Knock or a tap ?

[mark_fitzy]

Hi guys
Many of you have read my other post in the problems with my motor.

Question.
When the motor was breaking down with poor performance, I heard a tap/knock noise, but it sounded more lke a tap, but only when under load.

This noise that I heard was only when it was under load, not when it was at idle, even when reved higher in the idle position, No Noise.

Could it still be a bearing since it only appeared when under load and not at idle or high rev idle?

Thanks

 

[Fishermark]

Re: Knock or a tap ?

The problem with describing a noise is that everyone hears and describes things differently. It sounds more like pre-ignition pinging you are describing to me.

 

[mariner1900]

Re: Knock or a tap ?

As Fishermark has stated everybody hear taps and knocks differently, particularly when one doesn't know what he is hearing anyway.

As I mentioned in your previous post get the oil filter off the engine. Drain the oil from the filter and check for metal particles. Also cut the filter open to get at the filter material. Inspect the filter material for any signs of bearing and wear metals. These will look like small particles of glitter.

If there are no metal particles in the filter then there is a good chance there is no internal or bearing damage.

If there are metal particles then you have done some internal damage, most probably bearing damage. Generally, the more particles present the more damage.

Above is the only way that I know of to determine whether a failure has occurred or not. Short of dismantling the engine.

 

[mark_fitzy]

Re: Knock or a tap ?

Yea mariner1900 the heads are off and the oil is drained, Im am \ just trying to make a decission what to do. I have a blown head gasket. Now Im just down to the final stages in what to do.

I looked up what Fishermark said and I think he could be on the money with the pre ignition.

I will doing a little more investigation and then I will know what to do.

Thanks

 

[Bondo]

Re: Knock or a tap ?

Im am \ just trying to make a decission what to do. I have a blown head gasket. Now Im just down to the final stages in what to do.

Ayuh,... Blown Headgasket,..?? You've got a Junk Motor....
There's little to decide, other than are You rebuilding, or Buying...

 

[mark_fitzy]

Re: Knock or a tap ?

if it is pre-ignition or detonation, why not just change the head gasket?

 

[mariner1900]

Re: Knock or a tap ?

In your previous post you stated that you ran the engine for 4 days with water in the oil.

Before you can make a decision on just repairing the blown head gasket you need to determine that there is no internal damage to bearings, etc that is the cause of the "knock/tap" that you were hearing.

As I have already mentioned get hold of the oil filter, cut the filter open and see what is on the filter material. If there has been bearing failure you will see metal on the filter.

Also as the engine was supposed to have overheated I would be having a very close look at the cylinder bores for any sign of scoring due to to the pistons starting to seize.

As well you need to be making as decision soon as there will still be moisture in the crankcase that has the potential to cause corrosion of the internals.

The above is what I would be doing if it was my engine but hey it is your engine so you can take the advice or leave it.

 

[mark_fitzy]

Re: Knock or a tap ?

I will take your advice mariner1900, and appreciate all the advice I can get, the only problem is that the oil filter is long gone,as there has been a few oil changes trying to get the water out.

The strange knock I am hearing was only there when under load, which is now what I believe could be(after reading more about it) detonation. Am I right in saying that if it is a broken bearing I would hear the knock all the time?

I dont trust the mechanic that has the boat now and dont really want him to do any more work except put it back together so that if I take it to another mechanic at least I know all the parts are there. If he puts a new head gasket on while putting the motor back together, there just might be a chance it might be ok,

If it turns out that there is a broken bearing, well then I will change the motor by a new mechanic, knowing all the parts of the motor are there. eg carby, nuts bolts springs and everything else etc

Whats your thoughts?