1hdfte timing belt replacement question

[Wawanderer]

Hi all,
Can anyone please tell me why the manual says to rotate the engine so the BDC marks line up instead of using the TDC marks ?
What is the reason for not using the TDC marks when changing the timing belt ?
Cheers

 

[Petunia]

You are in the southern hemisphere?

Wild guess number 2: the ......... nope no idea, if tdc and bdc are both marked and while your back is turned the naughty pixies rotate one component 180 ? how the hell you know? two sets of marks equals confusion, one set is bad enough?

 

[dno67]

It could be to do with the pump timing, l know my hilux's pump will ramp over if not careful. One of the easiest ways to be safe is mark with a paint pen both the belt and pulleys before removal. Then transfur the mark from the old belt to the new, then refit lining up all the mark the same as before removing the old belt.

 

[Petunia]

It could be to do with the pump timing, l know my hilux's pump will ramp over if not careful. One of the easiest ways to be safe is mark with a paint pen both the belt and pulleys before removal. Then transfur the mark from the old belt to the new, then refit lining up all the mark the same as before removing the old belt.

Been there done that, one tooth out an that infernal engine czech light chucks a mental, not to mention the sounds the injectors emit, it will fire and run, but sounds all wrong.

I reasoned if there are infact marks on bdc, another piston will be at tdc and the pump is going to do the same? no?

 

[dno67]

Been there done that, one tooth out an that infernal engine czech light chucks a mental, not to mention the sounds the injectors emit, it will fire and run, but sounds all wrong.

I reasoned if there are infact marks on bdc, another piston will be at tdc and the pump is going to do the same? no?

Being a fourstroke diesel, only one cylinder only will be on the firing stroke. Dose the pump fire a shot on every cycle ?

 

[Petunia]

Being a fourstroke diesel, only one cylinder only will be on the firing stroke. Dose the pump fire a shot on every cycle ?

we time the engine at TDC number one, the pump is squirting number one, we time the engine at bottom of the stroke, another piston is up raring to go and the pump is ready with tension on it to squirt the next one in the order, so i see no difference regarding BDC being simpler or stop ramp over?

 

[dno67]

Yer, don't know. Possibly worded like that, as best practice. Or it could be a carry over (copy) from the engine assembly procedure. I just mark the belt and pulleys and don't worry too much.

 

[Wawanderer]

Thank for all the replies.
As it turns out, having the No1 piston at BDC means none of the other piston are at TDC so there is no chance of any valves contacting a piston should the cam shaft move for any reason while undoing the cam pulley. Also the "square" section on the cam shaft for a spanner to fit and hold the cam shaft while undoing or tightening the pulley bolt lines up better at BDC.
As far as changing the Timing belt having the engine at TDC it is doable however a bit more care is needed.
I changed the timing belt, water pump, thermostat, idler and tensioner so I'm all good for the next 150,000km