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Discussion Starter #1
What is the part number for the "purple" service replacement #1 main bearing for the 4.9? I can't find it anywhere, or the TSB that lists it.
 

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I don't know the part number, but is this the bearing that is suppose to take away that annoying crank knock noise.

If so I am really interested in this too, as I hate that damn noise. It is only every once in a while but UGH. Coming from a hot rod background, when you heard that noise in a regular motor, your heart would sink, your stomach would try to come up and in some cases it was best to duck for cover from flying crank bits after ventilating your engine block.
 

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IIRC 1992 4.9 got rid of that problem.

Keep in mind, it will do NO damage to the engine, just be annoying...

but, it is the main bearing, all you gotta do is go do the dealer and tell them you want the updated main bearing kit ofr the 4.9... not sure on the exact name, but they'll know what you are talking about.

my 1993 4.9.....has never once had the knocking issue... I think it'll stay that way :)
 

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Night Wolf said:
IIRC 1992 4.9 got rid of that problem.

Keep in mind, it will do NO damage to the engine, just be annoying...

but, it is the main bearing, all you gotta do is go do the dealer and tell them you want the updated main bearing kit ofr the 4.9... not sure on the exact name, but they'll know what you are talking about.

my 1993 4.9.....has never once had the knocking issue... I think it'll stay that way :)

Uh oh, if you are right, then I either have an early production motor, or some seriously bad luck coming up.
 

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Well that makes 2 of us.

My Sedan deVille was manufactured in 4/92 and mine has the main bearing thump too.
I wonder if the 4.9 in mine was manufactured in 1991. Damn GM!
 

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Capt Fiero said:
Uh oh, if you are right, then I either have an early production motor, or some seriously bad luck coming up.
Yeah, the new bearing went into effect for the 1992 model, although I *have* heard/seen 1992 Caddy's with the problem... and like you said, they were early production... engines left over from 1991 and put into 1992 cars.

Later production 1992, all the way to 1995 *should* be fine... I have heard of a few cases from late '92-'95, but they seem to be isolated from neglect, abuse... and just general problems with an engine produced on such a wide scale.

I wish I could tell you a way to date your engine, but I don't know... sorry.
 

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BTW the "knock" usually when the engine is under a load, around 2,500RPM (put in gear, hold brake, hit gas) is from the main bearing... from just a few extra thousandths of an inch extra clearance. The way to isolate the infamous main bearing knock on the 4.9, from any other mechanical problem, is have someone (you trust :) ) in the car power braking it in such a way to duplicate the sound, then with a breaker bar, go over and relive tension from the serpintine belt, just lift up a little so it starts to slip.... if the knock goes away, it's the main bearing.

What happens is, the force from the belt around all the accessories puts a strain on the crank pully, and ever so slightly pulls it up, but obvisouly when the cylinders fire, it creates just enough uneven force to cause a knock form that bit of extra clearance... the updated bearing gets rid of all that though.

OT... for the guys with 4.9 in the Fiero, do they know the coolant has to be changed every 2yrs/24k miles and the coolant supplment *must* be used? if not, they are in for an early death of the head gaskets and internal coolant leakage...
 

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Night Wolf said:
OT... for the guys with 4.9 in the Fiero, do they know the coolant has to be changed every 2yrs/24k miles and the coolant supplement *must* be used? if not, they are in for an early death of the head gaskets and internal coolant leakage...
Thanks for the heads up on the bearing issue. I am going to keep a close ear on it to see how it goes or sounds for a while.

As for the coolant. A great deal of the Fiero guys with 4.9s change the coolant every 6-8 months. :hmm:

Cause at the race track we can't run antifreeze. :cool2:

So in the spring we drain out the cooling system and put in 3 crushed tablets plus a bottle of water wetter and fill with 3-4 gallons of distiled water.. Run the car like that during the summer, then in the late fall, drain the system again fill with 3 crushed tablets and water wetter and fresh green stuff.

Our Canadian winters are pretty mild not usually below -10 or -15 so I can get away with just 1-2 gallons of antifreeze.
 

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What track do you run at that you can't run antifreeze?

a dragstrip? hmmm... by us, they coudln't care less whats in the engine :)

Thats good about the coolant changes, I personally change mine every year, you mention 3 of the crushed tabblets? the ones from the dealer? it is reccomended you use all 5.

I have had people argue with me not to use that... ummm, just read the manual, look at the sticker on the freakin' car, and that stuff came in the engine when the car was new. the tubes of Barrs leak cooling system conditioner can also be used... it is the same exact thing, just crushed up, for the 4.9 you want 2 tubes.

I wish I could tell you more about what to look out for... but the 4.9 is so freakin reliable, that there isn't any thing else :) when people ask me what the ain problems are with the 4.9, it is simple... rough idle, thirst for premium (not a single issue for me) and the cooling system maintenace..... and they don't take well to overheats, so first sign of the water pump going, replace it, if it does overheat, shut it down as soon as possible.

For being deisgned around 1982, the engine does a pretty good job at what it does, I would say it is a very good alternative to the Northstar, in the Caddy or the Fiero. I have a thing for old school pushrods, not into the whole DOHC thing, so that is where the 4.9 gets a whole buncha brownie points in my book :)
 

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Night Wolf said:
What track do you run at that you can't run antifreeze?

a drag strip? hmmm... by us, they couldn't care less whats in the engine :)

Thats good about the coolant changes, I personally change mine every year, you mention 3 of the crushed tablets? the ones from the dealer? it is recommended you use all 5.

I have had people argue with me not to use that... ummm, just read the manual, look at the sticker on the freakin' car, and that stuff came in the engine when the car was new. the tubes of Barrs leak cooling system conditioner can also be used... it is the same exact thing, just crushed up, for the 4.9 you want 2 tubes.

I wish I could tell you more about what to look out for... but the 4.9 is so freaking Barr'sfreaking reliable, that there isn't any thing else :) when people ask me what the ain problems are with the 4.9, it is simple... rough idle, thirst for premium (not a single issue for me) and the cooling system maintenace..... and they don't take well to overheats, so first sign of the water pump going, replace it, if it does overheat, shut it down as soon as possible.

For being designed around 1982, the engine does a pretty good job at what it does, I would say it is a very good alternative to the Northstar, in the Caddy or the Fiero. I have a thing for old school push rods, not into the whole DOHC thing, so that is where the 4.9 gets a whole buncha brownie points in my book :)
Mission Raceway Park. Link to Mission Raceway Park Rules Page

It is an NHRA track with 1/4 mile, road course, you name it. They just don't want someone overheating and flooding antifreeze on the track which gets rather slick. The street legal nights have an outlaw class with some cars cresting 200mph at the top of the track, so you may have a pair of Honda's go down the track and then a pair of 2000hp Pro Street cars going right after them. It kinda sucks, but we have gotten use to it.

Looks like maybe I should up the amount of crushed stuff in the system. Thanks for the heads up.
 

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All it is, is basically crushed ginger.

On the 4.9 and N*, it is used to prevent internal coolant leaks, what happens is, if there is a microscopic leak, the stuff gets pulled to that area from the vaccum, and it simply beaver dams against it... and no more leak. It is also one of the best "stop leak" type stuff for when somebody is too cheap to get a new radiator... all natural, will not harm a thing on the engine, water pump, radaitor, hose or anything. the only "issue" with it I had, is the last coolant change i did (couple weeks ago) on the bottom of the coolant jug (which never appeared to be removed) was some loose chunks of the stuff, so I simply took it out and cleaned it (what I was doing anyway) and it is great now.

it's all realitive though, the Caddys have a pretty robust cooling system, I am not sure what setup you guys have and how much coolant is used... on smaller systems you don't need as much, but, more will not hurt it either, really can't over dose on it :)
 

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Basically we have a corvette style aluminum rad in the front of the car, and stainless steel pipes running from the front of the car all the way to the back of the car. I think the cooling system from empty is 6 gallons.

I run a 180' thermostat in my car as per request of the chip maker.

Car almost never goes over 210F even idling in the USA/Canada Customs line for hours on end.

The water pump on the 4.9 is curiously small in my opinion. My old Fiero V6 had a larger impeller on it.

But just to be on the safe side I did put on a new pump when I did the 4.9 for the Fiero.
 

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wow, thats about a gallon and a half MORE then the Caddy's.... I would defintily be using all those tabblets, and then some.

the factory water pump seems to be ok, but when it comes time to replace it, DO NOT use after market pumps (Advance Auto/Auto Zone) has they seem to last for only about a year on the 4.9..... AC Delco right from the dealer... you'll pay more, but it is worth every penny.
 

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Here is the part number you are looking for:

#1 service main 3545718

This is the part I am going to use for my 4100 to 4.5 conversion. it is the same for all HT4100's through to the 4.9.

Mike
 

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Discussion Starter #15
Thank you! The knock I hear in gear even at low RPMs. I use Rotella T oil 15w-40 and still hear it! I don't know if poor maintenance is to blame for it, but the car seems to be well taken care of by the previous owner, and I take excellent care of it. So I guess I'll try the bearing fix and see if that helps. It hasn't gotten any worse in the 24k miles that I've owned the car.
 

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It was a common problem with early 4.9's. It's really not a big deal, and the bearing is easy to replace. Just make sure the engine will still roll over when the bearing cap is torqued into place. The clearance is pretty tight.

Mike
 

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Discussion Starter #17
I thought it was a common problem with all the 4.9's not the later ones. My car was built in April 1994, so it's a later 4.9 with main knock. Thanks for the tips on replacing the main bearing!
 
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