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there is some material on this if you search but nothing especially definitive.
i pose this question to those with engine building or simply long 240 experience.
i have never seen or had an engine with a bad rod before and i have owned and worked hundreds of these cars. this includes very high mileage cars, engines with broken oil pumps and still driven lightly and cars badly overheated requiring a new head because the old warped so badly. yet in none of these cars was there ever a rod knock like i heard today in a genuine 120xxx mile 92 240 wagon in impeccable condition owned by the same woman since 1993.
oil pressure cold is 60 psi and drops only slightly once warm.
at cold startup the knock is so loud you can hear it 20 feet from the rear of the car. if seems to vibrate through the exhaust pipes. once the engine fully warms up the sound almost disappears.
i have had engines with piston slap but nothing ever like this. logic suggests to me that rod knock is always present and worse as your increase the rpms. can piston slap really mimic a bad rod knock in severity?
can a bad knock sensor cause what i am hearing at idle?
i welcome any suggestions to pin this down with more than guesswork and voodoo.
i hate to pull engine unnecessarily.
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I believe from a couple experiences that there is nothing as loud and hammering as knock from a loose rod cap. Highway speed to idle its loud. Think of the piston striking the head each up stroke and then the rod hitting the crank each down stroke. And its only a matter of a short time till those rod nuts back all the way off.
Check for exhaust leak with a hose to your ear.
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I've heard it said a few times that once the red block engine has piston slap even a rebuild won't cure it. How could that be? Is it just an old wives tale?
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Every piston engine has piston slap...it is inaudible in most engines. The short'ish skirt and very low mass below the piston pin mean the B230 design is more prone audible, cold start piston slap.
Without changing the piston style and fine tight tolerance machining, I doubt one of our engines will have no audible cold start piston slap...but some do get lucky.
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1. i pulled the plugs and found them wanting in age and twice the normal gap
installed new plugs gapped correctly
2. changed the oil to 10w40 with a fresh filter and added 6 oz of lucas oil treatment (i know its a stop gap, a band aid if you will.. nevertheless even band aids have their place)
restated the engine and the piston slap which was ridiculously loud and lasting is now normal in sound and lasts under a minute before quieting considerably before all but disappearing at full warmup.
out of curiosity i started the engine with only 3 plugs firing x 4 times... 1-4 and find that #3 cylinder appears to be the overwhelming bad boy. since they move in pairs i expected #1 to be a cohort but found it was #4 which added a tiny bit of the slapping noise. this seems odd to me since oil flow in this engine begins at #4 the back of the block and moves forward. i would have thought it would opposite.
on a side note non sequtir i found water pump and power steering pump too noisy due to over tightened belts. this IS cautionary tale for shortening the life of both.
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Hi again,
Glad to hear that you made the car run a little bit quieter.
I'am afraid that is about all you can expect for working on it from the outside.
It was interesting to read that the oil was changed "supposedly religiously" yet a tune up on the plugs, new or not adjusted, had been so far between. I wonder who does the oil changes or sings very well from some lessons. She said he use to be a mechanic?
I feel by closing up the gap with a set of new electrodes helped the combustion chambers burn cleaner and most likely corrected a timing deficiency. Since you have had that engine in your hands, I would like to add in this later edit, that you probably have removed some carbon build up in the cylinders.
In most cases these engine are not prone to becoming caked inside. Her short runs on low octane gasoline can do wonders in that direction.
I hope you advised her to run only 89 octane, it's in her owners manual, or higher as for what little gas she probably buys she cannot possible consider it over spending.
As we know a longer spark jump requires high voltages in order to NOT get blown out like a candle. We cannot double the voltage but having better octane volatility can only help.
The whole ignition system could be in the same shape as the plugs. So, I bet you were wise to advise her where she stands on that. That is if she was there for it becoming to hard start in the first place.
I noticed that you used some Lucas oil thickener or "Bandaid" that I suspect would be the same as going to a 20w50 oil. Either would allow more oil "cling."
I thought the quantity needed for a Lucas product was more in the range of 20 percent, or more, of the sumps capacity to work. I doubt six ounces would do a whole lot but you must know better than I.
The Lucas name started with a "drag racing cult" background and they burn alcohol for fuel! They run their oil sump "on near dry" so the excess oil will not slow anything down. They worry about dilution of what slick film they can keep up in a very loose fitting engine.
Again with racing, a quarter mile, a few times and it's rebuild time.
As a side comment of fun like in bumper cars.
Beats me why they don't build a flat rail or roof over the top of the track and attach a spring from the car to the top to hold down the rear wheels, that need a rack and pinion setup on them anyway!
Sure save lots of rubber and the car would be gone!
Of course, whole drive train and the car has to get a lot stronger because the whole car would just twist up on the other end.
You know, As soon as they built a track like that, someone, one jump up and say "I am going to try an electric motor in my car and tie into a nuclear reactor somewhere!"
Imagine the booster cables hooked to that contact spring! (:-)
Check this out.
They are only thinking of plugs and only two styles maybe. You got to be kidding me with how many makers of these cars wanting to play on both sides.
Tesla is going into home roofing and guess with whom? Musk and his cousins, owners of SolarCity.
http://m.industryweek.com/environment/white-house-announces-us-electric-car-recharging-network?NL=IW-07&sfvc4enews=42&cl=article_1&utm_rid=CPG03000005733027&utm_campaign=15480&utm_medium=email&elq2=01b4b16e6269408d8a417e3dcacfd62c
Phil
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hello
with winter coming on i am reluctant to go 20w50 or over add lucas making it tougher to start on single number temp days. once fully warmed up as denoted by the water temp gauge it runs pretty quiet and strong. i suggested she take it out and really run it at highway speed a few times a month but who knows.
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Just as a note--pistons 1 and 4 move together as a pair--2 and 3 as a pair.
If your motor is quieting down after warm-up I highly doubt you have a rod bearing problem. Piston slap will diminish gradually as the piston expands on warm-up. A rod bearing that's going may rap on start-up but once it's truly "gone" it will continue to rap - especially when accelerated -- and at that point the motor isn't long for this world. My near 300k mile '80 B21F sounds like a diesel on start-up--quiets down to normal after a drive (or maybe my hearing is shot from driving this noisy beast). -- Dave
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While I haven't experienced a bad connecting rod bearing in a B230, I have experience with bad connecting rod bearings in other engines. The noise is not as bad on a cold engine, but gets worse on a warm engine (thinner oil) with more RPM.
--
john
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hi john
this engine is the opposite which is leading me to very bad piston slap.
the owner also told me she used it to go to work and home with little long distance driving and she worked close enough to home it is possible the car spent the equivalent of years of driving without ever being run hard at highway speed for a distance.
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Hi,
I'm no expert by any measure, and have had no issue with red blocks, but I can recall 3 experiences with definite rod knocks.
The first 2, a 50 IHC and a 55 Chevrolet developed the knock while driving and neither made it home under their own steam. Both sent the rod through the block in under 10 miles.
The third was a 62 Rambler with a flat head Continental. This also developed suddenly but I was able to somehow baby it 50 miles home, holding my breath the whole way. The knocks were pronounced at idle and never diminished with warm up. At higher revs they turned into more of a roar.
I have a recent experience that is not exactly as you describe, but similar enough that I thought I'd throw it out there.
I bought a 90 245 this spring that had sat 7 or 8 years in a garage without being started. I got it going and made it home, but it ran so poorly and had noise coming from so many places it was hard to know what I had.
I eventually sorted everything out until all that remained was a knock at cold idle. It quieted down after warm up or higher revs, but wouldn't completely go away. With the hood up and jerking the throttle at idle it sounded exactly what I remembered of rod knock. When I pulled either the plug wire or injector connector on #1 the knock completely disappeared, so I was expecting the worst.
I've heard of piston slap, but I wouldn't know it if I heard it. Searching the brick board on that, somebody mentioned the exhaust manifold gasket and I thought it was worth a look, but I was doubtful. I've replaced several but none ever produced anything vaguely similar to what I was hearing.
Sure enough, when I put my fingers under the #1 exhaust port with engine cold and idling I felt something. I pulled the manifold to find a tiny crack in the gasket and replacing it was all it took to reclaim my $400. investment.
Peter
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Yes, it is a learning experience to find out how metallic a leaky exhaust gasket can sound.
--
Art Benstein near Baltimore
The State with the highest percentage of people who walk to work: : Alaska
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thanks guys
i spoke with the owner just now and she says and i believe her the oil and filter have been changed every 3000 miles since 93. she also said about 10 years ago it started making this noise and her brother, a mechanic but no longer, diagnosed it as sloppy piston which seems to confirm what i am hearing and y'all are saying to me.
i just never heard it so LOUD before now.
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First. I thoroughly enjoyed reading the two previous responses. I don't hesitate to respond, even though I am fully aware my knowledge of cause and effect in this arena is minuscule.
It is interesting to me to hear this is a '92, which is by my understanding the last year before squirters were added to the B230 to take care of piston slap. The add-on nature of the squirters has come to cause me to speculate why it seems so many '93 owners have problems which seem to possibly be related to cam oiling, as if diverting some oil flow from the upper regions created a more critical need to keep it clean and unblocked. Every time I hear of another head gasket failure or stripped timing belt on a squirter block, I think of this. But, our only 93, fairly new to us, and hardly ever seen by me, is quiet.
Two of ours, an 89 and a 91 came to us with what I believe is piston slap. Both in the mid-300K range. Now, Ted mentions being able to hear this 20 feet behind the '92. I can definitely say I hear this "piston slap" from that distance easily, despite my hearing loss. The 89 is so pronounced, it sounds no different to me from a Diesel, and invites admonishing remarks from those reminiscing about their own dealings with clogged hydraulic lifters. But it goes away, entirely, after it warms up. And these cars have been making this imitation of an MB 240D ever since we first acquired them in 2003 with no change. Yes, the valve clearance was one thing I checked on both cars, so I believe this is "piston slap."
I have heard rod knock. But the memory is old - at least 30 years. And for Oldduke's benefit, I'll mention it was a 73 Dart with a slant six owned by a neighbor. It was never run long enough to learn whether it would "go away" with warmup. One thing I believe about rod knock is the condition will quickly grow worse with miles. Maybe just feet. No rod knock heard outside the car would survive a month of driving?
As regards the knock sensor, I don't believe it can be a cause of knocks. It is a microphone, and it retards timing if detonation occurs within a narrow, per cylinder window of time, decreasing fuel economy. If the microphone does not sense the detonations in the correct time windows, per cylinder, the EZK will know it is not working and set a code, and keep the spark timing in a safe region.
--
Art Benstein near Baltimore
Men can read smaller print than women can; women can hear better.
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If it's a rod knock, it will get worse as the motor warms and oil thins. Oil pressure will also be low. A rod knock will usually disappear under load and come back immediately when load is removed.
Think your problem is unrelated to piston slap or rod knock but don't have a guess as to what it might be. Tom
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Hello Ted,
I hesitate to make a reply since you aimed your inquiry towards those people who have rebuilt red blocks or one that have extensive knowledge and experience with them.
I consider myself as not having those qualities to offer as I was never an automotive machinist even though I'm familiar with the machining principles used.
Since I have six of the engines in my possession (one on a stand) ranging in years from the B21 of '78 to the present '92 I will give you observation and hope it helps.
I too, have notice an increase of piston noise starting with the 1986 after about 250K where as my '91&'92 have slightly more noise with less mileage.
I want to blame the increase with the B230 "design changers." It is my belief that, Somewhere, in the late eighties they started trying to lighten the internal components for a quicker response for revving up.
It is my understanding they narrowed the width of the rods on the big end or the whole thing for that matter. I don't know about the wrist pin end in the piston.
The next thing they did, like many other manufacturers, is they reduced the piston skirt length to reduce weight.
From what I knew or know about the purpose of the piston skirt it is necessary to have one for piston and rod support in the cylinder.
The piston is actually a bearing support for the rods lateral or radial thrust down the cylinder on the power stroke.
The rings seal and support the upper part but the skirt also guides and aligns.
The piston or its skirt is actually made "out of round" in relation to the top of the piston by a few thousandths of an inch at a right angle to the wrist pin.
The skirt is made to fit the cylinder with minimal clearance when new.
They get away with this because tha area expands at a slower rate than the rest of the piston due to it being farther away from the combustion zone. So now, when cold, it does not rattle or clack like a soup can when it's being pushed down.
If a piston runs colder than the others due to consistent misfires or mixture issues for various reasons, it will wear considerable faster.
In this cars case, with low milage, it is likely that it had lots of around town "cold" short runs.
I suspect it's possible that you are hearing two Pistons at the same time alternating together since there are always two up and two down. That would make for the greater noise if they were real bad.
What I believe happens is the piston beats or wear themselves round over time because they do not have that length of oil and fit support.
The nineties cars seem to have this issue a little worse than earlier engines due to "upping the ante."
In some racing circles this is done routinely because they only care about a few hundred miles of going in stupid circles.
So what we gain in quickness, we lose in longevity or quietness. The battle of the "Q's" for easier thinking along with the "quest" for greater sales against competitors. All kinds games were at play here.
I have always been told that piston slap goes away with warmth and piston swell. On my air cooled motorcycles I alway warmed the cylinders until I felt some healthy heat from the fins.
A water cooled engine has less piston clearance than air cooled engines because they can, so for longevity, it was a good practice. Never had a piston slap sound from them.
A rod noise begins just as small and sounds similar, that is, until it can't take it anymore then gets louder and sooner rather than later it can go away permanently.
60 pounds sounds like a lot for an idle pressure to me, but what do I know, I have never check one of my engines as I should have.
There might be an oil flow blockage to rods? That would come on suddenly with bad maintenance.
I believe you are saying some of the same things with your experiences.
Have you tried killing any cylinders, on purpose, with a rod tipped stethoscope on the blocks exhaust side?
I have also tried listening to the pan for a bad rod. I'm not sure if it's possible to be conclusive? I stick with the slight piston slap idea and drive them.
Now that I got that out there. You brought up spark knock and if "variances" can cause these sounds, I assume at idle mostly?
In this area we also do not know what kind of gas is used by her but the knock sensor is suppose to take care of that. If is bad, you may be on to something.
The knock sensor works off the CPS and we know they can act weird at times.
A really rough idling engine, that's almost trying to die, sure can knock loud but it's a really clack when it's the timing.
These systems can and do adjust very quickly and mask what they are doing to keep it running.
With that said, I see your point of thought very quickly.
I also understand the point of the other poster, that thing are not being said, but then, maybe it is not the right questions being asked from her.
Did she bring the car, I assume new to you, after this just started or has this knock been going on for quite sometime? Is she a regular customer?
I have found out, over my time of fixing things, is that the owner that uses the equipment that usually has experienced changes. They have not thought about them in awhile and get use to them.
If questioned correctly, they might have some clues that they don't know they have.
Ask how she uses the car from day to day and who has cared for the car or drove it the most?
Your best source for reasoning some of this stuff out might be standing right in front of you.
You know it's about being detective. (:-)
I hope this was not guesswork and definitely not voodoo on this night! (:-)
Phil
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posted by
someone claiming to be CB
on
Mon Oct 31 18:54 CST 2016 [ RELATED]
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I, Hercule Poirot, my little grey cells tell to me ...there is something in this womans story that she is not telling to you.
keep us informed...we may have a Brickboard Episode
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