Lotus Elan

Head to Block Breather Tube Issue

PostPost by: david.g.chapman » Mon Nov 06, 2017 11:27 am

I am in the process of replacing the rubber tube above, because its leaking again.

Out of curiosity I have cut the old one in half, and offered up each half to the block and head holes. The fit in the head is not bad, but could be tighter. The fit to the block hole is appalling, with a sideways movement of nearly 1 millimetre away from the sealing fins!

My block hole diameter is 20mm with a 21.5mm lead-in. The hole has also been reamed out at some stage in the past. I recall from other posts that at least one other owner has the same size hole.

I can get around the problem by super-gluing a thin o-ring in-between two fins, then the tube will be a nice interference fit in the block.

Anyone else noticed this issue? Perhaps other blocks have smaller unreamed holes with a cast finish?

Dave Chapman.
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PostPost by: tonyr27 » Mon Nov 06, 2017 1:49 pm

We fitted a new tube when the head was refitted last winter. It was fine for a couple of months but now leaks very badly from the connection into the head. I've tried pressing silicone sealant and letting it cure, it then lasts for about 10 minutes.
I'm beginning to think it's another Lotus component that has been sourced from China.

Having another go this afternoon.

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PostPost by: alan.barker » Mon Nov 06, 2017 1:55 pm

I make sure i degrease in the head and the block with acetone. Then use loctite silicone and no problems after
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PostPost by: tvacc » Mon Nov 06, 2017 6:39 pm

We fabricated one a few years ago. I made a tube out of two sizes that slipped into each other about the sme diameter as the rubber one that expanded to allow you to slip it in place and then to open up to fit the height. I soldered on a washer top and bottom about 1/4 inch below each end. that allowed me to fit and locate it in each hole. I then use high temp RTV to seal it in place.

Works great. Never have to worry about it again.

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PostPost by: david.g.chapman » Mon Nov 06, 2017 6:56 pm

I was in the process of making up something from a VW engine pushrod tube, but I can see a problem sealing it to the hole in the block, and the o-rings I was thinking of might squeeze out under pressure resulting in a massive oil leak.

The idea of using two tubes is a good one as long as you have the right sizes.

I am fairly confident that my standard rubber tube with a thin o-ring contained in the block hole will work. I have bought some e-z weld black sealant (like RTV but without the vinegar smell) which is oil resistant. This should add some insurance to the sealing.

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PostPost by: tvacc » Mon Nov 06, 2017 7:02 pm

After I pushed up the tube...I used a hose clamp to lock the two tubes together.
I think you are over thinking it. Hi Temp RTV from permatex works great.
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PostPost by: RichardHawkins » Mon Nov 06, 2017 7:27 pm

Dave,

I took the advice of Keith Franck (vintage technology garage) and made two brass hose tails one fits the head, and the other fits the block. Both hose tails have 'O' rings to form a seal. A short length of fluoroelastomer lined silicon hose (from Leyland Hose) then joins the two together.

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PostPost by: seniorchristo » Tue Nov 07, 2017 2:08 am

My engine, a tall block converted before my purchase, has both the block and head sealed at these openings. A breather from the cam cover is the only breather and may be why my car has excessive leaks. Lotus Marques use to offer an aluminum tube which I think sealed with o rings and they guaranteed wouldn't leak if installed properly
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PostPost by: david.g.chapman » Tue Nov 07, 2017 3:13 pm

Thanks for your responses.

My new rubber head to block tube arrived from SJ Sportscars today - and I noticed that its not the same size as the old one I cut up :o

Both the head and the block finned hole entries are at least 1mm bigger, which means I no longer have to think about adding a o-ring to it. The thickness of the tube is also greater, and the whole thing is much stiffer than the old one. So it should fit well.

After larding my sealant on each end and heating up the tube as much as I dared it was time to fit it - with the head on.

Much swearing and sweating then ensued, but I eventually fitted it.

So I would check the dimensions of any new part you buy - they may not be what you expect!

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PostPost by: RichardHawkins » Tue Nov 07, 2017 7:21 pm

Dave,

Your last comment is very good advice. Another Elan owner said "never throw anything away" as you may need it for reference to compare with the new item which you may assume to be correct. I now check everything I possibly can, and still miss stuff that is wrong.

An MG owning friend tells a story about door seals that dont fit. My friend returned these seals to the supplier, who responded "I know the seals don't fit, but people keep buying them so why should I correct them?" We need to be constantly aware of poor quality products.

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PostPost by: cbguerrajr » Thu Nov 23, 2017 5:29 am

I'm also suffering from major oil leaks coming down from the hole at the bottom of the head, where the oil-return / breather hose goes in. I have no desire to take the head off again to fix that, so I have came up with a slight variation on the ideas mentioned above in order to correct the problem with the head still on. I wonder if this has been tried before. I essentially made the standard part adjustable for length by cutting out about 1cm and then using a modified brass garden hose repair coupling to connect them. The coupling had barbs on both sides, but because the internal diameter of the tube is tapered, I removed the barbs on one end so it would fit in the small end (the bottom). so the bottom goes in the block first, with the upper part slid down so that it clears the head, and once in place, the upper half is pushed up to seal against the head and everything secured in place with hose clamps. plan to use plenty of RTV make-a-gasket stuff at all the connections. I suppose removing the carbs and airbox will be necessary to gain access.
Something like in picture below...
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PostPost by: 512BB » Thu Nov 23, 2017 6:49 am

You need to visit the board more often Carlos, great idea.

I can't see that you would need to add sealer at hose clamp ends, they will seal themselves. Just at the head and block, where the rubber tube enters.

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PostPost by: david.g.chapman » Fri Nov 24, 2017 1:23 pm

Nice one Carlos!

Changing the tube with the head on is now much easier, and It also gives the advantage of controlling the vertical pressure the pipe exerts on the block and head.

If I need to change the pipe again with the head on I will consider this.

Cheers,

Dave Chapman.
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PostPost by: miked » Fri Nov 24, 2017 4:18 pm

Neat idea Carlos, simple soloution but clever idea. Mr Chunky would be proud of you, I think. I too would be well happy to use it. I have pulled a few heads to find the rubber pushed over to one side restricting oil return. Always really careful lowering head down on rebuild to avoid problems. I bet there are a few leakers out there with restricted returns.
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PostPost by: borge » Fri Mar 27, 2020 8:24 am

Hi

Has anyone tested this solution for changing the Block Breather Tube made by Carlos G?

breather.JPG and


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