12 replies to this topic

[MiniLuke]

Hi, now have my new engine running, and it runs quite well, however....

I have noticed oil coming from the timing cover seal > which during rebuiild was replaced, along with every other seal!

Now, after tinkering whilst it is running I have noticed the following,

- if I lift the dipstick up so it isn't sealing, the engine runs better (idles smoother)
- if the oil cap is removed during running the same.
- if i pinch the existing breather pipe it runs worse.

The engine is equivalent to a 998 cooper, i.e 12G295 head, "D" top pistons. It has only one breather on the tappet cover connected to the carb.

Questions are,
Is pressure in the block a bad thing?
Should I source a rocker cover with an extra breather pipe, if so what does this connect to? I assume a 3 way connector to the other breather pipe?
Do I need to consider a breather on the flywheel housing and/or timing cover?
Is the oil from the timing cover likely to be due to the pressure, or a knackered seal?

Also I have good compression across all cylinders, and the car drives very well so hopefully nothing too serious.......

Any advice appreciated please.

[il-barba]

to me it looks like you have an overly rich mixture. and the seal is a separate problem.

[MiniLuke]

to me it looks like you have an overly rich mixture. and the seal is a separate problem.

Ok, not sure I understand how the mixture being rich would cause this, could you explain at all please? would a rich mixture increase block pressure?

[Ethel]

Sounds like it's behaving as it should, blocking the breather pipe limits air being drawn out of the crankcase and acts like the throttle on the idle speed. Removing the dipstick or filler cap lets more air in and does the opposite.

Try slackening the screws around the chain cover so it can centralise the shaft in the oil seal before nipping them back up.

[il-barba]

not sure you have extra pressure in the block. but adding an extra breather surely helps

but when you open the dipstick/rocker cover you are introducing extra air which leans out the mixture and the engine runs better. are your spark plugs black?

[Carlos W]

not sure you have extra pressure in the block. but adding an extra breather surely helps

but when you open the dipstick/rocker cover you are introducing extra air which leans out the mixture and the engine runs better. are your spark plugs black?

I'm not sure that's true!

[Dan]

Why not? It is you know. The crankcase ventilation system is connected into the inlet system, and draws a fixed amount of air through the engine via a metered and filtered opening in the oil cap. The rest of the crankcase should be sealed. Open the cap or any other port on the crankcase and you allow vast amounts of additional air into the system, just the same as pulling the hose off the carb. If the engine runs better with more air, it's too rich. If the block were pressurising there would be oil leaking out all over it.

[dklawson]

As a historical footnote to the comments made above, on early engines where the PCV valve was first introduced, an indication that the system was working "correctly" was that removing the filler cap on the rocker cover would cause the engine RPM to increase.

[MiniLuke]

Try slackening the screws around the chain cover so it can centralise the shaft in the oil seal before nipping them back up.

Good idea, the seal is new, so should be ok. I'll try that.

[bmcecosse]

The breather system is working exactly as it should - the leaky seal problem is either down to a damaged or incorrectly fitted seal, or - did you fit the thrower correctly behind the seal ?

Edited by bmcecosse, 05 February 2011 - 08:20 PM.

[MiniLuke]

not sure you have extra pressure in the block. but adding an extra breather surely helps

but when you open the dipstick/rocker cover you are introducing extra air which leans out the mixture and the engine runs better. are your spark plugs black?

Thanks, yours and the other explanations make sense.

I'll check the plugs, however I have set the carb so that pushing up the little tester thingy on the back does not change the engine speed, therefore if increasing the air intake that way does not affect the engine speed, why would letting more air into the crank casing, and therefore more through the tappet chest breather and into the carb increase it?

Can anyone tell me what the breather pipe on some rocker covers should be connected to?

Also, some comments suggest the air is going into the engine via the cap, I was under the impression the air was coming out, I guess I was mistaken. However if the air is going in this way I am confused as to the function of a breather on the rocker cover, if it should be connected to the breather pipe going back to the carb.

Anyway, I am rambling now, any further thought are appreciated.
Luke

[MiniLuke]

The breather system is working exactly as it should - the leaky seal problem is either down to a damaged or incorrectly fitted seal, or - did you fit the thrower correctly behind the seal ?

Knowing me, and my foul up of putting the leads back assuming the dizzy went clockwise, it is quite possible the thrower is not on properly. I will actually check it not still on the bench....

[bmcecosse]

Yes - rocker breather to carb side port