74 replies to this topic

[BobbyMax]

Hi Ethel, i have changed the rocker shaft for a new one but would assume they are all the same?

[nicklouse]

So you say your compression and leak down tests are good. The oil will not be coming from the breather then.

a drive how long was that?

low pressure leaks that will just drip down, half moon seal. 
low pressure leaks that can get thrown around. Crank oil seal.

high pressure leaks oil galley plugs. 
 

clean it all up and get some UV oil dye. Then you might actually see where it is leaking.

[Spider]

Hi Spider,thanks for your input.
Definatly comming from breather. Started engine brought rpm up to 3.2 and watched it come through breather

 

 

 

Hi Nicklous,why should Ibe pulling the engine?

 

Have done a leak-down test, no pots higher than 25% Loss.

 

 

While I don't place a lot of faith in leak-down tests, at around 25% your rings (or valves) simply are not sealing . This is resulting in a fair bit of your combustion pressurising the crankcase and blowing oil probably from every orifice on the engine, but most noticeable from the crankcase breather.

 

A 'normal' range would be in the order of 5 to 10% for a worn but OK engine. above about 20% it's knackered.

[timmy850]

If you’ve only got one breather and it’s spewing out of there then it does sound like a severe blow-by condition like other have mentioned

What’s it like with the oil cap off when it’s running? Is it pushing oil out of the dipstick hole?

The top end (rocker shaft, rocker arms) should be coated in oil but not drowning in oil. If the cam bearing was installed backwards it’ll send excess oil to the top end. Equally, if the head gasket or the rocker posts have been mixed up you might have no oil on the top end

[BobbyMax]

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Edited by BobbyMax, 12 December 2025 - 10:12 AM.

[BobbyMax]

So you say your compression and leak down tests are good. The oil will not be coming from the breather then.
a drive how long was that?
low pressure leaks that will just drip down, half moon seal.
low pressure leaks that can get thrown around. Crank oil seal.
high pressure leaks oil galley plugs.

clean it all up and get some UV oil dye. Then you might actually see where it is leaking.

[BobbyMax]

Definatly coming from breather. watched it flooding out.its almost like the whole cover filled up then overflowed out the top of the chimney

[coopertaz]

compression test reults 'no higher than 25%' what were they? and can you hear any air comming from breather whilst doing the test?

[nicklouse]

Definatly coming from breather. watched it flooding out.its almost like the whole cover filled up then overflowed out the top of the chimney

Ten back to my first comment. Pull it and remeasure everything as you have something very wrong.

[Lplus]

Definatly coming from breather. watched it flooding out.its almost like the whole cover filled up then overflowed out the top of the chimney

If the timing chain cover is filling up then it might be the drain holes in the front main cap are partially blocked so the oil from the main and cam bearings can't get back to the sump fast enough.  I assume the level does fall after the engine is stopped.

[Ethel]

There's a huge passage through the end plate as well. If the mains cap is blocked, it would fill up closer to the the level of the breather, but it ought to still drain. Maybe not, if there's any sloshing going on if it moves.

[BobbyMax]

Im kinda thinkig a blockage somewhere as i didn't have a problem with blow-by before changed the cam and rockers and had head off for a skim. I did adjust the cam timing but cant see how that would cause problems... only needed 1 degree. Thinking as Nicklouse said im prob going to have to pull the engine unless I have a eureka moment
if I do pull it what should I be looking for

[Lplus]

There's a huge passage through the end plate as well. If the mains cap is blocked, it would fill up closer to the the level of the breather, but it ought to still drain. Maybe not, if there's any sloshing going on if it moves.

There is indeed though on the A+ 1275 block I just checked the matching hole in the block is only 3/4 inch dia and it is effectively level with the breather hole.  Assuming it filled to that level and then the oil was stirred by the chain and the engine had some blowby it seems possible that a fair amount of oil and air could get into the breather.  I think the OP's engine only has the one breather.

[PoolGuy]

What’s it like with the oil cap off when it’s running? 
 

Have you tried this yet?

[BobbyMax]

Going to take another look at it on Sunday.

Remove dip and filler cap.

Was thinking if i fit a tranfer case breather aswell and it still happens can I rule out blow-by?