Loud tapping in the engine

Alright fellas, I got one for ya. Lately, my on my '88 3.8L Riviera, there has been a loud tapping coming from the engine. As you hit the accelerator it becomes a little erratic until you hit about 2000 RPMs. Once you hit that RPM range the tapping levels out/disappears. So I am currently doing cheap test to figure out where this tapping may be coming from. The tapping isnt coming from any of the pulleys. So I just did a dry compression test.

Cyl 1: 175 PSI
Cyl 3: 182 PSI
Cyl 5: 185 PSI
Cyl 2: 180 PSI
Cyl 4: 177 PSI
Cyl 6: 177 PSI

My Haynes manual only give me a minimum reading not a healthy one. I've also performed a vacuum test and the reading is a steady 19 Inches of Mercury. What can I take away from these readings? Should I perform a "wet" compression test? Should I try a leak down test?

It is a high pitch tapping or a low knocking sound? My gut says a stuck lifter if high pitch.

It is a higher sound yes. I was told from a couple guys at work about adding C-foam? or Marvel Mystery Oil? to help lubricate the rockers/lifters and such. Worth a shot before diving into a top engine rebuild. I was also told to get a stethescope or something similar to pinpoint where the tapping is the loudest.

I recently recorded a video that you can hear the tapping. Headphones help isolate and amplify the sound better then standard computer speakers. Here is the link:

https://www.youtube.com/watch?v=jjiugOcbcb0&feature=youtu.be

how often do you change the oil and what do you use?

you might want to do one oil change with Pennzoil ultra if you can find it. It is a tweaked dino oil but it will scavenge sludge.

I normally use Mobil 1 Clean 5000 5W-30. It really helped my gas mileage, i know that. The engine had great torque response as well with that oil, but the tapping was very loud. With my last oil change I used 10W-30 and it seemed to quiet the tapping significantly, and now, after it has run for a while with it, it doesn't seem to make a difference. I change my oil about every 3 months. And, since I don't drive the Buick as much as I drive my Mitsubishi Galant, it's rare to hit 3,000, but I like to go by color sometimes. No more then 4,000 miles between changes though.

I would measure oil pressure. That sounds pretty bad.

Oil pressure is kind of erratic, but levels out when the car warms up. It stays around 70 PSI til it reaches the top of its temperature range about 185-195 degrees. Then it drops and steadies around 50-60 PSI. The video amplifies the tapping quite a lot. So it is not as loud as it sounds in the video, trust me.

If I replace the rockers, is there a left and a right rocker I should be considering, or are all the rockers the same? And yes, I know one is for the intake valve and one for the exhaust valve, but are they manufactured the same.

Don't think that's right 70 psi for a 3800 at start up and 50 60 when fully warmed???

Yeah it has seemed a bit high. I'm not sure how that's happening in the first place. Regardless, I need to reorganize here. Assuming it's a lifter causing the tapping, can I replace the lifters by going as far down as removing the valve covers, rockers, push rods and intake manifold? Or do I need to remove more to reach them?

Sounds like your next move is to get a factory service manual set off of Bay.

I already have a service manual, just didn't feel like reading at the time. I just hope I can find all the parts I need. Doing my price checking tonight at RockAuto.com, Autozone, Advance Auto Parts, Napa Auto Parts. Anywhere else I should look?

flyineagle96 wrote:

Don't think that's right 70 psi for a 3800 at start up and 50 60 when fully warmed???

No, that is right.  I have had an Autometer mechanical oil pressure gauge in my Riviera for about 8 years now.  With 5W/30 Amsoil, pressure is about 70 psi at start up.  At full operating temperature, the oil pressure is 63 psi at anything over 1200 RPM, and at idle, in gear, about 35 psi.  The 3800 has awesome oil pressure.  I wish my big block had that kind of pressure.

Wolfmaster579 wrote:

I already have a service manual, just didn't feel like reading at the time. I just hope I can find all the parts I need. Doing my price checking tonight at RockAuto.com, Autozone, Advance Auto Parts, Napa Auto Parts. Anywhere else I should look?

Don't assume it is your lifters.  It could be a damaged rocker arm and or push rod.  Take the valve covers off and inspect everything first.

Thanks for the PSI reassurance Larry. I was starting to get worried about it. And I will check everything under the valve covers first. Just finished my list for every part i may need for a decent overhaul anyways. No one has Right Hand Rockers though. Only Left Hand. I wonder if Left Hand can be used as Right Hand. Not sure. Either way, total is about $1000. I will try some Marvel Mystery Oil this weekend to see if it helps lessen the tapping for the time being.
All in all, I really can't do much with the Riv until the wife and I get some stuff paid off and have some extra money. I'll stick with the smaller things first.
I need to get it to a transmission shop after the engine work so they can properly diagnose the rough shifting (under load) and maybe so they can replace the Case Gasket. I will have to do some research on how much I have to remove to replace the case gasket. I have the tools for it, just not sure if I want to dive into it myself. It's has been leaking decently, but only if I have driven the car for a long period of time, or pushed it too much on the highway.
I'll keep you posted as I complete things. I'm hoping by the end of the year, my Riv will be ALL road worthy and cruisin in the fast lane once again. Til then, I'll just use it to hit up the grocery store. Can't keep it garaged all the time.

Tried out some Sea-Foam. If anything it certainly didn't quiet the tapping. It made it louder. And a lot easier to locate. The sound is coming from directly beneath the Intake Manifold. That seems to me to point more toward the lifters. I will still take my time and check all the push rods and rockers first before I tear down that far.

Isn't there a balance shaft on the 3800? Might there be a problem with that? Lifter problems are very uncommon with the 3800.

http://www.google.com/imgres?imgurl=http://www.thinkythings.org/3800/19-intakePorts.jpg&imgrefurl=http://www.thinkythings.org/3800/&h=480&w=640&sz=85&tbnid=RwCeMvX-n7KyfM:&tbnh=94&tbnw=125&zoom=1&usg=__aCcEuPX0FMxH7jTLL4Vb2BgRNes=&docid=DgnSIfksXwR7AM&sa=X&ei=OXH0UdK7M-bj4APXj4GABA&ved=0CDoQ9QEwAw&dur=2718

Any vibration with this noise?

LARRY70GS wrote:

flyineagle96 wrote:

Don't think that's right 70 psi for a 3800 at start up and 50 60 when fully warmed???

No, that is right.  I have had an Autometer mechanical oil pressure gauge in my Riviera for about 8 years now.  With 5W/30 Amsoil, pressure is about 70 psi at start up.  At full operating temperature, the oil pressure is 63 psi at anything over 1200 RPM, and at idle, in gear, about 35 psi.  The 3800 has awesome oil pressure.  I wish my big block had that kind of pressure.

This is not a sc3800,it's a 88 3800 na motor and mine has always been 50psi on cold start and 40 psi fully warmed up in gear with scan gauge!!! My 2000
sc 3800 on cold start is 63psi and never under 40 warm had Mobile1 all it's life!!!

No vibration. just tapping.

flyineagle96 wrote:

LARRY70GS wrote:

flyineagle96 wrote:

Don't think that's right 70 psi for a 3800 at start up and 50 60 when fully warmed???

No, that is right.  I have had an Autometer mechanical oil pressure gauge in my Riviera for about 8 years now.  With 5W/30 Amsoil, pressure is about 70 psi at start up.  At full operating temperature, the oil pressure is 63 psi at anything over 1200 RPM, and at idle, in gear, about 35 psi.  The 3800 has awesome oil pressure.  I wish my big block had that kind of pressure.

This is not a sc3800,it's a 88 3800 na motor and mine has always been 50psi on cold start and 40 psi fully warmed up in gear with scan gauge!!! My 2000
sc 3800 on cold start is 63psi and never under 40 warm had Mobile1 all it's life!!!

Makes no difference whether the engine is SC or not.  The 3800 engines use a different oil pump than earlier Buick V6's and it is an excellent pump.  There is nothing wrong with 70 psi at start up.  Actual pressures observed will vary with oil, and actual bearing clearances,  and gauges used. According to my FSM, normal oil pressure is about 60 psi at 1850 RPM, at full operating temperature using 10W/30 oil. I would expect this with any 3800 engine.  His oil pressure isn't the cause of his tapping.  There is a mechanical problem, and I doubt it is a lifter.  I wouldn't buy any parts until I was sure of the cause.

Removed the front Valve Cover today. Man there is a lot of dirt in around my intake manifold. But that's besides the point. I removed and checked the rockers and push rods. No stress cracks, no excessive wear marks, rods are straight as can be. I did notice a thin layer or schlack on the bottom third of the push rods. Also, cylinder 5 had a push rod that was clogged down at the lifter. There is also little deposits of metal shavings mixed with some oil, copper in color. Not sure what that could be from.

Strange thing is, besides the tapping, my engine never seemed to have a loss of power. It has always run strong. I hope I find something when I remove the rear valve cover. We shall see. I will keep you posted. Bonus to all this is that my engine parts will be getting a well deserved cleaning.

Update on the engine teardown

I have removed the rear valve cover, throttle body, water pump and intake manifold (and everything else that was in the way). Rear push rods are straight and clean (bit of sludge build up on them), rear rockers and pivot are in good shape.

I have a question about a healthy valve lifter. I removed all the lifters. I have a couple whose roller bearings sound a bit rough (Left lifter on cylinders 4 and 6). the "plunger" in the middle of the lifter, the part where the push rod sits, is stiff. Rather I can't push down on them at all. They are stuck i suppose. I took one of the bad roller bearing lifters apart and cleaned it up real good. I checked for interior wear and tear and put it back together. After being put back together, the lifter's center cylinder moves up and down on the spring inside. Shouldn't they all do that?

And Larry, I checked the balance shaft as well. It seems to move quite nicely, but there is the tiniest play in it. A wiggle if you will. Barely even a millimeters worth. I'm not sure if that is normal or not.

Let me know what you guys think. and thanks in advance.

Thanks for the update, Wolfmaster. I would be concerned about the rocker operating above the clogged push rod. Make sure its bearing is still operating smoothly.

Our lifters are the hydraulic type. They pump up with oil during operation to pre-load the push rod. Without oil pressure, the lifter should feel loose, imo. If not, it's stuck.

I have a couple other questions. Shouldi continue to take apart and clean each lifter? And when I return them to the engine, should i soak them in oil to let them fill up, or should i load them in dry?

You can. Might consider replacing the lifters that are stuck, or take the opportunity to replace all with LS7 lifters for $110/set. When installing, you should lube with assembly lube, but no need to drench them in oil or fill them up.

I replaced the lifters in my Series I L67 with the LS7 lifters, I'm glad I did. Easy to do, perfect fit.

You would be better off replacing the stuck lifters. Just cleaning them won't account for the internal wear (why is it stuck??). They are pretty cheap.

Agreed with deekster, please don't clean them, just replace them. They're stuck for a reason...

I purchased a new lifter and it acted the same as the lifters I removed from my engine. I cant push down on the push rod seat because the oil pressure in the lifter is preventing it. When taken apart and if you push on the check ball inside, the oil comes out and the interior cylinder moves up and down on the spring again. so the reason it moved after it was cleaned was because there was no oil under the interior cylinder.

I do plan on just buying new. That way I have a warranty in case one fails.