Hydraulic Tappets

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Post Reply
gjb02
Posts: 287
Joined: 20 Jul 2002, 20:37
Location: United Kingdom
My Cars:

Hydraulic Tappets

Post by gjb02 »

Just got my cylinder head back from being refaced, valves cut, seats cut, etc.
On the advisement of the engine specialist I've cracked the pressure of the hydraulic tappets then dismantled, cleaned and reassembled. He told me the tappets would have set themselves to the old position the valve were in, and after the recutting, they will be tighter. So in effect the tappets may not allow the valves to close causing misfires and even bent valves (worst case).
I've heard of air getting trapped, does the air get bled out?? So I need to know if, I have to recharge them with oil, partially recharge or not bother and just let the oil pressure do it for me??
I need a quick answer on this, I have read conflicting ideas on hyd tappets across the Web. And I need to get this thing back together before the weather turns.
oilyspanner
Posts: 1246
Joined: 26 Oct 2003, 16:08
Location: United Kingdom
My Cars:

Post by oilyspanner »

Which Engine is this?
Stewart
wheeler
Posts: 6847
Joined: 21 Sep 2002, 19:07
Location: United Kingdom
My Cars:
x 717

Post by wheeler »

squeze the oil out of the tappets by using a vice to compress them & re fit them,before you start it up crank the engine a few times in bursts of about 5 seconds or so with the spark plugs removed (and the fuel pump disabled) so it can build up oil pressure easily.
alan s
RIP 2010
Posts: 2542
Joined: 26 Jan 2001, 15:53
Location: Australia
My Cars:
x 6

Post by alan s »

My son recently rebuilt a BX 16V engine. Upon reassembling, he was told by the engine rebuilder to take the the small centre piston looking arrangement out of each tappet assembly, individually, wash them give them a few drops of fresh light engine oil, reassemble & test & they should depress in a smooth & resistent manner. Some were rock hard when tested and the centres had to be removed using a pair of pliers used for removing wire type hose clips on washing machines.
I have been told in the past to be very careful of even hair thickness scratches as it will make the tappets rattle.
Ideally, I personally feel that all these hydraulic tappet assemblies should go back in the hole they came out of but in the heat of the moment when disassembling the motor, most just get pulled out of the head & chucked into a box so by now this advice is possibly redundant. I feel that some of the sewing machine sounds that often come out of redone motors is caused by making this basic mistake of not matching the lifters with the aperture they've worn in on.
Alan S
gjb02
Posts: 287
Joined: 20 Jul 2002, 20:37
Location: United Kingdom
My Cars:

Post by gjb02 »

The engine is 2.0 XU10J4 from a ZX 16V, I did keep all the tappets in the correct order. I put them all, individually, in resealable freezer bags and wrote on the labels. I basically dismantled and cleaned each one, I used a 1200 grit to reface the bucket, and the head of the tappet piston. So apart from the light coat of oil for reassembley, they should be left for the oil pressure to fill, yes??
As far as the cams go, is there any further requirement than a good coating of fresh oil before initial cranking?
Thankyou again, I'll get on and reassemble the head now.
alan s
RIP 2010
Posts: 2542
Joined: 26 Jan 2001, 15:53
Location: Australia
My Cars:
x 6

Post by alan s »

There is a special oil that they use when reassembling so as to let everything do a first couple of rotations on a lubed surface. It's the kind of oil that is light but tends to cling.
I suppose if you were using a race engine it would be a necessity but they've been using engine oil for generations on production cars so I really don't think it will do any damage.
Alan S
Post Reply