How do you bend a rod?

How do you bend a rod?

Author
Discussion

Frimley111R

Original Poster:

10,710 posts

190 months

Saturday 27th June
quotequote all
I appear to have done so on my Megane R26. Although high mileage the engine seemed very strong but the racket its making after a TD appears (from other forums) to indicate a rod is bent. How does that actually happen? The engine wasn't highly modified, just a basic map that had been on for years. I guess its 'dead' now but in the interests of avoiding this in future....

LimSlip

444 posts

10 months

Saturday 27th June
quotequote all
What makes you think it's bent a rod? Bent rods most often occur from engines ingesting water and hydrolocking, but a big end bearing seizing can also cause bent rods. However if the engine was seized, then it wouldn't be making any noise.

If the engine is knocking badly then you may have trashed a big end bearing due to oil starvation, but that doesn't mean a rod is bent.

Pit Pony

2,827 posts

77 months

Saturday 27th June
quotequote all
I once had a rod come through the side of block on a MK2 Cavalier Sri130 SEH 8V.

It also smashed the starter motor into pieces and ripped the sump apart.
How? Why ? I suspect the big end bolts snapped at the red line.

I also bent a rod on an RD350LC at erm more than 69 mph. Close to the red line in 3rd.
In that the actual piston had no oil and seized.
Previous owner ran it on premix and never mentioned it. The oil pump was badly adjusted so was barely getting any stroke oil into the engine.


paintman

5,909 posts

146 months

Saturday 27th June
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The only way you're going to know for certain what's actually happened is to strip the engine & inspect.

stevieturbo

14,879 posts

203 months

Saturday 27th June
quotequote all
Frimley111R said:
I appear to have done so on my Megane R26. Although high mileage the engine seemed very strong but the racket its making after a TD appears (from other forums) to indicate a rod is bent. How does that actually happen? The engine wasn't highly modified, just a basic map that had been on for years. I guess its 'dead' now but in the interests of avoiding this in future....
you appear to have done so...with zero evidence to support it, other than someone on the internet saying theirs did ?


hmmmm. gonna be another one of those threads.

Frimley111R

Original Poster:

10,710 posts

190 months

Saturday 27th June
quotequote all
stevieturbo said:
Frimley111R said:
I appear to have done so on my Megane R26. Although high mileage the engine seemed very strong but the racket its making after a TD appears (from other forums) to indicate a rod is bent. How does that actually happen? The engine wasn't highly modified, just a basic map that had been on for years. I guess its 'dead' now but in the interests of avoiding this in future....
you appear to have done so...with zero evidence to support it, other than someone on the internet saying theirs did ?


hmmmm. gonna be another one of those threads.
Well it wasn't just one, quite a few of them said it was the rod. Here's the death rattle video...

https://youtu.be/P1oHbFhm4wY

Boosted LS1

19,115 posts

216 months

Saturday 27th June
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You need evidence, for example a bent rod laid out on a bench. It could just as easily be an oil starved carbernerkle.

Elliot2000

682 posts

132 months

Saturday 27th June
quotequote all
That is no way to diagnose a bent rod. Could be a whole manner of things and a bent rod wouldn’t be top of my list of suspected things - the only way to find out is to take it to a mechanic and let them have a look.


stevieturbo

14,879 posts

203 months

Saturday 27th June
quotequote all
Elliot2000 said:
That is no way to diagnose a bent rod. Could be a whole manner of things and a bent rod wouldn’t be top of my list of suspected things - the only way to find out is to take it to a mechanic and let them have a look.
And most wouldnt have a clue how to look.

There are ways to diagnose...but of course it depends how badly bent and in what axis.

You may get a visual if you remove the sump though, or see something amiss if you pull the head.

A running compression test might show something too.

Either way, with a noise like that it needs to come part regardless.

Elliot2000

682 posts

132 months

Saturday 27th June
quotequote all
stevieturbo said:
And most wouldnt have a clue how to look.

There are ways to diagnose...but of course it depends how badly bent and in what axis.

You may get a visual if you remove the sump though, or see something amiss if you pull the head.

A running compression test might show something too.

Either way, with a noise like that it needs to come part regardless.
I wouldn’t have much faith in a kwik fit fitter thy only does brakes and exhausts checking it out, but actual mechanics at dealers or independents-
Even a mechanic who’s just finished an apprenticeship should know the basics.


the tribester

837 posts

42 months

Saturday 27th June
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Frimley111R said:
Well it wasn't just one, quite a few of them said it was the rod. Here's the death rattle video...

https://youtu.be/P1oHbFhm4wY
Big end.

Evoluzione

3,945 posts

199 months

Saturday 27th June
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You haven't bent a rod, forget that for an idea. It wouldn't be running if it was.
You will bend a rod if you carry on driving it though.

Chris32345

960 posts

18 months

Saturday 27th June
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Elliot2000 said:
I wouldn’t have much faith in a kwik fit fitter thy only does brakes and exhausts checking it out, but actual mechanics at dealers or independents-
Even a mechanic who’s just finished an apprenticeship should know the basics.
They say you can't get quicker then ak lwick fit fitter


Or is it sh**** then a Kwik fit fitter?

LimSlip

444 posts

10 months

Saturday 27th June
quotequote all
Frimley111R said:
Well it wasn't just one, quite a few of them said it was the rod. Here's the death rattle video...

https://youtu.be/P1oHbFhm4wY
And now you know that the internet is chock full of "experts" that would like you to think they know a lot more than they actually do. That video sounds like have at least one knackered big end bearing. On a track day a common cause is oil surge, which itself becomes much more likely if your oil levels were low.

stevieturbo

14,879 posts

203 months

Saturday 27th June
quotequote all
Elliot2000 said:
but actual mechanics at dealers or independents-
Even a mechanic who’s just finished an apprenticeship should know the basics.
That's the funniest comment in this thread yet. I would class most main dealers in the same category as the likes of Kiwk Fit, as largely all they do is minor services and change parts. No actual knowledge or ability is needed.
Now of course there are some very rare exceptions to that, but they are rare.

And finding a bent rod is not basic, unless it's completely and utterly bent stupid and obvious even to a blind man.

Competent garages are just in a very small minority, which is so bad to see.

stevieturbo

14,879 posts

203 months

Saturday 27th June
quotequote all
Still better than most garages lol


Elliot2000

682 posts

132 months

Sunday 28th June
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stevieturbo said:
That's the funniest comment in this thread yet. I would class most main dealers in the same category as the likes of Kiwk Fit, as largely all they do is minor services and change parts. No actual knowledge or ability is needed.
Now of course there are some very rare exceptions to that, but they are rare.

And finding a bent rod is not basic, unless it's completely and utterly bent stupid and obvious even to a blind man.

Competent garages are just in a very small minority, which is so bad to see.
Having worked in the trade for a long time, and working with plenty of people I wouldn’t trust to work on a lawn mower, I know there is plenty of bad mechanics. But most places, including main dealers, also had a fair percentage of extremely good mechanics - doesn’t help that everyone their works in a rush all day long though so fk ups happen.
Even the worst mechanic at my last place would find the cause of the noise like that without too much of a struggle.
Also - It is not hard diagnosing a bent rod with the right knowledge and equipment, even a minor deformed rod - don’t worry yourself if you don’t think you could manage it tho.

stevieturbo

14,879 posts

203 months

Sunday 28th June
quotequote all
Evoluzione said:
You haven't bent a rod, forget that for an idea. It wouldn't be running if it was.
You will bend a rod if you carry on driving it though.
Plenty of rods have been bent and driven on without issue.

I bent a rod and blew part of the cylinder head off and drove it on ( albeit for a short period to get off a main road )

Rods will bend from almost un-noticeable...to totally fked.

stevieturbo

14,879 posts

203 months

Sunday 28th June
quotequote all
Elliot2000 said:
Having worked in the trade for a long time, and working with plenty of people I wouldn’t trust to work on a lawn mower, I know there is plenty of bad mechanics. But most places, including main dealers, also had a fair percentage of extremely good mechanics - doesn’t help that everyone their works in a rush all day long though so fk ups happen.
Even the worst mechanic at my last place would find the cause of the noise like that without too much of a struggle.
Also - It is not hard diagnosing a bent rod with the right knowledge and equipment, even a minor deformed rod - don’t worry yourself if you don’t think you could manage it tho.
I'd say you have rose tinted glasses on with that perception of main dealers. And them working in a rush ? Never seen that in a main dealer ever.

And LOL.

Elliot2000

682 posts

132 months

Sunday 28th June
quotequote all
Well that confirms you have no experience of what a main dealer workshop is actually like.

Most workshops mechanics don’t earn great basic salary- it’s made up for in bonuses by selling more hours - I.e a service has a book time of day an hour but the tech finishes it in half hour - that extra half hour will add to his bonus. These bonuses can make up a third of total pay and turn a piss poor salary into an ok one- this means you have a workshop full of mechanics working flat out pretty much all the time and also why u get certain techs trying to avoid certain jobs because it will be a time loser.

Whilst ur sitting out front drinking your free coffee - the tech will have knocked out your job in less than the poor allotted time. You will then continue to sit there and wait for your free wash and waiting for the service advisor to get some free time to try and invoice and up sell you something - the only people that don’t rush about in dealers is the salesman