Cam chain tensioner

[Zxrob]

Evening all

Quick question

I,ve got an oil weep from the chain tensioner, @Carolyn has very kindly provided me with the "O" ring and once I clear the garage to get the car in, its one of the things on my to do list, now, quickly reading a few "how too's,  it appears you dont have to set any of the pistons to TDC, is that correct

Cheers Rob

[Joesson]

@Zxrob
I've done this twice on two different 2's and did not set a piston to TDC.
The definitive "How to" produced by @Carolyn is on here in Academy / How to :
/ Your chain tensioner :

https://www.mr2roc.org/forum/index.php?topic=56959.0

[scm2004red]

About to do mine following the "how to", nobody mentions a gasket or sealant on the tensioner flange, seems the logical thing to do to prevent oil leaks?

[Joesson]

@scm2004red
I believe the @Carolyn How To specifically says do not do this.
The seal is effected by the ( correctly sized) O ring in the port so no external gasket or sealant is required or necessary.

[scm2004red]

I think the Carolyn advice is not to ease the tensioner flange out slightly and squirt sealant around it and retighten, ie without fully removing the tensioner, advice I would agree with.

My comment was to query why a gasket/sealant was not used when replacing the unit, would seem a more long term solution rather than relying upon an O ring.

[Zxrob]

@Zxrob
I've done this twice on two different 2's and did not set a piston to TDC.
The definitive "How to" produced by @Carolyn is on here in Academy / How to :
/ Your chain tensioner :

https://www.mr2roc.org/forum/index.php?topic=56959.0

Yeh, read that, I was just wandering as am I in the process of shim adjustment on one of my motorbikes and you always set #1 or #4 piston to TDC to remove the tensioner

EDIT
Forget the above, i'm removing the cams, sorry, its been a long day

Cheers Rob

[Carolyn]

I think the Carolyn advice is not to ease the tensioner flange out slightly and squirt sealant around it and retighten, ie without fully removing the tensioner, advice I would agree with.

My comment was to query why a gasket/sealant was not used when replacing the unit, would seem a more long term solution rather than relying upon an O ring.

Over the years. quite a few folk have tried sealant and not got a result.  The oil you're keeping back is under pressure and it has away of getting past the flange, if the O ring is not doing its job. O rings are a proven sealing method in high-pressure situations - they are used in hydraulic systems up to many bar.

[scm2004red]

For clarity, it was not my intention to do away with the O ring, but to utilise the flange joint as an additional joint seal ( I hate oil leaks!), and I am not keen on metal to metal bare joints.

[Joesson]

I think the Carolyn advice is not to ease the tensioner flange out slightly and squirt sealant around it and retighten, ie without fully removing the tensioner, advice I would agree with.

My comment was to query why a gasket/sealant was not used when replacing the unit, would seem a more long term solution rather than relying upon an O ring.

My response was:
I believe the @Carolyn How To specifically says do not do this.
The seal is effected by the ( correctly sized) O ring in the port so no external gasket or sealant is required or necessary.

To explain:
While the tensioner assembly is not part of a hydraulic system, in the true sense of the term, the assembly is subjected to "hydraulic" pressure/ the crank case pressure. In an hydraulic system seals are used, rather than gaskets or sealants, as they provide a resistance to the hydraulic forces that, because of the seal design and shape, increases with the applied pressure. A gasket or sealant is reliant upon the clamping pressure of the components.
The chain tensioner mounting flange is not designed to provide such clamping pressure.
An O ring could, in theory be used between the face of the mounting flange and the opposing face if both were machined to accept an O ring. However this arrangement is prone to failure as it relies on a clamping force that if insufficient or lessens will cause the O ring to deform and exude between the clamping plates causing leakage.
(I have seen, rectified and reported on the effects of such a failure in a relatively high pressure hydraulic safety system. It is not a fail safe solution).
A correctly sized O ring used on the shaft of the tensioner, will when subjected to pressure act to effectively seal against that pressure. Any failure in this condition would be gradual and due to ageing and consequent deterioration of the elastic qualities of the seal.
Components designed and machined to accept a sized and ( material) specified O ring is the accepted method of sealing a shaft in a bore, this sealing effect can be enhanced by the use of chevron type seals where the shaft is sliding in a bore.
NB. In some service circumstances it may be necessary to abrade the bore to remove residue or mechanical damage. Any such abrasion should be fine and circumferential as longitudinal abrasion tracks could form a path for the fluid.

[Carolyn]

I think the Carolyn advice is not to ease the tensioner flange out slightly and squirt sealant around it and retighten, ie without fully removing the tensioner, advice I would agree with.

My comment was to query why a gasket/sealant was not used when replacing the unit, would seem a more long term solution rather than relying upon an O ring.

My response was:
I believe the @Carolyn How To specifically says do not do this.
The seal is effected by the ( correctly sized) O ring in the port so no external gasket or sealant is required or necessary.

To explain:
While the tensioner assembly is not part of a hydraulic system, in the true sense of the term, the assembly is subjected to "hydraulic" pressure/ the crank case pressure. In an hydraulic system seals are used, rather than gaskets or sealants, as they provide a resistance to the hydraulic forces that, because of the seal design and shape, increases with the applied pressure. A gasket or sealant is reliant upon the clamping pressure of the components.
The chain tensioner mounting flange is not designed to provide such clamping pressure.
An O ring could, in theory be used between the face of the mounting flange and the opposing face if both were machined to accept an O ring. However this arrangement is prone to failure as it relies on a clamping force that if insufficient or lessens will cause the O ring to deform and exude between the clamping plates causing leakage.
(I have seen, rectified and reported on the effects of such a failure in a relatively high pressure hydraulic safety system. It is not a fail safe solution).
A correctly sized O ring used on the shaft of the tensioner, will when subjected to pressure act to effectively seal against that pressure. Any failure in this condition would be gradual and due to ageing and consequent deterioration of the elastic qualities of the seal.
Components designed and machined to accept a sized and ( material) specified O ring is the accepted method of sealing a shaft in a bore, this sealing effect can be enhanced by the use of chevron type seals where the shaft is sliding in a bore.
NB. In some service circumstances it may be necessary to abrade the bore to remove residue or mechanical damage. Any such abrasion should be fine and circumferential as longitudinal abrasion tracks could form a path for the fluid.

Actually -the tensioner IS part of a hydraulic system as the tension is applied by oil pressure.

[Joesson]

I think the Carolyn advice is not to ease the tensioner flange out slightly and squirt sealant around it and retighten, ie without fully removing the tensioner, advice I would agree with.

My comment was to query why a gasket/sealant was not used when replacing the unit, would seem a more long term solution rather than relying upon an O ring.

My response was:
I believe the @Carolyn How To specifically says do not do this.
The seal is effected by the ( correctly sized) O ring in the port so no external gasket or sealant is required or necessary.

To explain:
While the tensioner assembly is not part of a hydraulic system, in the true sense of the term, the assembly is subjected to "hydraulic" pressure/ the crank case pressure. In an hydraulic system seals are used, rather than gaskets or sealants, as they provide a resistance to the hydraulic forces that, because of the seal design and shape, increases with the applied pressure. A gasket or sealant is reliant upon the clamping pressure of the components.
The chain tensioner mounting flange is not designed to provide such clamping pressure.
An O ring could, in theory be used between the face of the mounting flange and the opposing face if both were machined to accept an O ring. However this arrangement is prone to failure as it relies on a clamping force that if insufficient or lessens will cause the O ring to deform and exude between the clamping plates causing leakage.
(I have seen, rectified and reported on the effects of such a failure in a relatively high pressure hydraulic safety system. It is not a fail safe solution).
A correctly sized O ring used on the shaft of the tensioner, will when subjected to pressure act to effectively seal against that pressure. Any failure in this condition would be gradual and due to ageing and consequent deterioration of the elastic qualities of the seal.
Components designed and machined to accept a sized and ( material) specified O ring is the accepted method of sealing a shaft in a bore, this sealing effect can be enhanced by the use of chevron type seals where the shaft is sliding in a bore.
NB. In some service circumstances it may be necessary to abrade the bore to remove residue or mechanical damage. Any such abrasion should be fine and circumferential as longitudinal abrasion tracks could form a path for the fluid.

Actually -the tensioner IS part of a hydraulic system as the tension is applied by oil pressure.

Thank you Carolyn, to my mind that reinforces my comments and will hopefully satisfy the OP.

[scm2004red]

I suspect we have drifted away from the query posed by the OP, who seems to have resolved his own problem!

However, thanks for all the erudite explanations which I am sure make absolute sense, but to satisfy my own peace of mind, (and many years classic restoration experience) the flange may get a smear of RTV sealant.