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Geoffrey Navin

Bmc1.8

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My brother and I have a small fishing boat with a bmc 1.8 and we recently did a top end rebuild because we were losing oil through the exhaust  but we have found after only two hours running we are a plnt of oil down the engine doesn't smell like its burning oil and it doesn't  smoke is there any way we could find out if it is burning oil thanks for any advice Geoff 

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I'd see what happens with another hours running first. It's about 2 pints between the marks so you'll be safe if it uses another pint

 

I'm assuming the engine isn't dumping oil into the bilge

 

Richard

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Where does the crankcase ventilation go?

Some have a breather pipe on the rockerbox, but there is a side breather on the forward tappet chest cover under the exhaust manifold.

If these are dumping oil into the air cleaner, you will lose oil.

Try putting them into a bottle instead and see how much oil the crankcase compression is blowing out. If its excessive then its rings and bores I am afraid.

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1 minute ago, hider said:

If these are dumping oil into the air cleaner, you will lose oil.

I would expect a pint of oil going up the inlet to cause lots of smoke.

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13 minutes ago, RLWP said:

I would expect a pint of oil going up the inlet to cause lots of smoke.

So would I but its a fishing boat at sea, probably running hard and fast. Maybe they didn't notice if the wind was blowing the exhaust away on the lee side.

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When you did the top end rebuild did you put valve stem seals on the stems of the exhaust valves? If the answer is yes I have a suggestion about the possible cause of the problem.

Mike.

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50 minutes ago, Mike Jordan said:

When you did the top end rebuild did you put valve stem seals on the stems of the exhaust valves? If the answer is yes I have a suggestion about the possible cause of the problem.

Mike.

Which you are not prepared to share here?

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RLWP I'm not sure what you are referring to but my question still stands. I experienced a similar but smaller problem a number of years ago with a 1.8 and I will be happy to explain the cause and cure applied.

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16 minutes ago, Mike Jordan said:

RLWP I'm not sure what you are referring to but my question still stands. I experienced a similar but smaller problem a number of years ago with a 1.8 and I will be happy to explain the cause and cure applied.

Carry on then. We like sharing knowledge and experiences here, what was the cause and cure?

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The inlet valves have oil seals, non on the exhaust valves.

Though you can fit them to all the valves, they are standard BMC B series cup seals.

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You are right in saying that you can fit seals to the exhaust valve stems as well as the inlet valves, but if they are not up to spec as mine weren't they can be welded to the valve stem by the heat and then go up and down with the valve and make a very effective set of four little pumps each of which pumps oil droplets down the valve guides into the exhaust.

In my instance all the joints in the exhaust system dripped oil into the engine room, soaked the exhaust lagging and made an obvious mess.

Most fishing boats have a wet exhaust and the engine will be working much harder than in a canal boat so that may be the answer.

The problem has been on here before but I can't find the posts.

Its easy enough to take off the rocker cover and look through the springs.

It is possible to remove the seals without lifting the head off.

  • Greenie 1

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