Is valve damage from incorrectly timed timing belt repairable?

My dealer just replaced the timing belt on my Honda Pilot. They said that the engine was rough during the test drive and that the valves were damaged. They said that this was because the timing wasn’t calibrated properly. They’re going to replace the valves at no charge. What sort of other damage could have happened? Could there be any permanent damage? Could the damaged valves have caused damage to anything else?

If the timing was “off”, that is because the belt was not installed correctly.
And, yes, it can cause valve damage.
The valve damage results from the valves coming into contact with the tops of the pistons.
Those nicks in the pistons can cause hot spots on the pistons, and can cause major engine problems in the future.

In my opinion, the dealership is on the hook for tearing the engine down and replacing valves and pistons.

They’ll remove the head(s) and inspect the damage that was done. But out of all of the Hondas that I’ve repaired with damaged valves from a failed timing belt, not once have I had to do anything with the pistons.


A complete valve job should be performed and this means regrinding any other valves along with all of the valve seats. If they do not do this any repair may be short lived.

Often when the valves hit the piston they will nick the surface of the pistons to some degree. This can leave sharp edges which may glow red and cause detonation when the engine is running. Any sharp edges should be smoothed off or rounded with a file or Dremel tool.
In some severe cases it’s possible for pistons to crack or rod bearings to become damaged but that’s not the norm.

Did these guys replace the tensioners and water pump also? If not, strike two. Strike one was not double checking their work, rotating the engine by hand a few times, and then triple checking the timing marks again before starting it up.

Ask if the valve lifters were damaged. Ask if the valve stems are still a tight fit in the valve guides. Ask if the cam or cams are bent. They might all be ok but ask anyhow. It sounds like your timing belt job was assigned to a new mechanic.

Could this be part of the reason Honda and most other manufactures no longer use rubber timing belts? It just hasn’t worked out…

Honda still uses belts on the 6cyl motors.

I think I’d want to see the damage once the head is removed and if there’s damage to the pistons I’d try to make them replace them. It’s possible there could be damage that wouldn’t show up for several thousands of miles. It’s their error make them correct it to your satisfaction even if you have to get a lawyer to do your talking for you. Hopefully it won’t come to that, but they are responsible for all the damage not just part of it. I’m not sure of this since I’m not an internal engine person, but for some of the more experienced mechanics isn’t it possible this could also have weakened the piston where they might crack later on or couldn’t it have bent a rod? I’m sure the dealer has insurance to cover the expenses so get everything back the way it should be.

I think I’ll just stick with my old Fords with non interference engines. To me it never made sense for any manufacturer to use timing belts on interference engines.

This is great information. Thank you everyone.

The update from the dealer is that they will be replacing all of the valves, and will check the pistons for nicks. If there are any, then they will smooth them.

The summary from all of your posts is:

  • Pistons should be replaced since the nicks could cause hot spots which would result inserious engine damage thousands of miles from now.
  • Pistons could be cracked
  • Rod bearings could be damaged
  • Rods bent?
  • Tensioners replaced?
  • Water pump replaced?
  • Valve lifters damaged?
  • Valve stems still a tight fit in the valve guides?
  • Are cams bent?

This is my wife’s car, which she uses to drive our children. Next weekend she’s supposed to take it on a long road trip. I’m not sure that I will trust this car. If the repair is not done properly or completely, what’s the risk? What sort of thing might happen if this causes a failure while driving?

many thanks to everyone who’s helping me!

In most cases the only damage that occurs is that the intake valves will bend due to contact with the pistons and the piston tops may get nicked up. It’s always possible that something like a cracked piston, damaged rod bearing, etc. could occur but the odds of this are pretty remote.
(The intake valves rather than the exhaust valves are generally the ones to bend because they have larger diameter valve heads. In most cases the exhaust valves will clear.)

There is the possibility of valve train (lash adjusters, cam lobes, etc) damage because apparently the engine was operated while running roughly during the test drive. This means things are being slammed around pretty hard. All of the valve train components should be thoroughly inspected for any nicks, pitting, ridges, etc. and the cylinder head should be checked for flatness and surfaced if necessary. If the engine had died in the shop with this incident happening in a second or so this would not be as big an issue but the test drive makes it one.

Just some food for thought here but is there any way a rental car could be used for this trip? The thing that would concern me would be that considering how they botched the job before, the issue of putting 100% trust in them is pretty shaky. Maybe keeping the Honda close to home and driving it around for a few weeks or so to make sure things are right would be an idea worth considering?

Hope that helps.

Fortunately for you did the work at a Honda dealer. They have good insurance for this and will correct it properly and warranty their work. This is not some independent losing his shirt on it.

@ok4450 is dead on right, the chance of any of those other things happening are remote. The valves are the weak point, and therefore the most likely to be damaged. I am sure once they are replaced the Pilot will be fine for a VERY long time!

It’s not six months later. The dealer says that the timing belt tensioner needs to be replaced. Do you think that the tensioner could have been damaged when the timing belt was replaced and incorrectly calibrated six months ago?

The tensioner spring can get old and ‘tired’ and fail to hold sufficient tension.

When installing the tensioner the plunger must be pressed in against the spring tension s-l-o-w-l-y. If pressed in to quickly the hydraulic buffer can be damaged.

More often than not the tensioner

is re-used when replacing the timing belt on the Pilot. That tensioner is common to many Asian imports.

The spring on the timing belt tensioner has nothing to do with the tensioner going bad 6 months later. The spring only sets the initial tension, then a bolt through the center of the bearing clamps the tensioner in place, permanently. If the dealer says the tensioner is bad, then it has a bad bearing, but I have yet to see one go bad, even after 300k miles.

Now with a timing chain, the tensioner spring is usually kept active.

It is also possible that the mechanic who didn’t know how to install the belt in the first place did not know that the tensioner had to be torqued down so that it did not cause the belt to be under spring tension. That would cause issues 6 months later.

In another thread the OP refers to a rhythmic ticking sound which was diagnosed as a bad belt tensioner.
Considering the track record of the dealer on this problem maybe this ticking is due to excessive valve lash on at least one valve lifter; especially considering that one or both heads were supposedly reworked.

You might take a second look at the layout of the tensioner and tensioner pulley Keith. The tensioner that is shown in my link keeps spring tension on the tensioner pulley lever. The tensioner pulley is pre-tensioned then the pin is removed from the tensioner.

They own the engine at this point. Any short term or even longer term issues up to about 30k miles on top of where you are now, regardless of the years. They really messed up and a new engine is not out of the question at this point. At least a new rebuild would have a warranty.

The dealer did the repair without charging us. I guess they agreed that the problem was their fault.

Thanks for everyone’s comments.