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Post by jefferdp on May 17, 2021 14:56:31 GMT
Some advice plz,
I have just managed to remove the head for the 3rd time in 2 years, to replace the core plug.
However every time I get a head gasket set there are 8 little black plastic caps included?
At first I thought they may go on the push rods but could not see where so I never used them.
However now looking at the head there seems to be some sort of round plastic caps inside the valve spring, some of which seem to be breaking up.
Am I correct in now thinking that these black caps fit over the value stems and push onto the head?
Regards Dean.
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Post by rogeru7 on May 17, 2021 15:35:00 GMT
You are correct the black rubber caps should have a single row wire coil on them, they slide down the valve stem and push them onto the valve guides
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Post by jefferdp on May 17, 2021 16:15:22 GMT
Brilliant,
Thanks for coming back so quickly on this.
So I'm now going to have to remove the springs to replace these black collars.
It likes to keep me on my toes this Bug.
Thanks Again Dean.
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Post by vannin on May 17, 2021 19:30:45 GMT
Valve stem oil seals, they should be nice and supple but go hard then can break up with age. Classic sign when they are past their best is the engine will be a bit smokey on start up for a few minutes as the engine burns off the oil that has got past the worn valve stem oil seals.
Always worth checking them whilst the head is off and the ones you replace them with are the same depth and diameter.
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Post by cdb15 on May 17, 2021 19:33:22 GMT
Brilliant, Thanks for coming back so quickly on this. So I'm now going to have to remove the springs to replace these black collars. It likes to keep me on my toes this Bug. Thanks Again Dean. I don't have a drawing to hand but it sounds to me like these are oil seals. In the early days valves didn't have them, partly because folks wanted oil to drain down into the valve guides to lubricate the valve stem, and partly because the rubbers or polymers available at the time wouldn't stand the high temperatures (hence the embrittlement and subsequent breaking up). But with improved seal materials and better oils and even improvements in valve steels, plus concerns about oils being drawn into the engine, burning and adding to undesirable emissions, seals around the valve stems were introduced to prevent oil draining down into the guides. Or at least, prevent too much oil draining - enough for lubrication but not so much that it added to the emission figures. They're known as valve stem seals or umbrella seals - the idea being they keep the 'worst' of the oil off the stem, but not all of it. Modern valves have a groove around the stem about 5-10mm or so from the top end of the stem. The seal sits in this like a collar. Some valves simply have an O-ring, it does the same job. If your valves don't have this groove then the seal is stopped from sliding off the end of the stem simply by the presence of the rocker end being in contact with the stem, or, if your clearances are properly set, only a few thou away from it.
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Post by cdb15 on May 17, 2021 19:40:24 GMT
Valve stem oil seals, they should be nice and supple but go hard then can break up with age. Classic sign when they are past their best is the engine will be a bit smokey on start up for a few minutes as the engine burns off the oil that has got past the worn valve stem oil seals. Always worth checking them whilst the head is off and the ones you replace them with are the same depth and diameter. Well, Mark confirms my thoughts. Usual good practice is ALWAYS replace old ones whenever the valves are disturbed (or even just whenever the head is off) because there is no way of knowing (that I've ever heard of) of when they will fail, break up or whatever.
Although they go on soft and pliable, they go very hard when aged, and if particles break off and get washed down the stem (because the seal is no longer keeping the oil off...) the very next place they will come to is the valve seat, and as you know any debris trapped on that will lead to loss of compression, seat burning and goodness knows what else.
So ALWAYS replace them when you have the chance.
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Post by cdb15 on May 17, 2021 19:50:44 GMT
Just a little general addendum to all that: On some engines outside the Bug world, you may get seals only on the inlet valves, and you can also find different seals for the inlet compared to those for the exhaust valves. This is just down to the overall engine and lubrication system design, so always check what is intended for the particular engine and valves you are working on.
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Post by jefferdp on May 19, 2021 7:22:40 GMT
Hi, All
Thanks for all your comments, recommendations and advice.
Never thought my first post would generate such an interesting thread.
It goes to prove the old adage "your never to old to learn a new trick"
All the best Dean.
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Post by jefferdp on May 25, 2021 15:46:02 GMT
Well,
Thanks for the advice on the black caps people. I thought I would give you an update just in case anyone was interested on how I got on.
It may be small this car but it does throw up some very large problems. For me anyway as I am more of a 2 stroke man.
So thought I would set about replacing these caps as they were shot and I had found bits of plastic in the sump pan. All of which seemed so simple when looking at it.
I purchased a cheep ( I should have know better ) value spring compressor off Ebay for £15, thinking how much pressure do you need to compress a spring for god sake.
Well it seems you need a "beep lot of pressure" when the valve retaining clips will not give in. The compressor which started off a nice "U" shape ended up looking like a "V" as the retainers stuck solid.
I then went looking for answers about these retainers on the internet, fortunately there are is a lot of advice about this on there.
I decided to use a massive "G" clamp with a socket over the spring top to try and crack them.
Well the good news is that it worked however I have never heard such a BANG as the first set give up to the clamp. On the internet they said it would be a pop sound, well POP sound my foot. I honestly thought that I had snapped the valve. I must have jumped a foot in the air when it finally went with the socket flying across the room and it was the same with the rest of them.
After returning the spring compressor to a nice "U" shape it then worked fine on the cracked value spring.
So, Black caps fitted, New core plug fitted, just need some nice weather now to be able to start the rebuild. Figures crossed this will be the last time I have to take the head off this car.
Dean.
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Post by vannin on May 25, 2021 16:46:14 GMT
Hi Dean,
It's always nice to get some feedback and updates from owners who are experiencing difficulties with their Bugs and have been on here for advice and guidance.
It sounds like you've cracked it with your valve stem oil seals, and by the sound of it they haven't been changed in donkeys
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Post by rogeru7 on May 25, 2021 19:51:53 GMT
Hi Dean it’s not unusual for the valve retaining cap to need a bit of a clout to release the valve retaining collets especially if they have been assembled for many years.
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