Thankfully, a forum member told me WHY and WHAT is causing my terrible knock at cold startup...I've got a collapsed piston.

Now I understand that the piston is moving other than up and down...its moving side to side! Thats pretty much all I understand about collapsed pistons. I want to fix this but i've got TONNES of questions and I figure you guys are the best to ask.

A)What is a collapsed piston?
B)Does the block have to be honed out to get rid of scoring?
C)Does this affect (connecting) rod bearings at all?
D)Why does the knock go away after its reaching normal running temp?
...etc

I just need a step-by-step understanding of how to fix this before the HARSH winter strikes, and rougly how much this should cost, what work is needed...etc.

Just let me know all the info you can give me!

Thanks a bunch
Steven Rossi

------------------

In my 25+ years of working on cars, I have never heard of a collapsed piston unless it is a catastrophic failure. What you are describing sounds like piston slap to me. This is usually caused when you are using forged pistons because the clearance between the bore and piston is greater than with cast pistons. The bigger clearance is needed because forged pistons expand more as they heat up, if the clearance is too small the piston could sieze up. Piston slap will go away at normal operating temps because the clearance is reduced enough too keep the piston fromn rocking in its bore. Severe slapping could result from the bore and/or piston rings wearing enough to open the clearance. this condition would probably cause bore damage because the flank of the piston will rub against the bore. This can also put more stress on the con rod and bearings. Another thing that could cause problems is a wrist pin that has come loose on the piston too. But as for collapsed piston, I don't think that is what you have, for a piston to be collapsed would mean to me that there is a severe malfunction in the engine and it is not going to go away as the engine warms up.
If anyone else knows about a collapsed piston I would like to hear exactly what it means also.

[This message has been edited by TONY_C (edited 10-23-2003).]

[This message has been edited by TONY_C (edited 10-23-2003).]

I've had a broken piston before, but that was noisy all the time. is this a stock motor? hows your oil pressure? hows does your oil look? I've heard of a collapsed lifter. I've heard the same thing with forged pistons (as mentioned above) slapping around untill they heat up & expand. I'm thinking this is more a low oil pressure/restricted oil flow problem. How long does it knock? does it go away quickly or not untill theres some heat built up? if you shut it off hot, wait 5 mins, and start it again, will it knock then?

I think he ment "collapsed lifter"

In the mornings, when its dredfully cold. I start it up and it knocks louder then I've ever heard an engine knock. The oil is brand new and its 5W50 (thick). After about 5 minutes of driving (slowly), it begins to shut up...once the engine temp is about 1/2 way...its 99% gone...if you listen VERY quietly you can hear a SLIGHT knock...only ay low RPM's...Its hardly there. The engine just passes Emissions and Cert...It has nearly 200 000KM on it and did have a time of LOW oil, it was very black and dirty, however, this doesnt seem to be a rod knock.

...onto other things...
Whats a lifter?
...the rod that goes from the Cam to the rocker? could it be that the rocker is loose?

THanks for the imput this far!

Steve

------------------

This is in your 4.9l Caddy Car? Arnt the 4.9's well known for having bad cold startup noise, of course there is probley a limit to the allowable noise. My Poor ol' Saturn makes lots of noise on start-up too.. But its got 300k+ on the engine.

Later;

No No, the 4.9L is a different story, this is actually with regards to my 1.6L Suzuki Sidekick...I want that thing to last me another few years (untill the end of University). Im thinking of saving up cash, buying a used engine and rebuilding her myself.

------------------

I agree with Bill "a collapsed lifter" may have been what he was trying to say. I would think that if the lifter was collapsed it would miss not knock?......Paul

Ater reading your description of the problem with your engine these are my thoughts.
1 Wristpin will knock during acceleration then go away at a steady RPM.
2 Collapsed lifter will cause missing and rough idle.
3 Collapsed rings not piston missing not knocking

At this stage of the game it sound like you are going to rebuild unless you find a good low milage motor your best bet is do it your self and save a ton of money unless you are not planning on keeping the vehicle labor alone is going to kill you giving out to a shop.

------------------
Tuners of the Quickest 4.9
12.51@118 mph

A)What is a collapsed piston?
B)Does the block have to be honed out to get rid of scoring?
C)Does this affect (connecting) rod bearings at all?
D)Why does the knock go away after its reaching normal running temp?
...etc

A. the side of the piston skirt is smashed in. allowing the piston to rock on the pivot pin in the cylinder and slap the cylinder wall. That is the knock sound. The piston looks more like [/ instead of [].

B. if it’s been slapping the wall of the cylinder for very long, you had better use a bore gauge and check it. If it’s only been a few days you’ll be ok.

C. no

D. the piston swells at temp and doesn’t rock as much.

As far as im aware the engine KNOCKS, doesnt really MISS...the idle is 90%, a little rough but good enough.

I'll look into a rebuild kit.

Steve

------------------

quote Originally posted by stevenrossi: No No, the 4.9L is a different story, this is actually with regards to my 1.6L Suzuki Sidekick...I want that thing to last me another few years (untill the end of University). Im thinking of saving up cash, buying a used engine and rebuilding her myself.

well, that rules out lifter, huh?! isnt that an OHC motor?

Yep

OHC, Im gonna shoot here and agree that its the pistons...Not Rod Bearing

I can probabaly get a engine with lower mileage then my own for cheaper. For now I'll invest in a remote car starter and block heater.

------------------

I don't think those Suzuki engines were designed for oil that heavy. Good luck trying to start it when it starts to get really cold.... However, changing your oil to recommended manufacturer's specs won't make your noise go away, either.

I'm not too familiar with the Suzuki engine, but if it's anything like other Japanese engines (like Honda, for instance), you might have adjustable rocker arms so you can properly adjust valve lash. This sort of problem would be loud at start-up in cold weather, but would quiet down once the engine was warm. If you do have adjustable rocker arms (yes, it's possible to have an OHC engine with rocker arms), and have never adjusted them, it certainly wouldn't hurt to do it with your kind of mileage - even if this isn't the source of your problem.

quote Originally posted by stevenrossi: The oil is brand new and its 5W50 (thick). After about Steve

5w50 isn't what I'd call thick, it's still only a 5w oil. 30w or 20w50 is thick oil, the number after the w is a detergent level

quote Originally posted by Shadow_Wolf: 5w50 isn't what I'd call thick, it's still only a 5w oil. 30w or 20w50 is thick oil, the number after the w is a detergent level

The second number is the viscosity of the oil. A 10W30 is a multi visc oil. There is no detergant rating in 5W50.

Steve...I'd say you just have a slapper motor. The newer chevy truck V8 before 2002 are known slappers, they make a whole lot of noise when cold but once warm the quiet down. I'd let the motor be for now. However I don't think I'd run 5W50 I go for something more like 10W40 ish.

Cool, Thanks guys!

I'll live w/ it...thats the only option I have for now. I'll change the oil, check under the valve cover and run some of that Oil Additive stuff that cleans everything out GOOD.

Thanks a tonne

Steve

------------------