Engine sealing

[kstrutt11]

After putting it off for a year I finaly got round to stripping my engine ready to repace the water pump with home made cartridge type, and fix some of the oil leaks, good news is it all came apart with no problems and internally looks clean and in very good order, the main oil leaks being between the front cover and block and rubber the grommet between head and block at the rear.

The oil leak around the front cover is the one that worries me, it's pretty clear the paper gasket was not sealing very well and is soaked in oil, also the backplate is not perfectly flat which does not help. With only 4 fixings and placed as they are I can't really see how there is ever going to be a even clamp load on the gasket. My thought is to ditch the gasket and use a bead of RTV around the water pump hole , across the top and down each side, my reasoning being it works on most modern engines and therefore should work on this, has anyone else tried this?

Kevin

[Jeff@Jae]

I really don't know why your front covers have a paper gasket between them because they never did originally. Use your favorite sealer (Hylomar works great) instead of the gaskets and be sure to lap down the cover surfaces. There is a waxy paper gasket between the rear plate and the block and I use Permatex Hi-Tac there myself along with the gasket paper. Another chronic leak source is the area between the head/block/front cover where the oil feed to overhead cams is located. The well is outside the crush ring of the head gasket and always produces a leak. We weld that kidney shaped well up, surface the head and drill a restricted passage well within that crush ring at an angle with a small plug for the vertical drilling.

[bcmc33]

Proper advice to use good RTV and not a gasket.

Something silly to remember - don't let the RTV block the oil hole that lubricates the timing chain. Difficult to understand how - but it has been known to happen.

[69S4]

After putting it off for a year I finaly got round to stripping my engine ready to repace the water pump with home made cartridge type, and fix some of the oil leaks, good news is it all came apart with no problems and internally looks clean and in very good order, the main oil leaks being between the front cover and block and the rubber grommet between head and block at the rear.

The oil leak around the front cover is the one that worries me, it's pretty clear the paper gasket was not sealing very well and is soaked in oil, also the backplate is not perfectly flat which does not help. With only 4 fixings and placed as they are I can't really see how there is ever going to be a even clamp load on the gasket. My thought is to ditch the gasket and use a bead of RTV around the water pump hole , across the top and down each side, my reasoning being it works on most modern engines and therefore should work on this, has anyone else tried this?

Kevin

Like you I've had oil leaks around the front cover area. Nothing that a bit of wiping down from time to time couldn't cope with but annoying just the same. As I'm replacing the water pump at the moment as well I've been taking a look at the cover components trying to work out where the oil has been coming from. The joint between the cover and the backing plate doesn't have a gasket so sealing depends on metal to metal contact - usually assisted with some kind of sealing compound. Bolting mine together on the bench and checking the joint with feeler gauges revealed loads of gaps. The chain tensioner / carb side wasn't bad with a max of around 2 thou but the dynamo / exhaust side was all over the place with up to 10 thou gaps in places.

A bit of careful analysis and resurfacing has it down to a consistent 1-2 thou all round with everything test bolted-up on the block so the next decision is which sealant to use. As I understand it stuff like Hylomar / Wellseal etc will cope with gaps around 1-2 thou but not much more whereas RTV based ones will work with larger gaps (up to 10 thou?) and cope better with eg thermal expansion movement but not with very narrow (under 2 thou) gaps as it gets squeezed out to the point where there's none left when the components are bolted together. Before, with gaps varying between zero and 10 thou, nothing was going to work for long so it probably explains the oil leaks. Delving back in the archives, trying to see what others have used, has been the usual mix of conflicting answers with advocates for both RTV and "normal" sealants. Those of you who remember Keith Franck may recollect his suggestion that RTV was the way to go but to overcome the squeeze-out problem by cutting a slot in the middle of the mating faces where the RTV could form a thicker layer. Sounds sensible (to me anyway) but does it work? Anyone tried it?

Any input from those of you with greater experience in this area would be more than welcome. As usual I'm just floundering in the dark!

[gordont]

I always thought ?t's a lotus" they all leak..

[bcmc33]

I always thought ?t's a lotus" they all leak..

Only when not assembled properly. I had a small leak after I put the engine back together last year - totally my fault, and easily fixed.

However, having said this, I do have a problem getting the dipstick/tube not to leave traces of oil along the top of the engine/sump line. I have what I thought was a nice seal between the dipstick and tube via a rubber plug cap, but it's not totally effective. I proved this by putting a piece of kitchen roll around the tube and found that it did in fact collect some traces of oil.

[GrUmPyBoDgEr]

Delving back in the archives, trying to see what others have used, has been the usual mix of conflicting answers with advocates for both RTV and "normal" sealants. Those of you who remember Keith Franck may recollect his suggestion that RTV was the way to go but to overcome the squeeze-out problem by cutting a slot in the middle of the mating faces where the RTV could form a thicker layer. Sounds sensible (to me anyway) but does it work? Anyone tried it?

Any input from those of you with greater experience in this area would be more than welcome. As usual I'm just floundering in the dark!

Having recent experience with liquid sealants on modern car engines I can back up the statement made by Keith Franck.
The groove method has been used to seal the joint between crankcase upper & lower halves where, due to the crankshaft main bearings a precision joint is mandatory.
However the sealant is normally injected into the groove after the parts have been fitted together.
More commonly for other less critical joints a simple chamfer on the inner edge of one of the components will provide a Vee shaped area where a bead of sealant will be retained & not squeezed out.
The reasoning behind these design solutions is that the differential thermal expansion of the two mating components places shear forces on the sealant & a thin or barely existent film of sealant will break down & result in a leak.
The prescribed bead of sealant will be able to compensate for the joint movement without breaking down.
The Vee form is cheap to manufacture & is often already present on components such as pressed steel oil pans; where the bend radius at the intersection of the fixing flange & sump provides sufficient volume for the liquid sealant.
There is of course a proviso; excessive sealant can/will part company from the components & eventually end up, amongst other places, in the oil pick-up sieve, the results of which are to say the least variable

Cheers
John

[twincamman]

if you want something that does not leak and is comfortable buy a caddy --ed

[69S4]

Having recent experience with liquid sealants on modern car engines I can back up the statement made by Keith Franck.
The groove method has been used to seal the joint between crankcase upper & lower halves where, due to the crankshaft main bearings a precision joint is mandatory.
However the sealant is normally injected into the groove after the parts have been fitted together.
More commonly for other less critical joints a simple chamfer on the inner edge of one of the components will provide a Vee shaped area where a bead of sealant will be retained & not squeezed out.
The reasoning behind these design solutions is that the differential thermal expansion of the two mating components places shear forces on the sealant & a thin or barely existent film of sealant will break down & result in a leak.
The prescribed bead of sealant will be able to compensate for the joint movement without breaking down.

Cheers
John

So, it sound like 5 mins with a grinding disc on my Dremmel, a tube of RTV and all my oil leak problems may be over

Actually given the gaps that I found between the front cover and the backing plate I'm surprised how little oil actually came out. I'm pretty sure I used Wellseal on the joint, as well as on the backing plate gasket, last time so some of the larger gaps would not have remained sealed. With the chain thrashing around in there I'd have thought oil would have been plastered everywhere and been oozing out of the gaps in some quantity. Is the little oil hole the major supply in the area or does it mainly come in from top?

[GrUmPyBoDgEr]

Having recent experience with liquid sealants on modern car engines I can back up the statement made by Keith Franck.
The groove method has been used to seal the joint between crankcase upper & lower halves where, due to the crankshaft main bearings a precision joint is mandatory.
However the sealant is normally injected into the groove after the parts have been fitted together.
More commonly for other less critical joints a simple chamfer on the inner edge of one of the components will provide a Vee shaped area where a bead of sealant will be retained & not squeezed out.
The reasoning behind these design solutions is that the differential thermal expansion of the two mating components places shear forces on the sealant & a thin or barely existent film of sealant will break down & result in a leak.
The prescribed bead of sealant will be able to compensate for the joint movement without breaking down.

Cheers
John

So, it sound like 5 mins with a grinding disc on my Dremmel, a tube of RTV and all my oil leak problems may be over

Actually given the gaps that I found between the front cover and the backing plate I'm surprised how little oil actually came out. I'm pretty sure I used Wellseal on the joint, as well as on the backing plate gasket, last time so some of the larger gaps would not have remained sealed. With the chain thrashing around in there I'd have thought oil would have been plastered everywhere and been oozing out of the gaps in some quantity. Is the little oil hole the major supply in the area or does it mainly come in from top?

I had a little chuckle at that
Yes I was referring to my experience with modern engine designs but it's no too long ago that liquid sealants were treated as black magic or just unheard of.
The poor old twincam's front cover was drawn up (designed?) as a way to convert a stock Ford engine to take a TOHC cylinder head & although it fulfills that purpose it doesn't do it very well on any count, sealing being just one of its problems.
However I don't see why certain liquid sealants should not provide a solution even with that component.

Cheers
John

[Robbie693]

I believe Brian Buckland makes his own gaskets for the front cover, mentioned in his book. He wrote that despite many people saying there shouldn't be a gasket there and will cause trouble if there was (no idea why?) he hasn't had any problems..

Robbie

[bcmc33]

I believe Brian Buckland makes his own gaskets for the front cover, mentioned in his book. He wrote that despite many people saying there shouldn't be a gasket there and will cause trouble if there was (no idea why?) he hasn't had any problems..
Robbie

Not exactly the same issue, but Ford deleted the gasket on the English diff casing as it was found to be the root cause of leaks. (I'm sure someone here will know exactly when this took place).
When I took the Elan diff apart a couple of years ago it had a gasket - it was reassembled with RTV only. And the new engine I'm building will also have the front plate and cover with RTV only. But I must remember not to make a mistake with the cover to head silicone gasket this time.

[kstrutt11]

Thanks for all the replies, Mine was fine between the two halves of the cover (had silicone on this joint) it was the back plate to block that leaked, I am going to go for silicone in both places and see how this works.

[elansprint71]

Ach.... all this talk about gaskets and modern sealants.... the problem was solved years ago by Ford at Boreham on the Twin-Cam Escort rally cars.... the answer is.... cotton wool and yellow road-marking paint. I thought you guys were supposed to be experts!


Think I'm making this up?

I just read it on page 64 of Miles Wilkins' T-C engine bible.

[GrUmPyBoDgEr]

I suppose the simple solution is to wrap the whole thing up in a nappy (diaper) & just change it occasionally
Applies only for Baby Elans of course

By the way, why the so regular use of:-

Cheers
John