Lawman31

Hey all... My engine has a noise that is only present after the car warms up and the oil pressure drops below the middle line on the gauge. I had all the lifters replaced, did nothing. My mechanic isolated cylinder number 8 as the cause by unplugging the injector when running and the noise stops. He tells me that he thinks the car may have been overheated in the past and wants to replace the pistons, rings and rod bearings in #6 and #8. I was wondering if I should just replace the oil pump at the same time. This is a picture of the oil pressure gauge, not my car I only have 72,000 miles, or so I think since the speedo sensor was damaged like someone removed the wires to it, but who knows. The car does seem to be a true 72K car when you evaluate everything.

Anyway, I must be getting old since I am writing so much to get to a point that requires way fewer words LOL.

When cold, my oil pressure gauge sits above that halfway line on the gauge and won't drop below it at all for like 6-7 minutes until warm. After that it sits right where this picture shows and when accelerating it won't push past that middle line at all. Is this normal? I just want to make sure my problem isn't simply oil pressure related before I have two new pistons installed.

I need your help and guidance here and really appreciate it.

Kevin.

JimLentz

That is where my oil pressure sits at idle once my 92 is full warmed up and I have 44 K miles and no noises in the engine.

jmgtp

FASTAZU

Looks good for an LT1

aklim

Has anyone done a test on the gauge to ensure it IS accurate? I'd hook up a mechanical gauge to make sure that it is reading right.

How much does he want for the job? Price it out with what it is vs getting a reman motor.

Lawman31

So when I brought it to him he was certain it needed new lifters, so he tore it down and installe 16 new lifters, put it back together... No improvement. I wasn’t happy. I paid himabout $500.00 to cover parts and he also found a few other things that he fixed like the oil filter conector wasn’t installed correctly and the oil filter was basically not doing anything.
I picked up the car and am taking it back to him.. The replacement of two pistons, rings, rod bearings, pan gasket, head gasket etc... will cost another $700.00, so all in all I will be out of pocket about $1,000.00 total for the repair after everything else has been calculated in.

I just hope this fixes things, not much else it could be at this point... I hope. Overall cost doesn’t seem bad to me, but what do you think?

Whaleman

These numbers seem too low, in my opinion.

kenmohr

Lawman31

It’s all about the circumstances and how things played out I guess. I agree, at this pricing the mechanic isn’t making much money, but it’s his fault. When I first brought the car to him I wanted a set of KYB shocks installed, the price was about $275.00. I asked him to diagnose the engine noise and he told me that he was certain that it needed new lifters and it would cost me $1,500.00 to fix. I negotiated this price down to $1,000.00 and since he needed the business, he agreed.
Since his original diagnosis was wrong, he is taking the responsability for the error and I just paid for the parts, shocks and a couple other items and paid him $1,000.00 which covered all his work for the lifters, shocks and a few other little things related to the oil filter and speedo sensor etc... he agreed that the total after replacing the pistons would now be $1,700.00, so since I already paid him the $1,000.00 I will pay the rest, or $700.00.
No, he is not making any money here, but due to his initial misdiagnosis. All in all, maybe he makes 3-4 hundred labor total after parts, but what else can he do at this point? He is going to work all day Sunday to fix it, so he feels bad I guess.
He has been in the business for 30 years, but not as good at diagnosing engine noise as perhaps he should be after so many years right?
At the end of the day I wish I had taken the car somewhere else, but there are no guarantees anywhere I guess. After I subtract the shocks and other miscelanious items he corrected, my total cost to fix the engine noise will end up somewhere around $1,200.00 instead of the $1,000.00 we originally agreed to. Or..... I may spend this money and things don’t get any better and I waste $1,200.00. I am going to ask him for a guarantee that after the pistons are replaced it’s fixed or I don’t pay anything? The whole reason you bring your car to seasoned mechanics is because they supposably know more than you about cars, so they need to be held accountable if they makes mistakes.

How much is a whole new short block? I hate to get in over my head in value on this car, that’s why I am trying to go the lowest cost route here.

Thx guys...

Gibbles

Maybe you should get several opinions of the noise.
also pick up an automotive stethoscope and start listening in all sorts of areas.

If all else falls, maye time for some full roller rockers (not just roller tip).

​​​​​​​Rollers can make a bit of noise, i think it sounds like a well oiled and adjusted sewing maching going to town.

Also... Listen close to the bottom end.
A rod knock can sound like a bad lifter.
A friend in highschool drove his camaro around for weeks with what everyone thought was a bad lifter before the rod went...
​​​​​​​I assume it got much worse, but he did not go into much detail.

hcbph

Well the poster said the mechanic disconnected the injector on #8 and the sound stopped and apparently based his diagnosis on that. How about when it's warmed up and making noise disconnect the plug wire on the same cylinder and see if it still makes noise. You can't discount a bad or noisy lifter masking something.

As far as oil pressure goes, I'd want to see a mechanical gauge plugged into the engine to see if the dash gauge is accurate or not. Pressure could be fine and the gauge could be wrong.

I agree on using a stethoscope and try to narrow it down some. Had a noise like a power steering pump started making noise on my truck. Lacking time, I took it to the dealership and they diagnosed it as same thing. Before changing anything, the power steering fluid was changed out (needed it anyway) to see if that would take care of it.
Long story short, didn't fix the noise. A week or two later I had a chance to look at it and got out the stethoscope. Turned out it was 2 things, an idler pulley on the serpentine belt along with the belt tensioner. I changed both out and the noise was gone. It cost a lot less than replacing a power steering pump, and had I replaced the pump it would not have fixed the noise issue.

sounds don't always tell you what's wrong all the time. Some times it takes more work to find the cause.

Lawman31

Thanks guys, so the noise is always there, just very muffled when the engine is cold. After the oil is hot the noise is easy to hear. At idle you can't hear it, when you rev the engine to about 3,000 RPM it comes on and sounds like a clacking noise. When driving it has a point where it's louder than at other times and so far I have been driving it very easy so I don't hear it too much while driving. Another time you hear it is when you let off the gas and slow down under engine drag, so sloppy while revving and again on down speeding, though the noise is louder while under power. I spoke with the mechanic again today telling him I wanted to start by just dropping the pan and replacing the rod bearings, but he assures me it's not a rod bearing. He said that if a rod bearing was making this type of noise, it would smash itself pretty quickly and spin causing much worse of a situation. He strongly feels that the noise is coming from either a sloppy piston, and/or the pin that connects the rod to the piston. The clacking noise does hold up to this theory as a valid evaluation, I guess we'll see. To better describe the noise, imagine revving to 3,000 rpm and letting off the throttle, you would hear a gradual clacking that corresponds with the speed of the motor. The clacking noise is very noticeable and would be obvious to anyone, though not to a point where you think the engine is about to blow up. I am pissed at myself for not identifying this during my inspection when buying the car, but it could be worse I guess, the overall car is pretty nice.
Any more ideas? I am scheduled to have the car back in the shop Sunday, one week from tomorrow. In the mean time, I will be accepting offers to buy the car for $11,900.00, which is actually not a bad deal. Other than this issue, pretty clean Torch red on Black leather, Automatic with 72,000 miles and a California car, climate control and dual power seats. I may or may not advertise it until it's fixed...

aklim

Exactly why I always recommend an independent person do the PDI. They are less likely to be caught up in the Corvette Fever and gloss over things.

I'm sure you will. So the question is how well you sleep when you "forget" to tell the buyer that this is an issue while you try give him the Corvette Fever and hopes he goes along with it. That is the price for a very clean car and not one with a potential motor failure which is what your mechanic is trying to band aid around.

Lawman31

Well not sure I would call it a band-aid, Slick-50 might be a band-aid right? I am looking to repair it correctly, but not spend a fortune either. I wouldn't sell it without disclosing what I know and that price includes the repair.. I don't think it would be a good idea to post in a public forum all the details then try and pull the wool over someones eyes... I understand being able to sleep at night no worries... Me selling is not because of this issue, it will be fixed... I would sell just because a 24 year-old car may be too much of a gamble for me moving forward. I don't have the energy to work on cars like I did when I was young....

VenkmanP

More details on this?

Does this indicate that this was some kind of bailing-wire and duct tape special?

mickey5

This sounds like a money pit. How do you play it when the crank journals are scored/ out of round after you pull off the caps?

aklim

Slick50 is snake oil. Trying to do one or two cylinders doesn't seem worth the trouble. I'd refresh all 8 holes and see how bad they are if I am going to replace pistons and rings.

Point I am making is that for $12k it has to be much better and not in this condition. Knowing what I know, for $12K, it better not have this sort of issue.

aklim

If it requires a new piston, I'd refresh the motor entirely. Hone cylinders, new bearings, assuming the crank isn't damaged.

Lawman31

The mechanic explained to me that the car has an adaptor that allows the oil filter to clear the pan, which he showed me. This adaptor has oil inlet and outlet holes in it and the gasket used to connect it had blocked the holes, so the filter was connected but not recieving oil in or out.

Lawman31

So I hear you about money pit, but I need to be optomistic for now until I identify a scored crank etc... if that happens I will need to make a decision to sell cheap and cut my losses, or just install a rebuilt engine. I’ll cross that bridge when I get there.