Hi,
Can someone fill me in on how the hydraulic tappets work [?]
I've seen some photographs, but I can't work out exactly what is going on. I could do with either an exploded diagram, or someone who can tell me how the systems works.
The cam bears on a rocker, I think, but where the fulcrum is and how the hydraulic thing is used is not clear to me.
many thanks,
Russell
2.1 TD hydraulic tappets
Moderator: RichardW
Basically it's a closed cavity - comprised of a small cylinder and spring operated piston - with a non-return valve to fill the cavity with oil.
Once the oil has allowed to get in by the piston moving out (by the spring) - the oil can not get out again - thus the piston stabilises in a certain position when the tappet is fitted - because the piston can not compress the oil.
You then have a self adjusting valve shim.
That's a very rough explanation.
Known problem is if air is allowed to get in during oil starvation - the shim becomes springy - and the associated valve lift accordingly will be less - leading to engine running problems. This should be possible to detect by a certain strange "popping" sond emanating from these tappets during engine idle.
On Gabor's BX DIY site (XM pages) there is a description on this problem : "Changing adjusters - by Nastasic" :
http://www.tramontana.co.hu/citroen/eng ... ngine.html
Also AlanS from aussie has done quite some fiddling with hyd tappets on a BX 16V - he may well have valuable info on any problems you suspect on these hyd tappets.
read about his experience here :
http://citroenz.com/forum/viewtopic.php?t=497
Once the oil has allowed to get in by the piston moving out (by the spring) - the oil can not get out again - thus the piston stabilises in a certain position when the tappet is fitted - because the piston can not compress the oil.
You then have a self adjusting valve shim.
That's a very rough explanation.
Known problem is if air is allowed to get in during oil starvation - the shim becomes springy - and the associated valve lift accordingly will be less - leading to engine running problems. This should be possible to detect by a certain strange "popping" sond emanating from these tappets during engine idle.
On Gabor's BX DIY site (XM pages) there is a description on this problem : "Changing adjusters - by Nastasic" :
http://www.tramontana.co.hu/citroen/eng ... ngine.html
Also AlanS from aussie has done quite some fiddling with hyd tappets on a BX 16V - he may well have valuable info on any problems you suspect on these hyd tappets.
read about his experience here :
http://citroenz.com/forum/viewtopic.php?t=497
Hi Anders,
Many thanks for your reply. Um, I need an explanation even more basic than this, though it has helped, and I can now make some guesses how the valve train operates. But I'm still unclear how or where exactly the rocker is operated by the cam, and the geometry of the whole thing, hydraulic (clearance)lifter, rocker, pivot point, cam and valve.
But I now get the idea that the hydraulic lifter just provides some reference point that always takes up clearance, (somewhere), between a rocker and the cam and valve it operates on. It sounds like it can't possibly go up and down itself, and just takes up clearance, provided the valve is working, or the oil delivery system. And slowly jacks up over time to compensate for wear.
But if air is trapped in the lifter, it presumably takes up a lot of the rocker movement rather than the valve. Can an inlet or exhaust hydraulic lifter be removed and cleaned and replaced without removing the camshaft on the 2.1TD [?]
Cheers
Russell
Many thanks for your reply. Um, I need an explanation even more basic than this, though it has helped, and I can now make some guesses how the valve train operates. But I'm still unclear how or where exactly the rocker is operated by the cam, and the geometry of the whole thing, hydraulic (clearance)lifter, rocker, pivot point, cam and valve.
But I now get the idea that the hydraulic lifter just provides some reference point that always takes up clearance, (somewhere), between a rocker and the cam and valve it operates on. It sounds like it can't possibly go up and down itself, and just takes up clearance, provided the valve is working, or the oil delivery system. And slowly jacks up over time to compensate for wear.
But if air is trapped in the lifter, it presumably takes up a lot of the rocker movement rather than the valve. Can an inlet or exhaust hydraulic lifter be removed and cleaned and replaced without removing the camshaft on the 2.1TD [?]
Cheers
Russell
Whoops, you answered already, the link explains pretty much everything.
http://www.tramontana.co.hu/citroen/eng ... ngine.html
Cheers
Russell[:)]
http://www.tramontana.co.hu/citroen/eng ... ngine.html
Cheers
Russell[:)]