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Pulling a knocking 3.8.

W

WOLF257

New member
My 01' GT developed a rod knock so I'm going to drop the pan and see just how bad things look.
The car has 142k on it and has had the oil changed at the recommended intervals so unless it's a weak oil pump, I'm not exactly sure what happened.
Most likely the engine will have to come out so is there anything peculiar to this car or engine that I need to be careful of when I pull it?
Thanks in advance for any advice or suggestions.

Jim
 


usually rod knock occurs if coolant has gotten in your crankcase and what not due to LIM gasket failure.

did this happen?
 
I haven't drained the oil yet but what was on the dipstick wasn't showing any obvious signs of coolant contamination but I'll definately look for it when I drain the oil.
This is the first GP I've owned in years, last one was a 73' model with a 455, and the first frontwheel drive model so I'm not really familiar with this particular engine.
I did notice that it was a cast iron block/heads engine which I wasn't expecting, thought everything these days was aluminum.
Thanks for the headsup on the gaskets, anything else about this motor you think I need to keep an eye on?

Jim
 
LIM is a big problem leaky valve covers if you gonna pull it out i would do the 2 coolant elbows that come out of the intake. If its a rod knocking you can either 1 have the crank and rods machined and go with oversized bearing or go the cheap route and find a good salvage yard engine.
 
These motors are very similar to old school designs, cast iron block push rod engine, just fwd.

If you're positive you have rod knock it's probably just best to replace the bottom end, seems that's the consensus on the cheapest and easier way out.

But as far as the motor you have once it's running fine. The LIM gaskets are most notorious, of course if you tear it down and replace the bottom end or whatever you decide to do, you will have that covered just make sure you use the aluminum intake gaskets they are the 2nd design. Also with 142k miles it wouldn't hurt to get a new plenum (your upper intake manifold), it develops a leak near the EGR. Those are the two things that pop in my mind as far as risk factors on your 3.8. Tis a good motor otherwise.

I'm curious to see why you have rod knock. Good luck.
 
WOLF257 said:
last one was a 73' model with a 455, and the first frontwheel drive model so I'm not really familiar with this particular engine.
Jim
Click to expand...

i think your thinking of another car back in the day, grand prix were RWD in the 70's.

caddy eldorado and olds toronados were fwd tho.

and if the bottom end is knocking, just get a used short block or long block. rebuilding them costs to much, lots of machine shop work needs to be done, a used block will be so much cheaper. and will last for many years. lots of people here buy used engines and mod them up good, and they hold.
 


Thanks guys, I checked around and can get a crank kit for a couple hundred bucks so I'll probably just got that route.
I haven't built an engine in a number of years so what's the current opinion regarding clevite bearings for this particular engine?
I used to use clevite in everything I built and always got good service out of them but some people I know didn't like them because they were harder than standard bearing material.
Since I'm probably going to have to pull the engine I'll build it while I've got it out, I'm not real confident about just building the bottom end of the engine.
I'll keep you updated as to what I find since there weren't any warning indicators or errors, thing was running fine last Friday and it started knocking as soon as it was started Saturday.
 
I should have been more specific, this 01' is the first front wheel drive model I've owned.
The 73 was definately rear wheel drive and nowhere near stock so I kept the local tire store in business.
 
post a vid of the knocking if you can. could be a bunch of things, from cracked flywheel to lifter tick.

from all the vids ive seen here of bad bearings, they all seem to squeal first, and then knock , (aka rappin rodney) where as in the 2 v8s i killed, they just start to knock like a hammer to the heads.
 
when i spun a bearing it never was a gradual thing. it was just a squealchy knocking noise.

ive also had a cracked flex plate as well.
 


use a lighter or torch to heat the oil on the dipstick..

Any bubbling then there is coolant in it... Oil doesnt bubble, just burns/smokes...
 
I bought a complete L67 (supercharged V6, complete motor, SC included) for $750 from dallas, it came from a bonnie, but after changing over a couple parts off my old engine, it dropped in without a problem. Paid another $700 to the tech at the shop I work at to put it in and shes been fine for the past year and a half, almost at $20k on the engine with me. Definately worth the money and I bought a more expensive engine because I wanted lower miles. Its much cheaper, especially if you can put it in yourself, I didn't have the tools to do it or the time so I just paid the tech.
I spun the bearings on cyl 1 & 2, not sure the reason, thinking oil pump gave up but with only 83,000 on the car it was really odd. Definately buy a new motor and change the gaskets and drop it in, you will be much better off.
 
I'll check around and see if there's a used engine within a reasonable distance.
My buddy at the machine shop owes me some favors and said he'd do the the machine work for the cost of the parts so that should save me several hundred dollars.
A lot of what I end up doing is going to depend on the condition of the block, if it's going to take more than .010" to clean up the cylinders I'll probably have to find another engine or just junk the car.
I don't think the cooling system is good enough to stand up to a .020"+ overbore or I'm just not enough of a gambling man to find out, especially with how hot it can get here in the summer.
The more I read about this engine the more it reminds me of the old 3.8 Buick V-6 with it's weak bottom end, lousy oil pump and lube system.
 
If its a rod knock, the cylinders will likely be fine with a hone then just put new rings on the current pistons..

If you need a replacement rod, I have a few you can have for the cost of shipping...
 


I'm in the same boat with having to replace engine due to rod knock. Found a used 3.8 out of a Buick Century Custom with only 80k for $400. Anyone know if this will go into my 99 GP GT?
 
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