Volvo AQ151C has ticking noise when at idle (video link)

[fishalope]

Re: Volvo AQ151C has ticking noise when at idle (video link)

I did the compression test in neutral with the engine warm. Should I compression test at WOT?

 

[Don S]

Re: Volvo AQ151C has ticking noise when at idle (video link)

Follow this service bulletin

http://www.boatfix.com/merc/Bullet/97/97_25.pdf

 

[fishalope]

Re: Volvo AQ151C has ticking noise when at idle (video link)

Follow this service bulletin

http://www.boatfix.com/merc/Bullet/97/97_25.pdf

Thank you Don. I will have to wait until monday when the shop is open again to test the compression. Idle speed is at 900 currently.

 

[fishalope]

Re: Volvo AQ151C has ticking noise when at idle (video link)

That is a worn out engine if the readings are right and would fit with my saying it sounds like piston slap.

My Volvo guy mentioned the piston slap thing as well Bubba.

 

[cc190cc]

Re: Volvo AQ151C has ticking noise when at idle (video link)

Greetings,

Low compression would not cause that noise, that noise is in the valvetrain, have the lifters adjusted and have them inspect for cracked springs or damaged parts. Why is it leaking water??? Did the engine freeze up?? If it froze up the cylinder head could have been damaged or cracked which could cause the noise. The noise does not sound like it goes away at high idle, just gets faster so you cant hear it as clear, def not a compressions issue, compression issues cause smoking and rouch idle. I would say if the noise sounds like it is coming from #2 cylinder then probably look at the valvetrain for that cylinder, have the lifters adjusted and go from there, definately a valvetrain/top end noise.

Chad

 

[cc190cc]

Re: Volvo AQ151C has ticking noise when at idle (video link)

I completely understand what piston slap is, that is not piston slap. That is a valvetrain issue/noise. If the compression was so low that it was causing that knock, the motor would be running rough and likely smoking. In this case the motor starts right up, seems to run fairly well, just has a valvetrain noise.

Chad

 

[fishalope]

Re: Volvo AQ151C has ticking noise when at idle (video link)

I did the new compression test with WOT and the results were 150-151-152-151 with the engine cold. Those seem like better numbers than the 1st time

 

[Silvertip]

Re: Volvo AQ151C has ticking noise when at idle (video link)

Timing belt, timing gear, or timing chain -- doesn't make any difference what drives the camshaft. Slop in that system will cause a rattle like this engine exhibits. I've obviously not been inside one of these but since the cam is belt driven, one might ask if the cam drive pulley bolts are tight. If you listen to that video carefully, the noise drops with only very slight throttle. Again, the slight additional loading removes the slack and things quiet down. If the cam drive system has a belt tensioner it is suspect. It has been determined that valve clearances are right. Compression appears to be good which doesn't cause piston slap. Piston to wall clearance issues causes that. A collapsed piston skirt would cause the noise all the time. The noise seemed to increase dramatically at the front of the engine therefore considering what has been checked and verified, my money is still in the cam drive system or perhaps even in a cam bearing or thrust bearing if there is one.

 

[Brucetafer]

Re: Volvo AQ151C has ticking noise when at idle (video link)

95% sure thats cam timing, those 151 motors are interference motors only if they have the 631 heron head, and when you gas it, it goes away, whens the last time the tentioner was checked??? i would start with timing belt, also, the water leak is a common area for those to leak, get the volvo gasket kit for the heat exchanger, will be a total of 2 for the freshwater intake tubes or copper ones, but get 4, double them up and it seals them great... these engines are built like tanks, they just keep going, so do the first thing and order those seals, when you take off the exchanger, theres 1 thermostat oring gasket, get 4 freshwater gaskets, and check the seawater pump gaskets as well, i would change em all just for insurance...

check timing, sometimes the old mechanical advance distributors will stick, pull your cap and turn the rotor and see if it is nice and freeplay, it should snapback...

keep us informed, if worse comes to worse, you might have spun a rod bearing, ive heard 350s sound like that...

 

[sqbtr]

Re: Volvo AQ151C has ticking noise when at idle (video link)

Those compression numbers look pretty good and the engine appears to run pretty smooth.

Have you isolated the area the noise is coming from?
Could be as simple as a drive coupler, or loose flywheel.
I doubt the tensioner would make that much noise, if it is cam drive related you should be able to see the offending component with a flash light and mirror.

 

[fishalope]

Re: Volvo AQ151C has ticking noise when at idle (video link)

UPDATE: I took the boat out to run it and put a can of Seafoam in the fuel in the hopes that it would stop the ticking. After about 20 minutes of running, it started running rough and idle speed dropped substantially. I took it back to the shop and ran another compression test. This time, all normal except for #2 that was at 0. I retested it with some oil in the cylinder and still at 0. I ran a scope inside the spark plug hole and saw that the valve was stuck open with no visible obstructions. I also removed the valve cover gasket and was able to rotate the valve on the exhaust side of #2 from the top while I watched it turn 360 degrees from the scope underneath. I think I may have a broken valve spring and that was the cause of all the ticking from the beginning and now the spring gave way fully and the valve is left in the open position. Does that sound correct?

 

[fishalope]

Re: Volvo AQ151C has ticking noise when at idle (video link)

Greetings,

Low compression would not cause that noise, that noise is in the valvetrain, have the lifters adjusted and have them inspect for cracked springs or damaged parts. Why is it leaking water??? Did the engine freeze up?? If it froze up the cylinder head could have been damaged or cracked which could cause the noise. The noise does not sound like it goes away at high idle, just gets faster so you cant hear it as clear, def not a compressions issue, compression issues cause smoking and rouch idle. I would say if the noise sounds like it is coming from #2 cylinder then probably look at the valvetrain for that cylinder, have the lifters adjusted and go from there, definately a valvetrain/top end noise.

Chad

Good call Chad, I think you are correct.