Bradford engine oil leaks

[David Morris]

Dear All,

We have been contacted by a member, Ty Payne of Frampton Cotterell, near Bristol, who is not on JowettTalk, for help please with his Bradford. He has had the engine ( a CB I believe) overhauled and this is now running in the Bradford. However, he is losing considerable quantities of oil from the breather pipe, to the extent that you can see from the trail on the road exactly where he has been!

I have very little experience with Bradfords, however, my Jowett Generator Set has, I understand, a CB engine fitted. But I have not experienced the same problem.

Ty would be very grateful for some assistance/advice, which if you could send to me, I will pass on to him. Alternatively, you might like to call him, his number is in the register? I recollect that I have a vague memory that the engine breather can give problems, and I asked Ty if this had been changed and he confirmed that he has just changed it. Could this have led to his problems I wonder?

Many thanks,

David

[Keith Andrews]

"Considerable" indicates excessive blow by past the rings...
Which is likely to be combined with the filter/ valve type system between the crankcase vent tube and crankcase being dirty of faulty.
Start with the filter/ valve, clean, check vanes etc 1st.
Check cyclinder compression, blow by and excessivly low cyclinder pressure go hand in hand.

[george garside]

a ccouple more possibilities

Wrongly assembled breather valve or vanes incorrectly set.

grossly overfilled sump although by the sound of it that should be self curing!

however I think blowby resulting in cra nk caes pressure rather than depression/

To Do

check crank case depression using manometer

check compression

if early CB fitted with oil level indicator that is not floating the sump could be overfilled

george

[David Morris]

Hi George and Keith,

On behalf of Ty, many thanks for your comments. I know that the engine has just been professionally overhauled, so I am assuming that the compression is probably ok, but as Ty has just fitted the crankcase breather valve, do you have any advice on how this should be assembled?

George, you mention that it may be that the vanes in the breather valve are incorrectly set or that it is wrongly assembled. Can you point us towards any instructions? As it seems to be the same valve as on my stationary engine, I will have a look in the manual for the engine and see if there are any instructions?

Many thanks,

David

[Tony Fearn]

Here's a sketch of the pre-war breather vanes, but I must admit I don't know whether the CB Bradford has the same set-up
Tony.

Of course, as George says, don't overfill the sump.

Perhaps P.B. will reveal all when he 's in the U.K. again.

[george garside]

CB breather valve is same as pre war type.

george

[Nigel Woodford]

Hi Guys,

Let me start by declaring I have no Bradford experience.

I looked at the breather on Ty's Bradford van yesterday and it appears to be different from the drawing Tony kindly provided.
The breather cover is aluminium and flat rather than domed. It has 2 bolts fixing it to the engine.
Looking at the inside of the cover/breather pipe there is a central ring which resembles a thin washer which is held in place by 3 domed head rivets.
I could not see the star shaped piece in the drawing.

I presume the drawing is of a CA Bradford breather which I believe is held in place by a single stud / bolt and is much more of a convex shape.

Nigel Woodford

[David Morris]

Hi everyone,

I have had a look at the breather used on the Jowett war-time stationary engines. It is very like the sketch provided by Tony Fearn, and the hole at the bottom is tiny, about 1.5mm in diameter, so could easily get blocked?

However, talking to Nigel while he was at Ty's, the breather on Ty's engine is quite different, as Nigel has explained above.

So, we need advice from someone who has experienced this model of Bradford. It looks as though there is pressure within the crankcase? The Jowett stationary engine manual states that there should be a vacuum in the crankcase, of about 10" water gauge.

Not having had a Bradford, we really need help from someone here to pass onto Ty.

Many thanks,

David

[george garside]

the breather valves on all the twins are very similer. That on the CB consists of the following parts. breather valve diaphram, breather valve stiffening plate, breather valve cover plate. It is much the same as pre wa and CA Brad exept that the central bolt is beneath the cover plate rather than going through it. From the description posted it seems that the diaphram is missing i.e the star shaped thing with the hole in the midle for the bolt. If this is the case there is effectively no breather valve so the crankcase will be pressurised instead of having a depression therein. I think the club spares section can supply the parts required.

george

[Tony Fearn]

In the JowettGallery, which all registered members should be able to access, the section called Technical Library contains a 'Bradford Album'.

After clicking the Bradford Album you get the first page on the screen.

Below this page in blue writing it says:- Download photo in original format.

Click and then run the file and there's lots of info about the Bradford and modifications. It's a good read.

Below I've copied a few lines from the publication which bear on this thread.

ITEM No. 15. BREATHER VALVE MODIFICATION
It is essential to prevent external oil leaks particularly Tappet oil leaks, for the Breather Valve to operate efficiently. When this Valve is efficiently adjusted it is inclined to be noisy, which is reported as objectionable to some owners.
This objection can be overcome by flattening the Breather Pipe End to form a Fish-Tail with a wide gap.
On no account must the Breather Valve be adjusted to reduce the noise or the efficiency of the Valve will be affected. (See “Breather Valve,” Page 2 General Technical Information.) I haven’t seen a copy of this.
CRANKCASE BREATHER.
The breather is fitted in the rear of the timing case and is designed to act as a non- return valve to allow displaced crankcase air to escape at the same time restricting the intake of air.
The breather consists of a base plate which is located by a dowel. The breather diaphragm and stiffening vanes are secured to the base plate by a hollow brass rivet and the diaphragms must be set to completely blank off the 3/16” (4.762 mm) drillings in the plate.
Breather operation may be checked in the normal manner using a depression gauge as
detailed on Page 2 of the General section of the Bulletin. I haven’t a copy of this either.

It is most important that the tappet covers are sealed correctly. This is interesting.
If this is not given careful attention, the crankcase depression will be lost. In addition the passage of air from the crankcase will carry an excessive amount of oil spray to the valve stems.
Either of these points may cause excessive oil consumption.

[george garside]

Tony
The breather valve article you have posted originates from a factory service bulletin for the CC Bradford hence the reference to seeling the tappet covers ( on the CC the valve springs etc are in a chamber forming part of the cylinder casting and this is in effecct open to crankcase depression unlike the pre war and CA/CB. ) Also the CC breather valve whilst being available in component form as was the CB et c it was also available as a complete unit . If bought in component form the parts had to be rivetted together using the hollow rivet supplied ( hollow so the retaining bolt could pass through it). The complete unit was rivetted by the factory. The setting/manometre testing etc in the bulletin apply to the earlier non rivetted breather valves

george

[StevenGray]

Nigel
Parts 57 and 58 are the breather vane and travel limiting plate for the CB Bradford.



Have had a look at a spare CC engine that I have and this has a single bolt mounting for the breather cover so the inner parts are almost certainly different,
it has been a long time since I saw inside the cover so dont remember

Steve

[george garside]

not sure whether or not the diaphram ( the star shaped bit) is the same diameter on CA,CB & CC buthrough the cover plate the principle is exactly the same. The CA and CC have the central stud through the cover plate that also locates the breather valve assembly which is made up of seperate parts mounted concentricalyon thbetween e stud. The CB is different from the CA only in that the cover mounting bolts (2 of) only hold the cover in plaace and the breather assembly is located by a central bolt under the cover . The CC is different in that the breather components are rivetted together for greater accuracy and once again are held in place by a central stud whcih passes through the cover and secures it.

I can't remember whether of not the CC type breather valve assembly will fit the CA/CB and vice versa

george

[PAUL BEAUMONT]

Prompted by the Honourable member for Accrington I make this post!
In my experience oil leaks on the Bradford stem from one of 2 causes if we discount a seriously knackered engine:
1 air leaks into the crankcase usually caused by some well meaning but deluded individual drilling a hole into the oil filler cap (or as has been mentioned tappet chest gasket leaks on the CC)
2. The crank case breather
I talked Nigel thru this last night at JCS and we shipped a new breather and stiffener out to him (original breathers tend to rust away as a result of condensation in the crankcase so JCS parts are stainless steel)
The CB breather is exactly the same as the earlier models, but is fitted slightly differently (the CC model is completely different)
On the CB model it mat be found easier to access if the dynamo support bracket and even the fuel pump is first removed.
The breather pipe terminates at its top in a flat casting that is secured to the crankcase with 2 fasteners. Removing the cover gives access to the breather which consists of 2 parts - the breather vane and its stiffener which are fitted with a central screw. Once the old parts have been removed it is a good idea to clean the area as it does gunge up. In particular the drain hole needs to be clear. Reassembly requires the vane to be fitted first such that its fingers cover the holes in the crankcase. Then the stiffener is positioned on top so that the points of the stiffener are central in each vane. The breather is secured with the central screw, taking care to ensure that the vane remains correctly positioned. Finally the cover is refitted and any other parts removed for access.
The breather ensures that the crankcase pressure is less than atmospheric so that the laws of nature mean that air tries to get in rather than oil out.
Crankcase pressure management is common to all 2-cylinder 4- stroke engines and BMW motorcycles and the large "V" twins of Harley Davidson and Moto Guzzi etc all use similar systems to address the same problem.
Hope that this helps!


Paul