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Proper way to fix piston slap issues (grin)


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Uh, here is one way of fixing piston slap noise in the 2003 models.

The tech next to me did a "decarb" procedure on this Deville and

managed to hydrolock the engine as he was pulling off the lot.

Little chunks of aluminum block came spraying out the bottom of

the car. For your viewing pleasure:

http://members.shaw.ca/ianrmac/Images/DSC02345.JPG

http://members.shaw.ca/ianrmac/Images/DSC02346.JPG

http://members.shaw.ca/ianrmac/Images/DSC02348.JPG

http://members.shaw.ca/ianrmac/Images/DSC02347.JPG

http://members.shaw.ca/ianrmac/Images/DSC02343.JPG

Now it gets a brand new motor...no more piston noise

in the morning (for a few kilometers anyway) Heh heh!

Ian

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Interesting at least that was one way to cure the piston slap..I thought the slap was corrected with the new coated pistons??? Great pic Just curious What caused it to hydrolock??

Jim

The new design pistons do fix the problem, but we hadn't gotten

that far yet on this one. GM wants us to perform decarb procedures

until it's determined that "that" wont fix the problem. The decarb

procedure seems to work for most of the engines. Either that,

or the customer gets tired of being put off and just decides to

live with the noise.

I believe that what happened with this engine...is that the tech

introduced the cleaning fluid into the intake, and then allowed

the engine to quit. Then he later started the engine up, idled

it out of the shop, but as soon as he opened the throttle up,

it gulped a shot of fluid from the intake and "instant" blown

motor. These intakes can pool fluid quite easily, so a person

has to be careful.

Ian

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I can't believe that! How could he have avoided this problem? How hard did he get on the throttle for this to happen? Can you explain what hydrolock means in this instance? I thought hydrolocking involved ingesting water through the intake. Do you mean that the fluid hydrolocked the engine spontaineously at high rpm and hydrolocked the engine causing this? How does this happen? Does the fluid acts like a wall and the piston hits the 'wall' and the rod or other weakpoint spontaineously blows at some point?

Someone on the other board had an engine blow about a month ago, he was getting a knocking, JohnnyZ I think. He took the car out to do the decarb procedure and his engine blew. I wonder if it could be related to this hydrolocking. Thanks, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Mike,

Sounds like what he did was let the engine ingest the fluid through the intake til it choked itself and shut down, leaving some fluid pooled in the low spots in the manifold. When he restarted it there was not enough vacuum at idle to draw it into the cylinder but when he got on it there was and it filled a cylinder with (non-compressable) fluid. At that point something has to give, usually a rod.

I think the proper proceedure would have avoided the problem, and that is to fill and remove the fluid thru the spark plug holes thus avoiding hydrolock potential.

Hydrolock means , locking the engine hydroliclyby any means. Fluid being noncompressable acts about the same as putting a steel cylinder in the cylinder. When the piston runs up against it, it's gonna stop....abruptly.

I think Jonny Z's problem was a bit different.

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Good example of a severe half case leak.

================================

As we know liquid tends to pool in the intake of the Northstar. Some condensed oil vapor and heavy parts of fuel, I believe.

I know in mine there was several ounces of fluid when I checked it out.

I was just thinking, about being into the throttle on a road that gets rough, and the fluid in the intake starts splashing around while under hard suction.

While I have not heard of anyone sucking up this fluid and hydro-locking the engine, is this a possibility, or does the fluid build to diminishing returns?

-George

Drive'em like you own 'em. - ....................04 DTS............................

DTS_Signature.jpg

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While I have not heard of anyone sucking up this fluid and hydro-locking the engine, is this a possibility, or does the fluid build to diminishing returns?

I'm convinced that THAT is the brown stuff you see when you WOT it after a period of babying it around. Residue builds up in the intake and when you get that high suction at WOT, it cleans it all out. That's my theory anyway. :)

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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Just curious about the replacement engine for the Deville.  Did the customer have to pay for it or did the dealer take responsibility for its own actions and replace it for them.  Thanks

The vehicle is still under warranty, and I believe that GM will pay the tab. Of course we would take responsibility if the vehicle was not under warranty, or if GM decided they weren't going to participate. I don't know what kind of dealerships they run down in the States, but up here, we take responsibility for our actions.

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OUCH!  :o  Is he still employed? If he is, I'm sure you guys will never let him live it down.

Oh yeah, he's still employed. He's actually an excellent tech. He's our Duramax Diesel specialist, and he likes working on the Corvettes too (which is fine, he can have them). Look, he made an error in judgement and it bit him. This kind of thing has happened to all of us at some time or another. Our shop is quite reasonable about these things ( part of the reason is that finding good techs is almost impossible these days).

But we will have fun with it. Today, I brought in a 2004 Venture van to replace

the engine (it made it 400 kilometers before something went south inside and it lost oil pressure and cooked the motor) and it was on the point of siezing up. It was making a terrible racket, squealing and squawking. Some of the other techs wandered over and wondered what the hell was going on. I just casually said, "oh, I was just doing a decarb treatment and the engine blew up". The other tech took it all in good fun. Who knows, later on I'll screw something up, or run into something, and then he'll call me "crash" for a few weeks. Of course, I'll make sure I don't pull any such stunt...heh heh.

Ian

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Ian...just wondering....what did you tell the customer? did your dealership admit that they possibly made a mistake? or did they blame it on the engine design etc. I assuming you took responsibility "I don't know what kind of dealerships they run down in the States, but up here, we take responsibility for our actions" And yes...some dealerships are run much much differently than yours, that is why I will never take my car to a dealership again :(

A.J.

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What's not to believe??

The likely explaination was described above. The tech likely put too much "top engine cleaner" thru the throttle body too fast and stalled the engine with a lot of liquid still in the intake manifold. It started up and idled and as soon as the thru put thru the engine was increased by opening the throttle to drive away one cylinder gulped the liquid and hydrostatically locked. End of story and engine.

Thanks bbobynski, I just could not believe that it was possible to lock an engine doing maintanance like the tech was doing. I thought it only could happen if the engine ingested water. I WILL be MUCH more careful if I use that TOP ENGINE CLEANER going forward for sure, Thanks, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Ian...just wondering....what did you tell the customer? did your dealership admit that they possibly made a mistake? or did they blame it on the engine design etc. I assuming you took responsibility "I don't know what kind of dealerships they run down in the States, but up here, we take responsibility for our actions" And yes...some dealerships are run much much differently than yours, that is why I will never take my car to a dealership again :(

I don't know what they told the customer. I wasn't privy to that discussion. I do know that GM is replacing the engine on their dime. What the shop foreman told the DSM (district service manager) I also don't know. I did talk to the foreman one morning, and he's reluctant to lay blame, but I think we all know what happened.

Ian

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I did talk to the foreman one morning, and he's reluctant to lay blame, but I think we all know what happened.

Ian

Ian, how could this be avoided, letting the engine ingest the TEC slowly and keeping the idle very high to stop the stall? If it DID stall what would you do at that point, do you gradually raise the RPM to ingest the excess slowly? Is this an easy thing to have happen, if you do it yourself? I had used the TEC on my 91. Thanks, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Ian, how could this be avoided, letting the engine ingest the TEC slowly and keeping the idle very high to stop the stall?  If it DID stall what would you do at that point, do you gradually raise the RPM to ingest the excess slowly?  Is this an easy thing to have happen, if you do it yourself? I had used the TEC on my 91. Thanks, Mike

I've introduced both a chemical cleaner (as you are supposed to in the ring cleaning procedure) and water into Northstar engines a number of times.

There is no real secret, other then do not let the engine stall and have a way of metering the amount of liquid that is going in. I happen to have a clear hose with a valve on it so that I can watch the flow of liquid and meter the flow. I usually just bring the rpm to about 2K and then listen as I introduce the liquid. You will hear the engine beginning to slow down. At that point, I either increase the throttle opening, or decrease the amount of liquid flow. You find a balance point where you can maintain both a certain rpm and flow rate until the liquid is used up. It's important to keep the engine running for a while after the procedure is finished. I keep the revs up, but I don't go crazy and I keep the revs at one level. IE: I'm not blipping the throttle up and down. Then I usually take the vehicle for a good road test to clear anything that might be left in the intake or exhaust system. Works for me so far, haven't blown up any engines this way yet.

Ian

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Thanks Ian, that was great! Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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