Help - Engine Knock - Volvo Penta 8.1GXi

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Help - Engine Knock - Volvo Penta 8.1GXi

Postby JNelson90 » Mon Aug 07, 2017 11:15 am

After a boat run Thursday night with a period at WOT my Port engine started knocking. Back at the dock and looking/listening closer it does sound deeper than a ping and seems to be in the centerline of the engine. Others indicated they thought it may be a wrist pin on piston. I did some research and people indicated that bad wrist pins or piston rod bearings tend to not make noise at idle or tend to get worse under load or higher RPM. The knocking in my engine does not appear to change with load or RPM (other than the rate of knocking) and putting the engine into gear has no impact on the noise as well. I am planning some more basic troubleshooting by removing the serpentine belt and checking the water pump, alternator, etc. + the status of the belt. Also, trying to use a long screwdriver to better detect where the sound is coming from. I will also change the oil and check the oil filter for metal shavings. May try Marvel Mystery oil and Risoline engine treatment - read some good feedback on those items.

My engine only has about 250 hours on it and it is a 2006 model year engine. I am really hoping this isn't something that I need to pull the engine to fix and any help with direction or troubleshooting would be greatly appreciated.
Kindest regards, Jeff

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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby gofast24 » Mon Aug 07, 2017 11:25 am

JNelson90 wrote:After a boat run Thursday night with a period at WOT my Port engine started knocking. Back at the dock and looking/listening closer it does sound deeper than a ping and seems to be in the centerline of the engine. Others indicated they thought it may be a wrist pin on piston. I did some research and people indicated that bad wrist pins or piston rod bearings tend to not make noise at idle or tend to get worse under load or higher RPM. The knocking in my engine does not appear to change with load or RPM (other than the rate of knocking) and putting the engine into gear has no impact on the noise as well. I am planning some more basic troubleshooting by removing the serpentine belt and checking the water pump, alternator, etc. + the status of the belt. Also, trying to use a long screwdriver to better detect where the sound is coming from. I will also change the oil and check the oil filter for metal shavings. May try Marvel Mystery oil and Risoline engine treatment - read some good feedback on those items.

My engine only has about 250 hours on it and it is a 2006 model year engine. I am really hoping this isn't something that I need to pull the engine to fix and any help with direction or troubleshooting would be greatly appreciated.

Jeff,
My thoughts =
Save your money with the "mystery" oil etc. and a long screw driver wont tell you much unless you have many years of engine diagnosis experience ! What is your warm oil PSI at idle and above 2000/2500 RPM out of gear? When did you change oil and/or what is the current level on your dip sticks? If possible I suggest draining a half pint or so of your current oil and get a oil analysis before doing anything major. You can check on the internet for oil analysis companies, they send you a small bottle that your fill and return freight pre paid. Wait for the analysis before doing anything else!
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby JNelson90 » Mon Aug 07, 2017 11:30 am

Thanks gofast24,

My oil was changed when I took the boat out of the water in October 2016 - using Volvo Penta synthetic oil. The dip stick is reporting my oil is full and the oil pressure gauges appear the same for both my port and starboard engines - consistent with what they always appear from using the boat for several years. I will have to check the actual numbers from the engine computers (tied to my MFDs) to properly answer your question about warm oil PSI at idle and at 200/2500 RPM. I like the idea of testing the oil and was planning on changing the oil just in case. Thank you again.
Kindest regards, Jeff

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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby gofast24 » Tue Aug 08, 2017 11:56 am

Jeff, your welcome!
My thoughts =
If your oil level is at full (or above "add" as you indicated) then (hopefully you still have old school oil gauges, what do they read?) Are you getting a low pressure warning alarm from the OBD-M ECU?
The gauges should be fairly close on your relatively new vessel? Yes, piston pin or big end rod bearings noise will increase with load more that RPM. Crank main bearing not so much from no load to full load)
It think it is great you are using full synthetic oil! What SAE viscosity are you using? I have been using a 10W-40 Castrol full synthetic for many years now on our 4160 (around $6.50 / quart) .
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby JNelson90 » Tue Aug 08, 2017 1:53 pm

I have not been back down to the boat to check the oil pressure gauge values but I believe it was reading around 38psi (slightly below center of gauge) and fluctuates a little bit based upon RPM - both engines act the same and I am not getting any low oil pressure alarms. Since I connected my engine J1929 network to my NEMA200 I can get true (digital) numbers from the engine computer as well. I have always purchased the Volvo Penta Synthetic oil - it was originally SAE 30 but they replaced that with 10w-40. I suspect that I could use a less expensive oil but I have not wanted to take any chances with my vessel.

I am very nervous that my knock issue may be somewhat major. I can assume that I would need to have the engine removed from the boat to service a wrist pin, rod bearing or crank bearing – correct? I have always taken great care of the engines and am very thorough with my annual services and winterizing. Are those failures somewhat common or highly unlikely? I did see a you tube video of an engine noise (sounded a lot like mine) and it was the serpentine belt that had a small piece missing in it. I am hoping for an easy fix like that but I am terrified that it is much worse!
:o
Kindest regards, Jeff

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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby nawtical1 » Tue Aug 08, 2017 5:21 pm

I would start with the simple. Check belts, tensioners, sample oil, etc. before you jump to any conclusions. I once had a Regal that loss power in one engine. I checked everything and could not figure out why. It turned out to be a broken spring in the serpentine belt tensioner. Go figure.

For what its worth, I have not heard of any ROF member or any other owner of the 8.1's fail with such magnitude like you fear with yours. This is especially true with an owner who is meticulous as you seem to be with your maintenance. I have the same engines and have over 600 hours and they are still running strong.

As Gofast mentioned, its wise to have your oil examined by a qualified lab. I include that with my annual maintenance.
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby RufusNapkin » Tue Aug 08, 2017 8:07 pm

Also think as far back as you can about what changed to possibly lead to this: bad gas, part changed, etc.

Several yrs. ago I had replaced the shafts and seals and almost a yr. later the shaft seal leaked. All mechanics advised AGAINST engine alignment because I had "no vibrations." They just wanted to replace the seal after ONLY a yr.

Finally I convinced a mechanic to do an alignment anyway. Shaft should move freely when turned by hand; my wasn't. He re-aligned the engine. Leak stopped immediately.

Get psychic if all else fails. Investigate.
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby JNelson90 » Wed Aug 09, 2017 8:22 am

Thanks to all of you for your feedback and I feel more optimistic this morning about my situation. I have already ordered an oil analysis kit from Blackstone Labs and will hopefully will know more after investigating this weekend. I am REALLY hoping this isn't something major. :D
Kindest regards, Jeff

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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby aviator1 » Wed Aug 09, 2017 9:37 am

Jeff,
The 8.1 liter is a massive mass moving around and while I agree the knock could be coming from something in the oil system and an analysis is good. A knock is caused by an uneven burn of the fuel/air mixture and this could be caused by a bad spark plug, excessive carbon build up in the head or cylinder walls and the one that gets people the most is poor fuel. If your crankshaft is getting uneven loads from your connecting rods, you will also get a knock. Not to alarm you but I wouldn't run the engine for extended periods of time trying to diagnose this, you could spin a bearing.

May I suggest the following and in order:

Inspect your harmonic balancer.

Run the engine on known good clean fuel source at idle.

Take the boat somewhere that can accomplish a cylinder drop test with a laptop.

Replace your spark plugs, since you don't know what cylinder, replace them all...while the spark plugs being replaced, do a compression check, your there anyways.

If and when you get your oil sample, getting the sample is important, the sample is only as good as the way you took it.
Oil has to be warm, if your hooked up to the NMEA, oil temperature has to be over 150 degrees, engine temperature and oil temperature vary drastically. Suck or drain about a quart of oil than take your sample.

Good luck and keep us posted.
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby gofast24 » Wed Aug 09, 2017 10:52 am

JNelson90 wrote:Thanks to all of you for your feedback and I feel more optimistic this morning about my situation. I have already ordered an oil analysis kit from Blackstone Labs and will hopefully will know more after investigating this weekend. I am REALLY hoping this isn't something major. :D

Oil analysis is Best thing you can do first!! Wait for the oil analysis (you will need to pull out a 1/4 pint or so of warm oi, fill up the bottle and indicate the brand/SAE viscosity,type of oil ( synthetic or dyno oil) and engine hours on the engine before you send the sample back) before going any father with $$. Yes a fowled spark plug can cause un even cylinder firings but not a knocking noise> just get the oil analysis that you mentioned your doing first! Blackstone Labs report should tell you if you have aluminum ( pistons) , cast iron ( cylinder walls), chrome (piston rings), or bearing material (rod big end bearings, main bearings) etc . When you get the analysis it maybe post a copy of it on the ROF? Good luck!!
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby gofast24 » Thu Aug 10, 2017 10:36 am

Additional thoughts=
First, how many hours on the engines?
How many hours on the VP synthetic oil since last change?
Spark plugs? Depending on hours on your 2006 engines they should have platinum / iridium plugs, dont need to change but inspecting them would not hurt! Our 2001 8.1L VP's with approximately 850 hours on them still have the original plugs installed! Last check at 800 hours the plugs look almost new, light grey in color and gap still within the VP specifications (0.060") !

If you run the engines until warm and you pull your oil sample out of the dip stick tube (the dip stick tube is typically a half inch or more above the bottom of the oil pan) you dont need a quart of oil before collecting the sample. Would be slightly different if draining the oil from the oil pan drain plug where all the sediments collect after shutting down the engines.!
Hope you can post the results of your oil analysis! Blackstone Labs report will give you a indication if any thing suspect and what they recomend your next step should be!
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby JNelson90 » Thu Aug 10, 2017 11:18 am

Thanks for your continued efforts and help! Here are some answers for your questions.

1. About 250 total hours on the engines
2. About 40 hours since last oil/filter change (oil changed annually since the total annual hours don't warrant changing more often)
3. Changed all spark plugs at 155.8 hours on 08/16/14 - used OEM Volvo Penta plugs VP part #3861326 - gapped to 0.060" + torqued to 20 ft/lbs.
4. I hope to get the oil analysis kit by Friday so I can collect the oil this weekend. I will post the results once I get them.

Thanks again!
Kindest regards, Jeff

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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby RufusNapkin » Thu Aug 10, 2017 3:25 pm

aviator1 wrote:Jeff,

May I suggest the following and in order:

Inspect your harmonic balancer.



Aviator1, how would you inspect the harmonic balancer?
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby aviator1 » Thu Aug 10, 2017 4:01 pm

Visually, ensure the core rubber material is even all the way around.
After what I went thru on my engine...I got to be pretty familiar with harmonic balances.

His oil sample will come back normal, if there was something failing and causing the knock...it tends to not live for too long before you see something else develop other than a constant knock.

Its hard to this via a forum but being there in person we could look at a lot of things and hear things that would certainly change my view on this.
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby gofast24 » Fri Aug 11, 2017 11:31 am

aviator1 wrote:Visually, ensure the core rubber material is even all the way around.
After what I went thru on my engine...I got to be pretty familiar with harmonic balances.

His oil sample will come back normal, if there was something failing and causing the knock...it tends to not live for too long before you see something else develop other than a constant knock.

Its hard to this via a forum but being there in person we could look at a lot of things and hear things that would certainly change my view on this.

Maybe wait for the results of the oil analysis? Highly unlikely a 2006 engine with 240 hours on it has a defective ballancer? A mal functioning c/s balancer would induce "torsional" vibrations thru the crank shaft to the gear couplings/ gear/prop shaft and not a engine knocking sound from my experience.
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby JNelson90 » Fri Aug 11, 2017 12:54 pm

Thanks again to everyone for their continued input - I am impressed by your knowledge and insight. I felt like I had a good grip on the technical systems of a boat but I have a lot to learn when it comes to engines. I will post again once I have a chance to work on the engine this weekend. I am praying for an easy to modest fix and not a major overhaul.
Kindest regards, Jeff

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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby JNelson90 » Sat Aug 12, 2017 3:52 pm

Worked on the engine today to see if I could isolate the knock. No issues with the serpentine belt, harmonic balancer, alternator, water pump/impeller or spark plugs. Had a mechanic or two look and listen, they removed the coil wires one at a time and the sound never really changed which they felt that proved that the problem is not in the lower end (wrist pin, etc.) and they believe it is a collapsed lifter or broken rocker arm spring. My plan is to remove the intake manifold tomorrow to see if I can identify a bad lifter. I picked up the fuel line quick disconnect tool so I can remove the fuel lines from the intake manifold. I have a few questions - are there differences in the gaskets? The Volvo Penta intake manifold gasket is about $160 and the gasket from NAPA for 8.1L GM large block is about $30. What is the torque required for the intake manifold bolts and is there an order to tightening? I also read that an exhaust leak at the exhaust manifold can produce a knocking sound - but the sound I hear seems to be more physical than what I believe I would hear from an exhaust leak. Lastly, I did not get the oil kit from Blackstone Labs yet for testing the oil. It will probably arrive next week.
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby gofast24 » Sun Aug 13, 2017 12:03 pm

JNelson90 wrote:Worked on the engine today to see if I could isolate the knock. No issues with the serpentine belt, harmonic balancer, alternator, water pump/impeller or spark plugs. Had a mechanic or two look and listen, they removed the coil wires one at a time and the sound never really changed which they felt that proved that the problem is not in the lower end (wrist pin, etc.) and they believe it is a collapsed lifter or broken rocker arm spring. My plan is to remove the intake manifold tomorrow to see if I can identify a bad lifter. I picked up the fuel line quick disconnect tool so I can remove the fuel lines from the intake manifold. I have a few questions - are there differences in the gaskets? The Volvo Penta intake manifold gasket is about $160 and the gasket from NAPA for 8.1L GM large block is about $30. What is the torque required for the intake manifold bolts and is there an order to tightening? I also read that an exhaust leak at the exhaust manifold can produce a knocking sound - but the sound I hear seems to be more physical than what I believe I would hear from an exhaust leak. Lastly, I did not get the oil kit from Blackstone Labs yet for testing the oil. It will probably arrive next week.


Suggest you not do anything until you get results of oil analysis! Your checking all the items above and finding nothing is good news (actually if it just happened to be one of those items it would be a cheep fix, but not the case, belt tensioners, alternators, sea water pumps do not create knocking noise). Dont think a bad lifter or valve spring would cause a "knock", especially at idle RPM and if the two mechanics pulled every cylinders plug wire one at a time and nothing changed don't believe valve spring or hydraulic lifter ! After a oil analysis report without unusual high metallic components in the oil the next guess (not knowing the results of the oil analysis) possibility exists that a defective lifter but again, that normally would not make a loud knocking noise, just valve floating at higher RPM' and loss of power! Again, a defective crank shaft torsional (your correct in your terminology "harmonic balancer") vibration damper wont create "knocking noise" as its only function is to "dampen" torsional vibrating in the crankshaft/gear/ coupling/ drive shaft.
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby RufusNapkin » Mon Aug 14, 2017 1:09 am

JNelson90 wrote: I have a few questions - are there differences in the gaskets? The Volvo Penta intake manifold gasket is about $160 and the gasket from NAPA for 8.1L GM large block is about $30.


Unless you can compare them side by side in-person, the ONLY way to save money on a boat is by wrenching it yourself - IF YOU KNOW WHAT YOU ARE DOING. If not, it is not possible to save money while owning a boat AT ALL.

I would like to be proven wrong.
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Re: Help - Engine Knock - Volvo Penta 8.1GXi

Postby gofast24 » Mon Aug 14, 2017 12:14 pm

RufusNapkin wrote:
JNelson90 wrote: I have a few questions - are there differences in the gaskets? The Volvo Penta intake manifold gasket is about $160 and the gasket from NAPA for 8.1L GM large block is about $30.


Unless you can compare them side by side in-person, the ONLY way to save money on a boat is by wrenching it yourself - IF YOU KNOW WHAT YOU ARE DOING. If not, it is not possible to save money while owning a boat AT ALL.

I would like to be proven wrong.

I dont think the ROF wants to prove you wrong? Yes, some of the folks on the ROF are not IC engine experts so they ask questions and we can all answer with our thoughts and experience. Many times folks think they know what their problem is but just guessing. A lot of guys on the ROF are pretty good at advising corrective actions or requesting further info to better give experienced advice..
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