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Grace
Hagerty Employee

Piston Slap: Running on a dead cylinder?

Brooklynn writes:

 

Hi, I have a 2002 Chevy Impala 3.4-liter with a bent connecting rod and broken piston. My fiancé and I got into a debate on if the car could still run with only five pistons functioning and one completely removed, or if it would have coolant mixing in with the oil somehow. I don’t think the pistons have anything to do with the coolant and oil mixing, but I would like to know who is right here. I've Googled it with no luck so I figured might as well ask somebody!

 

Read the full article on Hagerty.com: https://www.hagerty.com/media/advice/piston-slap-running-on-a-dead-cylinder/

7 REPLIES 7
Tim
Instructor

I thought that excess oil would end up flowing through the exhaust and eventually clogging the catalytic converter (assuming the engine would otherwise last that long). Technically, that wouldn't stop the engine from running, but would just be another reason why running that engine is a bad idea. 

Sajeev
Community Manager

In general yes, but in this case they are suggesting to remove the broken rod/piston so everything will just fall down into the oil pan. 

coastr
Pit Crew

Maybe take the rod out and JB weld the piston in the cylinder, pull the injector and spark plug lead?  That way you're keeping the oil (mostly) out of the intake/exhaust.  

 

Either way I give it 10-15 minutes run time before death.

 

As for the vibrations...would you be able to tell the difference from a normal rattle-can V6?  (i kid, i kid)

Sajeev
Community Manager

I received a fantastic comment via email and figured it's worth sharing since he nailed it and I kinda got it wrong: 

 

Your answer on the one missing piston/rod is pretty good except I think you missed one detail: How much oil pressure do you think that engine is going to have with the unrestricted oil flow from the missing rod? Or were you thinking they would cut the rod down so that the crank journal would still be covered without the end of the rod punching a hole in the block or oil pan.

 

I had a pretty impressive failure on a Ford Taurus V-6 that had bent a rod after suddenly stalling out driving through flood waters. It ran well except for the rod knock for about 2 minutes before the rod failed catastrophically and very loudly punch a hole through the block.

Swamibob
Instructor

Thank you Sajeev!  So many old Cadillac V8-6-4 jokes indeed....  🙂  Oh the good old days of GM, in the 80's, where bad engineering could be outshined by bad execution.  Porsche and Mercedes were also working on the 'Displacement on Demand' concept then, but neither of them brought it to market (that I remember) and seeing the complicated mechanisms of the Cadillac system, way back in the day, I really wondered why that ever made it out.  My only thought was some VP, at GM, had spent so much political capital (or maybe it was cocaine capital?  It was the time of hot and cold flowing cocaine fountains in industry and other places) and other resources on that system, they had to do something to try and get some value out of the costs.  Unfortunately, just another production failure, much like the caddy that zigs (Cadillac Catera), the Allante or that awful Cadillac 'J' car; the Cimmaron.  

Thanks Sajeev.  Now I'm thinking about the old Ford Stratified Charge engines from that same time period and some early rumors from Chrysler involving variable valve timing; on top of the old V8-6-4.  Now I've got a huge headache.  🙂  So many memories running around in my head...

Sajeev
Community Manager

You are very welcome, @Swamibob. I reckon these DoD implementations get the green light mainly because of EPA/CAFE concerns so they can minimize their impact to the company's bottom line. If so, it's not a great idea for Cadillac back int he 1980s, but all the new 5.3's that fail normally happen well, well after the warranty expires. 

 

llawrence9
Intermediate Driver

I met some people that limped a Volvo Amazon 300 miles to Mardi Gras, on three cylinders and a hole in the block caused by a broken rod. The block was  patched with some cotton socks.