"Valve noise" at rear of engine - not

[rlaggren]

I've developed a "tick" that sounded like a loose valve - except it wasn't; got me to adjust valve clearance, though. <g>

So what is it? Regular as clock work, sticks with engine speed, sounds just like a lifter, emanates from cyl 5-6 area. I've felt around the manifold some and can't feel any (exhaust) leaks, but didn't try up from the bottom yet.

Tomorrow I hope to try cracking the injector lines and see if that changes it. I'll try the old hose-to-ear thing too.

All ideas welcome.

Rufus

[diesel-man]

How many miles? What has been done to it lately? Anything out of the ordinary? How did you first notice it... not I lifted the hood and there it is. Crack the injector lines as you said to see which cylinder it is. Is it valve speed or piston speed? (Valve speed is half of engine speed.)

Maybe sludge from the intake on top of a piston getting sqeezed each revolution? Did you see an odd cloud of smoke behind you while driving one day along with some "extra" clatter?

Did someone new drive it lately and give it a good blowing out for you? or maybe that is what it needs?

Any "chocolate pudding" type stuff up under the valve cover?

Just trying to find out which way you lean when you cough...

Once you find a particular cylinder, you could try swapping that injector with one near the front. Any port in a storm.

[asavage]

Valve noise and cracked piston or rod bearing give noise at the same frequency, due to piston/brg noise only emanating during the power stroke. Valve noise is much more of a "tick" though, very nearly identical with an exhaust leak (cracked manifold, blown gasket at the exhaust port) or a head gasket blown to the outside (common on certain engines, notably the Ford 6.9l diesel: I had one).

You might start with an "Italian Tune-up": spirited run-up under maximum load you can find to the governor. Which is really screamin' on the LD28, but you really can stand on the accel in neutral and it really will go up to a certain governed speed and no higher. I know, I've done it many times. But it sure sounds like you're flogging it if you haven't done it before.

The ITU I refer to has to be performed under load, though. Really wind it out. While I personally believe that it is mostly useless for a gasser, it really ib]can[/i] move some solids around in a diesel that's been driven gently. Ideally, your LD28 would be running so clean (clean fuel, clean burn, etc.) that this wouldn't be necessary, but the EGR/crankcase vent system alone is a good reason to get a lot of airflow through every so often. May even extend the intake-cleaning interval requirement.

After that: I agree with diesel-man, crack the last two injectors and see if the noise dies.

• No: look at valves again, including possibly a cracked or worn rocker arm.
• Yes: swap the injector with one at the other end of the engine.
  • Noise moved: replace/rebuild injector.
  • Noise did not move:
    • a) (budget) plan on acquiring another engine.
    • b) (masochist) plan on teardown & inspection, looking particularly at piston condition, piston-to-bore clearance, small-end bushing wear, and rod brg clearance.

[Carimbo]

Before cracking the injector feed lines and/or moving the injectors around, how about

Holding non-contact (infra-red?) thermometer to each exhaust port outlet region on the exhaust manifold BEFORE the engine gets much up to temp and warms the whole exh. manifold? Compare temps for each. If done correctly, this should give an indication of a malfunctioning injector, as the EGT on that particular outlet port would be less than the others.

[asavage]

Well, yes & no.

An injector that is leaking will dribble fuel such that it will be wet on the compression stroke and fire early ("nailing", which is hard to mistake for anything else) and will also dribble long after it should have shut off, which will heat up the EGT just like retarded timing would.

I don't know enough to properly interpret the results of a comparison of individual port EGTs other than to infer that "something may be amiss".

[rlaggren]

I noticed the noise from the drivers seat about a month ago. The car has 166xxx on it; no odd smoke I've seen. No or very little smoke I can see on acceleration; no smoke on start when it fires instantly but a puff when I don't use the GP button and need to crank twice. No sludge in valve area but maybe Steve cleaned it out; however, from his records the car was maintained well so it's probably been clean.

Cracked the injectors and noted distinct drop in RPM for all cylinders. Didn't note change in noise but I fear I wasn't concentrating or that. But the test was easy so I'll get to it again.

The noise seems about 1 click per second at idle. So let's see... 600RPM = 10 Htz; divide by 6 (cyls) = about 1.6 Htz; divide by 2 (4 stroke engine) = about 3/4 Htz. for valve noise at idle. So it might be valve speed - idle is probably more like 700 or so.

The hose-ear trick didn't work as far as pinning a specific location. If I can dig the IR gun out of the AC pile I'll see what the engine looks like under various conditions. Just gotta find the right pile...

I'll try the ITU next time I get a decent hill ina couple days. I ran it 78mph for a 1000 miles while getting it here but never hit the limiter and rarely under much load; noise appeared some months later.

Good info - thanks to everyone for the thoughts.

Cheers, Rufus

[philip]

After that: I agree with diesel-man, crack the last two injectors and see if the noise dies.

• No: look at valves again, including possibly a cracked or worn rocker arm.
• Yes: swap the injector with one at the other end of the engine.
  • Noise moved: replace/rebuild injector.
  • Noise did not move:
    • a) (budget) plan on acquiring another engine.
    • b) (masochist) plan on teardown & inspection, looking particularly at piston condition, piston-to-bore clearance, small-end bushing wear, and rod brg clearance.

I have to awe Al's triage!

[rlaggren]

Well, I almost commented on his bedside manner... Any relatives named House? <g>

But yeah, solid pith there. Give him Power Point and he'd be dangerous!


Rufus

[rlaggren]

Got a chance to run it up a hill (for some load) in 2nd (for max RPM); normal 3rd gear w/lock on this hill is 50mph, tending to slow. Full throttle it ran up to 60-61 mph and held there for about 30-40 secs (to my exit at the top). I'm pretty sure it was on the limiter because speed rose steadily and then leveled with no increase in grade; also cuz the owners guide says don't run 2nd gear over 55 and less for diesel. No tach so don't know what RPM. Temp gauge climbed to 2/3 and looked like it might be willing to go higher (normal light duty at 1/3, hard'n'fast is normally about 1/2). Some smoke visible in rear but not much - had to look careful to see it. Seems to run about the same as always.

The "valve" noise remains so it's back to cracking the IP lines again and listening close. Gonna start looking around for injector shops.

Rufus

[Mechiel]

Rufus, I am experiencing the same symptoms. What was the outcome of the noise?

[rlaggren]

Mechiel

No better or worse. I'm about 203k miles now and that makes almost 40k since I noticed the noise. I'm suspecting piston slap in one of the rear cylinders or maybe it's a loose bearing like Al suggested. Last year I had the injectors checked and they all checked out w/in 5% or so (don't recall exact) at about 2000# and no leaks.

I run the thing relatively hard on the limiter in 2nd (auto tranny) at times, going up hills at 55mph because I use oversized rear tires so the gear ratio is a little tall for this engine/load combo; SOP, I'd rev it once a day average, though when going cross country it's more like 10 times a day. IOW, I beat it some and so far all seems good. MPG figures steady, oil usage depends on average RPM but more or less steady at about 1/2 qt/4000mi city or 1 qt/4000mi at 75mph.

Just keep my fingers crossed cuz I'm not going into the engine willingly.