Bent Push Rod

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pos

pos

Well-Known Member
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3,685
Location
West Yorkshire
Hello,

Earlier this year I replaced the timing belt on my 200tdi but I am convinced that something went wrong. All the timing marks lined up correctly with timing pins in place on both the injection pump and the fly wheel BUT...when I got everything setup and removed the pins and turned the engine over by hand, there was a "thwacking" sound like a compressed valve spring shooting back up very very quickly. I stopped, checked all the timing marks again and everything was spot on. I turned the engine over by hand again and all was fine so I left it be. Anyway, a few weeks ago I decided to check the push rods to rule them out as a possible cause of the idle misfire and blue smoke on a cold start and I found one bent push rod. Now my question is this. The timing was spot on according to the marks and the timing pins, I even had a second opinion at the time from a Land Rover mechanic, so what was the thwacking sound and why did I bend a push rod? I have since replaced the bent push rod and reset all the valve clearances, but could I have done some more damage that is causing the occasional hunting / misfire? I'm thinking cam follower / valve?

Any thoughts?
-Tom
 
Monitor the valves clearances for a few weeks to see if any more rods bend.
The if all okay ignore it




Lynall
 
lynall said:
Monitor the valves clearances for a few weeks to see if any more rods bend.
The if all okay ignore it




Lynall
Click to expand...

Thanks Lynall. I will be checking the valve clearances and the push rods again next month. I am a little concerned that I may have already done some damage to a valve / follower though. It only misfires when it's warmed up a bit (it idles perfectly from cold) but it bellows out blue / white smoke from a cold start. There is no blow-by.

-Tom
 
Hi Tom,

Think of it this way, when you setup the timing you are setting it up for the whole system, it repeats itself for the other 3 cylinders. So if the timing was shot it would have bent 4 rods. It sounds to me like the rod was damaged some other way.

Could have been caused by a stuck lifter for example, or some other sort of mechanical interference.

If the new rod is in and working fine, I would do as suggested above, then pull the rod and see if it's still OK. If it is I would think the issue has sorted itself, or it was caused during work being done on the engine. Have you ever had the rod out before? Was the valve clearance OK albeit on the bend rod?

There are quite a lot of things that can cause this, can you think of any anomalies with your engine, also did it fix your smoke on idle?
 
Last edited:
discomania said:
Hi Tom,

Think of it this way, when you setup the timing you are setting it up for the whole system, it repeats itself for the other 3 cylinders. So if the timing was shot it would have bent 4 rods. It sounds to me like the rod was damaged some other way.

Could have been caused by a stuck lifter for example, or some other sort of mechanical interference.

If the new rod is in and working fine, I would do as suggested above, then pull the rod and see if it's still OK. If it is I would think the issue has sorted itself, or it was caused during work being done on the engine. Have you ever had the rod out before? Was the valve clearance OK albeit on the bend rod?

There are quite a lot of things that can cause this, can you think of any anomalies with your engine, also did it fix your smoke on idle?
Click to expand...

Hi Disco,

That was my thinking too. The engine runs and revs beautifully, it is just problematic at idle and bellows out white / blue smoke from cold starts, so there has been no progress made on this front. I have now had my injectors rebuilt and checked with good quality nozzles and they are all spot on. I have checked and set the valve clearances twice within the last year but there would be no harm in checking them all again. I will be taking all of the push rods out again just to check that they are all straight. If I do happen to find another bent push rod, what would you suggest the problem may be? Are there any visible checks that I can do on the cam follower assembly looking down the push rod hole? The idle problem is still very inconsistent. Sat at traffic lights ten minutes ago it stopped and idled perfectly and then I could feel and hear the engine starting to struggle a little. It then drops down into what I would describe as a lower, rougher idle and the engine bobbles around quite a lot, missing every now and again. What in the hell is going on here, could I have a damaged lifter? The lift pump, injection pump and fuel lines are all new with no air in the fuel line between the filter housing and the injection pump.

Thanks,
-Tom
 
Last edited:
Can't see how it could cause the problem, but is the follower the correct way around....need to lift the head to check though :(
 
Badger said:
Can't see how it could cause the problem, but is the follower the correct way around....need to lift the head to check though :(
Click to expand...

None of the followers have been removed and it ran well previously. I will check the rocker is not showing any signs of wear / failure, take the rods out to check that they're all straight and if that shows nothing up, I'll begin stripping it ll down.

Thanks,
-Tom
 
It is a strange one, if more than one had failed then it'd point to a bigger problem, but for one to fail then one Cam lobe/Follower/rocker/valve has to have stopped doing what it was whilst everything else carried on...

did you check the clearance on the rockers when you put the new rod in, perhaps the locking nut worked loose...?
 
Badger said:
It is a strange one, if more than one had failed then it'd point to a bigger problem, but for one to fail then one Cam lobe/Follower/rocker/valve has to have stopped doing what it was whilst everything else carried on...

did you check the clearance on the rockers when you put the new rod in, perhaps the locking nut worked loose...?
Click to expand...

I know, it's had me scratching my head for months :doh: I think the most logical step would be to do both a compression test and a leakage test. At least then, if there are any problems internal to the engine, I can single out the cylinder(s) at fault and tackle the problem directly. Of course, I might get a bit carried away and re-ring it with new big end shells etc. whilst I've got the head off. To answer your question:- Yes, I did check and "fine tune" the valve clearance for the new pushrod, I worked through them all. I will check them out again next week.

Thanks,
-Tom
 
Chrisfrain2007 said:
Did you defo set tappet on correct stroke?
Click to expand...

Good question! As far as I am aware I did yes. I work on the principle of having piston no.1 at top dead centre, so both valves are rocking and then I move to cylinder 3..4,2. Rule of 9 works best but I didn't use it last time. I will be giving them another look over.

Thanks,
-Tom
 
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