LD28: broken cam shaft

#1

has anyone experienced a broken/snapped cam shaft? mine recently was snapped. dunno what caused it but still wondering how this happened. any ideas?

#2

Check all the valves working? Make up a pry tool so you can feel how much force you're exerting to try to open a valve...

IOW, what else may have a problem which froze the rear end of the cam shaft? Got something in one of the cylinders to KO a valve?

FWIW

Rufus

#3

Yours is the first I've heard break.

Going with Rufus' guess: lack of lube at one or more of the cam towers.

#4

i dunno what happened. it started out like this, i was driving shifted from 1st to 2nd gear. the engine began shaking as if it wasnt receiving fuel. car moves like a sloth and releasing clutch or gas pedal will bring it to a half. thinking air got in to the engine i pumped the hell on the priming pump. had my friend come over and loosen the lines to the nozzle and that made the shaking ease a bit. drove it to a mechanic shop. i was advised that the priming pump caused it so we replaced it. it didnt solved the problem. so we decided to bring to another shop since they suspect that the IP is broken. they checked the engine too and was surprised to see that the cam shaft was broken giving me 2 equal parts. what would caused it? will the car still run with that broken cam shaft or driving it to the 2nd shop caused it? or it snapped when theyre trying to diagnose what caused the problem? im really confused

#5

Breaking a cam shaft makes no sense assuming you didn't feed it something bad or run out of oil or such. Needs a lot of history, info, hands on examination, etc. Not something we can help you with here. The first mechanic (priming pump) sounds pretty far out in left field to me so was maybe a good idea to take to somebody else. But driving a sick car often causes problems, if you dont' know exactly what you're doing. It will have to be carefully examined by somebody who has a clew.

Have you actually _seen_ the break in the cam shaft? Make sure you do before deciding anything. Mechanics don't train on these engines any more (not for a long time). Means that the usual same-ol'/same-ol' type of guy won't do you much good. You need somebody who actually understands what he's doing, what's behind it, why he's doing it; also somebody who gives a damn about seeing the thing fixed. Maybe somebody who works on old Mercedes diesels; along with _old_ VW's and Volvos and Peugeots they're about the closest match you'll find to the Maxima diesel engine. It doesn't help either that pieces of that engine are worth money, so if you start thinking of walking away, make'm give you dollar$ for the car as-is. $400 would probably let them make a profit. Unfortunately if there is something seriously wrong with the engine paying somebody to fix it (assuming you find a good mechanic) will cost you more than just buying another car.

But it might be worth reviewing the existing situation carefully if you can find somebody knowledgeable enough that you trust.

Rufus

#6

thanks for the reply rufus. ive taken it to a mechanic that calibrates (re-builds) ignition pumps. he is willing to give extra time to check other possible cause of the broken cam shaft. apparently he said that possibly lack of oil supply on the shaft post. weak fuel supply as well on the rear distribution might caused the breakage too. thanks for you feedback

#7

I've seen the head bolts snap at the top and either it or the washer eventually moves to where it locks up the cam.

#8

had a hard time searching for a replacement

#9

That is a strange place for it to break for sure. My bet is casting flaw that finally gave way, or previous owner or someone had it out and dropped it or used it for a pry bar or something.

I think casting flaw though.

just a guess

Paul

#10

will lack of fuel supply on the rear nozzle caused it? or maybe not?

Tomslide50 · #11

if you had a lubrication, valvetrain, or cylinder issue then the affected lobe/journal would be scored/wiped. cams are very hard and therefore very brittle. they can crack from casting failures but overwhelmingly the reason cams crack is because people remove cam caps unevenly, applying a "bending" force to the cam. since cams are too hard to bend- they snap. sometimes it can happen while disassembling(seen it), or sometimes they just crack on disassembly and break when run later.

#12

got the camshaft replaced. also refaced the cylinder head and valve and guides were replaced (according to the mechanic). paid hell of money to get it fixed. still few issues, engine is too noisy and smokes excessive black smoke on 3rd to 5th gear. got it to another mechanic to check and hand him over the manual. to my surprise all valves have .014 clearance. i will have him also check the timing belt next week. what worries me is the engine noise and some shaking that is felt when the clutch pedal is pressed lightly. issues of hard starting too every morning. will have to check the GPs.

inspite these issues im still happy when i saw it turned to 330k. cant imagine whats the correct millage coz speedo cable was broken for some 2-3 years

#13

Did your mechanic use the proper tools to set the IP timing? Dial gauge, plunger rod/housing? Your description seems like the IP is mis-timed.

#14

seems like no proper tools was used. its not a normal practice here in the Philippines. there are several workshops that uses standard tools but i bet they're pricey. ill have him check it again.

another inquiry, a bit off topic. i got curious the other day and removed the instrument panel. planning to put some LED behind the panel face to give it a backlit and found out that i need to rip the panel apart and do some rewiring. what worries me when i found out that the flexible plastic circuit board is toast to crisp and one wrong handling will tear it apart. just wanna know if there is a way to get a replacement?

#15

Used would be the easiest source. It's conceivable that Nissan used the same board for both the diesel and gasser - just used different gauges wired differently. If so, finding a replacement might be possible. I don't recall what's been said here on this topic. Al our host is probably the person who's spent the most time inside the dash; he might know if a gasser board is the same.

PCB can be fabricated, but likely to be pricey. To make that possible, the original would need to be in good enough shape for the PCB shop to copy it. If it's in _real_ bad shape, before it dies try to take high resolution pictures in varying lighting - idea is to get one of each side that shows the detail of the tracings on the board. Measure and record the board dimensions exactly, including thickness. Don't toss it just because it won't work any more - there may be things on it that would need to be put back on a new one. When taking the pictures, place a measuring tape or rule (full length) against each side; it's usually easier to get an exact index if you place the "1" (or "10" or whatever the major gradations are) at the starting point instead of trying to get the end of the tape to line up exactly. If the photo is a good high res in-focus shot, a person working graphics software can then use the markings on the tape to establish exactly the size and locations of all the board markings and fixtures.

Probably easier to find and work off the used board from a gasser (figuring you won't find a used diesel board).

Rufus

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LD28: broken cam shaft

LD28: broken cam shaft

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