Is this rod knock?

dtw · 02-04-2008, 05:27 AM

I have never heard an engine with rod knock before, other than a brief online clip of a Subaru engine. So, I don't know what's going on with the engine I've got now.

This is a 3.0 that I resurrected yesterday, the car has not been started in a couple years. All head studs intact, engine looked good but just sorta dirty. I cleaned everything up and put a few items in order that were missing, and fired it up. Plenty of oil in the heat exchangers. Anyway - I noticed after a minute or two that there was a loud, metallic clanging noise coming from the engine. Did not isolate where, too much smoke to get under the car from all the oil burning off. It sounded like light hammer blows. It was RPM dependent, but at idle was very distinct. It was not an oscillation, but distinct clangs. At idle it seemed much slower than actual engine revs. I wonder if it doesn't instead have a really badly adjusted valve, or a stuck valve?

88911coupe · 02-04-2008, 06:18 AM

Not sure but "clanging" sounds like it may be something else, since I have read rod knock is a lower frequency...although light hammer blows does not sound good. Have you considered adjusting the valves to see if it makes any difference, or just to eliminate one problem?
I assume you put fresh oil in before it was fired up.

dtw · 02-04-2008, 06:31 AM

Quote:

Originally Posted by 88911coupe

Not sure but "clanging" sounds like it may be something else, since I have read rod knock is a lower frequency...although light hammer blows does not sound good. Have you considered adjusting the valves to see if it makes any difference, or just to eliminate one problem?
I assume you put fresh oil in before it was fired up.

It was Superbowl-time before there was time left for a valve adjustment. I think I have a set of gaskets and new hardware lying around. Guess I'll do that next. Clanging, yes. Makes me think of a rocker whacking away on a valve stem.

eapcpa · 02-04-2008, 07:12 AM

Hey Dave,

Try this for a quick test. Hook a timing light to any cyl and start it. See if the strobe is in time with the knock. If it is it is valvetrain noise, if the knock is double time it is likely bottom end. Easier to see and hear than to try to isolate by sound only. Let us know how it goes.

Ed

911 tweaks · 02-04-2008, 07:22 AM

Hey Dave, You can easily do away with this knocking sound by just throwing the engine along with the 915 on the pallet... ;-)
I have herd this lite hammering sound that is slower than the appearing rpm and believe it or not it was bad/old gas that was pre igniting spuradically but with a consistancy as the pistons were wacking the sides of the cyls... just an idea to consider... get out the 12" pc of broomstick and place it on cyls, sides of case,... till you find the area then you can focus in on what parts may be involved.
Also, keep a fire extinguisher handy as a budy of mine thought the oil would burn off and it actually ignited the oil in them when they heated up... you're probably not going to run that long but be careful there as they might be loaded up...
Best of luck here!!!
Bob

dtw · 02-04-2008, 07:33 AM

Ed - that's a slick, easy idea to quickly home-in on top vs. bottom. I love it! Thanks, I'll try that next. BTW, that 2.7 is all ready to assemble, and I can't wait to get to it. I bought these two parts cars at the end of the year though, which is sidetracking me quite a bit...

Bob - well, I would slap the engine on the pallet, but I know how clean you like your parts. This engine would not meet your standards

. Interesting thought on the gas - I am indeed running some old gas in this engine right now. Maybe I'll change the gas out. What's up with the broomstick, now? Is that a divining rod of sorts? Will the sound become louder, or am I going to feel the vibration when I locate the source?

The fire extinguisher is always close at hand in my garage. Yesterday I got the engine up and running with the old carb cleaner trick, until the CIS fuel injectors woke up enough to take over. There was a bit of carb cleaner left in the airbox, then the engine farted through the intake and out through the popoff valve, igniting a nice carb cleaner fire. Fortunately I blew it out as quickly as it started.

3.2 CAB · 02-04-2008, 08:00 AM

You have some very good info so far, to be able to check further. A+++++

911 tweaks · 02-04-2008, 09:12 AM

Dave... holly sh^t!!! That is good that you were able to see and blow out the air cleaner fire.
The broom stick idea was explained to me this way... the wood has all the grain running the length of the shaft, which is important. This allows the harmonics to "flow" with the grain of the wood, and the sounds are magnified & some vibes will be felt also as you picked up on.

Great ideas from Ed also... I need to remember that. Nice going Ed!!

What ever you do today Dave, don't forget your shipping duties.
Thanks, Bob

Eagledriver · 02-04-2008, 06:34 PM

There was a thread similar to this recently. It ended up being a dry rocker from a pluged spray bar hole.

-Andy

john walker's workshop · 02-05-2008, 06:23 AM

sometimes you can isolate the noise from a piston/rod by pulling one plug wire at a time to see if the noise level drops off.

dtw · 02-09-2008, 07:13 PM

Alright, here's an update.

First, I swear these 3.0s are a force of nature. The more this thing runs, the better and more smoothly it runs - except of course for this knocking.

I used a wooden hammer handle and a wooden paint stir stick and poked around - the vibration seems to be most prominent on the right bank/valve covers/chain box. I guess good news, when I put a paint stick or hammer handle on the case, I feel nothing.

This afternoon I pulled the valve covers on the right bank. Nothing seemed amiss. All rocker shafts were in place and dry. All the valves seemed well-adjusted, and I went ahead and re-adjusted them anyway since I was in there. No problems. Then I fired up the car with the upper valve cover off, for giggles, to see if the cam spray bar was firing. After I got done cleaning the oil off my next-door neighbor's car, I put the valve cover back on and ran it that way for a minute, then removed the cover. All the intake rocker oiling holes had oil in them, so at least the upper rockers are getting oil. I am not sure how to check the exhaust valve rockers? Is there anyway to test the spray bar without removing the engine?

Also - pulling spark plug wires does not change the character of the knock, or eliminate it.

I'm linking a big video here - about 30mb. As you can see/hear, the knock seems to be like a hearbeat, with two distinct parts to the knock. Makes me think there is something going on with a rocker as it comes on and off cam. Also, as you can see/hear in the video, the noise is definitely in time with the timing light (GREAT idea, Ed).

So far I like Andy/Eagledriver's theory best, but I can't see what's going on!! None of the cam lobes seem to show any damage from running dry, but I do need some input on how to check the exhaust rocker oiling and/or the cam spray bar.

Lastly - Is there any chance this could be chain tensioner related? I don't think so due to how well-timed the noise is to the strobe light.

Am having problems with the video hosting - I'll try to get a link up tomorrow. Welcome further thoughts in the meantime!

BoxxerSix · 02-09-2008, 08:25 PM

You can usually note a rod knock by a pair of tones, rather than one single knock. IE, you'll hear two "thuds/clunks" per revolution. One thud for the rod smacking the crank journal, and the other on the opposite end of the stroke where the piston/rod moves and slams the crank journal on the other side.

Easier to hear with one of those cheap metal probe stethoscopes that you can touch to the case while engine is running, but can be heard with a hand to ear if your exhaust isn't too loud

Crashly · 02-09-2008, 08:32 PM

Get a stetascope in there and pinpoint that noise. Harbor freight has them for a few dollars. My exhaust valves were making a very distinct noise like a clapping sound. I could only isolate the problem with the scope.

Walt Fricke · 02-09-2008, 09:37 PM

Just about anything will serve as a stethoscope. A really long screw driver, for instance. Though it is best to get one. Cheap, simple, and you will use it on down the line too.

You need to pull the exhaust valve covers and check there for a loose rocker as well. If you jack the car way way up on one side, you can remove that exhaust cover without losing too much oil.

But don't repeat the oil thy neighbor's car trick. No need to. If a spray bar hole is clogged you will probably find that the affected cam lobe is a circle, not a lobe. Too late to do anything. I don't think of spray bar clogging as being super high on the list of possible ailments, though of course it can happen. Most of the messing we do with them is when rebuilding things, just to make even more sure that it won't happen. Besides, this isn't going to be the cause of you knock.

If you still don't find anything, you might pull the chain housing cover plates to see how the tensioners are doing. While you aren't describing the classic "chains being dragged out of a steel garbage can" tensioner failure sound, when I had one fail it didn't quite sound that way either.

Jacking the rear of the car way way up will minimize oil drizzle for that chore, though you may well find you will benefit from muffler removal, along with a bit of the sheet metal surround.

And good jack stands make for longer mechanic lives.

Walt Fricke

TibetanT · TibetanT's Garage

Subscribing for information purposes.

Good luck with this one, Dave! Cam tower loose maybe??

dtw · 02-10-2008, 07:13 AM

Walt...I did pull the right-side exhaust valve cover. All rockers in good shape, I just am not sure how to tell if those rockers are getting oiled by the spray bar.

BoxxerSix · 02:56 PM

Quote:

Originally Posted by dtw

Walt...I did pull the right-side exhaust valve cover. All rockers in good shape, I just am not sure how to tell if those rockers are getting oiled by the spray bar.

If they have been running dry for some time the affected lobe(s) will be blued and hammered badly from the rockers. Lobes will be fairly dry as well. You can wipe everything clean, pop the covers on with one nut, and then go fire the motor up for just a couple seconds to pressurize the spray bars and coat the cam lobes. Remove the covers again and look for dry lobes. Any dry lobes any you've got a clogged spray hole(s) in the bar.

not a horrible fix, but definitely going to require some extensive repairs to cams and /or replacement parts(rockers, rocker shafts, etc). If one lobe is running dry it's just best to pull everything and start from the ground up to ensure it doesn't happen xxxxxx amount of miles down the road to another lobe.

How's the oil pressure on the motor looking?

dtw · 02-10-2008, 03:41 PM

Checked compression today - 145 to 155 across the board. Pretty good! Cut the plugs, they all look great. All the oil in the heat exchangers is now burned off, so I was able to get down under the car and poke around. Putting a screwdriver on various places under the car - crankcase was almost no vibration. Cylinders 1-3 and 6, no vibration. Cylinder 5, some vibration, and cylinder 4, the most vibration. Cam is lubed on 4 and 5, and rockers are properly adjusted. That's all I know to do under the valve covers. I'm going in! Will let y'all know what I find inside.

dtw · 02-16-2008, 05:06 PM

Wanted to get these pics up before disassembling this side of the engine - anyone think the tensioner looks collapsed? I'm not used to chain tensioner collars, so am having a hard time gauging travel, here.

dtw · 02-16-2008, 05:16 PM

Ah ha! Finally got the video of the strobe/noise uploaded and online. This file is about 32mb. Here we go:

http://www.hungoverracing.com/dtwinters/Cap0001.mpg