300 TDI Snapped Cam Belt

The cam belt snapped on my 300 tonight while on the motorway.
Any advice on the job before I start to strip down and rebuild it???

No advice, but commiserations and good luck.

sorry to hear it mate, mine snapped a while back. If you're lucky the only damage will be the push rods which are cheap as chips...if the cam gear hasnt been upgraded like mine wasnt I have a spare if you need it

Normaly as mentioned just replace all the pushrods even if the look straight. replace the tensioner as well whilst in there, good luck

regards

Dave

Thanks for all the moral support guys!

...well this is what I found today...

firstly water ****ed out of the timing housing, I think this failure was a result of leaving in the wading plug...doh .... note to self... remember to remove plug after deep wading.

Every push rod was bent, cam belt was well and truly broke, and only one single rocker was sheared off. All back together now with new parts... engine running but very lumpy. Will play with the timing tomorrow... had enough of it today and need a beer!!!

How did the water get in there in the first place if the plug was fitted?

Shame a rocker was broke, if the engine is running rough it may be an idea to see if another rocker/rockers have hairline cracks that are only opening under pressure when operating the valve. The valves rarely bend as they are vertical in the head, it is possible though that one or two got bent.

Try loosening an injector one at a time to see if you can isolate the cylinder that is down on power, assuming timing is all ok. Unless you have a compression tester to suit a diesel?

regards

Dave

i had water in timing chest on my 90 years ago even with plug fitted, put it down to condensation build up ( i hadn't fitted a breater), maybe thats a crap theory but it goosed my belt tensioner.

The Cam belt went on a Renalt I used to have, when I put ip back together it was also lumpy, turned out I had the belt out by one tooth on one of the places, took it off and rectified it, worked well after that, untill some one stole it!

The pushrods are the weak link in these engines when the belt goes, which is fortunate really. I've worked on a few of these engines when the belt has snapped, and on all occasions the valves have remained intact, so the head can stay on which makes the job easier/cheaper.

As advised, I'd be doubly sure the timing is correct first, it's the most logical reason for the engine running lumpy after the belt has been replaced. Did you lock the pump, crank, and cam sprockets at TDC with a kit before replacing the belt?

Failing that, I'd have another very close look at the rods and rockers to see they're all right.

I'd doubt there's any valve or valve guide damage meaning a sticky valve or a valve not seating, as the valves are mounted vertically on these engines, as opposed to at an angle on DOHC engines they tend not to bend/distort things in the head.

Matt TDi said:

The pushrods are the weak link in these engines when the belt goes, which is fortunate really.

I'd doubt there's any valve or valve guide damage meaning a sticky valve or a valve not seating, as the valves are mounted vertically on these engines, as opposed to at an angle on DOHC engines they tend not to bend/distort things in the head.

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Sadly, the valves can be bent in these disasters because of the huge hollow in the top of the pistons. Even if the piston crowns were dead flat, valves could become bent under such catastrophic stresses. Only a tiny bend is sufficient to kill the compression and cause problems. Battenberg is on the trail with a length of garden hose now, and will tell us which valve it is that is bent, because he can be pretty sure one of them is.

I already told Battenberg that my bet is number three inlet ... I just have a feeling ...

And, I am an expert!

CharlesY

Fooking ell evening CharlesY I thought yu'd drawn ya pension & buggered orf to spain or summat?? It's been a while since yu was on here??

CharlesY said:

Sadly, the valves can be bent in these disasters because of the huge hollow in the top of the pistons. Even if the piston crowns were dead flat, valves could become bent under such catastrophic stresses. Only a tiny bend is sufficient to kill the compression and cause problems. Battenberg is on the trail with a length of garden hose now, and will tell us which valve it is that is bent, because he can be pretty sure one of them is.

I already told Battenberg that my bet is number three inlet ... I just have a feeling ...

And, I am an expert!

CharlesY

Click to expand...

In which case I must be one of the luckiest diesel mechanics around!

I've done (give or take) 4 200s, and 2 300s which have had snapped cambelts in the past 5/6 years, and in all those cases replacing the pushrods and a couple of rockers on occasion, then re-timed and in all cases it's resulted in a complete fix.

I hear what you're saying about how even vertically mounted valves can bend, I have seen that myself, they've bent in a small S shape under the impact, but in the TDis and the Transit (early pushrod ones) engines I'd done at work, they'd all been fine after the rods and rockers were changed, I'd thought that was because the rods took the impact and saved the valves.

As I said, I must be really lucky then.

toyahwilcox said:

i had water in timing chest on my 90 years ago even with plug fitted, put it down to condensation build up ( i hadn't fitted a breater), maybe thats a crap theory but it goosed my belt tensioner.

Click to expand...

I put it down to packington ford the other day in flood, water over the bonnet and splashing 2" up the windscreen for60 meters..!

Well I got out a section of garden hose, (Thanks for the advice Charles) and listened for any hiss on compression. couldnt make it out so... off came the inlet manifold and the turbo to try to get closer into the engine, and I found a large section of the gasket missing on inlet 3 (whether this has always been like this who knows??? or maybe it blew out when the belt went)


I took out the glow plugs to turn the engine over by hand, I felt just the slightest abnormal ressistance on cylinder 3 top compression stroke, so my best guess is that I had got the clearence wrong on the rocker, and indeed it was tight..!

so, maybe this error in tollerence, could now have bent the Valve or the new pushrod....Doh...!!!

anyway, spend all day on it, so tommorow get a new gasket and start the rebuild.

never know a tdi bend a valve when belt has gone and timing correct and was doing at least one a day during the "glory years" of 300's, ie before land rover admitted there was a problem. can bend valves if timing has slipped prior to snapping though. also are al the lash caps in place on top of the valves and not worn through?

the lash caps all seemd fine, but i didnt measure them, I reckon it was the tight tappet, gonna go over them again tomorrow with the feeler guage and reset them. once i get hold of a new manifold gasket

found this link: tappetts - LR4x4 - The Land Rover Forum

should help me set them up better...

Matt TDi said:

In which case I must be one of the luckiest diesel mechanics around!

I've done (give or take) 4 200s, and 2 300s which have had snapped cambelts in the past 5/6 years, and in all those cases replacing the pushrods and a couple of rockers on occasion, then re-timed and in all cases it's resulted in a complete fix.

Click to expand...

Not only you... my neighbour who has about 15 years experience on landrovers, when my mate snapped his cambelt I asked him about that and if more damage could have been done..

he said in about 50 he has done...maybe 2 had more than pushrods and rockers..

CharlesY said:

Sadly, the valves can be bent in these disasters because of the huge hollow in the top of the pistons. Even if the piston crowns were dead flat, valves could become bent under such catastrophic stresses. Only a tiny bend is sufficient to kill the compression and cause problems. Battenberg is on the trail with a length of garden hose now, and will tell us which valve it is that is bent, because he can be pretty sure one of them is.

I already told Battenberg that my bet is number three inlet ... I just have a feeling ...

And, I am an expert!

CharlesY

Click to expand...

Welcome back CharlesY.

In a vehicle as large and heavy as a Disco, I'm guessing that there would be little or no point in balancing rods / valves etc, and opening up the head a little?

I know that it is a stupid question, I know that you know that I know what the answer will be, but I'm asking anyway.

re the bent valves I have done about 10 or 12 of these engines with snapped belts and only 1 had a valve ( I cannot remember if it was no 3 charlesy but your not often wrong) but it can and does happen on occasions.

regards

Dave

well no bent valves...new manifold gasket and rocker gasket, just badly adjusted tappets, so checked them , marked them, checked them again, marked them again, pinned up the pump and flywheel, set the timing... now running sweeter than ever...

...sorted... a beer and a curry to celebrate..!!!