4.3 volvo knock suggestions

[dasnively]

I recently purchased at a very good price a 2000 Larson Sei 186 with a 4.3 volvo I/O. I bought it as is, with the knowledge that if something was wrong with the motor or outdrive, I am perfectly capable of repairing it. I am a mechanic by trade. I changed engine and outdrive oil prior to starting it. It ran with the garden hose for 20 minutes with no overheating issues. I took it to the river and and ran it around to gain confidence in it. I ran it down the river at about 3600 RPM until I started hearing a noise. I opened the engine cover and noted that the knocking was not heard at idle, but began at about 1800 RPM and increased in loudness with engine RPM. It sounds like a metallic rattling. It is present with the engine out of gear also. Any suggestions as to what direction to look before I pull the engine? Such as bellhousing, gimball area? Thanks.

 

[captk]

Re: 4.3 volvo knock suggestions

With the engine running turn the drive hard over, and trim up. Does the noise increase? if so pull drive and check u joints and gimbal bearing. Hard Knock , U joints, metalic rattle gimbal brg, light rattle loose dust cover on flywheel?

 

[Maclin]

Re: 4.3 volvo knock suggestions

Sometimes us car guys need to be reminded that it is a boat! and that the ujoints and top gearset in the outdrive are always turning with the engine even when not in gear. The "transmission" is in the middle of the outdrive. So anytime the engine is running the drive shaft ujoints and bearings will be in play, and could make rattling noises even out of gear if they are in need of service. Most will also remind you to not start or run the engine with the drive all the way up as it places unneeded stress on the u-joints.

 

[rndn]

Re: 4.3 volvo knock suggestions

Welcome to the forum!!

 

[bjcsc]

Re: 4.3 volvo knock suggestions

I had almost the exact same symptoms with nearly the exact same engine. In fact, it's what brought me to this forum. For the long story, click here. The short story is that my distributor cap was making an intermittent connection and a new one solved the problem (and it was very easy to change since I had the engine on a stand by that point ).

 

[dasnively]

Re: 4.3 volvo knock suggestions

Thanks for the suggestions. Now that I am done with my weekend shift I will start as soon as I finish putting the riding mower back together. I am going to check the compression, listen with a stethoscope, pull plug wires one at a time, etc. before I pull the engine. I will also pull the outdrive off and check the engine alighment prior to pulling the engine. One of the mounts does not look quite right.

 

[bruceb58]

Re: 4.3 volvo knock suggestions

Another thing you can do is to run the engine without the drive on. You just have to supply cooling water.

 

[dasnively]

Re: 4.3 volvo knock suggestions

Completed all compression checks. All cylinders at about 165. Pulled each plug wire individually and only no. 4 seemed to make a difference, but not much. Removed the right valve cover just to make sure the valves were adjusted properly. Nothing noted. I removed the outdrive (that was easy). The gimball bearing is smooth, u-joints feel brand new. Connected water to the transome and started the engine again. Knock is still there. Time to pull the motor. Time to go back to work tomorrow, so the saga continues next week.

 

[Silvertip]

Re: 4.3 volvo knock suggestions

Balance shaft 4.3's can develop some balance shaft bearing noise that is a characteristic of the beast but has no bad effects on engine longevity. From your description it doesn't sound like that's the issue however as the balance shaft noise occurs under part throttle.

 

[dasnively]

Re: 4.3 volvo knock suggestions

The noise begins erratically about 1800 rpm and increases in magnitude as the engine speed increases. It is loud at 2500.

 

[Lakester]

Re: 4.3 volvo knock suggestions

The noise begins erratically about 1800 rpm and increases in magnitude as the engine speed increases. It is loud at 2500.

hello,

sorry to hear of ur woes...

if this was my project, before pulling engine, i would consider spinning it over with all the plugs out. any noise? i would also try it with all the eng acc belts off. any noise? if it did not spin fast enuff, i would try 24v for a few revs with it set up NOT to start. any noise?

be sure ur bellhousing bolts are torqued to spec. i once had a car with them loose. no noise at idle or slow speed. then as engine load increased it would intermittantly howl. it got worse. last time it happened, i had to turn around. i searched all over the engine. the loose bellhousing bolts let engine walk on block to bellhousing pins and the flywheel kissed the dust shield as load increased. once tightened, etc the problem never returned.

also, i would pull distr and ck it out very closely. and i would spin it with distr out. any noise?

good luck.

lakester

 

[dasnively]

Re: 4.3 volvo knock suggestions

Unfortunately, the engine does not make noise until about 1800 RPM. I did spin it with all the plugs out and there was no noticeable noise. I believe I am down to pulling the motor. I have climbed all over this thing, I am convinced it is inside.

 

[dasnively]

Re: 4.3 volvo knock suggestions

Well, here it is. The motor is out. Tore it down and found the no. 4 rod bearing spun. Time to rebuild. Crank actually looks pretty good. The bearing was stuck on the crank so it might need a new rod. Nothing looks particularly scarred up. I am going to replace the oil pump also just for good measure.

 

[dasnively]

Re: 4.3 volvo knock suggestions

Machine shop said the crank is toast. They ordered a reman crank for $249. They resized the rod end. I am thinking I should replace the oil pump to be on the safe side since it spun the bearing (possible oil starvation??). What is the recommendation about going with a high volume pump? Would I need a larger oil pan, or should I just stick to the oem pump?