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Hi everyone,

I've had 2 different engines break just one rocker lately. I'm sure the timing is correct, tension is fine and locking pins always line up.

Do HDI rockers have a habit of breaking WITHOUT piston -> valve contact? I'm aware they are designed to break upon a valve hitting a piston, but does that in itself create an inherent weakness leading to random failure of the rockers?

I've searched, but all I keep coming across is cambelt/timing issues ruining rockers, nothing about them just failing.

This has happened to 2 DW10ATED (HDi 110hp) engines now, within weeks of each other.

Any advice/experience would be great

Hi & welcome aboard.

I'm no expert, but I've never heard of this other than a result of timing problems

(Someone who knows stuff should be along soon).

I'm not an expert either but as far as I'm aware nobody's ever come on the forum with this problem before. Maybe they were weakened by a previous cam belt failure or, as you suggest, they're designed to break so maybe they just do it anyway, perhaps as a result of fatigue (how many miles have these engines of yours done?). Any ideas of the build dates (DAM/RPO) on these cars? Maybe they were a duff batch

is it the exhaust rocker on no3 from the cambelt end?

Odd - Found my 110 HDi had broken 2 rockers this weekend. Symptoms were a loud ticking at idle. Timing is spot on (It timed up perfectly when I took it apart). Replaced the 2 rockers (Cylinders 3 & 4, cant remember if inlet or exhaust) and all seems fine again touchwood.

Cant work out for the life of me why they failed! It seems that the pin hoding the roller the cam acts on has just become loose and come out of the side of the rocker - See pic below.
Build code is 9709 - Be interesting to see if others are similar, would point to a faulty batch being fitted at the factory.

how much power are you running as this is common on the 306hdi's running 150+bhp

this is beveled to be build up back presser in the manifold causing valve float and then slamming the valve in to the rocker arm

Ah this is a possibility... I have remapped it to about 140bhp and I ran into the follower problem on an early version of the map (Injection advance was too retarded at 4000rpm). However, that was about 10k miles ago. I suppose its not beyond the realms of possibility that it was weakened and has slowly failed over time!

Interesting I'd have never have thought of that (need to spend more time on other forums I guess )

Did they find any sort of solution for it on the 306s? Other than replacing them every oil change...

port the head and manifold as this would increase flow and reduce back presser and make more power.

the way the port on the hdi works is hi speed.

the hi speed gives better economy but hi flow would give more power.

it's not a common problem at 140bhp but yes the map could have exasperated the fault.

there's sum thing fishy going on hear as i have faults with no3&4 cylinders (not like this tho) on my two and i bet that there's a lot more out there like it to.

Easiest solution is to get the mapping correct if you have a medium power remap! Lower the boost a bit and advance the injection timng, this should lower the exhuast manifold pressure to within acceptable limits. Essentially what happens in some maps is you are running increased boost and fuel, but the injection advance is standard and so the "End of injection" time is very retarded.

Of course if you are aiming for high power, then yes porting the head and a new turbo is the way to go!

The issue is quite noticeable when it happens - Essentially the engine is pulling hard and all of a sudden its like 'hitting the wall', its like hitting a rev limiter.

This only happened once or twice on mine until I twigged what was happening and tweaked the boost and advance maps slightly. THis was several thousand miles ago hence I didnt make the link between that and the tapping noise which only showed itself up about a week ago.