Jump to content
Nigel Triumph

Timing Cover Oil Seal

Recommended Posts

Not strictly a TR6 engine, but a 2500 saloon engine I've recently fitted to my GT6. So to all intents it's the same.

I've got a persistent oil leak from the timing cover seal. I rebuilt the engine before fitting it to the GT6, new seals and gaskets all through, not to mention other much more expensive stuff! After 250 miles the front oil seal was weeping, so when doing the first oil and filter change I took a look. There's a slight wear groove on the crank sleeve where the seal lip runs but I've seen worse. I polished the sleeve with emery and put it back with a new seal. 20 miles more and it's leaking worse than ever, so I've started stripping it out again.

Before removing the timing case, I've measured the clearance between the oil seal opening on the front of the timing case and the crank sleeve. The gap varies around the circumference, 62 thou one side and 54 thou diametrically opposite. To my limited engineering brain, that means the oil seal centreline is 4 thou off from the crank centre line. I've just measured the timing case on the old 2 litre engine pulled from the GT6 and find 56 thou clearance all round; it doesn't leak either.

So please could the wise ones comment? Is a 4 thou offset enough to cause a seal to leak? I think I know the answer... And what should I try next? The timing cover is dowelled in (theoretically) correct alignment, so I'm thinking of offering up up the timing cover from the old 2 litre engine. They are the same part on both engines, so fitting a known good cover and measuring clearance again should show exactly the cause of the misalignment.

All thoughts and suggestions welcome. I really don't want to do this job again and am hoping for 'third time lucky'!

 

Nigel

Share this post


Link to post
Share on other sites

Thank you. I've got a new sleeve though it's a bit tight on the crank nose. Will try heating it before fitting tomorrow. Should have said, I already tried turning the old sleeve around and it was no better.

Nigel

Share this post


Link to post
Share on other sites

I fitted a new sleeve too, and a double lip seal, which keeps the dirt away from the inner lip. But I don’t think that dirt is the issue.

And use some sealant on the sleeve too, as it may leak between shaft and sleeve, especially around the key.

The misalignment (4 thou) doesn’t seem much.

Waldi

Share this post


Link to post
Share on other sites

Thank you Waldi. I'm going to trial fit all again tomorrow. 

Nigel

Share this post


Link to post
Share on other sites

Hi Nigel,

you’re welcome.

I forgot to say, i used a little bit of sealant (hylomar blue) between the cover and the oil seal too, this is normally not needed for an oil seal in a machined bore, but with this steel pressing I did this just to be sure.

And have you checked the crank case pressure? If there is a lot of blow by, or the vent is blocked, oil will be pushed out. If you remove the oil filler cap with a running engine, and there is a lot of oil mist escaping, that would not be right. Cannot  define “ a lot”.

Regards,

Waldi

 

Share this post


Link to post
Share on other sites

Hi Waldi,

Thank you for the extra info. I will use sealant around the new oil seal.

The engine has just been rebuilt, including a rebore, so it's possible it is brathing a bit heavily under load while the new piston rings bed in. Removing the oil filler cap at tickover doesn't show excess pressure or misting.

Nigel

Share this post


Link to post
Share on other sites

Hi Nigel,

The casing pressure should be ok then. On a worn engine, if you press your hand on the filler opening and remove your hand  after say 10 seconds, you hear (feel) a whoesh (strong blow).  (Hope that’s the right expression).

Waldi

Share this post


Link to post
Share on other sites
14 hours ago, Nigel Triumph said:

Not strictly a TR6 engine, but a 2500 saloon engine I've recently fitted to my GT6. So to all intents it's the same.

I've got a persistent oil leak from the timing cover seal. I rebuilt the engine before fitting it to the GT6, new seals and gaskets all through, not to mention other much more expensive stuff! After 250 miles the front oil seal was weeping, so when doing the first oil and filter change I took a look. There's a slight wear groove on the crank sleeve where the seal lip runs but I've seen worse. I polished the sleeve with emery and put it back with a new seal. 20 miles more and it's leaking worse than ever, so I've started stripping it out again.

Before removing the timing case, I've measured the clearance between the oil seal opening on the front of the timing case and the crank sleeve. The gap varies around the circumference, 62 thou one side and 54 thou diametrically opposite. To my limited engineering brain, that means the oil seal centreline is 4 thou off from the crank centre line. I've just measured the timing case on the old 2 litre engine pulled from the GT6 and find 56 thou clearance all round; it doesn't leak either.

So please could the wise ones comment? Is a 4 thou offset enough to cause a seal to leak? I think I know the answer... And what should I try next? The timing cover is dowelled in (theoretically) correct alignment, so I'm thinking of offering up up the timing cover from the old 2 litre engine. They are the same part on both engines, so fitting a known good cover and measuring clearance again should show exactly the cause of the misalignment.

All thoughts and suggestions welcome. I really don't want to do this job again and am hoping for 'third time lucky'!

 

Nigel

Hi Nigel,

You can be fooled into thinking that the timing cover oil seal is at fault as this happen to me but the cause in the end was traced back to the sealing block behind the timing cover where one of the threads was just about to strip and another one was suspect. Both were Heli coiled and the leak was gone. Apparently this is a common fault! I have since found out that TR GB can supply one made out of MS and not Mazak. What are the threads like in yours?

Bruce

Share this post


Link to post
Share on other sites

Hello Nigel

Was going to suggest you check the old sleeve with a dial micrometer to see how near circular it is. Also maybe the hole through it might be slightly off centre. Compare it with the new one. 4 thou would be enough to cause an oil leak. Can you fit the cover in situ without tightening it in place making sure the seal is fitting to the sleeve evenly and gradually tightening it up. If it doesn't fit exactly then is it possible to "adjust" the bolt/dowel holes on the cover a fraction with a file?

I seem to remember back in the 60's using old corn flakes box cardboard as a gasket for the timing cover on a mini. No expense spared in those days!

Keith

Share this post


Link to post
Share on other sites

Thank you all for so many helpful replies.

Bruce, I'm 99% certain it's the timing case seal that's leaking. I fitted a stainless sealing block from Jigsaw when rebuilding the engine, so the threads are good. If it's necessary to change the sealing block, for a GT6 it can only be done with the engine out, so I wasn't prepared to take the risk.

I wasn't supposed to be in the garage this morning but couldn't resist. Checking the old sleeve shows its 1-1.5 thou out of round, whereas a new one is within 0.5 thou. The old sleeve also has a visible wear groove from the seal lip which can just be felt with a fingernail. I've fitted the new sleeve to the crank nose. It's worth noting that the new sleeve needed heating before it would slide onto the crank nose; I've never found that with old ones.

Rotating the crank and remeasuring the gap between timing cover and crank sleeve shows a consistent difference from one side to the other of about 8 thou. Removing and refitting the cover a couple of times made no difference. It's the cover or the dowels in the block that are out of true, not the sleeve.

Following Keith's suggestion I've 'adjusted' the dowel holes in the cover with a round file and I can now get it perfectly aligned. It's going to need some care when I finally tighten the cover bolts as the cover tends to be pushed away from perfect alignment by the thrust from the timing chain tensioner.

Thanks again for all your input.

I will post again when it's reassembled and running to let you know the outcome.

Nigel

Share this post


Link to post
Share on other sites

Not uncommon for the cover not to be flat as others may have used it to leaver against it. 

Share this post


Link to post
Share on other sites
1 hour ago, ntc said:

Not uncommon for the cover not to be flat as others may have used it to leaver against it. 

I'm sure you're right, though I did check it with a straight edge before reassembly.

When I first stripped this particular engine there were enough signs that I wasn't the first person to pull it apart.

The previous time I stripped a Triumph 6 pot engine about 3 years ago, it was obvious that it hadn't been bodged touched since leaving the factory. That engine fitted back together easily and hasn't leaked yet.

Nigel

Share this post


Link to post
Share on other sites

Now I'm intimately acquainted with the 6 cylinder timing cover, here's another thing I've learned recently. The thickness of the cover gasket is important.

Most gaskets sold nowadays are thin, about 0.7mm. Mark Field at Jigsaw told me that original gaskets are thicker, and he's had them remanufactured. I'm using one of his gaskets which is 1.7mm thick.

Maybe the thicker gasket seals better but that's not the point. The gasket also functions as a spacer, without which the duplex timing chain doesn't align properly with the tensioner blade. It's clear from the witness marks that one edge of the chain is almost slipping off the tensioner with a thin gasket.

Worth knowing when rebuilding a 2.5 litre engine with duplex timing chain. It's won't be so important with engines that use a single row timing chain.

Nigel

Share this post


Link to post
Share on other sites

Hi Nigel,

Thanks for that, my tensioner was worn a bit off-centre too. 

Waldi

Share this post


Link to post
Share on other sites

Time for an update...

And it's not great news.

Yesterday, having filed the dowel holes in the timing cover slightly to improve the oil seal alignment with the crank, I reassembled it. I fitted a new sleeve on the crankshaft nose, so the oil seal has a perfect surface on which to run. A new oil seal was carefully pressed into the timing cover with a little sealant around the edges. I oiled the crank sleeve and oil seal lips then refitted the timing cover and carefully aligned it so the oil seal aperture in the cover was centred to the crank sleeve to within 1 thou.

With everything tightened up, radiator back in place and refilled, I nervously went for a test drive. After 10 miles, the seal was leaking again. The clean engine oil dripping out has a black discolouration, presumably due to microscopic particles of seal lip being ground into it. I cleaned it up and drove another 10 miles. Still leaking, though perhaps a little less than at first (and yes, there's still plenty of oil in the engine!).

It is possible for a new oil seal to leak at first then bed in? I'm not counting on it but will drive a bit further today to see what happens.

My expectation is that I will have to pull it apart again and fit another new seal in the timing cover from my 2 litre engine, which did not leak when removed from the car. I can't wait!

 

Nigel

Share this post


Link to post
Share on other sites

Sorry Nigel,

no, it should not leak or have to bed in.

Waldi

Share this post


Link to post
Share on other sites

Hi Nigel,  I am following this topic as I have exaexactly the same problem. I have replaced oil seal twice with double lip version and replaced sleeve, mine still has leak in exacrly the same place as it originally did . I am currently typing this underneath my car (its on a ramp) awaitng  friend to view and try and help. I will let you know if I can fix problem. Not looking forward to removing everything again.

Paul

Share this post


Link to post
Share on other sites

Good luck Paul.

I've replaced this seal on several different Triumph engines in the past. It's never been a problem before, fit the new seal, reassemble, oil leak gone. The only component that hasn't been replaced now is the timing cover itself. By a process of elimination that must be the problem??

Nigel

Share this post


Link to post
Share on other sites

Hi Nigel,

a couple of thoughts:

Is the surface roughness of the new sleeve ok? It should be smooth finish. 

Also, is the lip seal inner diameter correct?

Also, Does the  seal have a steel re-inforcing casted in the rubber?

Sorry for asking this: Have used some oil or grease when sliding the cover with seal over the sleeve?

Good luck, you will solve this.

Waldi

Share this post


Link to post
Share on other sites
2 hours ago, Nigel Triumph said:

Good luck Paul.

I've replaced this seal on several different Triumph engines in the past. It's never been a problem before, fit the new seal, reassemble, oil leak gone. The only component that hasn't been replaced now is the timing cover itself. By a process of elimination that must be the problem??

Nigel

Hi Nigel

I am thinking it might be the case with the timing cover also. I will try the pressure test to see if it is excessive and maybe the problem. If not I will have to source a new cover and will probably suffer the leak until later on in the season and strip it all down again. I did it last time with the bonnet off for ease of access so might do this again as it gives you chance to clean up a few things at the same time, Hey ho TRs are fun.

Paul

Share this post


Link to post
Share on other sites

Waldi,

No problem to ask as many questions as you like! I've used seals from two different but well-know Triumph parts suppliers. The first seal was the best, it only weeped a little clean oil but the second and third seals are from another supplier and leak worse, with the leaking oil discoloured black from the seal. All of them looked similar, though I never examined the first one very carefully as I had no reason to expect this problem. All of them felt like the correct size when fitting into the timing cover and when sliding onto the sleeve. In all cases I lubricated the sleeve and the seal lip with oil. All three seals have a steel ring inside the rubber, plus a circular spring behind the lip.

The new sleeve feels similar to the original for roughness.

Paul,

It's becoming a pain, I'm sure you feel it too! At least for me, working a GT6 access is excellent, and with all the practice I'm getting it doesn't take long to get the timing cover off.

I've talked to a few respected experts, who are all baffled. The proprietor of the machine shop I use is very critical of the quality of some aftermarket oil seals and says he would only fit genuine Payen. Mark Field at Jigsaw has a double lipped seal which I will try next, in the timing cover off my old engine. It's going to be a few days before I get time to change the seal again but will report back in due course.

Nigel

Share this post


Link to post
Share on other sites

Hi Nigel,

we are drying out of options.

Because I have no better idea, I would also replace the cover by another item, as you plan. But I can’t say why you should.

Is there free space behind the seal, when you install the cover on the engine?

The little spiral spring should be facing rearwards, but you know that off course (sorry again).

The black stuff coming with the oil still makes me suspect the sleeve roughness. Maybe polish it with 600 grit   (Or finer) sandpaper?

Waldi

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.