Tappet chest gasket replacement

[Rose taupe]

Yes I have the dreaded oil leak coming from the tappet chest and I would like to know from anyone who has replaced these gaskets, what is the easiest way to replace them, ( do I need to remove the manifolds )
Thanks.

[les]

You should be able to get to them. Why not try before dismantling anything else, if you can’t, then yes remove the manifold.

[svenedin]

You don’t have to remove the manifolds but you need to be able to see what you are doing so some illumination from underneath is useful. It’s a very common place for a leak. Don’t over tighten the bolt and remember to clean up the mating faces. There’s a rubber washer round the bolt under the cup washer too and oil can leak there as well as from a failed gasket.

Stephen

[Rose taupe]

Thank you for the advice, I shall give it a go.

[philthehill]

The rubber washer under the cup washer is only fitted to 1098cc 'A' Series engines. The earlier 'A' Series engines had a plain fibre washer.
The cover bolts are different lengths for the concave and convex tappet covers.
Not all the parts are interchangeable.

[mike1864]

I'd get the gasket securely fitted to the cover first, using gasket sealant. I've found that if you fit it to the head first, it can misalign into the cover's groove.
This happened to me once, with the gasket twisting 45 degrees along some of its length, and oil leaking out from the resulting edge contact, and spraying all over the engine (and France!).
I only discovered the cause when a generous top-up (at Dover) dribbled straight out the offending section.
Also, don't rely on an old gasket. The cork may have dried out, and they can shrink so much that they clearly won't fit!
And - unless recently done - I'd check/adjust the valve clearances while you've got the access.

[myoldjalopy]

I'd get the gasket securely fitted to the cover first, using gasket sealant. I've found that if you fit it to the head first, it can misalign into the cover's groove.
This happened to me once, with the gasket twisting 45 degrees along some of its length, and oil leaking out from the resulting edge contact, and spraying all over the engine (and France!).
I only discovered the cause when a generous top-up (at Dover) dribbled straight out the offending section.
Also, don't rely on an old gasket. The cork may have dried out, and they can shrink so much that they clearly won't fit!
And - unless recently done - I'd check/adjust the valve clearances while you've got the access.

Yes, but the OP is referring to the tappet chest gaskets, not the rocker cover gasket......

[svenedin]

I'd get the gasket securely fitted to the cover first, using gasket sealant. I've found that if you fit it to the head first, it can misalign into the cover's groove.
This happened to me once, with the gasket twisting 45 degrees along some of its length, and oil leaking out from the resulting edge contact, and spraying all over the engine (and France!).
I only discovered the cause when a generous top-up (at Dover) dribbled straight out the offending section.
Also, don't rely on an old gasket. The cork may have dried out, and they can shrink so much that they clearly won't fit!
And - unless recently done - I'd check/adjust the valve clearances while you've got the access.

Yes but if it’s a 1098cc later engine the tappet chest gaskets are neoprene and much better than cork.

Stephen

[Andmurph]

I am going to start addressing the pickup oil leaks on Wednesday. I’ve done the front seal earlier in the year and the timing cover remains dry. Front of the sump is wet as is the rear engine plate so I’m going to do the sump and the Tappet chest gaskets.
I have all the seals and gasket sets but have never done Tappet chest seals before. Do they benefit from sealant or are they good with just a little rubber grease to hold them in place?

I fear this is just the start of a bigger endeavour but if the top of the engine and sump are crucial be an improvement and easier to spot emerging issues.

Behind the rear engine mount is badly covered in thick oil and grime. Perhaps an earlier leak but I do get two distinct puddles underneath the jiggle pin. One black and one clear oil. I’m hoping that they can wait for warmer weather so I can get the Midget out and make space in the garage.

[svenedin]

I can see that you have the 1098cc convex covers. Are you using neoprene or cork gaskets? If neoprene (and good quality) they are retained by the lip in the cover and sealant is not necessary. Having said that, I did once have some neoprene gaskets that were a poor fit due to being the wrong size! Note that there should be a rubber seal under the bolt cup washer. Don’t overtighten the bolt as it tears up the rubber washer and can distort the gasket.

Stephen

[philthehill]

The 1098cc covers should not be fitted with the flat cork gaskets as the gaskets are not thick enough. With the 1098cc covers you should always fit the neoprene seals. The neoprene seals in the cup washers under the heads of the cover bolts should also be replaced.

[Andmurph]

Thanks Stephen, Phil.
I have new neoprene gaskets, seals and cup washers. Hopefully a fairly quick job then. I want to be sure the outside engine is dry from oil. The dipstick tube is well past its best and will also be replaced. I have it in the freezer currently. I replaced the one on the Midget last year and it was a mighty tight fit. I bent the first one I tried when it was 3/4 in. A week in the freezer definitely helped.

Cheers

Andrew

[brixtonmorris]

Regarding Andmurph's photo of the excessive oil from the rear of the engine.

Oftern this is caused by worn engine main bearings.

When the bearing is worn it allows excessive oil to flow between the crank and the big end bearing.

Shown by oil on the back plate and from the split pin in the gearbox housing.

There is no oil seal fitted to the gearbox end of the crank.

An archimedean spiral is cut into the crank to try and send the oil back into the sump.

A crank regrind and new bearings will slow the leak down.

But it will never be 100%

[Andmurph]

Replacing the tapper chest gaskets, dipstick tube and sump gasket seems to have fixed the worst of it. The engine and backplate are now clean and dry after 600 miles. There’s a small leak of clean oil from the split pin and the gearbox oil level was 1/2 inch below the threads. I’ve topped up for now and will investigate when it’s warmer and I can pull the engine and gearbox and change the clutch.

Many thanks

Andrew

[svenedin]

Replacing the tapper chest gaskets, dipstick tube and sump gasket seems to have fixed the worst of it. The engine and backplate are now clean and dry after 600 miles. There’s a small leak of clean oil from the split pin and the gearbox oil level was 1/2 inch below the threads. I’ve topped up for now and will investigate when it’s warmer and I can pull the engine and gearbox and change the clutch.

Many thanks

Andrew

Good news. Well done!

Another cause of persistent engine oil leaks is unrelieved crankcase pressure from a blocked engine breathing system or from a very worn engine (piston blow-by). This usually manifests itself with oil leaks from the back of the engine but in severe cases the leaks can be from all over the place.

The clean oil you notice from the jiggle pin is obviously gear box oil as you noticed the gearbox oil was a little bit low. That can be investigated by peering in to the gearbox bell housing by removing the rubber side bung opposite the clutch fork. Unfortunately, if it is likely to be the first motion shaft oil-return scroll that is worn but it is possible you have a modified gearbox front plate with a neoprene lip seal. Another possibility is the gearbox front plate gasket but less likely.

Stephen