Is my crank done for or am i just paranoid

[iliketocrash]

now that the weather is nice again i decided to start working on my car some more. this time i noticed while running the engine that i get a sort of rapid a consistent knocking sound at around 2500rpm but only when i the throttle. if i let off the throttle and let the revs drop the knocking isn't there. its kinda hard to tell if its my crank or not because i'm running an open downpipe and some stuff my not be bolted down securely but the knocking seems to consistent and rhythmic to be anything else. also, i noticed the knocking a lot more with my ear over the two coil packs nearest the firewall. oh, and my car still runs like ***. looks like i might be scrapping this project.

[boost_boy]

now that the weather is nice again i decided to start working on my car some more. this time i noticed while running the engine that i get a sort of rapid a consistent knocking sound at around 2500rpm but only when i the throttle. if i let off the throttle and let the revs drop the knocking isn't there. its kinda hard to tell if its my crank or not because i'm running an open downpipe and some stuff my not be bolted down securely but the knocking seems to consistent and rhythmic to be anything else. also, i noticed the knocking a lot more with my ear over the two coil packs nearest the firewall. oh, and my car still runs like ***. looks like i might be scrapping this project.

If you're hearing knocking at 2500 and it's a consistent rattle, then it could very well be a rod bearing. I tried to explain in my other thread about the issue with a ceramic clutch and the issues itmay pose.

Do a compression test and see if the #3 rod bearing is a bit on the low side? If so, you may just be able to save your engine by removing the oil pain and replacing the bearing inserts. Hopefully it's not that, but just a figment of your imagination. Good luck with this and keep us posted.

Dee

[float_6969]

I've got a knocking too, but it's at all RPM's and it increases in frequency as the RPM's increase. I'm about 90% sure it's a bad lifter though. I made the mistake of taking them all out and trying to flush all the old oil out of them. Ooops...

[iliketocrash]

the sad part is that the car never ran right from day one and i already gotta pull the damn thing apart. hoorah. you have an reccomendations on who to buy the bearing inserts from?

[biosehnsucht]

For flushing the lifters, get some small baking pan things from walmart (like 3-4"x6-8"x2-3"ish, not sure how big they are) and put the lifters in right side up (you can just barely fit 8 per), then fill with kerosene until they're covered.. you'll see **** ooze out of the tops of them almost immediately..

Let them sit a day or so, then drain and refill this time with something like 20w oil, altho you might want to repeat the kerosene step a few times depending how disgusting they are. the 20w oil is just so you have a light enough oil it'll go in on its own easily and so it'll have oil not other stuff in there.. a little 20w mixed in w/ whatever you normally run won't be a big deal and you could always change the oil after running it a bit (and if its a fresh rebuild you ought to after breaking it in anyways).

[iliketocrash]

even if i replace the bearings won't the same thing eventually happen again?

[Neil]

Ive read before that the best thing to do for a CA is replace its rod bearings before you get it in the car.

Here's a test, rev the motor by hand till it starts rapping then remove and put back on the plug wires one by one. If the noise stops or becomes significantly quieter while one of the wires is off, it's unlikely that the bearings don't need replacing. I just replaced mine on my KADE, the bearings were $40. Assuredly theyre more expensive for a CA. I put about 350 miles on the car with an obvious loud knock, even found one of my friends on the highway and hit the speed limiter a couple times... and the KA's crank was fine. The bearings were blue in spots, worn badly and small chunks of surface were missing but the crank was thankfully happy. 'bout 1800 miles so far since their replacment with no hint of problems.

[iliketocrash]

well if doing the thing with the coilpacks lessened or got rid of the noice then what does that mean besides my bearings are fine?

[Neil]

Im afraid you misread, my bad i shouldnt have written the sentence that way... i was trying to say if the sound lessens when you take off one of the coilpacks its a near sure thing that cyl's rod bearing is bad. If its valvetrain related the sound wont change.

[iliketocrash]

ah. that's for clearing that up.

[boost_boy]

ah. that's for clearing that up.

Did you inspect the engine, yet?

Dee

[iliketocrash]

unfortunately not. i've been too busy with my POS beater ('95 mazda 626 5-spd). The transmission is stuck in reverse and the car has 225k miles on it..... i talked to my neighbor (who i bought it from) and he said that it happened before and they added some transmission fluid and the problem went away... so i added 4 quarts of transmission fluid and the capacity is only 3.6 quarts and from past expierence i've been told to check the fluid level by sticking a finger in the filler hole but i feel absolutely nothing.... not even with a small metal rod.... so yeah dunno where all the **** is goin to. my priorities are getting this piece fixed or buying another POS because i'm making no money by not goin to work and i'm getting real behind in my classes.... so the ca18 project might get scrapped or be put on hold for yet ANOTHER year, depending on future cash and time restraints. i wish the world could just stop for a little while so i can get my baby runnin'. is that so much to ask?

oh yeah, and thanks for checkin up on my problem. the ca18det community rocks.

[Vetal]

Do a compression test and see if the #3 rod bearing is a bit on the low sideDee

Please explain how the compression is connected to the bearing wear-off?Thanx

[boost_boy]

Please explain how the compression is connected to the bearing wear-off?Thanx

Just like I stated, a bad rod bearing will have the rod and piston somewhat out of sync. With that little bit of play from the bearings, the rod and piston will never reach it's full height on the compression stroke, thus causing the compression #s to be lower than it's brothers and sisters (kinda like having a thicker headgasket). Radius wear means a loss of some millimeters which means alot in combustion engines.

Dee