BENT VALVES in the head: tell me how that happens....

[BLAZINBLUEVITZ]

just like topic says. please tell me how valves in the head wind up getting bent????

[Tamago]

over revving.. stretching of the timing chain... vvti solenoid going bad and allowing too much timing advance..

or in my case.. snapping a connecting rod.

[BLAZINBLUEVITZ]

got an 08 tc which was in before and had motor/head replaced under warranty for a ticking noise in the valvetrain. customer is back 3 months and 15,000 miles later and now ALL of the valves in the head are bent?

[jkuchta]

So what's the customer's story?

[Tamago]

Originally Posted by BLAZINBLUEVITZ

got an 08 tc which was in before and had motor/head replaced under warranty for a ticking noise in the valvetrain. customer is back 3 months and 15,000 miles later and now ALL of the valves in the head are bent?

what weight of oil is he running?

wait.. you're coming to YARISWORLD for tech support?

[BLAZINBLUEVITZ]

Originally Posted by jkuchta

So what's the customer's story?

and i quote " i drive 200 miles a day and never go above 70mph on the highway" and "all i did was get gas and car statred to lose power afterward"

car has intake and header( which were removed before he brought in) as well as secondary cat delete and megan exhaust.....

[Tamago]

Originally Posted by BLAZINBLUEVITZ

and i quote " i drive 200 miles a day and never go above 70mph on the highway" and "all i did was get gas and car statred to lose power afterward"

car has intake and header( which were removed before he brought in) as well as secondary cat delete and megan exhaust.....

customer did a 1-2-1 shift or a 2-3-2 shift. he over-rev'd the engine.

warranty DENIED

edit: have the tech pull off the crankshaft pulley and look for scoring on the roll pin.. you'll find it's most likely bent or almost broken.

[Russelt3hPirate]

Assuming the install was done correctly Tamago is probably right.

although if the install wasn't done right it could be numerous things.

[Altitude]

Originally Posted by Tamago

wait.. you're coming to YARISWORLD for tech support?

...and that's a problem because?

[rob323]

Does the timing chain still have tension?

[Tamago]

Originally Posted by rob323

Does the timing chain still have tension?

iirc the newer chain tensioners are oil pressure activated and ratcheting... so they'd take up any slack.. so yeah, you may want to check that the teeth on the tensioner are not worn off.. but i still sniff a mis-shift.

[Tamago]

Originally Posted by Altitude

...and that's a problem because?

not as much a problem as a slight source of amusement to me.. because most of the 'knowledge' on this forum orbits around what offset wheel you can run without rubbing and what weight of oil you can/cannot run...

so a question about bent valves being asked here where the OLDEST yaris on the forum (US, anyway) is approaching 3yrs old.

[BLAZINBLUEVITZ]

Originally Posted by Tamago

not as much a problem as a slight source of amusement to me.. because most of the 'knowledge' on this forum orbits around what offset wheel you can run without rubbing and what weight of oil you can/cannot run...
.

probably because any talk of STREET RACING or ripping around the twisties with a new part installed is off limits....

[FunctionSpec]

Valves were probably adjusted too tight if they had to do any kind of valve adjustment. Tight valves would lift too much causing contact with the piston and bending the valves.

[MadMax]

Does the Yaris have a rev limiter like my old Passat? I don't drive mine as wildly as I did my old VR6, plus it is an auto, so I don't know...

Cheers! M2

[SilverBack]

Yes, it's set at 6K RPM. Valve damage would occur if driven for too long like that because of strain and overheating.

[Tamago]

Originally Posted by FunctionSpec

Valves were probably adjusted too tight if they had to do any kind of valve adjustment. Tight valves would lift too much causing contact with the piston and bending the valves.

lol dude...

tight valves.. lifting too much... yet somehow coming in contact with the pistons??

the valve springs lift the valves, the cams push them down..

blazinblue did your tech check the crankshaft pulley yet?

[Loren]

Barring extremely unusual circumstances, don't valves only get bent when they come into contact with pistons? There's really only one way that can happen... the valve timing has gone off in a major way. Typically, that means something broke (timing chain broke or stretched, VVT messed up, whatever) or the engine was severely over-revved to the point that the valve springs couldn't keep up and one or more valves stayed open when they should have been closed.

I'm going with the "3-2 shift". Winding up 3rd and missing 4th, dumping the clutch in 2nd gear with the car going 80 mph. Ponder that for a moment. If the engine turns about 6200 rpm at 60 mph, you can easily zing it past 8000 in this manner... instantly. And if you're not quick enough to realize it instantly (or quite possibly even if you are), you can do some damage in a hurry.

I did it once in my old Saturn, but I realized it before I even got the clutch fully engaged and no damage occurred. From what I'm seeing with my son as he's learning the finer points of driving a stick... if he did it, he'd more likely fully engage the clutch and leave it there and wonder "why don't I have any power" until valves started poking holes in the hood. And I don't think my son is all that unusual as far as young folks learning to drive stick go.

Remember, a rev-limiter can save you from over-reving under power. The engine will simply never rev ITSELF far enough to hurt itself, the ECU won't let it. But NOTHING can save you from a botched shift! The solution is to learn to trust your shifter. Don't FORCE your shifts, "guide" your shifts. The shifter is spring loaded and will go into the proper place if you let it.