatter got very loud and then gave one more louder metallic slap. This sound was from the front top on the engine. Does that sound plausable for this engine?

11-08-08, 12:33 PM
Very rare but not impossible....broken chain due to excessively worn hydraulic chain tensioner or worn slipper. A broken chain is no fun to do in the car. Lots of alignments and adjustments. (There are 3 chains - crank to intermediate sprocket, intermediates (2) to cam sprockets.)

Use a good, bright flashlight and see if you discover anything down in the oil filler cap hole: that looks directly into the chaincase.

11-08-08, 12:45 PM
By moving the crank I know that the crank to intermediate sproket is good and the one going to the front most cam sprockets are good because I can see it move the pulley at the other end that goes to some kind of accessory. The only one I can't tell for sure is the chain going to the back cams. I think that was where the aforementioned noise was coming from. I wish I could tell for sure. Is it hard to remove the rear cover (the one under the ICM)?

Also, replace the chain in the car? I thought that was pretty much impossible.

11-08-08, 03:24 PM
Several other members and AJ and ewill3rd know a world more about a '94 than I. I DO know that replacing timing chains with the engine in the car is literally hell on wheels. You probably have to rock the engine forward to lift the rear cam cover. There's a special set of bolt-in gauges used for locking the cam sprockets while you work.

From what I've read in here the job is not amateur work nor for the faint-of-heart.

This may sound pessimistic, but what if the rear chain is broken and has bunched up and maybe punched a hole or crack in there somewhere ??

11-08-08, 04:09 PM
I know. It could be worse than I think. Anyone have an idea on what a shop would charge to check this?

11-19-08, 11:40 AM
I had the caddy towed to a shop to confirm my guesses. He found the rear chain still on, but broken pieces of the plastic guides. He thinks the chain may have gotten loose and jumped timing. It has definately been loose. I think that since I was just turning the engine over with the starter when it happened, there is a real good chance nothing else got hurt.

Does the engine have to be pulled to replace the guides and tensioner and put the chain back to the correct timing?

11-19-08, 07:21 PM
I got the quote. Geez! Has anyone ever heard of a complete timing chain kit for the Northstar V-8? I got quoted one of those for $1300.00 and 13 hours of labor. I can find the parts individually at places like GM Direct and Autozone (for 1/3 the cost), but can't find any reference to a kit anywhere on the internet. Anyone here a certified Cadillac mechanic, or someone that has had this done, that can tell me if I am getting my chain yanked?

11-19-08, 07:40 PM
Not familiar with a chain kit, but would guess that the 3 chains, static and hydraulic slippers are not cheap. I would hope that the term "kit" is used to include the necessary gaskets, seals, etc. If you take a good, hard look at the cam covers and the front of the engine mechanical arrangement its obvious that the work involved to R&R everything is quite involved (and that's being generous.....).

11-19-08, 10:36 PM
tell me if I am getting my chain yanked?LMAO, sorry but your choice of words.............. Good luck with the repair. :eek: