MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Oil filler cap

I'm trying to help a young lad (on another forum) sort out his car and teach about regular servicing and fully servicing the car when you first get it

Of course he hasn't and now has problems

he did buy the owners Handbook so a good mark there

anyway the question

does anyone know for certain
if the normal (service item) plastic vented oil filler cap fits an ally rocker cover please?
Nigel Atkins

I know the the normal (service item) plastic vented oil filler cap is better for breathing is this supposed to fit or should it be the vented chrome?

just thought has this been push in instead of bayonet twisted in as it should have?

please forget about which looks best


Nigel Atkins

Hello Nigel,


If by an ally cover, it is an alloy cover you meant. Usuallly plastic cap is not suitable. But there are models with vent on cap.

Have a look at:

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=52431


Cheers,

Jean G.
Jean Guy Catford

cheers Jean, yes I did mean alloy

I've seen vented chrome oil caps on them but you would for cosmetic reasons but I wonder if the normal plastic cap would fit (and why they did allow for it to fit)
Nigel Atkins

Two different animals. The factory oil cap won't fit the alloy covers, only the chromed ones, that were specifically made for the alloy covers, are suitable for the job. Why, is anybody's guess. RAY
rjm RAY

I must beg to differ. My MGA came with a Moss type alloy rocker cover, and an MGB plastic, vented filler cap. The cap fits securely onto the filler neck with a bayonet style quarter turn, exactly the same as the same cap fits on my MGB onto its original pressed metal rocker cover.
(Personally I prefer the original look, and I'm currently refurbishing an original pressed metal rocker cover to fit to my MGA).


T Aczel

Here's the identical filler cap on my MGB. It fits just the same.


T Aczel

I have the regular cap on an alloy cover (From Brown & Gammons)
Michael Beswick

thanks for your replies, sorry I missed them until now

- it would seem it depends on who made the alloy cover

I much prefer the plastic service unit and change it every 12 months - not so bad at MGOC prices £4.03

Michael
last one I got from B&G and was shocked when I got home to see it was £10.50, I check their parts on line and price was correct, same price as Moss

I bought x4 from MGOC next time I was over there £16.12
Nigel Atkins

Nigel,

You said something in your second post about the vented cap being better for breathing.

The choice of vented or non-vented depends upon the rest of the components on the engine. That is, there are several methods of crankcase ventilation, and you pick the cap depending method employed.

Changing the plastic cap every 12 months seems a bit over cautious to me. Does it say to do that in the owners manual (inside joke)?

Charley
C R Huff

Hi Charley, sorry what I mean is the normal (service item) plastic vented oil filler cap is better for breathing than the vented chrome cap

you cant really check the plastic cap other than perhaps doing some sorted of metered test on a new one and then at services

at £4.03 each why risk it

this lad has probably spent many times this amount in topping up the oil and risked seals, gasket and so on

I've not got a (very essential) owners Handbook for a B but my midget one says every 12 months or 12,000 whichever is sooner (along with the rest of the servicing schedule)

the owners Handbook is a great investment I think every potential, new and existing owners should have a copy as there's so much information in them about the car, driving, ownership and full and proper servicing

http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html

yes I am that fan :)

Nigel Atkins

Well, how about that, Nigel? I thought I was just joking about the manual saying to replace the cap every 12 months. I suppose I should take your advice and get the book.

The cap on my B is a non-vented plastic cap that I drilled and tapped. Then I threaded in a brass barb fitting that I brazed and drilled to the size of the air intake of the original valve cover. My cast cover had no vent.

Charley
C R Huff

My Owners club alloy cover accepted the normal plastic effort no probs.
It's only got a wire mesh inside, could be washed in degreaser/petrol and then lightly oiled.
Allan Reeling

1965 MGB Handbook Part Number AKD 3900

Maintenance Summary
Page 61
12000 mile service
1 Engine
8th item ...... change oil filler cap and clean crankcase breather valve

Are the cheap caps the ones without the oil brands names moulded in the top ie plain and in my experience with sharp edges?

George
251 GRW
MGB50 September 23 2012 Blenheim Palace www.mgb50.com

G R Wilder

I used my stock vented oil filler cap, with the original valve cover, for over 20 years and never replaced it as a service item. I periodically cleaned it with carburetor cleaner. Replacement is overkill, in my opinion. RAY
rjm RAY

Charley
- the USA cars tend to be more complicated than the UK cars

The owners Handbooks are full of information

Also DVDs are available with loads of factory publications on them - clink on the links to the relevant model from here – http://www.motoringclassics.co.uk/heritage-range/c380

Allan, Ray,
- I wonder if the caps have changed or we’re talking about different items, the caps are a one piece item with only a very small inlet aperture, about ¼” flush cleaning them I would think would time consuming and you have to spray a lot of carb cleaner in

probably is excessive now with modern oils but for an additional £4 a year I don’t mind changing it as I like to keep my car in good condition so that if I feel like giving it a spirited run I don’t have to worry too much about the additional wear and I know it will go well and be reliable, mine’s an everyday car and I only enjoy driving it not working on it

George,
- no the £4.03 ones from MGOC have all the names on as do the £10.50 ones but the expensive one look cheaper made!

Part number is now GFE6003, I’ll put a photo up if I remember
Nigel Atkins

Some caps are not vented, some are. Depends as Charley said on the rest of the breather system. The ones with vents have a filter. If you snap the inner plastic disc out, you can take the filter out and wash it.
Covers with metal caps may be vented via a small hole, or not vented at all. These may be the older caps like MGA, or versions of common Brit motorcycle (or Morgan) fuel/oil tank caps. Or fancy racy Monza/Aston type flippy top lock down caps. Or lever top ones that can be sealed for LeMans and such.

FRM
FR Millmore

my hands are in the air

I am wrong

apoligises to Allan, Ray and all, based on what FRM put I looked at the cap and yes the bottom pops out giving access to wire

sorry, I know not why now but I thought the unit was one piece - and sealed !

I wondered how long it would take to clean just using the 3 mm hole in the bottom

I'm an idiot (yet again)

taking the wire out I can see the two protected oblong vent holes at the top and can imagine the unit would vent well

I don't think I'd trust the bottom to snap back in and stay there more than once or twice on these modern caps but that means 2 years life at least

sealed one piece unit ! not sealed and not one piece, another brain and memory f*rt from me !
Nigel Atkins

Don't feel badly Nigel, it took me a while to figure that one out. But, I had a really dirty cap and needed it in the middle of the night, so I used the old theory that somebody put it together, How?

FRM
FR Millmore

wouldn't be so bad if I hadn't been moaning at the lad for him assuming something

you know the training day saying " assume makes an ass out of u and me"

and he'll probably see this now I've posted it

it's bad enough not knowing much but then to be forgetting what little I used to know - I suppose I get the joy of learning it again . . . and then again and so on
Nigel Atkins

Just to add another perspective (this from someone who still doesn't get the whole vented versus non-vented setups), I put an alloy cover on my UK-spec car's 18V engine (1971), and it came with a metal cap with a small hole in it (~1.5mm).

Trouble was, with positive pressure under the rocker cover (not sure of the exact aetiology of it - the side cover filter is clean and flowing, and car has had a recent head job and new gasket - ?? cylinder blow-by) a fine mist of oil was exiting the hole and staining under the bonnet. So I switched to a non-vented plastic cap, so far without any obvious undue side effects!

First pic:
The cap I have now (http://www.mgbmga.com/images/MGB_65-69_valve_cover.jpg)

Second pic:
The metal cap that originally came with the alloy cover (http://www.musclecars.net/parts/parts-images-large/mga-and-mgb-alloy-valve-cover-with-fitting-kit_310271674921.jpg)
Curtis Walker

Sorry - second pic not working - should be:
http://www.mgbsource.com/images/parts/englishparts/bpnw/fullsize/8G612CP_m.jpg
Curtis Walker

Curtis, both your caps wre vented

the chrome with the 1.5ish mm vent hole and the standard vented plastic service item - http://www.mgbmga.com/images/MGB_65-69_valve_cover.jpg)


the two vent holes in the stansard plastic vented oil cap are not easy to see they are between the finger grip top and the seal plate (the bit that sits above the rocker cover neck)

on this photo, finger grip then seal plate and seal before bayonet locating groves - so vents are just above finger grip top

there clear as mud


Nigel Atkins

Thanks for the clarification. And I did have to gently file of a couple of mm's from the inside of the cap and the locking lugs for it to fit properly on the alloy cover.

At least the venting on the plastic cap doesn't mist oil under the bonnet!
Curtis Walker

Curtis, as long as the plastic cap fits securely

this whole thing started because of blocked breather pipes so just do a quick check of yours perhaps
Nigel Atkins

This thread was discussed between 12/05/2011 and 25/05/2011

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.