Bent Rods: How to identify?

[igdrasil]

Hey people, I was wondering. How do we identify when the rods are slightly bent? Except with the cylinder compression/leak test...how does the engine behaves? I mean:

Hows the power on low rpms?
Hows the power on high rpms?
EGTs?
A/F?
Vacuum readings?
Noise?
Smoke?

I noticed that when I first blew 2 of my pistons, the one that has the most damage is bent too. But the pistons where so damaged that the problem was obvious with all that smoke.

But if there is no broken piston...then there is no leak, no smoke at all!
(dunno)

 

[kcbhiw]

But if there is no broken piston...then there is no leak, no smoke at all

That's not necessarily true. The rings could be shot.

 

[igdrasil]

Broken pistons and bent rods caused by a hydraulic lock: This type of failure can be identified by the bent rod with no physical marks on the rod indicating something hit the rod to bend it and rod will also have the appearance of having buckled under pressure rather than just plain bending. Hydraulic lock is caused by a small amount of liquid in the combustion chamber and liquid will not compress. When the engine is started, the force of the crankshaft combined with the inertia of the flywheel starter, etc., will create enough power to bend the rod. The liquid could come from the coolant leaking into the combustion chamber, flooding, defective or leaking carburetor allowing gas to drain into the intake manifold and be sucked into a cylinder when the motor is first started.

 

[Installshield 2]

In my experience it can be noticed as a "lump" at idle...depending on the severity it can be more noticable in some cases...With a bent rod, the torque angles of the crank/rod mesh points change from the others, in some cases that particular portion of the crank could be recieved more or less torque than the rest causing a brief surge or stumple during idle...It actually sounds more like Harley, just without the exhuast note...it just kind of lumps and pops at idle, and will get more unsmooth with increased rpms...It is very difficult to explain, and if the bend is minor it may not be noticed at all which makes this even more fun...

If nothing is noticed, there is virtually no other way to identify it...but just a slight bend will make a very inconsistent unsmooth engine which hopefully be noticed...

 

[igdrasil]

Thats interesting Installshield 2. Mine doesnt do that but my car did have water in the pipes.
Maybe the intercooler still has some inside?

 

[Installshield 2]

Thats interesting Installshield 2. Mine doesnt do that but my car did have water in the pipes.
Maybe the intercooler still has some inside?

I am assuming you mean the intake side has water in it...are you sure that water got all the way inside the engine? If you did indeed induct water you did not neccesarily bend a rod...in some cases the head takes the brunt from the compression doing a number of things to the upper part of the engine...

If you meant water was in the turbo manifold, that in some cases can be normal...Water and CO2 are the two main by-products of the combustion process, and the water sometimes condenses on the walls of the exhuast system...don't worry about that as much, this is why exhuast systems sometimes rust from the inside out...

 

[igdrasil]

I found water in the intake, bov recirculating hose and in the intercooler pipe that goes to the throttle body, so yes, water got the way into the engine.

But the car is fine as of today. Solved 99% of issues, BOV was leaking, vacuum hoses were bending.