Urgent Help request - Timing problem

[Dave2000]

At this point I would make a cup of tea, then go back out and pull the valve cover, check and record valve clearances. A bent valve will show a gap way too large.

Having said that, I an not entirely sure you have the timing right, anyone about you can call to confirm?

Normally valve damage would be very noisy.

Regards

Dave

 

[Brett]

Hi Dave, thanks for the reply. You are right, it's probably worth checking. It's not particularly noisy, by that, I mean I can't notice any unusual noises over the general diesel engine, pump and exhaust noise. It is however, shaking a lot, missing and billowing thick white smoke, not coolant,I think its diesel.

I can't face it tonight. I'll maybe start stripping it tomorrow.

 

[Towpack]

Don't write the engine off yet. A bent valve is easy enough to diagnose but the symptoms of rough running and excess smoke point more to incorrect injection timing IMO. A bent valve would cause rough running from the obvious loss of compression but smoke?
Not sure wether one tooth out would cause piston/valve contact. These are interference engines but, personally, I wouldn't have thought they are that critical.

 

[Brett]

Hope you are correct Towpack but I'm not very confident it's undamaged.

For info, timing marks are now spot on.

 

[chapel gate]

I've heard that before but it's likely broken something else, I've heard something to do with the cam followers/ rockers can break? Other problem I've also heard (not sure if its true?) you can't source all required components separately from Toyota for a top end rebuild. You have to buy a complete head (new or secondhand).

Im sure you wont be needing them but for reference last year i procured camshaft, valves, rockers, etc for a customer, all still available from toyota.
as dave said, i still dont think you have the timing right.
The world always makes more sense after a brew..

 

[frank rabbets]

You could have just whiskered the valves and bent them very slightly as the engine still runs. I take it the camshaft was retarded by one tooth? That means you would have had to rotate the camshaft clockwise to realign or crank anticlockwise depending on which approach you adopted.

A definitive test would be a compression test. If low compression the tappets need checking to make sure they are not too tight but you say the engine ran OK before soooooooo.

The valves nearly touch the pistons on the overlap TDC where they are both open so one tooth out could bend the valves. I did measure the clearance once but can't find figures. Something like .025 inch.

 

[frank rabbets]

Actually it may not just be a story about bent valves. If you over rev an engine you can bend valves but in that case there is nothing mechanically holding the valve in the wrong position. It's just not closing quick enough. However in incorrect timing the valve is being held in the wrong position by the cam and therefore when the piston hits the valve stresses are transmitted to the valve mechanism. It's all very brittle and not very springy so breakages can occur. Sometimes the cam shaft bearing caps fail. These are the parts which can't be bought separately as they are line bore as one with the cylinder head.

 

[Brett]

Thanks for all the replies Gents,

I'm no further forwards yet.

I'm going to have another look this weekend. Probably going take the rocker cover off and check what's going on.

The engine needs to be rotated twice to get the marks to line up again.

Regards

Dave

Dave, if the 1st rotation lines up the marks but the second rotation doesn't, how do you know which is correct?


,

 

[Dave2000]

Once the marks are lined up, it should be timed correctly but, by rotating clockwise SLOWLY once you will bring the crankshaft mark back in alignment, you will find the pump and camshaft marks are no longer aligned, another slow rotation ALWAYS clockwise and this time when the mark on the crankshaft align the second time, your camshaft and pump marks should be aligned.

It is entirely possible for a camshaft to be 180° out, but doubt this as yours only jumped the one tooth .

The reason to go slow is if something is out of alignment and contact is made between pistons and valves, the engine will simply stop, if rotating fast you run the risk of damage. Rotating clockwise is the natural running direction of most engines and this includes yours. By turning the crankshaft clockwise you are taking out play in gears and slack in the timing belt.

Regards

Dave

 

[Brett]

 

[Brett]

It looks like its only broken the rocker arm on cylinder 2.

 

[Brett]

 

[Dave2000]

Go back to my earlier post and check clearance on the other rockers Brett, this will give an indication of more issues. If not then you have to at least try another rocker before condemning the head, fingers crossed mate.

Regards

Dave

 

[Brett]

Go back to my earlier post and check clearance on the other rockers Brett, this will give an indication of more issues. If not then you have to at least try another rocker before condemning the head, fingers crossed mate.

Regards

Dave

Thanks Dave, I've run out of time today, will check the clearances another day.

 

[StarCruiser]

This tallies with the white smoke. I’ve heard of Vauxhall diesels that break rocker arms and emit clouds of white smoke.

If the diesel gods are on your side you may have 5 bent rocker arms and one broken one rather than bent valves as the hit would have been just before valves close. If you’re really lucky and your valve clearances were a bit sloppy you might have got away with the other rocker arms.

I have my fingers crossed for you.

 

[frank rabbets]

The valves are vertical c/w with the piston so on these engines it's almost impossible to bend a valve. It's like trying to bend a pencil by pushing on its top. You might find the clearances on the other 5 a bit large if those have bent slightly.

Putting the valve rocker shaft on is a nightmare as the rockers dangle everywhere. I used length of string pulled tight under them to keep them all horizontal. Make sure the pistons are nowhere near the top when you bolt back on.

I would pursue the supplier of the tensioner.

 

[Iwan]

That's a sorry to see sight there Brett.

On the 24v you would be able to check the other 22 valves by checking that the valve bridge is level and the clearance gap isn't too big. Then it's possible to very carefully rest a short bar on the cam shaft and lever the rocker by the roller end and carefully compress the valves.. to keep an eye on the valve bridge to see that it'll go down level. That way you will see the valves traveling to determine they're straight and good!

There's a bit of comfort in the fact that the followers break instead of bending valves!

 

[StarCruiser]

There's a bit of comfort in the fact that the followers break instead of bending valves!

From what Frank is saying this looks very much like the scenario. Plus the piston hits two valves instead of one so the forces (though undoubtedly great) are halved but focussed on the single rocker arm hence the break. I have to say I’m impressed/surprised where the break has occurred as I would have guessed under the pivot bar would have been the weak point.

Still got fingers very much crossed for you but I increasingly think the diesel gods may actually be on your side.

As Frank has said, I would pursue the adjuster supplier, so document it well (on here is as good a place as any) photos of everything as you find it and what you need to do to remedy the situation. You never know they could come good if given the chance. Don’t give up the faulty part without obtaining a receipt though.

 

[Brett]

This tallies with the white smoke. I’ve heard of Vauxhall diesels that break rocker arms and emit clouds of white smoke.

If the diesel gods are on your side you may have 5 bent rocker arms and one broken one rather than bent valves as the hit would have been just before valves close. If you’re really lucky and your valve clearances were a bit sloppy you might have got away with the other rocker arms.

I have my fingers crossed for you.

Hi, I haven't measured anything yet, but the engine is still turning by the crank and still runs,although rough. You can see why! The white smoke is clearly unburnt diesel.

I don't think you would actually bend the rocker arms, they are cast and very brittle,if they were going to go, they would snap I think. All the others look ok from a visual point of view but the feeler gauges will tell the tale.

For info, the valve clearances on this engine don't loosen over time, they tighten up. They wouldn't be loose as I when I did them last time, they needed very little adjustment.

 

[Brett]

The valves are vertical c/w with the piston so on these engines it's almost impossible to bend a valve. It's like trying to bend a pencil by pushing on its top. You might find the clearances on the other 5 a bit large if those have bent slightly.

Putting the valve rocker shaft on is a nightmare as the rockers dangle everywhere. I used length of string pulled tight under them to keep them all horizontal. Make sure the pistons are nowhere near the top when you bolt back on.

I would pursue the supplier of the tensioner.

Hi Frank,

I am going to contact the supplier tomorrow, now I know what has happened. I won't name on here yet, but they are very well known and respected. I've been a customer for years.

As a warning to others, the tensioner that failed was supplied in a cam belt kit with a belt and idler pulley. The tensioner is made by the OEM & looks identical to the one supplied by Toyota. I'll post a photo of it.