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Technical help required on Peugeot 406 with (XFZ) V6 engine problem.

Christo1

New member
Technical help required on Peugeot 406 with XFZ engine problem.
I admit I have next to zero knowledge of French engine design, I have enough of British, German, Swedish and Australian auto experience I would have thought to get by, but alas I am stuck.
The 2 photos tell the story, all valves bent and, looking at the witness marks on piston tops in photo of block, the exhaust valves took the brunt.
The problem I have is why? The engine just stopped. Quick leak-down check, air exiting both exhaust and inlet manifolds. The cam belt was still on and intact. A rudimentary alignment showed it was close enough to timing specs. for valves to have survived.
But looking at photo of pinion in its timing location, I expected to find piston of cylinder 1 at TDC or near enough, then looking at the photo of the block (sans head) we see piston No. 1 about half way up to the top. To get the No. 1 piston to the TDC position, the pinion is about 180 deg. out of sync.
I was just going to swap the engine out and put a four cylinder in it. But I am hoping that someone can tell me what is going on with the V6.
Things I have done (Apart from removing front cylinder head and all that entails) I also removed the pinion from crankshaft to make sure the key wasn’t sheared, also I could not see anyway the pinion could have moved (separated) outer in relation to inner.

If the French time the engines differently, just call me a dumbass and I will accept that I have no idea what I am doing with French engines.

I am not stranded, I have other transport and it’s not urgent, I just want to find out what the issue is if possible.

Sorry for the long post, hope you can help enlighten me.

Regards Chris
 

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Rally

Member
These engines are timed by inserting rods through the four cam hubs and the crank into holes in the block , then the cams are locked by doing up the bolts.
 

Christo1

New member
Thanks, I did check it (roughly) that way before I removed the head, (used pieces of 8 mm rod) BUT I didn't then lock the cams before removing the belt. I was concerned at that point as I had the plugs out and did a secondary check to see if the piston appeared at top of, or nearing top of travel and it wasn't. totally confused by then I just pulled it down to see what was actually going on. I had thought that the pinion may be a damper type and the outer had moved in relation to the crank, but it doesn't look like it.
Whilst the timing would obviously reference the relationship between the crank and cams does it not also reference No. 1 piston position ? by going on the position of the piston in relation to the pinion (in the photo)it doesn't appear to, if this is the case I suppose I am overthinking it, and I should be looking for another reason for the damage, which I may have made worse by not locking the cams prior to removing belt and stripping down.
Thanks again Chris
 

pugrambo

Going slightly mad
Was it running before this ?
How did the valves end up hitting ?
If belt was not broken nor any other issue had caused it to slip then they can't meet pistons
 

Christo1

New member
Thanks for the links, first one all good downloaded fine, will check it out now.
second link I am guessing needs a login, will try it again , the site though looks informative.
Thanks for the help.
 

seasink

1000+ Posts
The link above is shortened. Copy and paste the lot into the address bar. It's a well illustrated aid.
 

Christo1

New member
Was it running before this ?
How did the valves end up hitting ?
If belt was not broken nor any other issue had caused it to slip then they can't meet pistons
My thoughts exactly, yes was running, how the valves were hit is the issue, I have only 1 idea of what it might have been but it would have to be something weird. The timing belt was intact and not loose. However the auxiliary belt, damaged by the ever invasive oil leak from cam boxes, shredded itself, but not before (and I have never seen anything like it before) It entwined itself BEHIND the front pulley, behind the plastic timing case cover and wound itself around the pinion, between the pinion and the timing belt, (effectively enlarging the diameter of the pinion). I took photos before I cut the bits off (will find & put up) and unwound it from the crankshaft, and in doing so probably caused the issue myself by turning the motor over manually to unwind it, then I eventually removed the top mount, timing covers, etc. On inspection I found the timing of the pinion and cams to be extremely close, and started looking for the cause. Could it really have changed the engine timing enough to have caused this? (The light-bulb moment is in bold, with expletives deleted.) However why is no.1 cylinder only at mid travel when pinion is in correct alignment ? or doesn't it have any bearing on the way these are timed ? Photo to follow of the auxiliary belt, as soon as I stop banging my head on the table.
 

PeterT

1000+ Posts
I have no experience on the V6, but on other XU engines when you lock the crank, the pistons are indeed 90º BTDC and 90º ATDC. Thus impossible to hit a valve on a piston.
 

speaksgeek

1000+ Posts
I have no experience on the V6, but on other XU engines when you lock the crank, the pistons are indeed 90º BTDC and 90º ATDC. Thus impossible to hit a valve on a piston.
Same for EW engines, all pistons are mid bore when pinned.
 

Christo1

New member
Finally got the photos reduced, still not convinced this caused such a monumental collision between valves and pistons but there we go.

AuxBelt 2as.jpg IMG_0693.JPG aux belt 1as.jpg
 

Demannu

Demannu-facturing!
That is definitely the cause, and not uncommon. And not limited to Peugeot either, many timing belt engines are susceptible to this.

The accessory belt shreds, bits of it get into the timing belt housing and cause usually the crank to slip on the timing belt.
 

Dave

1000+ Posts
Yeah a previous 306 8v of mine lost a timing belt when the accessory belt went alien.

You might think accessory belts aren’t important but anything near the cam belt can cause collateral damage.

Dave
 

COL

Alpine A110
Same for EW engines, all pistons are mid bore when pinned.
This is a similar engine to what is in my 2002 Laguna V6.

It makes sense that the pistons are all down the bore when the heads are put on, so no matter where the valves are they will not hit the pistons as these are interference engines.

Timing is a relationship between the camshafts and the crankshaft. Forget the old way of doing it with #1 on TDC
 

Christo1

New member
(y) Thanks for the replies and advice everyone. I appreciate it as I was lost on this one.
knowing or at least having a better understanding on cause and effect makes a big difference. I will just take my time and rebuild it.
Regards Chris
 

Christo1

New member
Thanks , motor I wouldn't be able to manage from interstate, but could well be interested in the heads. (freight been cheaper and easier)
I am still finding my way around this forum, so haven't found a way to message you directly but will work it out.
 

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