2007 Peugeot 407, Model Timing Belt Issue

MAHROUQI

MEMBER
2007 PEUGEOT 407
113,000 MILES

Hello,

First of all, I would like to thank you for your effort to answer questions.

Secondly, I would like to ask about an issue that I had with my Peugeot 407, 2007 Model. I was driving the car when it suddenly stopped. I tried to restart the engine but with no success. I took the car to the dealer and they mentioned that they are suspecting that the “ cylinder head valves struck and locked the piston, in this problem timing belt and other connected parts completely damaged”. However, I am not quite sure if the problem can happen in this order or the timing belt get damaged first and then cause other parts to be damaged.

The timing belt was replaced by the dealer in July last year and the car has not done more than 20,000 kilometers since that. I am concerned that the dealer is trying to avoid responsibilities with regard to the timing belt, hence, they are saying that the cause of the failure is something else which eventually caused the timing belt to get damaged.

I would really appreciate to get a detailed description of the above scenario if it can happen as mentioned by the dealer.

Regards

1 Reply

CARADIODOC

MECHANIC
33,917 POSTS

First of all there are eight engines listed for your car model. We need to know the engine size when discussing an engine problem.

I'm not familiar with your car model but I am very familiar with what you're asking. The way the dealer described their suspicions is rather unusual but what they are referring to is an "interference" engine. That is one where if the timing belt breaks or jumps enough teeth the open valves will be hit by the pistons as they coast to a stop and will be bent. Nothing else will cause damage to the timing belt. The timing belt has to jump or break first, then the damage to the valves occurs. The cause could be the water pump if it is driven by the timing belt on your engine. Many are not. If yours is, it is customary to replace the water pump when the belt is replaced to insure the quality of the repair. Some customers don't want that done to save a little money which is very short-sighted. Some mechanics elect to not replace the water pump to save their customers some money. That is risking their reputation for doing quality work. The water pump in these applications becomes one of the idler pulleys for the timing belt, and any pulley that wobbles due to worn bearings will cause greatly accelerated wear on the belt and can allow it to become loose and jump a few teeth. If the belt jumps a tooth or two the engine will still run but power will be reduced a lot. That will give you some warning before more damage occurs.

Not all engines are interference engines, but on those that are, the valves will not lock up the engine while it is running. The pistons will hit and bend the open valves, then the engine will coast to a stop. It will still spin when you try to start it but it will sound weird. It will be spinning too fast and with little effort. That rarely damages a piston; just the valves which bend easily. The only time the engine will lock up is when the timing belt is removed or installed wrong, and you try to rotate the engine by hand. It will get stuck when a piston gets to the top of its travel and hits a valve that isn't supposed to be open at that time. You aren't strong enough to force the piston to keep moving until it bends the valve. That can only happen when the engine is already running, then the belt problem occurs and as the engine coasts to a stop the pistons hit the valves.

Of course there's always the exception. In most engines there is a means built in to cause the valves to rotate while the engine is running so heat builds up evenly and is given off evenly on all sides, and the seats, (for sealing), wear evenly. A bent valve could rotate a little when the mechanic tries to rotate the engine and that could bring a side of the valve around to where it again hits a piston and locks the engine. This is a minor detail that is hardly worth mentioning but that's better than just not pointing it out at all. It does more to confuse the description than to explain it.

Instead of guessing, which is what it sounds like someone at the dealership did, there are a number of things they should do to verify their suspicions about a timing belt problem. One is a compression test. If the valves are bent there will be no compression at all in any cylinder. There is also usually a cover that is easy to remove to inspect the belt and see if it is turning when you crank the engine. There are a lot of totally unrelated things that will cause an engine to stop without warning and given the belt was replaced not too long ago there is likely a much less serious cause for yours to do so.

If the dealer insists the timing belt broke and the valves are bent after it had the recent service, I would question them as to the value of owning one of their products. Why would they expect you to buy a car that can't be driven more than a year without incurring an expensive repair? I personally will never own an interference engine but for most European and Asian models that's what most of them are so you don't have much choice.

The mechanic working on your car might also be going on mileage, and may not be aware the timing belt was recently replaced. Regardless, he needs to do some tests or inspections to rule out other causes before committing to such an expensive diagnosis.