Dipstick oil-seal?
 

I was checking the engine oil-level in my 2 litre Amazon last night in preparation for a drive down to Cornwall. I noticed (for the umpteenth time) that the dipstick doesn't really seem to positively "locate" in its tube when I push it right in; it just feels loose and "rattly". It's also very easy to rotate the dipstick when it's right in. On all the other cars I've had over the years (VW beetle, series landrover, MGB) the dipstick has felt much more "secure" and "positively located", and I've usually felt at least some resistance to rotation. I'm just wondering, should there perhaps be some sort of seal either around the dipstick itself or around the top of the dipstick tube? I can't see one in any of the drawings I can find online though...

Going on from that, although the engine doesn't seem to use or lose much oil the bottom of the block and the outside of the sump usually have a slight coating of oil. It may be purely coincidental, but it looks as if this could be coming from the dipstick tube. If I get chance this evening I'll check that the crank-case breather is clear and that the gauze in the oil filler cap (smooth top - no pipe fitting) isn't clogged. But again it makes me wonder if there shouldn't be a bit more of a seal around the dipstick. Does anyone have any thoughts?

At the top of the stick, where there are 2 sections, the short section should be bent a bit to give it tension to stay in the tube. It's difficult to explain, but if you pull out your stick, you'll see what I mean.

However, I don't want to alarm you, but 2 things as there shouldn't be a misty spray around the outside of your engine.

• You say it's a B20. B20 have rubber valve stem oil seals and they go bad. They're pretty much a service item as far as I'm concerned. They let oil into the chambers causing smoking on overrun, but can also pressurise the block if really bad. They're very cheap, but even the new ones from the normal outlet are rubbish and much better from your local engineering firm. I'm just having to do mine again for this reason.
• You should consider a compression test. If there's enough blow-by past the piston rings, that will chuck oil out in the way of like a misty hue, for want of a better description.

You're doing the right thing by checking the oil breathers, but you could do a simple check by running the engine at idle with the breather pipes off. Is there smoke coming out?

Edit: Just re-read and saw that you have no pipe from your oil cap - that's non-standard for a B20. Is there a pipe from the crank case breather on the side of the block to the manifold or air cleaner? Or is it breathing to atmosphere?

H;

Welcome to this forum!

When new, split halves at the top of Dipstick were splayed apart a bit so they would have a gap and effectively have some preload when inserted into position...this would retain Dipstick and prevent it from being loose...Dipstick does not have a seal per se...gravity and this preload keeps it in place...

Crankcase should have a slight negative pressure due to (flow limited) connection to Intake Manifold by way of PCV sys. Positive crankcase pressure is typically due to blocked PCV and results in oil leakage...

Ref: http://www.sw-em.com/pcv_diagrams_and_notes.htm

Cheers from Connecticut!

Thanks Swedishandgerman - I'll slightly splay the two legs of the dipstick and see how that feels.

I wouldn't describe the oil on the block as a spray exactly - it looks more like it's run down rather than wafting out as a mist. I suppose it could even be the residue from careless topping-up. I never think to use the jug until I've let some oil dribble from the can!

I'll bear in mind what you say about the rubber valve stem oil seals but I haven't seen any smoking on overrun so maybe mine are OK for the time being?

I tested the compression last October and the figures seemed OK - 150psi±5% dry and 162psi±4% with a squirt of oil.

The crankcase breather connects to the air cleaner - I'll disconnect it as you suggest and check that there are some fumes coming out.

Would it be better if the crankcase breather were connected to the manifold? Not that I can do that immediately since there's only one connection to the manifold and that goes to the brake servo. Though thinking about it I might have a Y-piece somewhere...

Thanks for the welcome Ron!

Mine's one of the last Amazons so I'm not sure that it has the one-way valve in the PCV system. In any case it only connects to the air-cleaner so there's no suction applied to the pipe.

I had several MGBs years ago and went to a garage that worked on little else. Over the years I saw quite a variety of breather systems fitted to engines. The mechanic there always advised me to keep it simple and avoid in-line filters, filtered vents, etc, on the grounds that when they get blocked they cause more problems than they ever cured. He was in favour of a heavy-walled rubber tube venting to atmosphere somewhere low-down in the engine bay. Certainly not the most environmentally-friendly arrangement!

There's no great benefit of upgrading to a closed crank-case breather in my opinion other than reducing the smeech . Is smeech just a Devonshire word?!

If you were to just wang it into the inlet manifold without doing the rest of it, it won't run correctly.

As it is, you just have open air breathing which is fine. As well, you have nothing other than good old petrol and air going into the engine!

Thanks again Swedishandgerman!

Good day,Mr Swedish, like your Devonshire,what is smeech? smoke? wang is self explanatory ,and am I right in thinking that 'proper job' is one of your home grown? I remember a fellow on 'Scrap yard challenge' farmer,short chap,bursting with energy! from your fair county? used 'proper job' all the time.

Regards,Keith.

The theory of these PCV systems is that you should have both.

(1) A (free-flow) connection between crankcase and air filter: at high engine speeds the vacuum in the air filter, even though not much below atmospheric pressure, is sufficient to evacuate the crankcase. But it is not effective when the engine is idling because under those conditions there is essentially no vacuum in the air filter.

and

(2) A (restricted) connection between crankcase and inlet manifold: this comes into play when the engine is idling. At idling speed the vacuum in the inlet manifold is significant, so gives you the suction power you need to evacuate the crankcase. But you need a restriction in the connection, otherwise the vacuum in the inlet manifold is going to collapse. In the standard B20 carburetted engine the restriction is provided by a nozzle with a small hole (2mm diameter) in it that sits on the inlet manifold. That nozzle needs to be cleaned every now and then.