: Rattle in front of engine on first start up? Help!!



Ronm
03-21-04, 12:48 PM
The noise is there on first start or after the motor cools down for several hours. It sounds like a bracket rattling but is internal. It only happens under accerlation and goes away after a few minutes or until the engine reaches normal temp. Is this a sign of bad things to come??? I'm thinking maybe chain tenisoners. It's on a '97.

joeveto
03-21-04, 12:56 PM
I would wait until the engine is cold. Then, I'd put the front end up on some ramps and crawl underneath with a stethoscope (or a long screwdriver). If you're using the screwdriver, place the handle against your ear, and the blade to different parts of the engine, where you think the noise is coming from.

A few obvious points: Be careful. When the engine is running, there are moving parts that can be dangerous, especially when you're poking.

Also, the stethoscope works a lot better than a screwdriver. The stethoscope is more flexible. I bought mine from Harbor Freight for less than $3.00, and it has proven invaluable, whenever I want to scare myself into sleepless nights, worrying that what I heard was something terrible. That's when I run to the Forum and hope BBobyinski will talk me off the roof.

Enjoy. Without actually hearing it myself, I really can't say what it is. My ETC does something similar. I have found the most probable cause to be a noise A/C compressor. But honestly, until something breaks, I'm not going to worry. It's not worth it.

Lawrence
03-21-04, 01:25 PM
What you likely have is "cold carbon rap or knock". Check this link and do a search.

http://www.cadillacforums.com/forums/showthread.php?t=10025

BeelzeBob
03-21-04, 11:05 PM
The noise is there on first start or after the motor cools down for several hours. It sounds like a bracket rattling but is internal. It only happens under accerlation and goes away after a few minutes or until the engine reaches normal temp. Is this a sign of bad things to come??? I'm thinking maybe chain tenisoners. It's on a '97.

It may be the cold carbon rap....the next time you drive the car take it out on the freeway and do several wide open throttle accelerations from lower speeds up thru second gear.....merging on the ramp is an excellent place to really air it out. Clean the carbon out of the chambers with some WOT accels like this and then see if the noise persists.

Ronm
03-22-04, 08:13 PM
Actually I had 2 noises one was a light knocking that would come and go and the other one is this rattling. The light knock is gone after I did some full throttle blasts, boy did it blow out some black smoke, but this other one has me puzzled. You can only hear it when you accelerate, it is hard to hear when giving it throttle in park even when you are under the hood.
It's quite a bit louder in gear a with the car moving under a load at about 1/4 to 3/4 throttle A/C on or off.
I would guess the carbon rap sounds more like a rod knocking then a rattle right??
The noise I'm getting sounds more like when the guts of a catalitic converter comes loose.
I'm going to try and remove the belt and drive it to eliminate all the accesories. The only trouble is getting it away from my wife so I can take it in to work!!:D
Any other suggestions would be appericated.

Ronm

BeelzeBob
03-22-04, 09:11 PM
Remove the belt like you said to see if it is in one of the accessories or the belt itself. It may be the serpentine belt tensioner or the idler pulley.


Bang on the cat with a rubber mallet to see if it rattles....maybe it is the cat.


Keep up the WOT's until you don't see any dust/rust/smoke on the accels...then it is cleaned out. Do regular WOTs to keep it that way.


Sometimes you can hear a very light tapping that sounds like a valve lifter or such on startup. This particular noise will come in about 30-60 seconds after a cold start if you just start the engine and let it idle in park without revving it or touching the throttle. At about 30-60 seconds it will tick-tick-tick-tick for 15 seconds or so and then go away. Perfectly normal. You are hearing the floating wrist pins in the pistons. The floating pins are set up very tight to avoid this noise as much as possible but on the limit of the specs a limit-loose wrist pin will make the ticking noise until oil is splashed onto it during the idle....nothing to worry about at all. In fact, if you were to "blueprint" the engine for performance ALL the wrist pins would tick pretty much all the time. "performance" specs on floating pins cause them to tick pretty frequently. The factory Northstar pin clearances are on the tight side for floating pins to keep the noise down.

Ronm
03-23-04, 12:29 AM
Sometimes you can hear a very light tapping that sounds like a valve lifter or such on startup. This particular noise will come in about 30-60 seconds after a cold start if you just start the engine and let it idle in park without revving it or touching the throttle. At about 30-60 seconds it will tick-tick-tick-tick for 15 seconds or so and then go away. Perfectly normal. You are hearing the floating wrist pins in the pistons. The floating pins are set up very tight to avoid this noise as much as possible but on the limit of the specs a limit-loose wrist pin will make the ticking noise until oil is splashed onto it during the idle....nothing to worry about at all. In fact, if you were to "blueprint" the engine for performance ALL the wrist pins would tick pretty much all the time. "performance" specs on floating pins cause them to tick pretty frequently. The factory Northstar pin clearances are on the tight side for floating pins to keep the noise down.[/QUOTE]





I hear that on cold starts but usually after a cold night colder than 38deg. or so. Well that's cold for Houston anyway.
I'm still leaning towards timing chain tesioner since it only does it on steady accel.
How common is it to have a problem with the chains & or tesioners.
I would feel a lot better if it was a lite knock.

I had a customer that had a similar noise on a 4.0 Ford SOHC Explorer with less than 60k, they chose to ignore it and 9mo later the tesioner broke along with the chains.

This car is not worth putting $2000 into since right now trade in value is only $4000 or so. (half case leaking also) I won't do the work myself, internal engine work scares the crap out of me on these things. I'll probably trade it in before it gets real bad.

Ronm

BeelzeBob
03-23-04, 03:13 PM
[


I hear that on cold starts but usually after a cold night colder than 38deg. or so. Well that's cold for Houston anyway.
I'm still leaning towards timing chain tesioner since it only does it on steady accel.
How common is it to have a problem with the chains & or tesioners.
I would feel a lot better if it was a lite knock.

I had a customer that had a similar noise on a 4.0 Ford SOHC Explorer with less than 60k, they chose to ignore it and 9mo later the tesioner broke along with the chains.

This car is not worth putting $2000 into since right now trade in value is only $4000 or so. (half case leaking also) I won't do the work myself, internal engine work scares the crap out of me on these things. I'll probably trade it in before it gets real bad.

Ronm[/QUOTE]


The Northstar timing drive/chains/tensioners are very robust and it is extremely rare I would say to have a problem in that area...

Northstar engines are actually very easy and straight forward to work on. They are a little different from the typical pushrod engine but they are really pretty elementary if you get the factory service manual and read up just a little....just looking at the pictures will show you a lot you need to know.

If you suspect the timing drive or a tensioner you can take the cam covers off and see quite a ways down into the timing drive area and inspect for a chain with slack in it or anything like that....that would be indicative of a tensioner that is not racheting properly or locking into place. Pretty easy to inspect....

Definitely loosen the serpentine belt and make sure it is not an accessory making the noise before you jump to any conclusions.

Ronm
03-23-04, 07:43 PM
I would probably go ahead and and give it a try if I didn't have to pull the motor and heads.

I have Mitchell on demand so maybe I'll look into it.
Thanks for all your help!!

Ronm

joeveto
03-23-04, 11:20 PM
Remove the belt like you said to see if it is in one of the accessories or the belt itself. It may be the serpentine belt tensioner or the idler pulley.


Bang on the cat with a rubber mallet to see if it rattles....maybe it is the cat.


Keep up the WOT's until you don't see any dust/rust/smoke on the accels...then it is cleaned out. Do regular WOTs to keep it that way.


Sometimes you can hear a very light tapping that sounds like a valve lifter or such on startup. This particular noise will come in about 30-60 seconds after a cold start if you just start the engine and let it idle in park without revving it or touching the throttle. At about 30-60 seconds it will tick-tick-tick-tick for 15 seconds or so and then go away. Perfectly normal. You are hearing the floating wrist pins in the pistons. The floating pins are set up very tight to avoid this noise as much as possible but on the limit of the specs a limit-loose wrist pin will make the ticking noise until oil is splashed onto it during the idle....nothing to worry about at all. In fact, if you were to "blueprint" the engine for performance ALL the wrist pins would tick pretty much all the time. "performance" specs on floating pins cause them to tick pretty frequently. The factory Northstar pin clearances are on the tight side for floating pins to keep the noise down.
This is why I like this forum so much. Bobynski, we're screwed if you ever decide to pursue another mark.

BeelzeBob
03-23-04, 11:39 PM
I would probably go ahead and and give it a try if I didn't have to pull the motor and heads.

I have Mitchell on demand so maybe I'll look into it.
Thanks for all your help!!

Ronm


Hate to belabor this....but...what are you talking about...???...pulling the motor and trans.?? The cam covers come off easily for inspection of the timing drive without pulling anything other than the cam covers. You can take the front cover of the engine off with the engine in the car and replace the entire timing drive,chains, guides, tensioners, etc. if you should choose to do so without pulling the engine and trans. It really isn't that hard to do. They damper comes off thru the wheel well on the right side and most of the accesory and front cover fasteners can be reached thru there also.

What is a Mitchell...?? some sort of service manual..?? Get the factory manual published by Helms and save yourself some time and grief and misinformation.

Aurora By Olds
03-24-04, 01:02 AM
What is a Mitchell...?? some sort of service manual..?? Get the factory manual published by Helms and save yourself some time and grief and misinformation.
Mitchell seemed to be pretty accurate for me. It was detaled in places the Helm wasn't. It also didn't cover many of the things that Helm did. Both seemed to be pretty much equal with errors. The Helm is probably the most informative for the money, however. The only real drawback I found with my Helm, was the fact that the picture/details of the timing chain assy. showed the chains incorrectly. Other than that, I would say Helm is about the best. Its diagnostic flow charts and whatnot are pretty well detailed too.

Ronm
03-24-04, 08:57 PM
Hate to belabor this....but...what are you talking about...???...pulling the motor and trans.?? The cam covers come off easily for inspection of the timing drive without pulling anything other than the cam covers. You can take the front cover of the engine off with the engine in the car and replace the entire timing drive,chains, guides, tensioners, etc. if you should choose to do so without pulling the engine and trans. It really isn't that hard to do. They damper comes off thru the wheel well on the right side and most of the accesory and front cover fasteners can be reached thru there also.

What is a Mitchell...?? some sort of service manual..?? Get the factory manual published by Helms and save yourself some time and grief and misinformation.

I didn't say anything about pulling the trans.
Mitchell On Demand is a service manual & labor guide that most shops use when they work on more than one type of car. Has every make from A to Z. Kind of the standard for independent repair shops. Most if not all the info is taken directly out of the factory manuals. I've been a Mechanic for 19+ years & have been useing either the printed or Computer version the whole time.
If I remember right the time listed for timing chain replacement includes removal of the motor. I wasn't going to pull the motor just to inspect them.
It also looks like the heads have to come off seeing the chains go through them.
It's been a couple of weeks since I looked it up so don't quote me on this. I'll check again tomorrow to set myself straight.
If you say it can be done in the car without removing the heads then I'm assuming you have done it before and I'll take your word for it.
Do these things bend valves if the chain should break while running???
Again thanks for all the info so far.
Ronm

BeelzeBob
03-25-04, 03:42 PM
I didn't say anything about pulling the trans.
Mitchell On Demand is a service manual & labor guide that most shops use when they work on more than one type of car. Has every make from A to Z. Kind of the standard for independent repair shops. Most if not all the info is taken directly out of the factory manuals. I've been a Mechanic for 19+ years & have been useing either the printed or Computer version the whole time.
If I remember right the time listed for timing chain replacement includes removal of the motor. I wasn't going to pull the motor just to inspect them.
It also looks like the heads have to come off seeing the chains go through them.
It's been a couple of weeks since I looked it up so don't quote me on this. I'll check again tomorrow to set myself straight.
If you say it can be done in the car without removing the heads then I'm assuming you have done it before and I'll take your word for it.
Do these things bend valves if the chain should break while running???
Again thanks for all the info so far.
Ronm

You can positively change the entire timing drive on the Northstar with the engine in the car. The engine is build with the heads installed before the timing chains are installed so I HOPE you can get the chains back off without pulling the heads....LOL Yes, if the chains break or something happens to the timing drive you will definitely bend valves...not many 4 valve engines that are "free spin" capable....the valves are just too close to the perimeter of the combustion chamber in a 4 valve design to clear the pistons. But...that is why the Northstar has timing chains instead of elastomeric belts like much of the competition. Belts are cheap and easy and quiet....but they break eventually and scrap the motor. Chains are more difficult to engineer but they last the life of the motor.

Problems with the timing drive on the Northstar are exceptionally rare so I wouldn't suspect anything like that happening.