knock at start up

[harleynut]

I got a knock at start up on my 30 Phaeton. It goes away after about a minute or so. Tried shorting out cylinders 2 and 3 while knocking, produced no change. I use Rotella 15w40 oil, it's clean and up to level. Engine has about 1000 mi. on it. Any thought would be appreciated.

[J Franklin]

Tap? Knock? Or thud? It makes a difference in diagnoses.

[Chuck Sea/Tac]

If you go back several pages to (knock) by Chuck , there's a page of different types of knocks and diagnosis ,posted by John. Sorry I'm not sure how to link.
That being said, it sounds like you're not getting lubrication to something?

[mantta]

Camshaft thrusting back and fourth. Check your plunger & spring.

[Mitch//pa]

I have seen a knock at start up due to oil pan baffle drain back caused by pin holes from rust.

And you'll have a ton of other things to check also...

[tbirdtbird]

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why stop at shorting out cyls 2 and 3?

[Jon]

Have you checked the water pump? After rebuilding my transmission I got a knock. Figured it had to be the transmission so I pulled the rear end and trans out. Couldn't find anything so I started it up, still knocked. Found out the water pump was making the noise.

[Mitch//pa]

Removing the fan belt first would make sense

[Patrick L.]

We need some more info. Try and locate, as well as describe, this noise. Removing the belt as Mitch said will help by eliminating the pump and generator and maybe the front pulley.

[BILL WILLIAMSON]

Remove # 2 & # 3 plug wires, before starting. If NO KNOCK, center main bearing is LOOSE/WORN.
Bill W.

[Y-Blockhead]

Originally Posted by BILL WILLIAMSON

Remove # 2 & # 3 plug wires, before starting. If NO KNOCK, center main bearing is LOOSE/WORN.
Bill W.

Bill, see post #1.

[Tom Wesenberg]

1000 miles on the rebuilt engine, correct?
Did this noise always exist since the rebuild, or did it start after several hundred miles?
Was the engine overheated, which may have collapsed a piston skirt?

[Pete / MA]

I too have a knock at startup. It happens after week or two of sitting. I have found that if I crank the engine over a few times with the ignition off (pre-lube) I don't hear the knock when I start. I have assumed it is one of the babbit bearings drying out because of a little to much clearance. My plan is to drop the pan next winter (or sooner if it gets worse) and adjust the mains and rods and inspect the other "usual suspects". I will be interested in following this post to see what other opinions and experience I can learn from. When I do drop the pan I will make sure to report back to this forum (with pictures of course) of what I find.
Thank you..............Pete

[harleynut]

Me also Pete, I'll get back as soon as I get a chance to check out the suggestions from this post, starting with the easiest things first.

[BILL WILLIAMSON]

Originally Posted by Y-Blockhead

Bill, see post #1.

I wasn't SURE if he was shorting them both out, at the SAME Time.
I helped Claude diagnose one, where the rebuilder had FORGOTTEN to adjust the center main.
Bill W.

[CWPASADENA]

Originally Posted by mantta

Camshaft thrusting back and fourth. Check your plunger & spring.

I have had this problem on an engine and found that knock caused by a camshaft plunger and spring problem will occur all the time, not just at start-up.

I also think it may be due to loose main bearings or if it is a babbet engine, incorrect groves or "reservoirs" in the main bearing babbet that allows all the oil to drain from the valve chamber after the engine is shut off. It takes a little time for the oil pump to re-fill the valve chamber and once again get oil to the mains.

That is my thoughts,

Chris W.

[BILL WILLIAMSON]

[QUOTE=CWPASADENA;1312487]I have had this problem on an engine and found that knock caused by a camshaft plunger and spring problem will occur all the time, not just at start-up.

I also think it may be due to loose main bearings or if it is a babbet engine, incorrect groves or "reservoirs" in the main bearing babbet that allows all the oil to drain from the valve chamber after the engine is shut off. It takes a little time for the oil pump to re-fill the valve chamber and once again get oil to the mains.

I always add 1/2 bottle of STP to my oil, it really CLINGS & helps on a "DRY" bearing start.
Mitch will probably LECTURE me, save your ENERGY, Son!!
SA Dad

[Y-Blockhead]

Originally Posted by BILL WILLIAMSON

I wasn't SURE if he was shorting them both out, at the SAME Time.
I helped Claude diagnose one, where the rebuilder had FORGOTTEN to adjust the center main.
Bill W.

Bill, I just wanted to ensure you saw it.

So many times I've seen responses (NOT yours) that appears the 'respondee' just jumped to the end on the thread without reading ALL of the posts beforehand and repeating things numerous times.

[tbirdtbird]

amen to that, Y Block

[Mitch//pa]

[QUOTE=BILL WILLIAMSON;1312512]

Originally Posted by CWPASADENA

I have had this problem on an engine and found that knock caused by a camshaft plunger and spring problem will occur all the time, not just at start-up.

I also think it may be due to loose main bearings or if it is a babbet engine, incorrect groves or "reservoirs" in the main bearing babbet that allows all the oil to drain from the valve chamber after the engine is shut off. It takes a little time for the oil pump to re-fill the valve chamber and once again get oil to the mains.

I always add 1/2 bottle of STP to my oil, it really CLINGS & helps on a "DRY" bearing start.
Mitch will probably LECTURE me, save your ENERGY, Son!!
SA Dad

Put slick 50 in it