K serieds crankcase vacuum

[Wingnut]

Hi

Just wondered if anyone else has experienced this, I noticed that when I checked the oil with the engine running I was seeing no oil on the dipstick, however when I withdrew the dipstick from the engine I had to pull against a distinct vacuum, I tried checking the oil again but with the oil filler cover off and the engine running and the oil level was fine, as soon as the oil filler cover went back on, the oil level on the dipstick no longer showed. 

I have drained the oil from the crankcase and oil filter, and have measured it at the correct 4.5l and very healthy looking it is too, I have fitted a new filter and another 4.5 litres of oil, and obviously get the same result, oil pressure also looks good. 

I have recently refitted the original plenum, but with a 52mm throttle body instead of the original 48mm one, and hope that my problems may be related, although everything looks like it is fitted OK, and she seems to run fine. I have checked the plugs, they are all the same, a little rich, but I have only been running her at idle, so guess this is to be expected.

I was meant to be running her at Aintree tomorrow, but am really not keen on thraping her around a track if the oil is not getting where it is meant to be, I am tempted to take her to Wigan pier though, and just push her off the end to join the shopping trolleys and the canal boats..

Any recommendations for a K series specialist in the York/Pickering area?

Thanks

[revilla]

Presumably you are wet-sumped?

There should be a bit of vacuum in the crankcase at idle, but not usually noticeable removing the dipstick!

There should be two rubber breathers from the cam cover. One is a short rubber S-shaped hose from the rear (on EU3 at least) port that goes to the plenum. This is the PCV hose, it should be allowing the plenum vacuum to draw off crank case vapours at low power (e.g. idle). The other is a longer hose with a straight plastic section from the front (on EU3) port that goes back to the throttle body. This is the main breather hose. It should be allowing fresh air back in to flush the crankcase at idle. Under heavy loads when there is more blowby than the PCV can draw off, the excess gas escapes back out of the main breather to be drawn in through the throttle and burned.

It sounds to me like your crankcase is connected to the plenum but not properly vented. Is the main breather connected? I s it blocked? Are things connected as described above?

[revilla]

Some diagrams I drew to explain it earlier ...

Low Load / Closed Throttle

High Load / Full Throttle

[Jonathan Kay]

BlatChat will serve animated GIFs...

:-)

Jonathan

[revilla]

When you say "I have recently refitted the original plenum" - did you remove it for a while? And did you blank the breather when it was off?

If it's not breathing, you will get plenum vacuum in the crankcase at idle but more worryingly you will be pressurising the crankcase under load. If that's happening, you will be putting a lot of strain on oil seals - particularly you risk blowing out the crank rear seal, which is a big (engine out) job to replace. I'd sort it out before using it much if I were you.

[Wingnut]

Think its sorted, my local garage had fitted a new gearbox, and as the engine was coming out I asked them to fit the old plenum when everything went back in, the S tube that should have gone to the restricted orifice was connected to the front breather and the restricted orifice was blanked off as was the bottom breather on the throttle body, the S tube is now on the breather and I have cobbled together a pipe from the breather connection on the head to the throttle body, oil reading as it should on the dipstick and I think that I can call off littering Wigan pier for a short while.

I do not think any damage will have been done, she was brought back from the garage on a trailer because she could not be started due to immobiliser issues for me to fix (which I have only recently achieved), I am sure that if she had been running this issue would have been found by them.

Thanks for the quick responses its greatly appreciated.

Mark

[SM25T]

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[revilla]