Oil leaking from push rods

[ChrisE]

Hi,

we have a 7HP 1929 long4 with original engine. We are loosing a fair bit of oil from the direct push rods, that push the external springs on the valves, with oil coming out and running down the engine. We loose about 10mm on the dipstick every 20/30mins of travel. This only happens on one side cylinder, the other side seems fine.

There is a local garage that is supposed to be good with engines (it's beyond my expertise). What should we be looking for, what do we expect, and does anyone have a parts-list or diagram for the engine? I'm guessing that there is no modern type oil seal in there but maybe a bronze bush or something that will have worn and now lets oil pass? I guess someone would need to machine a new one?

ta
Chris

[Chris Spencer]

Chris - Where in the country are you located - then we can advise accordingly

[ChrisE]

Near Settle in Yorks Dales. The car is UU4792, prob known to you. It was our family car from the early 1970s to mid 1990s when dad sold it. In Aug 2018 we got a chance and bought it back

[k. rogers]

Welcome to the club and congratulations on returning this lovely car to your family! Sounds to me like it might need replacement valve guides - if you are able to wiggle the valves up and down more than a few thou then that's where the oil may be escaping. I'm not sure if the club do new valve guides for the vintage but I have a feeling they're different from the pre war 7 and may need machining in-situ. There is plenty of expertise in the club so you will soon have the answers.

[Chris Spencer]

Chris - I would highly recommend that you contact Michael Kavanagh - his contact details are in the membership list / handbook - Michael has a collection of vintage Jowett's along with all the expertise required to restore / maintain these vehicles - Michael & his son also own & run Cavendish Garage in Keighley, West Yorkshire - If I were to trust a vintage Jowett with anyone - this would be my choice - please keep us all updated with the progress or maybe you could reintroduce the membership to the car with a article in the 'Jowetteer' - you are welcome to contact me directly if you require any further help / information - my contact details are on page 3 of the 'Jowetteer' - Chris

[Tony Fearn]

Hello Chris(E).
Welcome to the pre-war and vintage Jowett scene.
I live about 20-odd miles from Settle in Clayton-le-Moors, and my address and telephone number are in the membership list if you want to get in touch.
Perhaps now that you've accessed JowettTalk, it would be better if you used the Pre-war section to ask further questions.
Ken has mentioned that the valve guides may be worn, but as these are within the cylinders, I don't think that's the problem. I presume you are talking about the tappets which protrude from the engine casing.

Some time ago I posted a few things in the pre-war section to do with this same problem for a young man from the South-West who had taken over his dad's 1934 saloon, and there was quite a conversation about it.

Perhaps viewtopic.php?f=4&t=676&p=3465&hilit=tappets#p3465 might just give you a start.

Let me know how you get on. Are you already a Club member? If not, I can't stress enough the advantage of being so.

Tony.

[Forumadmin]

by k. rogers » 06 Jan 2019 12:15 pm

Having only being used to the pre-war engines, the vintage engine has been quite a learning curve for me since I acquired the Sports. I have been steadily trying to reduce numerous oil leaks from the engine over the past couple of months, most of which I am sure were caused by excess crankcase pressure. It might be worth taking a look inside the breather valve which is the round contraption cast as part of the oil filler tube. The vintage engines used a flap of leather to cover the six breather holes, retained by a very light piece of sprung metal. Mine had been rigged up using a large washer soldered to a pop rivet held in place by a spring! It was only when the soldering failed causing a rattle inside the casting that I discovered this 'bodge'. I am sure this was allowing far too much pressure to build up in the crankcase and now I have replaced it with a simple flap of leather you can hear it 'popping' on and off the breather holes on tickover with the alternating vacuum and pressure caused by the pistons. While you have the breather cover off (held on by 2 bolts) make sure the oil return hole at the bottom isn't blocked.

[Forumadmin]

Hi KR,

first of all a bit of history. This car, a 1929 Full Four was our family car in the 1970s/80s/90s when we lived in Bradford. It was then sold but we got a chance and bought it back 6 months ago. It was then on the south coast and I understand it had been with 8-10 other cars of similar age, in a collection, in a dry garage but had not been run for maybe 10 years. We still have photos of Dad (now 87) driving us as kids (I'm now 55) about in it. My dad had a business that meant he was always driving about around Bradford so used it as an everyday car at least during summer.


Now to the engine, the pipe out of the breather is blowing well, a lot of air/gas/fumes/whatever out of it. I presume that means the leather 'valve' is working fine? Below are a couple of pics of the engine and oil leak. On each cylinder, there is one push rod that is fine/dry and the other leaks oil. One badly (in the picture) and the other side only half as bad.

CE-5cisk4.jpg

CE-30cc2ut.jpg

CE-2vn185j.jpg

CE-2m3oh39.jpg

[ChrisE]

Thanks for all the help- This is an update and a plea for help-phase 2!
So we had today sorted to take off the pots for sending away to be bored out on the push-rod-followers and lined although at the last minute the engineers I’d been speaking to about doing that said they could not and would not do it as they were too busy with ‘proper’ work and thought ours would be a messy fiddly job. The guy that was helping me is a local mechanic that does general car wok but also looks after a customer with a 1926 Rolls Royce and a couple of other similar special cars. I thought if he builds/fixes the Rolls Royce he will be probably able to take the step up to a Jowett!! He too had thought about the breather. See pic.



When we took off the filler cap while the engine was running, the gas/fumes/air forced out of that was a huge amount, all with oil in the vapour of course. It seemed like the breather was not allowing much, if any air through. When we did that the oil leak out of the push-rods virtually stopped too.
So the next thing we did was take that off and into the workshop.
We stripped the breather assembly down on the bench. The leather flapper valve, and any spring was completely missing and instead a metal pan-scrub type thing had been jammed in there, presumably to try and stem the oil/vapour flow.



The pan scrub is the swarf looking thing on the bench in the picture. It was stopping most of the airflow. It did too look like someone had drilled out the middle of the six holes to make an even larger hole. We took that out and as a temporary bodge put a small piece of tape across to try and catch as much oil as possible (which should run back down through a small hole) but while still allowing air to go around the side.



So we have put it all back together and it seems fine now, with only a small amount of oil leaking while the engine is running.



What I would like, is to know does anyone make or have a replacement for the parts we need (the leather and the spring)? I realise the likelihood is very remote. Failing that, does anyone have information or loads of detailed photographs, of what it should look like as the only other option is to try and make the missing parts or does anyone fancy just taking off their cover to photograph that for me (and the archive).

Thank you! Chris

[k. rogers]

Hi Chris, I'm pleased you have made progress and at least now know what may have been causing the leak. I don't know why anyone would drill out to make one big hole or what that was supposed to achieve, but also, don't know what impact it will have on the breather's function!
I would also welcome a picture of the set up as although I have made the leather flap, I don't have any idea what the spring should look like or how it's attached. I just cut an oblong piece of leather to cover the holes and screwed it in using the small hole near the bottom of the breather and it seems to be working just fine at present without the spring as the cover holds it in place once it's screwed on.

[k. rogers]

Just checked your pics and you can see the screw I used for fixing the leather just above the drain hole.

[ChrisE]

Thanks.
It would still be really useful to see a photo of the inside of the breather assembly if anyone has a photo, or can open it and take some photos, as I’ll need to make the leather valve and spring and would like some guidance.
The crankcase pressure does seem really high, if you take off the oil filler cap, it’s blowing a tremendous amount of gas out, like a puffing steam engine, which can’t be right? There is not too much power in the engine either although I fully understand it’s not going to pull like a V8 RangeRover!

I took the car out for a drive this afternoon (about 20 miles?) around Ingleborough in which it seems to have used about 20mm of oil on the dipstick. It’s not really burning it, just pushing it out of the engine as it’s all over the outside.

[Chris Spencer]

Chris - Can I make a suggestion that you contact a club member by the name of Michael Kavanagh who resides in Keighley - Michael will be able to assist / help you with this

[PJGD]

The thing to remember about a flat twin is that both pistons travel to BDC together, and then to TDC together. In doing so, they displace from the crankcase the same amount of air as the total swept volume (piston area x stroke) of both cylinders; that is to say if the engine displacement is [for the sake of argument] 800 cc, then that amount plus piston ring blow-by must come out through the breather and then a fresh 800 cc must return back into the crankcase for each revolution of the crankshaft. That is a lot of air and would require a large breather pipe, otherwise the work involved in constantly pumping that air in and out through a small breather pipe would be a definite parasitic to engine power.

What makes sense to me is that the Jowett breather is intended to let all the air plus blow-by out of the crankcase as the pistons travel to BDC but then prevent air from getting back in as the pistons move to TDC, thereby creating a depression in the crankcase. Then during the next 180° of crank rotation, the only air that needs to exit through the breather is the relatively small amount of gas blow-by past the piston rings, hence only a relatively small diameter breather pipe is perfectly adequate. Then the cycle starts again.

Therefore, it is necessary that the breather flap, whether it is made from leather, neoprene, or other compliant material, will form a positive seal over the breather hole under the vacuum conditions that temporarily exist in the crankcase. It also makes sense that there would be a light spring over the flap to encourage it to seal. When working properly, the advantage of this arrangement is that for 180° out of the 360° of crank rotation, there is a vacuum in the crankcase which is a strong deterrent to oil from leaking out of the engine through the crankshaft seals or out of the tappet bores. When not working properly, i.e. the flap is not sealing, then there exists a positive pressure in the crankcase which give the oil a strong incentive to leak out of every clearance available to it.

Philip

[ChrisE]

Thank you Philip.

That hadn’t occurred to me, however makes sense and looking into it I found a GIF that makes it all much more obvious. See https://upload.wikimedia.org/wikipedia/ ... mation.gif
Apparently it’ a big thing with Citroën 2CV engines too!
So I ordered some leather (I think I over estimated it as I have enough to make a sofa!) and made a flap-valve.



I packed the level so that it sits snug-flat on the aluminium plate.



Someone said there needs to be a very weak spring, I scratched my head about how to do that then came up with a brainwave and made it out of a tape measure.



I put the assembly to my mouth and blew/sucked and it seemed to work very well (although all I can taste now is oil!). It doesn’t make a clacking noise, maybe that comes once it is worn in a bit.



I ran the engine and can feel a good ‘blow’ coming out of the steel pipe so guess it’s working fine.

The weather’s not great at the moment (we’re under snow high up in the Dales here) but I’ll clean up the engine, go out for a run, and see if the oil leaks have lessened.

So far so good, thank you all!

Chris